SINCE 1973 good rubber strip has problem find trouble started chief source Pirelli factory near Milan Italy reorganized split off Pirelli company became part new company called Filati Pirelli company still makes sheet rub ber sold Filati strips size markets Beginning 1973 batch Filati tested writer varied widely energy storage appearance old fashioned product brown energy storage around 3300 foot pounds per pound 1973 test very black Filati gave 2250 foot pounds per pound 1974 gray batch tested encouraging 3310 1976 batch gave 2600 1977 batch gave 1500 foot pounds per Editors Note Mr Pearces time con suming research -another example scientific reporting MA occasionally does bonanza people fly rubber events Encouragement ex tended thinkers vast RC field others both CL FE March 1979 59 author launching 74 Wakefield won first both 1974 1975 Nationals What could worlds largest slingshot really Freds special test rig testing Wakefield motor 200-pound scale measures pull force Stretch distance calibrated edge frame category finds dedicated researchersfortunately TABLE RUBBER TEST RESULTS stretch method 75 degrees F SourceComment Brown ribbed Gitlow Tenny Cannizzo Zaic Zaic Sig Zaic Zaic F D Zaic Zaic F D Sig FAI Old Timer Old Timer Zaic Vintage Aero Vintage Aero Aeromodels Tsuda FAI FAI FAI FA FA Filati FAI FAI Cannizzo Gray smooth Repeat test brittle Repeat test brittle Repeat test brittle Black Gray smooth Gray smooth Vintage date Repeat test brittle Gray Gray smooth soft Repeat test Black Brown smooth Feb76 batch Aug76 batch Dec 76 batch Mar 77 batch Jun 77 batch Dark brown opaque Apr 78 spool 1 Apr 78 spool 2 Translucent yellow brown TestElong- Energy Dateationft lb lb Jan64 752940 Oct63 802980 Jan64 602890 Jan64 7A3300 1964813525 May70 763100 Aug75 692950 Jun71 783160 May72 833440 Aug74 793310 Aug 73803290 Jul73823310 Jul77733540 Apr 73772250 Jul73BA3140 Jul73782500 Aug75 783210 Jul 77793600 Oct74 823310 July76 903200 May77 833060 Apr 76812600 May77 662620 May77 733400 Sep76 802980 May77 773380 Jun77 783450 Jul77803320 Mar78 641570 Sep78 803440 Sep78 8252970 Sep78 813725 8 SAMPLESTRETCHENERGY D78PlRELLI81X3725 3-77FA178X3410 R VULCANIZED83X2970 77FILATI64X1570 I STRETCH INCHES pound test findings disap pointing performance experienced models fliers using Filat led seeking out new source problem appears under standing what model flier calls quality various manufacturers did get message rubber stores energy new supplies rubber coming forth ranged widely quality lately reaching level pre-1973 Pirelli change has now taken place Excellent quality rubber available again quote rub ber flier old school Mike Diko vitzky fun has put back flying rubber powered models Rubber complex mixture ingredients must mixed processed just right order produce product optimum characteristics given use Small changes ingredi ents mixing sequence vulcanization process can produce wide changes physical properties supply Pirelli became irregular initially no other manufacturer rose occasion fill gap understandable since very small demand model aircraft rubber strip consistent supply high quality strip judged model fliers became available after Ed Dolby perseverance work manufacturer over protracted period time response Eds speci fications manufacturer produced batches rubber characteristics thought would satisfy model builders Through several reiterations recipe developed tested model builders gave good results Once manufacturer understood correlate production good performance model airplane optimized recipe produce strip consistent high quality mid-1978 Pirelli again entered picture After five year lapse producing product referred Special Pirelli Model Fliers com pounded carbon black yellow brown almost translucent has ribbed texture old fashioned product new rubber gives higher energy storage rubber encountered author storage runs above 3700 foot pounds per pound 750 F addi tion FAI new Pirelli have several other sources rubber including two author has tested recently Sig Vintage Aero offering rubber reported give very good results Manufacture Strip Rubber Strip rub ber manufactured natural crude rubber synthetic rubber stearic acid zinc oxide sulphur carbon black small amounts catalysts conditioners such Altax Neozone D Accelerator 808 Titanox etc best quality rubber uses virgin stock reclaimed-rubber imports have poor characteristics gray 60 Model Aviation Vin tage 1958 1962 1963 1963 1964 1968 1968 1969 1970 1970 1971 1972 1972 1973 1973 1973 1974 1974 1974 1976 1976 1976 1976 1976 1976 1976 1977 1977 1977 1978 1978 1978 Type Pirelli Pirelli Gitlow Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Filati Sig FAI Pirelli Pirelli Filati Vintage Aero Vintage Aero Filati Japanese FA FAI FAI FAI FAI Filati FAI FAI Pirelli 20 16 12 CA 6 4 Figure 1 black color imparted carbon black Brown rubber contains little no carbon black recipes rubber manufacture almost always proprietary since element witchcraft obtaining desired characteristics guess recipe current smooth gray Ameri can manufactured rubber Ingredients Pale Virgin Crepe natural rubber Synthetic rubber Stearic Acid Zinc Oxide Altax Accelerator Catalysts Neozone D Activator Catalysts Sulphur Carbon Black about 16 inches long FAI rub ber little thicker 14 strands being about same length Pirelli takes about same turns 320 Sig Vintage Aero rubber generally thinner Pirelli require strands get equivalent cross-section area Rather strands better think equivalency skein length made up motors 85 See Table tabulation rubber 15test results since 1958 good Wakefield 1should able over 180 seconds 5 arts Weight 3 less 112 presumed product would improved deletion syn thetic rubber carbon black presumption remains determined mill ingredients mixed about 1200 F following order StepIngredientsMixing time INatural Rubber synthetic rubber 4 minutes 2Stearic Acid softens mixture 2 minutes 3Zinc oxide Altax Neozone D Carbon Black25 minutes 4Sulphur acts vulcanize during curing process15 minutes After mixing rubber run through roller produce sheet desired thickness typically 043 sheet comes out five six feet wide about 900 feet long dusted talcum powder keep sticking itself After rolling up put electronically controlled vulcanizing oven subjected steam about 2850 F around 30 minutes degree vulcanization has very dramatic effect tensile prop erties Vulcanization cross linking polymer chains brought about action sulphur high temperature After removal oven rubber allowed cool room temperature prior slitting process first step slitting rubber cut belts 75 inches wide sliced end end tapered glued joint total length now continu ous 75 inches belt about 9000 feet next step run belt through slitting mill set desired widths typically 1/16 3/32 1/8 3/16 1/4 inch strips After passing through slitting strip run off spools containing about pound rubber amounts 200 feet /4 inch strip typical batch weight about 1500 pounds new Pirelli about same size old Pirelli 388 gram dry weight Wakefield motor makes up 16 strands 6 14 2 10 0 z 0 0 bJ 0 0 LL6 4 2 Chris Matsuno tests close agreement Fig 2 compares results using two methods shows differences power curves due characteristic difference behavior rubber ing wound stretched Excluding strongly non-linear portions begin ning end curves torque wound sample varies proportionally 15 power number strands whereas pull force stretched rub ber varies directly proportionally ~1 TESTSAMPLEENERGY STRETCHED2 STRANDS 4135 GM3350 WOUND8STRANDS4135GM3350 -1 STREECHED ND 1 K 020 Figure 2 0 40 60 80 100 10203040506070 duration rubber over 3100 foot pounds per pound energy storage Like wise very good Coupe should over 120 seconds 3100 rubber See Fig comparison power curves Pirelli Filati FAI Rubber Rubber testing Rubber stores energy tension can produced either stretching winding Tests either method give comparable results writer has compared stretch tests over long period winding tests 120 -50 -40 30 20 -10 0 Si RETCH 80 TURNS number strands Both test samples same weight Both methods have same area beneath curve indicates identical energy storage areas products force times distance turns times torque respec tively represent foot pounds energy curves demonstrate identical results using either method determine energy storage much difficult wind motor ultimate capacity accuracy repeatability stretch its maxi March 1979 61 mum length Winding energy storage affected distance stretched put turns well percent age turns put various distances Hence standardized stretch testing order obtain consistency obtain comparable results test test felt necessary pull samples same ultimate tensile stress very close breaking point Figuring original cross-section pulling proportional force does job because stretchy rub ber would pulled higher tensile stress problem solved pulling motor two stages first pull computed following formula 45 X weight Force pound grams* Original Length inches force strong enough pull motors near maximum stretch second pull force computed following formula 430 X weight Force2 poundsgrams* Stretched Length F inches * purely metric versions formulas have constants 52 496 respectively F kilograms W grams L centimeters Applying F2 will stretch motors additional small amount near break ing point example March 1977 FAI Rubber sample two strands inch pulled F F2 pounds question arises would stretchier rubber pulled higher tensile stress thus store energy therefore reducing validity comparing dif ferent samples problem mitigated shape energy storage curve see Fig As pull rubber very high tensile stress change elongation becomes less less final result becoming climbing-the-wall situ ation get almost no change stretched length approach breaking stress Thus very little additional energy stored since incremental product force times distance very small rubber testing machine shown photograph has 200-pound scale