A S ginning Electric flier became very interested both propeller thrust propeller equations suggested predicting performance modeling done Idaho Falls Idaho elevation 4700 feetpredicting thrust Electric flight systems important wanted accurate measurements actual thrust particular system wanted know what thrust would available changed propeller rpm As first step designed built portable thrust-test stand portable test stand Im able measure propeller thrust anywhere comes handy will see second step testing suggested thrust equations explain own propeller thrust measurements tried applying equations found modeling liter ature None verified Some suggested equations predicted results almost 30% different static thrust measured equipment As result decided test general thrust equa tion full-scale propellers engineering text Engineering Fluid Mech anics John Roberson Clayton T Crowe biggest concern about using equation revolved around scale effect propellers Would shifting propeller diameters measured feet dia meters measured inches cause equation fail Roberson Crowe equation different other equations foundit included airdensity term test equation needed vary calculate air density measure rpm static thrust calculate static thrust coefficient Its easy change air density have trans portationjust change test location different elevation measured propeller thrust rpm portable test stand elevations ranging approximately 1400 feet locations 6800 feet Using same drive system propeller throughout testing process provided series measurements different air-density conditions discovered equation really works Lets look equation Roberson Crowe show development general thrust equation thrust propeller F 2 D4 Changing metric unit force ounces F f units ounces static thrust f grams per liter air density p rpm n meters inches/3937 propeller diameter D static thrust coefficient C[sub]t has no units Substituting F rewriting equation solve static thrust coefficient gives Ct l000f/pn2D4 Air density calculated using relationship p PI{ iXT -32 5/9] units inches mercury local station pressure P temperature degrees Fahrenheit T collected seven sets thrust measurements five elevations determine seven average values static thrust coefficient data set consisted measurements thrust rpm motor voltage motor current Table 1 contains typical data set location measurements made battery com binations possible process produced range values static thrust rpm data set plotted thrust rpm squared values data sets plotted values should produce straight line plotted points averaged single straight data line through origin graph After selected point data line gave convenient number thrust rpm squared calculation procedure smoothed data set increased reliability calculated value static thrust coefficient illustration consider data Idaho Falls example data set Convenient values rpm squared static thrust calculation rpm squared lOE7 static thrust ounces 36 Model Aviation cal data set thrust rpm measurements Location Idaho Falls Date/time May 171994 2000 hours Station pressure 2510 Hg Motor AstroFlight 15 geared Propeller Windsor 12 x 8 folding type Elevation 4740 feet Temperature 70 F Thrust ounces rpm Six cells 1733800 1603700 1563650 1563600 1473600 Seven cells 196 170 194 192 Eight cells 272 255 249 240 4100 3800 4050 4000 4700 4600 4600 4500 Fourteen cells 5386700 5136400 5056300 5486700 5306500 4966400 Motor Motor rpm2 amperes volts x 1OE-7 122 118 117 113 110 125 114 128 125 161 158 155 151 272 261 missed 290 280 270 69144 67137 66133 65130 64130 72168 66144 72164 72160 87221 86212 85212 84203 130 128 missed 136 133 130 449 410 397 449 423 410 Table 1 Calculated thrust versus rpm Windsor 12 x 8 80 70 60 Thrust ounces 50 40 30 20 10 0 12345678 Thousands rpm Note curves smooth quadratic Also note curves pass through origin ie zero rpm thrust zero Figure 1 T: r 50 Location conditions values static thrust coefficient Windsor 12 x 8 folding propeller Elevation Thrust Locationfeetcoeff Test conditions Coeur DAlene231 8*0123 est 450F P 275 Ha outdoors calm Grana average OT measurea vaiues static tnrust coefficient Windsor 12 x 8 folding propeller 0125 rcent * Airport elevation Tests performed close airport property est These station pressure air temperature values directly measured estimated extrapolation National Weather Service information Table 2 Portable static thrust test stand calibrated spring scale thrust measurementPhoto author Graphic Daaign Bill Thorabro October1995 37 Dillon MT5240*0125 700F P est 242 Hg indoors combination value rpm 6324 tests discussed propeller diameter 12375 inches 031441 12375/3937 meters air density data set 10066 grams per liter Therefore static thrust coefficient data set 1000488 C t 1 006663242 03 144 1 Ct 124 averaged thrust coefficient values seven data sets listed Table 2 Now validity test Does static thrust coefficient remain constant air density other parameters change measured thrust coefficient values different elevations very consistent Measurement error could account differences 5% Note values static thrust coefficient within 3% average value Therefore results well within range experimental error So what does show First Roberson Crowe s general thrust equation valid location elevation model-scale propellers Second portable static-thrust test stand assembled can used provide repeatable 3% values static thrust coefficient Third units chose static thrust coefficient Windsor 12 x 8 folding propeller 0125 coefficient can now used calculate expected performance under wide range air density conditions rpm used compare expected static thrust performance propeller other propellers different type Note density value becomes difficult calculate propeller tip speeds exceed Mach 03 4References Roberson John Crowe Clayton T Engineering Fluid Mechanics Houghton Mifflin Company 1975 pp 444-447 Manufacturers Windsor Propeller Company 3219 Monier Circle