handling full-size Wakefield motors 20-pound scale testing single loops rubber boat winch provided stretching samples along cali brated 150-in frame Test motors attached hook scale hook end rope travels around pulley far end frame back winch use testing procedure follows Weigh sample loop suitable 150-in frame say between 12 16 inches long Subtract out weight knot tag ends 2 Lubricate sample green soap glycerine type rubber lubricant Dont get knot soaked lube high stress will cause slip put extra talcum powder ends before tying square knot single granny knot top Saliva helps keep rubber tearing pulling knot tight 3 Compute pull force F break rubber pulling force 5 min utes Wait least hour before next 14 12 10 C 0 z 1 cc w C- 0 Li. 6 4 2 0 7 Correct stretch distances deflection force scale 8 Plot force stretch distance graph paper Measure area beneatl curve Typically integrate sum ot about dozen steps along stretch scale 9 area beneath curve fool pounds represents energy divided sample weight gets energy storage foot pounds per pound writer believes apparatus gives result 1% accuracy Foot pounds per pound reduces simply feet interpretation sample rubber could lift itself vertically SAMPLEWILL ENERGY TEST DATE 76VINTAGE 448 138 876 3140JULY76 AERO 76 VINTAGE 448 1306 833 3150 MAY 77 AERO 76FA1447143773380MAY77 I / d-y REFERENCE 1 K76 VA MAY77 16 VA JULY 76 / / Figure 3 20 406080 STRETCH INCHES step 4 Using stretched length first pull compute second pull force F2 5 Pull motor F2 taking care take about 15 seconds pull last 10% desired force 6 Immediately read record force stretch distance Backing off small increments step down about dozen steps zero tension recording step 100 2C distance equal its energy storage example sample 3300 could lift itself 3300 feet model airplane 25% its weight rubber could climb 25 X 3300 feet energy used 100% efficiency Standards Rubber Strip What standards good rubber past good Pirelli available good quality gave energy around 3300 foot pounds per pound stretched maxi mum about 8 times its original length 62 Model Aviation Rubber below 3000 considered defi nitely below par Rubber stretched less about 73 times its original length looked upon suspicion thought getting old Rubber stretched over 82 times thought soft probably under-vulcanized Some values rubber samples given Table Rubber below par energy storage typically has power curve such two lower curves Fig shape power curve can give trouble use cause sharp spike power utilized effectively model inclined too much after first few seconds cause torque falling rapidly airplane can respond effect especially noticeable ground turbulence model climbing very steeply easily stalled upset Rubber too soft good energy storage such lower curve Fig 3 also gives initial poor climb characteristic Aging Effects Rubber polymer Aging results continuation uncompleted vulcanization reactions usually resulting chain-lengthening increased crosslinking between chains pro cesses lead toughening rubber Aging rubber beyond optimum condi tion results chain scission decomposi tion resulting shorter chains combined increasing crosslinking exces sive nature product becomes creasingly brittle balance chain lengthening chain decomposition crosslinking can vary widely Generally good quality rubber will slowly lose its ability stretch slowly losing its energy storage capability Rub ber becomes tougher age eventually becoming brittle Brittle rubber tears knots slight imperfections also inclined explode breaking strands skein wound Fig 3 gives example undervulcanized rubber became tougher year age Its power curve initi ally sharp peak torque character istic undesirable characteristics described previously under Stand ards Rubber Strip Age helped shape power curve slightly lowering energy storage An oc casional example rubber will increase its energy storage age un common associated becoming dangerously brittle Note Table generally declining elongation age 1968 1972 Pirelli 1975 1965 1966 1967 1969 1970 Pirelli too brittle use although 1968 useable dangerous 1976 1972 Pirelli become dangerously brittle although its energy excellent note its elonga tion has declined 82 initially 73 today second article will appear next month handling new generation rub ber addition conventional ques tions making up skeins breaking winding maximum turns two additional topics will covered effect temperature energy storage effect holding fully wound motor energy storage NEW THIS YEAR Volume IlA handsome com panion Volume Frank Ehlings KIT PLAN BOOK containing reduced-size plans model airplane kits avail able Ace RIO Andrews Aircraft Model Co Astro Flight Bridi Hobby Enterpris es Cass Engineering Classic Models Cox Hobbies Flyline Models Carl Goldberg Models House Balsa Jetco Models Midwest Model Products Peck Polymers Rev Model Prod 3 ucts Sig Mfg Co Sterling Models Top Flite Models age Bob Violett Models VK Model Aircraft World Enginesl plans contained Volume Ace H/C Andrews Aircraft Model Co Carl Goldberg Models Chuck Gill Models Competition Models Jetco Models Junior Aero Space Co. Midwest Model Products Mini-Flite Co Nelson Model Products Sig Mfg Co Sterling Models Top Flite Models World Engines combined plans Volume II gives opportunity shop own home before plunking down dolla s types models included volume RC CL Scale FFsport compet t designs category volume produced AMA HQ com piled Frank EhI ng paperback s ze 9 x 12 $2 50 m AM HQ Supply & Service Section 815 Fifteenth Street NW Washington DC 20005 I__I Please PrintlU NameAMANoI Address City State Zip md March 1979 63 Kit Plan Books me @ $250 $ __________ enclosed .....Kit Plan Books- Volume II @ $250 Send check money order send cash through maill Close-up test rig special 20-pound precision scale being used sassing two-strand motors Note boat winch employed pulling rubber motors undergoing testing
Edition: Model Aviation - 1979/03
Page Numbers: 59, 60, 61, 62, 63
SINCE 1973 good rubber strip has problem find trouble started chief source Pirelli factory near Milan Italy reorganized split off Pirelli company became part new company called Filati Pirelli company still makes sheet rub ber sold Filati strips size markets Beginning 1973 batch Filati tested writer varied widely energy storage appearance old fashioned product brown energy storage around 3300 foot pounds per pound 1973 test very black Filati gave 2250 foot pounds per pound 1974 gray batch tested encouraging 3310 1976 batch gave 2600 1977 batch gave 1500 foot pounds per Editors Note Mr Pearces time con suming research -another example scientific reporting MA occasionally does bonanza people fly rubber events Encouragement ex tended thinkers vast RC field others both CL FE March 1979 59 author launching 74 Wakefield won first both 1974 1975 Nationals What could worlds largest slingshot really Freds special test rig testing Wakefield motor 200-pound scale measures pull force Stretch distance calibrated edge frame category finds dedicated researchersfortunately TABLE RUBBER TEST RESULTS stretch method 75 degrees F SourceComment Brown ribbed Gitlow Tenny Cannizzo Zaic Zaic Sig Zaic Zaic F D Zaic Zaic F D Sig FAI Old Timer Old Timer Zaic Vintage Aero Vintage Aero Aeromodels Tsuda FAI FAI FAI FA FA Filati FAI FAI Cannizzo Gray smooth Repeat test brittle Repeat test brittle Repeat test brittle Black Gray smooth Gray smooth Vintage date Repeat test brittle Gray Gray smooth soft Repeat test Black Brown smooth Feb76 batch Aug76 batch Dec 76 batch Mar 77 batch Jun 77 batch Dark brown opaque Apr 78 spool 1 Apr 78 spool 2 Translucent yellow brown TestElong- Energy Dateationft lb lb Jan64 752940 Oct63 802980 Jan64 602890 Jan64 7A3300 1964813525 May70 763100 Aug75 692950 Jun71 783160 May72 833440 Aug74 793310 Aug 73803290 Jul73823310 Jul77733540 Apr 73772250 Jul73BA3140 Jul73782500 Aug75 783210 Jul 77793600 Oct74 823310 July76 903200 May77 833060 Apr 76812600 May77 662620 May77 733400 Sep76 802980 May77 773380 Jun77 783450 Jul77803320 Mar78 641570 Sep78 803440 Sep78 8252970 Sep78 813725 8 SAMPLESTRETCHENERGY D78PlRELLI81X3725 3-77FA178X3410 R VULCANIZED83X2970 77FILATI64X1570 I STRETCH INCHES pound test findings disap pointing performance experienced models fliers using Filat led seeking out new source problem appears under standing what model flier calls quality various manufacturers did get message rubber stores energy new supplies rubber coming forth ranged widely quality lately reaching level pre-1973 Pirelli change has now taken place Excellent quality rubber available again quote rub ber flier old school Mike Diko vitzky fun has put back flying rubber powered models Rubber complex mixture ingredients must mixed processed just right order produce product optimum characteristics given use Small changes ingredi ents mixing sequence vulcanization process can produce wide changes physical properties supply Pirelli became irregular initially no other manufacturer rose occasion fill gap understandable since very small demand model aircraft rubber strip consistent supply high quality strip judged model fliers became available after Ed Dolby perseverance work manufacturer over protracted period time response Eds speci fications manufacturer produced batches rubber characteristics thought would satisfy model builders Through several reiterations recipe developed tested model builders gave good results Once manufacturer understood correlate production good performance model airplane optimized recipe produce strip consistent high quality mid-1978 Pirelli again entered picture After five year lapse producing product referred Special Pirelli Model Fliers com pounded carbon black yellow brown almost translucent has ribbed texture old fashioned product new rubber gives higher energy storage rubber encountered author storage runs above 3700 foot pounds per pound 750 F addi tion FAI new Pirelli have several other sources rubber including two author has tested recently Sig Vintage Aero offering rubber reported give very good results Manufacture Strip Rubber Strip rub ber manufactured natural crude rubber synthetic rubber stearic acid zinc oxide sulphur carbon black small amounts catalysts conditioners such Altax Neozone D Accelerator 808 Titanox etc best quality rubber uses virgin stock reclaimed-rubber imports have poor characteristics gray 60 Model Aviation Vin tage 1958 1962 1963 1963 1964 1968 1968 1969 1970 1970 1971 1972 1972 1973 1973 1973 1974 1974 1974 1976 1976 1976 1976 1976 1976 1976 1977 1977 1977 1978 1978 1978 Type Pirelli Pirelli Gitlow Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Filati Sig FAI Pirelli Pirelli Filati Vintage Aero Vintage Aero Filati Japanese FA FAI FAI FAI FAI Filati FAI FAI Pirelli 20 16 12 CA 6 4 Figure 1 black color imparted carbon black Brown rubber contains little no carbon black recipes rubber manufacture almost always proprietary since element witchcraft obtaining desired characteristics guess recipe current smooth gray Ameri can manufactured rubber Ingredients Pale Virgin Crepe natural rubber Synthetic rubber Stearic Acid Zinc Oxide Altax Accelerator Catalysts Neozone D Activator Catalysts Sulphur Carbon Black about 16 inches long FAI rub ber little thicker 14 strands being about same length Pirelli takes about same turns 320 Sig Vintage Aero rubber generally thinner Pirelli require strands get equivalent cross-section area Rather strands better think equivalency skein length made up motors 85 See Table tabulation rubber 15test results since 1958 good Wakefield 1should able over 180 seconds 5 arts Weight 3 less 112 presumed product would improved deletion syn thetic rubber carbon black presumption remains determined mill ingredients mixed about 1200 F following order StepIngredientsMixing time INatural Rubber synthetic rubber 4 minutes 2Stearic Acid softens mixture 2 minutes 3Zinc oxide Altax Neozone D Carbon Black25 minutes 4Sulphur acts vulcanize during curing process15 minutes After mixing rubber run through roller produce sheet desired thickness typically 043 sheet comes out five six feet wide about 900 feet long dusted talcum powder keep sticking itself After rolling up put electronically controlled vulcanizing oven subjected steam about 2850 F around 30 minutes degree vulcanization has very dramatic effect tensile prop erties Vulcanization cross linking polymer chains brought about action sulphur high temperature After removal oven rubber allowed cool room temperature prior slitting process first step slitting rubber cut belts 75 inches wide sliced end end tapered glued joint total length now continu ous 75 inches belt about 9000 feet next step run belt through slitting mill set desired widths typically 1/16 3/32 1/8 3/16 1/4 inch strips After passing through slitting strip run off spools containing about pound rubber amounts 200 feet /4 inch strip typical batch weight about 1500 pounds new Pirelli about same size old Pirelli 388 gram dry weight Wakefield motor makes up 16 strands 6 14 2 10 0 z 0 0 bJ 0 0 LL6 4 2 Chris Matsuno tests close agreement Fig 2 compares results using two methods shows differences power curves due characteristic difference behavior rubber ing wound stretched Excluding strongly non-linear portions begin ning end curves torque wound sample varies proportionally 15 power number strands whereas pull force stretched rub ber varies directly proportionally ~1 TESTSAMPLEENERGY STRETCHED2 STRANDS 4135 GM3350 WOUND8STRANDS4135GM3350 -1 STREECHED ND 1 K 020 Figure 2 0 40 60 80 100 10203040506070 duration rubber over 3100 foot pounds per pound energy storage Like wise very good Coupe should over 120 seconds 3100 rubber See Fig comparison power curves Pirelli Filati FAI Rubber Rubber testing Rubber stores energy tension can produced either stretching winding Tests either method give comparable results writer has compared stretch tests over long period winding tests 120 -50 -40 30 20 -10 0 Si RETCH 80 TURNS number strands Both test samples same weight Both methods have same area beneath curve indicates identical energy storage areas products force times distance turns times torque respec tively represent foot pounds energy curves demonstrate identical results using either method determine energy storage much difficult wind motor ultimate capacity accuracy repeatability stretch its maxi March 1979 61 mum length Winding energy storage affected distance stretched put turns well percent age turns put various distances Hence standardized stretch testing order obtain consistency obtain comparable results test test felt necessary pull samples same ultimate tensile stress very close breaking point Figuring original cross-section pulling proportional force does job because stretchy rub ber would pulled higher tensile stress problem solved pulling motor two stages first pull computed following formula 45 X weight Force pound grams* Original Length inches force strong enough pull motors near maximum stretch second pull force computed following formula 430 X weight Force2 poundsgrams* Stretched Length F inches * purely metric versions formulas have constants 52 496 respectively F kilograms W grams L centimeters Applying F2 will stretch motors additional small amount near break ing point example March 1977 FAI Rubber sample two strands inch pulled F F2 pounds question arises would stretchier rubber pulled higher tensile stress thus store energy therefore reducing validity comparing dif ferent samples problem mitigated shape energy storage curve see Fig As pull rubber very high tensile stress change elongation becomes less less final result becoming climbing-the-wall situ ation get almost no change stretched length approach breaking stress Thus very little additional energy stored since incremental product force times distance very small rubber testing machine shown photograph has 200-pound scale handling full-size Wakefield motors 20-pound scale testing single loops rubber boat winch provided stretching samples along cali brated 150-in frame Test motors attached hook scale hook end rope travels around pulley far end frame back winch use testing procedure follows Weigh sample loop suitable 150-in frame say between 12 16 inches long Subtract out weight knot tag ends 2 Lubricate sample green soap glycerine type rubber lubricant Dont get knot soaked lube high stress will cause slip put extra talcum powder ends before tying square knot single granny knot top Saliva helps keep rubber tearing pulling knot tight 3 Compute pull force F break rubber pulling force 5 min utes Wait least hour before next 14 12 10 C 0 z 1 cc w C- 0 Li. 6 4 2 0 7 Correct stretch distances deflection force scale 8 Plot force stretch distance graph paper Measure area beneatl curve Typically integrate sum ot about dozen steps along stretch scale 9 area beneath curve fool pounds represents energy divided sample weight gets energy storage foot pounds per pound writer believes apparatus gives result 1% accuracy Foot pounds per pound reduces simply feet interpretation sample rubber could lift itself vertically SAMPLEWILL ENERGY TEST DATE 76VINTAGE 448 138 876 3140JULY76 AERO 76 VINTAGE 448 1306 833 3150 MAY 77 AERO 76FA1447143773380MAY77 I / d-y REFERENCE 1 K76 VA MAY77 16 VA JULY 76 / / Figure 3 20 406080 STRETCH INCHES step 4 Using stretched length first pull compute second pull force F2 5 Pull motor F2 taking care take about 15 seconds pull last 10% desired force 6 Immediately read record force stretch distance Backing off small increments step down about dozen steps zero tension recording step 100 2C distance equal its energy storage example sample 3300 could lift itself 3300 feet model airplane 25% its weight rubber could climb 25 X 3300 feet energy used 100% efficiency Standards Rubber Strip What standards good rubber past good Pirelli available good quality gave energy around 3300 foot pounds per pound stretched maxi mum about 8 times its original length 62 Model Aviation Rubber below 3000 considered defi nitely below par Rubber stretched less about 73 times its original length looked upon suspicion thought getting old Rubber stretched over 82 times thought soft probably under-vulcanized Some values rubber samples given Table Rubber below par energy storage typically has power curve such two lower curves Fig shape power curve can give trouble use cause sharp spike power utilized effectively model inclined too much after first few seconds cause torque falling rapidly airplane can respond effect especially noticeable ground turbulence model climbing very steeply easily stalled upset Rubber too soft good energy storage such lower curve Fig 3 also gives initial poor climb characteristic Aging Effects Rubber polymer Aging results continuation uncompleted vulcanization reactions usually resulting chain-lengthening increased crosslinking between chains pro cesses lead toughening rubber Aging rubber beyond optimum condi tion results chain scission decomposi tion resulting shorter chains combined increasing crosslinking exces sive nature product becomes creasingly brittle balance chain lengthening chain decomposition crosslinking can vary widely Generally good quality rubber will slowly lose its ability stretch slowly losing its energy storage capability Rub ber becomes tougher age eventually becoming brittle Brittle rubber tears knots slight imperfections also inclined explode breaking strands skein wound Fig 3 gives example undervulcanized rubber became tougher year age Its power curve initi ally sharp peak torque character istic undesirable characteristics described previously under Stand ards Rubber Strip Age helped shape power curve slightly lowering energy storage An oc casional example rubber will increase its energy storage age un common associated becoming dangerously brittle Note Table generally declining elongation age 1968 1972 Pirelli 1975 1965 1966 1967 1969 1970 Pirelli too brittle use although 1968 useable dangerous 1976 1972 Pirelli become dangerously brittle although its energy excellent note its elonga tion has declined 82 initially 73 today second article will appear next month handling new generation rub ber addition conventional ques tions making up skeins breaking winding maximum turns two additional topics will covered effect temperature energy storage effect holding fully wound motor energy storage NEW THIS YEAR Volume IlA handsome com panion Volume Frank Ehlings KIT PLAN BOOK containing reduced-size plans model airplane kits avail able Ace RIO Andrews Aircraft Model Co Astro Flight Bridi Hobby Enterpris es Cass Engineering Classic Models Cox Hobbies Flyline Models Carl Goldberg Models House Balsa Jetco Models Midwest Model Products Peck Polymers Rev Model Prod 3 ucts Sig Mfg Co Sterling Models Top Flite Models age Bob Violett Models VK Model Aircraft World Enginesl plans contained Volume Ace H/C Andrews Aircraft Model Co Carl Goldberg Models Chuck Gill Models Competition Models Jetco Models Junior Aero Space Co. Midwest Model Products Mini-Flite Co Nelson Model Products Sig Mfg Co Sterling Models Top Flite Models World Engines combined plans Volume II gives opportunity shop own home before plunking down dolla s types models included volume RC CL Scale FFsport compet t designs category volume produced AMA HQ com piled Frank EhI ng paperback s ze 9 x 12 $2 50 m AM HQ Supply & Service Section 815 Fifteenth Street NW Washington DC 20005 I__I Please PrintlU NameAMANoI Address City State Zip md March 1979 63 Kit Plan Books me @ $250 $ __________ enclosed .....Kit Plan Books- Volume II @ $250 Send check money order send cash through maill Close-up test rig special 20-pound precision scale being used sassing two-strand motors Note boat winch employed pulling rubber motors undergoing testing
Edition: Model Aviation - 1979/03
Page Numbers: 59, 60, 61, 62, 63
SINCE 1973 good rubber strip has problem find trouble started chief source Pirelli factory near Milan Italy reorganized split off Pirelli company became part new company called Filati Pirelli company still makes sheet rub ber sold Filati strips size markets Beginning 1973 batch Filati tested writer varied widely energy storage appearance old fashioned product brown energy storage around 3300 foot pounds per pound 1973 test very black Filati gave 2250 foot pounds per pound 1974 gray batch tested encouraging 3310 1976 batch gave 2600 1977 batch gave 1500 foot pounds per Editors Note Mr Pearces time con suming research -another example scientific reporting MA occasionally does bonanza people fly rubber events Encouragement ex tended thinkers vast RC field others both CL FE March 1979 59 author launching 74 Wakefield won first both 1974 1975 Nationals What could worlds largest slingshot really Freds special test rig testing Wakefield motor 200-pound scale measures pull force Stretch distance calibrated edge frame category finds dedicated researchersfortunately TABLE RUBBER TEST RESULTS stretch method 75 degrees F SourceComment Brown ribbed Gitlow Tenny Cannizzo Zaic Zaic Sig Zaic Zaic F D Zaic Zaic F D Sig FAI Old Timer Old Timer Zaic Vintage Aero Vintage Aero Aeromodels Tsuda FAI FAI FAI FA FA Filati FAI FAI Cannizzo Gray smooth Repeat test brittle Repeat test brittle Repeat test brittle Black Gray smooth Gray smooth Vintage date Repeat test brittle Gray Gray smooth soft Repeat test Black Brown smooth Feb76 batch Aug76 batch Dec 76 batch Mar 77 batch Jun 77 batch Dark brown opaque Apr 78 spool 1 Apr 78 spool 2 Translucent yellow brown TestElong- Energy Dateationft lb lb Jan64 752940 Oct63 802980 Jan64 602890 Jan64 7A3300 1964813525 May70 763100 Aug75 692950 Jun71 783160 May72 833440 Aug74 793310 Aug 73803290 Jul73823310 Jul77733540 Apr 73772250 Jul73BA3140 Jul73782500 Aug75 783210 Jul 77793600 Oct74 823310 July76 903200 May77 833060 Apr 76812600 May77 662620 May77 733400 Sep76 802980 May77 773380 Jun77 783450 Jul77803320 Mar78 641570 Sep78 803440 Sep78 8252970 Sep78 813725 8 SAMPLESTRETCHENERGY D78PlRELLI81X3725 3-77FA178X3410 R VULCANIZED83X2970 77FILATI64X1570 I STRETCH INCHES pound test findings disap pointing performance experienced models fliers using Filat led seeking out new source problem appears under standing what model flier calls quality various manufacturers did get message rubber stores energy new supplies rubber coming forth ranged widely quality lately reaching level pre-1973 Pirelli change has now taken place Excellent quality rubber available again quote rub ber flier old school Mike Diko vitzky fun has put back flying rubber powered models Rubber complex mixture ingredients must mixed processed just right order produce product optimum characteristics given use Small changes ingredi ents mixing sequence vulcanization process can produce wide changes physical properties supply Pirelli became irregular initially no other manufacturer rose occasion fill gap understandable since very small demand model aircraft rubber strip consistent supply high quality strip judged model fliers became available after Ed Dolby perseverance work manufacturer over protracted period time response Eds speci fications manufacturer produced batches rubber characteristics thought would satisfy model builders Through several reiterations recipe developed tested model builders gave good results Once manufacturer understood correlate production good performance model airplane optimized recipe produce strip consistent high quality mid-1978 Pirelli again entered picture After five year lapse producing product referred Special Pirelli Model Fliers com pounded carbon black yellow brown almost translucent has ribbed texture old fashioned product new rubber gives higher energy storage rubber encountered author storage runs above 3700 foot pounds per pound 750 F addi tion FAI new Pirelli have several other sources rubber including two author has tested recently Sig Vintage Aero offering rubber reported give very good results Manufacture Strip Rubber Strip rub ber manufactured natural crude rubber synthetic rubber stearic acid zinc oxide sulphur carbon black small amounts catalysts conditioners such Altax Neozone D Accelerator 808 Titanox etc best quality rubber uses virgin stock reclaimed-rubber imports have poor characteristics gray 60 Model Aviation Vin tage 1958 1962 1963 1963 1964 1968 1968 1969 1970 1970 1971 1972 1972 1973 1973 1973 1974 1974 1974 1976 1976 1976 1976 1976 1976 1976 1977 1977 1977 1978 1978 1978 Type Pirelli Pirelli Gitlow Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Filati Sig FAI Pirelli Pirelli Filati Vintage Aero Vintage Aero Filati Japanese FA FAI FAI FAI FAI Filati FAI FAI Pirelli 20 16 12 CA 6 4 Figure 1 black color imparted carbon black Brown rubber contains little no carbon black recipes rubber manufacture almost always proprietary since element witchcraft obtaining desired characteristics guess recipe current smooth gray Ameri can manufactured rubber Ingredients Pale Virgin Crepe natural rubber Synthetic rubber Stearic Acid Zinc Oxide Altax Accelerator Catalysts Neozone D Activator Catalysts Sulphur Carbon Black about 16 inches long FAI rub ber little thicker 14 strands being about same length Pirelli takes about same turns 320 Sig Vintage Aero rubber generally thinner Pirelli require strands get equivalent cross-section area Rather strands better think equivalency skein length made up motors 85 See Table tabulation rubber 15test results since 1958 good Wakefield 1should able over 180 seconds 5 arts Weight 3 less 112 presumed product would improved deletion syn thetic rubber carbon black presumption remains determined mill ingredients mixed about 1200 F following order StepIngredientsMixing time INatural Rubber synthetic rubber 4 minutes 2Stearic Acid softens mixture 2 minutes 3Zinc oxide Altax Neozone D Carbon Black25 minutes 4Sulphur acts vulcanize during curing process15 minutes After mixing rubber run through roller produce sheet desired thickness typically 043 sheet comes out five six feet wide about 900 feet long dusted talcum powder keep sticking itself After rolling up put electronically controlled vulcanizing oven subjected steam about 2850 F around 30 minutes degree vulcanization has very dramatic effect tensile prop erties Vulcanization cross linking polymer chains brought about action sulphur high temperature After removal oven rubber allowed cool room temperature prior slitting process first step slitting rubber cut belts 75 inches wide sliced end end tapered glued joint total length now continu ous 75 inches belt about 9000 feet next step run belt through slitting mill set desired widths typically 1/16 3/32 1/8 3/16 1/4 inch strips After passing through slitting strip run off spools containing about pound rubber amounts 200 feet /4 inch strip typical batch weight about 1500 pounds new Pirelli about same size old Pirelli 388 gram dry weight Wakefield motor makes up 16 strands 6 14 2 10 0 z 0 0 bJ 0 0 LL6 4 2 Chris Matsuno tests close agreement Fig 2 compares results using two methods shows differences power curves due characteristic difference behavior rubber ing wound stretched Excluding strongly non-linear portions begin ning end curves torque wound sample varies proportionally 15 power number strands whereas pull force stretched rub ber varies directly proportionally ~1 TESTSAMPLEENERGY STRETCHED2 STRANDS 4135 GM3350 WOUND8STRANDS4135GM3350 -1 STREECHED ND 1 K 020 Figure 2 0 40 60 80 100 10203040506070 duration rubber over 3100 foot pounds per pound energy storage Like wise very good Coupe should over 120 seconds 3100 rubber See Fig comparison power curves Pirelli Filati FAI Rubber Rubber testing Rubber stores energy tension can produced either stretching winding Tests either method give comparable results writer has compared stretch tests over long period winding tests 120 -50 -40 30 20 -10 0 Si RETCH 80 TURNS number strands Both test samples same weight Both methods have same area beneath curve indicates identical energy storage areas products force times distance turns times torque respec tively represent foot pounds energy curves demonstrate identical results using either method determine energy storage much difficult wind motor ultimate capacity accuracy repeatability stretch its maxi March 1979 61 mum length Winding energy storage affected distance stretched put turns well percent age turns put various distances Hence standardized stretch testing order obtain consistency obtain comparable results test test felt necessary pull samples same ultimate tensile stress very close breaking point Figuring original cross-section pulling proportional force does job because stretchy rub ber would pulled higher tensile stress problem solved pulling motor two stages first pull computed following formula 45 X weight Force pound grams* Original Length inches force strong enough pull motors near maximum stretch second pull force computed following formula 430 X weight Force2 poundsgrams* Stretched Length F inches * purely metric versions formulas have constants 52 496 respectively F kilograms W grams L centimeters Applying F2 will stretch motors additional small amount near break ing point example March 1977 FAI Rubber sample two strands inch pulled F F2 pounds question arises would stretchier rubber pulled higher tensile stress thus store energy therefore reducing validity comparing dif ferent samples problem mitigated shape energy storage curve see Fig As pull rubber very high tensile stress change elongation becomes less less final result becoming climbing-the-wall situ ation get almost no change stretched length approach breaking stress Thus very little additional energy stored since incremental product force times distance very small rubber testing machine shown photograph has 200-pound scale handling full-size Wakefield motors 20-pound scale testing single loops rubber boat winch provided stretching samples along cali brated 150-in frame Test motors attached hook scale hook end rope travels around pulley far end frame back winch use testing procedure follows Weigh sample loop suitable 150-in frame say between 12 16 inches long Subtract out weight knot tag ends 2 Lubricate sample green soap glycerine type rubber lubricant Dont get knot soaked lube high stress will cause slip put extra talcum powder ends before tying square knot single granny knot top Saliva helps keep rubber tearing pulling knot tight 3 Compute pull force F break rubber pulling force 5 min utes Wait least hour before next 14 12 10 C 0 z 1 cc w C- 0 Li. 6 4 2 0 7 Correct stretch distances deflection force scale 8 Plot force stretch distance graph paper Measure area beneatl curve Typically integrate sum ot about dozen steps along stretch scale 9 area beneath curve fool pounds represents energy divided sample weight gets energy storage foot pounds per pound writer believes apparatus gives result 1% accuracy Foot pounds per pound reduces simply feet interpretation sample rubber could lift itself vertically SAMPLEWILL ENERGY TEST DATE 76VINTAGE 448 138 876 3140JULY76 AERO 76 VINTAGE 448 1306 833 3150 MAY 77 AERO 76FA1447143773380MAY77 I / d-y REFERENCE 1 K76 VA MAY77 16 VA JULY 76 / / Figure 3 20 406080 STRETCH INCHES step 4 Using stretched length first pull compute second pull force F2 5 Pull motor F2 taking care take about 15 seconds pull last 10% desired force 6 Immediately read record force stretch distance Backing off small increments step down about dozen steps zero tension recording step 100 2C distance equal its energy storage example sample 3300 could lift itself 3300 feet model airplane 25% its weight rubber could climb 25 X 3300 feet energy used 100% efficiency Standards Rubber Strip What standards good rubber past good Pirelli available good quality gave energy around 3300 foot pounds per pound stretched maxi mum about 8 times its original length 62 Model Aviation Rubber below 3000 considered defi nitely below par Rubber stretched less about 73 times its original length looked upon suspicion thought getting old Rubber stretched over 82 times thought soft probably under-vulcanized Some values rubber samples given Table Rubber below par energy storage typically has power curve such two lower curves Fig shape power curve can give trouble use cause sharp spike power utilized effectively model inclined too much after first few seconds cause torque falling rapidly airplane can respond effect especially noticeable ground turbulence model climbing very steeply easily stalled upset Rubber too soft good energy storage such lower curve Fig 3 also gives initial poor climb characteristic Aging Effects Rubber polymer Aging results continuation uncompleted vulcanization reactions usually resulting chain-lengthening increased crosslinking between chains pro cesses lead toughening rubber Aging rubber beyond optimum condi tion results chain scission decomposi tion resulting shorter chains combined increasing crosslinking exces sive nature product becomes creasingly brittle balance chain lengthening chain decomposition crosslinking can vary widely Generally good quality rubber will slowly lose its ability stretch slowly losing its energy storage capability Rub ber becomes tougher age eventually becoming brittle Brittle rubber tears knots slight imperfections also inclined explode breaking strands skein wound Fig 3 gives example undervulcanized rubber became tougher year age Its power curve initi ally sharp peak torque character istic undesirable characteristics described previously under Stand ards Rubber Strip Age helped shape power curve slightly lowering energy storage An oc casional example rubber will increase its energy storage age un common associated becoming dangerously brittle Note Table generally declining elongation age 1968 1972 Pirelli 1975 1965 1966 1967 1969 1970 Pirelli too brittle use although 1968 useable dangerous 1976 1972 Pirelli become dangerously brittle although its energy excellent note its elonga tion has declined 82 initially 73 today second article will appear next month handling new generation rub ber addition conventional ques tions making up skeins breaking winding maximum turns two additional topics will covered effect temperature energy storage effect holding fully wound motor energy storage NEW THIS YEAR Volume IlA handsome com panion Volume Frank Ehlings KIT PLAN BOOK containing reduced-size plans model airplane kits avail able Ace RIO Andrews Aircraft Model Co Astro Flight Bridi Hobby Enterpris es Cass Engineering Classic Models Cox Hobbies Flyline Models Carl Goldberg Models House Balsa Jetco Models Midwest Model Products Peck Polymers Rev Model Prod 3 ucts Sig Mfg Co Sterling Models Top Flite Models age Bob Violett Models VK Model Aircraft World Enginesl plans contained Volume Ace H/C Andrews Aircraft Model Co Carl Goldberg Models Chuck Gill Models Competition Models Jetco Models Junior Aero Space Co. Midwest Model Products Mini-Flite Co Nelson Model Products Sig Mfg Co Sterling Models Top Flite Models World Engines combined plans Volume II gives opportunity shop own home before plunking down dolla s types models included volume RC CL Scale FFsport compet t designs category volume produced AMA HQ com piled Frank EhI ng paperback s ze 9 x 12 $2 50 m AM HQ Supply & Service Section 815 Fifteenth Street NW Washington DC 20005 I__I Please PrintlU NameAMANoI Address City State Zip md March 1979 63 Kit Plan Books me @ $250 $ __________ enclosed .....Kit Plan Books- Volume II @ $250 Send check money order send cash through maill Close-up test rig special 20-pound precision scale being used sassing two-strand motors Note boat winch employed pulling rubber motors undergoing testing
Edition: Model Aviation - 1979/03
Page Numbers: 59, 60, 61, 62, 63
SINCE 1973 good rubber strip has problem find trouble started chief source Pirelli factory near Milan Italy reorganized split off Pirelli company became part new company called Filati Pirelli company still makes sheet rub ber sold Filati strips size markets Beginning 1973 batch Filati tested writer varied widely energy storage appearance old fashioned product brown energy storage around 3300 foot pounds per pound 1973 test very black Filati gave 2250 foot pounds per pound 1974 gray batch tested encouraging 3310 1976 batch gave 2600 1977 batch gave 1500 foot pounds per Editors Note Mr Pearces time con suming research -another example scientific reporting MA occasionally does bonanza people fly rubber events Encouragement ex tended thinkers vast RC field others both CL FE March 1979 59 author launching 74 Wakefield won first both 1974 1975 Nationals What could worlds largest slingshot really Freds special test rig testing Wakefield motor 200-pound scale measures pull force Stretch distance calibrated edge frame category finds dedicated researchersfortunately TABLE RUBBER TEST RESULTS stretch method 75 degrees F SourceComment Brown ribbed Gitlow Tenny Cannizzo Zaic Zaic Sig Zaic Zaic F D Zaic Zaic F D Sig FAI Old Timer Old Timer Zaic Vintage Aero Vintage Aero Aeromodels Tsuda FAI FAI FAI FA FA Filati FAI FAI Cannizzo Gray smooth Repeat test brittle Repeat test brittle Repeat test brittle Black Gray smooth Gray smooth Vintage date Repeat test brittle Gray Gray smooth soft Repeat test Black Brown smooth Feb76 batch Aug76 batch Dec 76 batch Mar 77 batch Jun 77 batch Dark brown opaque Apr 78 spool 1 Apr 78 spool 2 Translucent yellow brown TestElong- Energy Dateationft lb lb Jan64 752940 Oct63 802980 Jan64 602890 Jan64 7A3300 1964813525 May70 763100 Aug75 692950 Jun71 783160 May72 833440 Aug74 793310 Aug 73803290 Jul73823310 Jul77733540 Apr 73772250 Jul73BA3140 Jul73782500 Aug75 783210 Jul 77793600 Oct74 823310 July76 903200 May77 833060 Apr 76812600 May77 662620 May77 733400 Sep76 802980 May77 773380 Jun77 783450 Jul77803320 Mar78 641570 Sep78 803440 Sep78 8252970 Sep78 813725 8 SAMPLESTRETCHENERGY D78PlRELLI81X3725 3-77FA178X3410 R VULCANIZED83X2970 77FILATI64X1570 I STRETCH INCHES pound test findings disap pointing performance experienced models fliers using Filat led seeking out new source problem appears under standing what model flier calls quality various manufacturers did get message rubber stores energy new supplies rubber coming forth ranged widely quality lately reaching level pre-1973 Pirelli change has now taken place Excellent quality rubber available again quote rub ber flier old school Mike Diko vitzky fun has put back flying rubber powered models Rubber complex mixture ingredients must mixed processed just right order produce product optimum characteristics given use Small changes ingredi ents mixing sequence vulcanization process can produce wide changes physical properties supply Pirelli became irregular initially no other manufacturer rose occasion fill gap understandable since very small demand model aircraft rubber strip consistent supply high quality strip judged model fliers became available after Ed Dolby perseverance work manufacturer over protracted period time response Eds speci fications manufacturer produced batches rubber characteristics thought would satisfy model builders Through several reiterations recipe developed tested model builders gave good results Once manufacturer understood correlate production good performance model airplane optimized recipe produce strip consistent high quality mid-1978 Pirelli again entered picture After five year lapse producing product referred Special Pirelli Model Fliers com pounded carbon black yellow brown almost translucent has ribbed texture old fashioned product new rubber gives higher energy storage rubber encountered author storage runs above 3700 foot pounds per pound 750 F addi tion FAI new Pirelli have several other sources rubber including two author has tested recently Sig Vintage Aero offering rubber reported give very good results Manufacture Strip Rubber Strip rub ber manufactured natural crude rubber synthetic rubber stearic acid zinc oxide sulphur carbon black small amounts catalysts conditioners such Altax Neozone D Accelerator 808 Titanox etc best quality rubber uses virgin stock reclaimed-rubber imports have poor characteristics gray 60 Model Aviation Vin tage 1958 1962 1963 1963 1964 1968 1968 1969 1970 1970 1971 1972 1972 1973 1973 1973 1974 1974 1974 1976 1976 1976 1976 1976 1976 1976 1977 1977 1977 1978 1978 1978 Type Pirelli Pirelli Gitlow Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Filati Sig FAI Pirelli Pirelli Filati Vintage Aero Vintage Aero Filati Japanese FA FAI FAI FAI FAI Filati FAI FAI Pirelli 20 16 12 CA 6 4 Figure 1 black color imparted carbon black Brown rubber contains little no carbon black recipes rubber manufacture almost always proprietary since element witchcraft obtaining desired characteristics guess recipe current smooth gray Ameri can manufactured rubber Ingredients Pale Virgin Crepe natural rubber Synthetic rubber Stearic Acid Zinc Oxide Altax Accelerator Catalysts Neozone D Activator Catalysts Sulphur Carbon Black about 16 inches long FAI rub ber little thicker 14 strands being about same length Pirelli takes about same turns 320 Sig Vintage Aero rubber generally thinner Pirelli require strands get equivalent cross-section area Rather strands better think equivalency skein length made up motors 85 See Table tabulation rubber 15test results since 1958 good Wakefield 1should able over 180 seconds 5 arts Weight 3 less 112 presumed product would improved deletion syn thetic rubber carbon black presumption remains determined mill ingredients mixed about 1200 F following order StepIngredientsMixing time INatural Rubber synthetic rubber 4 minutes 2Stearic Acid softens mixture 2 minutes 3Zinc oxide Altax Neozone D Carbon Black25 minutes 4Sulphur acts vulcanize during curing process15 minutes After mixing rubber run through roller produce sheet desired thickness typically 043 sheet comes out five six feet wide about 900 feet long dusted talcum powder keep sticking itself After rolling up put electronically controlled vulcanizing oven subjected steam about 2850 F around 30 minutes degree vulcanization has very dramatic effect tensile prop erties Vulcanization cross linking polymer chains brought about action sulphur high temperature After removal oven rubber allowed cool room temperature prior slitting process first step slitting rubber cut belts 75 inches wide sliced end end tapered glued joint total length now continu ous 75 inches belt about 9000 feet next step run belt through slitting mill set desired widths typically 1/16 3/32 1/8 3/16 1/4 inch strips After passing through slitting strip run off spools containing about pound rubber amounts 200 feet /4 inch strip typical batch weight about 1500 pounds new Pirelli about same size old Pirelli 388 gram dry weight Wakefield motor makes up 16 strands 6 14 2 10 0 z 0 0 bJ 0 0 LL6 4 2 Chris Matsuno tests close agreement Fig 2 compares results using two methods shows differences power curves due characteristic difference behavior rubber ing wound stretched Excluding strongly non-linear portions begin ning end curves torque wound sample varies proportionally 15 power number strands whereas pull force stretched rub ber varies directly proportionally ~1 TESTSAMPLEENERGY STRETCHED2 STRANDS 4135 GM3350 WOUND8STRANDS4135GM3350 -1 STREECHED ND 1 K 020 Figure 2 0 40 60 80 100 10203040506070 duration rubber over 3100 foot pounds per pound energy storage Like wise very good Coupe should over 120 seconds 3100 rubber See Fig comparison power curves Pirelli Filati FAI Rubber Rubber testing Rubber stores energy tension can produced either stretching winding Tests either method give comparable results writer has compared stretch tests over long period winding tests 120 -50 -40 30 20 -10 0 Si RETCH 80 TURNS number strands Both test samples same weight Both methods have same area beneath curve indicates identical energy storage areas products force times distance turns times torque respec tively represent foot pounds energy curves demonstrate identical results using either method determine energy storage much difficult wind motor ultimate capacity accuracy repeatability stretch its maxi March 1979 61 mum length Winding energy storage affected distance stretched put turns well percent age turns put various distances Hence standardized stretch testing order obtain consistency obtain comparable results test test felt necessary pull samples same ultimate tensile stress very close breaking point Figuring original cross-section pulling proportional force does job because stretchy rub ber would pulled higher tensile stress problem solved pulling motor two stages first pull computed following formula 45 X weight Force pound grams* Original Length inches force strong enough pull motors near maximum stretch second pull force computed following formula 430 X weight Force2 poundsgrams* Stretched Length F inches * purely metric versions formulas have constants 52 496 respectively F kilograms W grams L centimeters Applying F2 will stretch motors additional small amount near break ing point example March 1977 FAI Rubber sample two strands inch pulled F F2 pounds question arises would stretchier rubber pulled higher tensile stress thus store energy therefore reducing validity comparing dif ferent samples problem mitigated shape energy storage curve see Fig As pull rubber very high tensile stress change elongation becomes less less final result becoming climbing-the-wall situ ation get almost no change stretched length approach breaking stress Thus very little additional energy stored since incremental product force times distance very small rubber testing machine shown photograph has 200-pound scale handling full-size Wakefield motors 20-pound scale testing single loops rubber boat winch provided stretching samples along cali brated 150-in frame Test motors attached hook scale hook end rope travels around pulley far end frame back winch use testing procedure follows Weigh sample loop suitable 150-in frame say between 12 16 inches long Subtract out weight knot tag ends 2 Lubricate sample green soap glycerine type rubber lubricant Dont get knot soaked lube high stress will cause slip put extra talcum powder ends before tying square knot single granny knot top Saliva helps keep rubber tearing pulling knot tight 3 Compute pull force F break rubber pulling force 5 min utes Wait least hour before next 14 12 10 C 0 z 1 cc w C- 0 Li. 6 4 2 0 7 Correct stretch distances deflection force scale 8 Plot force stretch distance graph paper Measure area beneatl curve Typically integrate sum ot about dozen steps along stretch scale 9 area beneath curve fool pounds represents energy divided sample weight gets energy storage foot pounds per pound writer believes apparatus gives result 1% accuracy Foot pounds per pound reduces simply feet interpretation sample rubber could lift itself vertically SAMPLEWILL ENERGY TEST DATE 76VINTAGE 448 138 876 3140JULY76 AERO 76 VINTAGE 448 1306 833 3150 MAY 77 AERO 76FA1447143773380MAY77 I / d-y REFERENCE 1 K76 VA MAY77 16 VA JULY 76 / / Figure 3 20 406080 STRETCH INCHES step 4 Using stretched length first pull compute second pull force F2 5 Pull motor F2 taking care take about 15 seconds pull last 10% desired force 6 Immediately read record force stretch distance Backing off small increments step down about dozen steps zero tension recording step 100 2C distance equal its energy storage example sample 3300 could lift itself 3300 feet model airplane 25% its weight rubber could climb 25 X 3300 feet energy used 100% efficiency Standards Rubber Strip What standards good rubber past good Pirelli available good quality gave energy around 3300 foot pounds per pound stretched maxi mum about 8 times its original length 62 Model Aviation Rubber below 3000 considered defi nitely below par Rubber stretched less about 73 times its original length looked upon suspicion thought getting old Rubber stretched over 82 times thought soft probably under-vulcanized Some values rubber samples given Table Rubber below par energy storage typically has power curve such two lower curves Fig shape power curve can give trouble use cause sharp spike power utilized effectively model inclined too much after first few seconds cause torque falling rapidly airplane can respond effect especially noticeable ground turbulence model climbing very steeply easily stalled upset Rubber too soft good energy storage such lower curve Fig 3 also gives initial poor climb characteristic Aging Effects Rubber polymer Aging results continuation uncompleted vulcanization reactions usually resulting chain-lengthening increased crosslinking between chains pro cesses lead toughening rubber Aging rubber beyond optimum condi tion results chain scission decomposi tion resulting shorter chains combined increasing crosslinking exces sive nature product becomes creasingly brittle balance chain lengthening chain decomposition crosslinking can vary widely Generally good quality rubber will slowly lose its ability stretch slowly losing its energy storage capability Rub ber becomes tougher age eventually becoming brittle Brittle rubber tears knots slight imperfections also inclined explode breaking strands skein wound Fig 3 gives example undervulcanized rubber became tougher year age Its power curve initi ally sharp peak torque character istic undesirable characteristics described previously under Stand ards Rubber Strip Age helped shape power curve slightly lowering energy storage An oc casional example rubber will increase its energy storage age un common associated becoming dangerously brittle Note Table generally declining elongation age 1968 1972 Pirelli 1975 1965 1966 1967 1969 1970 Pirelli too brittle use although 1968 useable dangerous 1976 1972 Pirelli become dangerously brittle although its energy excellent note its elonga tion has declined 82 initially 73 today second article will appear next month handling new generation rub ber addition conventional ques tions making up skeins breaking winding maximum turns two additional topics will covered effect temperature energy storage effect holding fully wound motor energy storage NEW THIS YEAR Volume IlA handsome com panion Volume Frank Ehlings KIT PLAN BOOK containing reduced-size plans model airplane kits avail able Ace RIO Andrews Aircraft Model Co Astro Flight Bridi Hobby Enterpris es Cass Engineering Classic Models Cox Hobbies Flyline Models Carl Goldberg Models House Balsa Jetco Models Midwest Model Products Peck Polymers Rev Model Prod 3 ucts Sig Mfg Co Sterling Models Top Flite Models age Bob Violett Models VK Model Aircraft World Enginesl plans contained Volume Ace H/C Andrews Aircraft Model Co Carl Goldberg Models Chuck Gill Models Competition Models Jetco Models Junior Aero Space Co. Midwest Model Products Mini-Flite Co Nelson Model Products Sig Mfg Co Sterling Models Top Flite Models World Engines combined plans Volume II gives opportunity shop own home before plunking down dolla s types models included volume RC CL Scale FFsport compet t designs category volume produced AMA HQ com piled Frank EhI ng paperback s ze 9 x 12 $2 50 m AM HQ Supply & Service Section 815 Fifteenth Street NW Washington DC 20005 I__I Please PrintlU NameAMANoI Address City State Zip md March 1979 63 Kit Plan Books me @ $250 $ __________ enclosed .....Kit Plan Books- Volume II @ $250 Send check money order send cash through maill Close-up test rig special 20-pound precision scale being used sassing two-strand motors Note boat winch employed pulling rubber motors undergoing testing
Edition: Model Aviation - 1979/03
Page Numbers: 59, 60, 61, 62, 63
SINCE 1973 good rubber strip has problem find trouble started chief source Pirelli factory near Milan Italy reorganized split off Pirelli company became part new company called Filati Pirelli company still makes sheet rub ber sold Filati strips size markets Beginning 1973 batch Filati tested writer varied widely energy storage appearance old fashioned product brown energy storage around 3300 foot pounds per pound 1973 test very black Filati gave 2250 foot pounds per pound 1974 gray batch tested encouraging 3310 1976 batch gave 2600 1977 batch gave 1500 foot pounds per Editors Note Mr Pearces time con suming research -another example scientific reporting MA occasionally does bonanza people fly rubber events Encouragement ex tended thinkers vast RC field others both CL FE March 1979 59 author launching 74 Wakefield won first both 1974 1975 Nationals What could worlds largest slingshot really Freds special test rig testing Wakefield motor 200-pound scale measures pull force Stretch distance calibrated edge frame category finds dedicated researchersfortunately TABLE RUBBER TEST RESULTS stretch method 75 degrees F SourceComment Brown ribbed Gitlow Tenny Cannizzo Zaic Zaic Sig Zaic Zaic F D Zaic Zaic F D Sig FAI Old Timer Old Timer Zaic Vintage Aero Vintage Aero Aeromodels Tsuda FAI FAI FAI FA FA Filati FAI FAI Cannizzo Gray smooth Repeat test brittle Repeat test brittle Repeat test brittle Black Gray smooth Gray smooth Vintage date Repeat test brittle Gray Gray smooth soft Repeat test Black Brown smooth Feb76 batch Aug76 batch Dec 76 batch Mar 77 batch Jun 77 batch Dark brown opaque Apr 78 spool 1 Apr 78 spool 2 Translucent yellow brown TestElong- Energy Dateationft lb lb Jan64 752940 Oct63 802980 Jan64 602890 Jan64 7A3300 1964813525 May70 763100 Aug75 692950 Jun71 783160 May72 833440 Aug74 793310 Aug 73803290 Jul73823310 Jul77733540 Apr 73772250 Jul73BA3140 Jul73782500 Aug75 783210 Jul 77793600 Oct74 823310 July76 903200 May77 833060 Apr 76812600 May77 662620 May77 733400 Sep76 802980 May77 773380 Jun77 783450 Jul77803320 Mar78 641570 Sep78 803440 Sep78 8252970 Sep78 813725 8 SAMPLESTRETCHENERGY D78PlRELLI81X3725 3-77FA178X3410 R VULCANIZED83X2970 77FILATI64X1570 I STRETCH INCHES pound test findings disap pointing performance experienced models fliers using Filat led seeking out new source problem appears under standing what model flier calls quality various manufacturers did get message rubber stores energy new supplies rubber coming forth ranged widely quality lately reaching level pre-1973 Pirelli change has now taken place Excellent quality rubber available again quote rub ber flier old school Mike Diko vitzky fun has put back flying rubber powered models Rubber complex mixture ingredients must mixed processed just right order produce product optimum characteristics given use Small changes ingredi ents mixing sequence vulcanization process can produce wide changes physical properties supply Pirelli became irregular initially no other manufacturer rose occasion fill gap understandable since very small demand model aircraft rubber strip consistent supply high quality strip judged model fliers became available after Ed Dolby perseverance work manufacturer over protracted period time response Eds speci fications manufacturer produced batches rubber characteristics thought would satisfy model builders Through several reiterations recipe developed tested model builders gave good results Once manufacturer understood correlate production good performance model airplane optimized recipe produce strip consistent high quality mid-1978 Pirelli again entered picture After five year lapse producing product referred Special Pirelli Model Fliers com pounded carbon black yellow brown almost translucent has ribbed texture old fashioned product new rubber gives higher energy storage rubber encountered author storage runs above 3700 foot pounds per pound 750 F addi tion FAI new Pirelli have several other sources rubber including two author has tested recently Sig Vintage Aero offering rubber reported give very good results Manufacture Strip Rubber Strip rub ber manufactured natural crude rubber synthetic rubber stearic acid zinc oxide sulphur carbon black small amounts catalysts conditioners such Altax Neozone D Accelerator 808 Titanox etc best quality rubber uses virgin stock reclaimed-rubber imports have poor characteristics gray 60 Model Aviation Vin tage 1958 1962 1963 1963 1964 1968 1968 1969 1970 1970 1971 1972 1972 1973 1973 1973 1974 1974 1974 1976 1976 1976 1976 1976 1976 1976 1977 1977 1977 1978 1978 1978 Type Pirelli Pirelli Gitlow Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Pirelli Filati Sig FAI Pirelli Pirelli Filati Vintage Aero Vintage Aero Filati Japanese FA FAI FAI FAI FAI Filati FAI FAI Pirelli 20 16 12 CA 6 4 Figure 1 black color imparted carbon black Brown rubber contains little no carbon black recipes rubber manufacture almost always proprietary since element witchcraft obtaining desired characteristics guess recipe current smooth gray Ameri can manufactured rubber Ingredients Pale Virgin Crepe natural rubber Synthetic rubber Stearic Acid Zinc Oxide Altax Accelerator Catalysts Neozone D Activator Catalysts Sulphur Carbon Black about 16 inches long FAI rub ber little thicker 14 strands being about same length Pirelli takes about same turns 320 Sig Vintage Aero rubber generally thinner Pirelli require strands get equivalent cross-section area Rather strands better think equivalency skein length made up motors 85 See Table tabulation rubber 15test results since 1958 good Wakefield 1should able over 180 seconds 5 arts Weight 3 less 112 presumed product would improved deletion syn thetic rubber carbon black presumption remains determined mill ingredients mixed about 1200 F following order StepIngredientsMixing time INatural Rubber synthetic rubber 4 minutes 2Stearic Acid softens mixture 2 minutes 3Zinc oxide Altax Neozone D Carbon Black25 minutes 4Sulphur acts vulcanize during curing process15 minutes After mixing rubber run through roller produce sheet desired thickness typically 043 sheet comes out five six feet wide about 900 feet long dusted talcum powder keep sticking itself After rolling up put electronically controlled vulcanizing oven subjected steam about 2850 F around 30 minutes degree vulcanization has very dramatic effect tensile prop erties Vulcanization cross linking polymer chains brought about action sulphur high temperature After removal oven rubber allowed cool room temperature prior slitting process first step slitting rubber cut belts 75 inches wide sliced end end tapered glued joint total length now continu ous 75 inches belt about 9000 feet next step run belt through slitting mill set desired widths typically 1/16 3/32 1/8 3/16 1/4 inch strips After passing through slitting strip run off spools containing about pound rubber amounts 200 feet /4 inch strip typical batch weight about 1500 pounds new Pirelli about same size old Pirelli 388 gram dry weight Wakefield motor makes up 16 strands 6 14 2 10 0 z 0 0 bJ 0 0 LL6 4 2 Chris Matsuno tests close agreement Fig 2 compares results using two methods shows differences power curves due characteristic difference behavior rubber ing wound stretched Excluding strongly non-linear portions begin ning end curves torque wound sample varies proportionally 15 power number strands whereas pull force stretched rub ber varies directly proportionally ~1 TESTSAMPLEENERGY STRETCHED2 STRANDS 4135 GM3350 WOUND8STRANDS4135GM3350 -1 STREECHED ND 1 K 020 Figure 2 0 40 60 80 100 10203040506070 duration rubber over 3100 foot pounds per pound energy storage Like wise very good Coupe should over 120 seconds 3100 rubber See Fig comparison power curves Pirelli Filati FAI Rubber Rubber testing Rubber stores energy tension can produced either stretching winding Tests either method give comparable results writer has compared stretch tests over long period winding tests 120 -50 -40 30 20 -10 0 Si RETCH 80 TURNS number strands Both test samples same weight Both methods have same area beneath curve indicates identical energy storage areas products force times distance turns times torque respec tively represent foot pounds energy curves demonstrate identical results using either method determine energy storage much difficult wind motor ultimate capacity accuracy repeatability stretch its maxi March 1979 61 mum length Winding energy storage affected distance stretched put turns well percent age turns put various distances Hence standardized stretch testing order obtain consistency obtain comparable results test test felt necessary pull samples same ultimate tensile stress very close breaking point Figuring original cross-section pulling proportional force does job because stretchy rub ber would pulled higher tensile stress problem solved pulling motor two stages first pull computed following formula 45 X weight Force pound grams* Original Length inches force strong enough pull motors near maximum stretch second pull force computed following formula 430 X weight Force2 poundsgrams* Stretched Length F inches * purely metric versions formulas have constants 52 496 respectively F kilograms W grams L centimeters Applying F2 will stretch motors additional small amount near break ing point example March 1977 FAI Rubber sample two strands inch pulled F F2 pounds question arises would stretchier rubber pulled higher tensile stress thus store energy therefore reducing validity comparing dif ferent samples problem mitigated shape energy storage curve see Fig As pull rubber very high tensile stress change elongation becomes less less final result becoming climbing-the-wall situ ation get almost no change stretched length approach breaking stress Thus very little additional energy stored since incremental product force times distance very small rubber testing machine shown photograph has 200-pound scale handling full-size Wakefield motors 20-pound scale testing single loops rubber boat winch provided stretching samples along cali brated 150-in frame Test motors attached hook scale hook end rope travels around pulley far end frame back winch use testing procedure follows Weigh sample loop suitable 150-in frame say between 12 16 inches long Subtract out weight knot tag ends 2 Lubricate sample green soap glycerine type rubber lubricant Dont get knot soaked lube high stress will cause slip put extra talcum powder ends before tying square knot single granny knot top Saliva helps keep rubber tearing pulling knot tight 3 Compute pull force F break rubber pulling force 5 min utes Wait least hour before next 14 12 10 C 0 z 1 cc w C- 0 Li. 6 4 2 0 7 Correct stretch distances deflection force scale 8 Plot force stretch distance graph paper Measure area beneatl curve Typically integrate sum ot about dozen steps along stretch scale 9 area beneath curve fool pounds represents energy divided sample weight gets energy storage foot pounds per pound writer believes apparatus gives result 1% accuracy Foot pounds per pound reduces simply feet interpretation sample rubber could lift itself vertically SAMPLEWILL ENERGY TEST DATE 76VINTAGE 448 138 876 3140JULY76 AERO 76 VINTAGE 448 1306 833 3150 MAY 77 AERO 76FA1447143773380MAY77 I / d-y REFERENCE 1 K76 VA MAY77 16 VA JULY 76 / / Figure 3 20 406080 STRETCH INCHES step 4 Using stretched length first pull compute second pull force F2 5 Pull motor F2 taking care take about 15 seconds pull last 10% desired force 6 Immediately read record force stretch distance Backing off small increments step down about dozen steps zero tension recording step 100 2C distance equal its energy storage example sample 3300 could lift itself 3300 feet model airplane 25% its weight rubber could climb 25 X 3300 feet energy used 100% efficiency Standards Rubber Strip What standards good rubber past good Pirelli available good quality gave energy around 3300 foot pounds per pound stretched maxi mum about 8 times its original length 62 Model Aviation Rubber below 3000 considered defi nitely below par Rubber stretched less about 73 times its original length looked upon suspicion thought getting old Rubber stretched over 82 times thought soft probably under-vulcanized Some values rubber samples given Table Rubber below par energy storage typically has power curve such two lower curves Fig shape power curve can give trouble use cause sharp spike power utilized effectively model inclined too much after first few seconds cause torque falling rapidly airplane can respond effect especially noticeable ground turbulence model climbing very steeply easily stalled upset Rubber too soft good energy storage such lower curve Fig 3 also gives initial poor climb characteristic Aging Effects Rubber polymer Aging results continuation uncompleted vulcanization reactions usually resulting chain-lengthening increased crosslinking between chains pro cesses lead toughening rubber Aging rubber beyond optimum condi tion results chain scission decomposi tion resulting shorter chains combined increasing crosslinking exces sive nature product becomes creasingly brittle balance chain lengthening chain decomposition crosslinking can vary widely Generally good quality rubber will slowly lose its ability stretch slowly losing its energy storage capability Rub ber becomes tougher age eventually becoming brittle Brittle rubber tears knots slight imperfections also inclined explode breaking strands skein wound Fig 3 gives example undervulcanized rubber became tougher year age Its power curve initi ally sharp peak torque character istic undesirable characteristics described previously under Stand ards Rubber Strip Age helped shape power curve slightly lowering energy storage An oc casional example rubber will increase its energy storage age un common associated becoming dangerously brittle Note Table generally declining elongation age 1968 1972 Pirelli 1975 1965 1966 1967 1969 1970 Pirelli too brittle use although 1968 useable dangerous 1976 1972 Pirelli become dangerously brittle although its energy excellent note its elonga tion has declined 82 initially 73 today second article will appear next month handling new generation rub ber addition conventional ques tions making up skeins breaking winding maximum turns two additional topics will covered effect temperature energy storage effect holding fully wound motor energy storage NEW THIS YEAR Volume IlA handsome com panion Volume Frank Ehlings KIT PLAN BOOK containing reduced-size plans model airplane kits avail able Ace RIO Andrews Aircraft Model Co Astro Flight Bridi Hobby Enterpris es Cass Engineering Classic Models Cox Hobbies Flyline Models Carl Goldberg Models House Balsa Jetco Models Midwest Model Products Peck Polymers Rev Model Prod 3 ucts Sig Mfg Co Sterling Models Top Flite Models age Bob Violett Models VK Model Aircraft World Enginesl plans contained Volume Ace H/C Andrews Aircraft Model Co Carl Goldberg Models Chuck Gill Models Competition Models Jetco Models Junior Aero Space Co. Midwest Model Products Mini-Flite Co Nelson Model Products Sig Mfg Co Sterling Models Top Flite Models World Engines combined plans Volume II gives opportunity shop own home before plunking down dolla s types models included volume RC CL Scale FFsport compet t designs category volume produced AMA HQ com piled Frank EhI ng paperback s ze 9 x 12 $2 50 m AM HQ Supply & Service Section 815 Fifteenth Street NW Washington DC 20005 I__I Please PrintlU NameAMANoI Address City State Zip md March 1979 63 Kit Plan Books me @ $250 $ __________ enclosed .....Kit Plan Books- Volume II @ $250 Send check money order send cash through maill Close-up test rig special 20-pound precision scale being used sassing two-strand motors Note boat winch employed pulling rubber motors undergoing testing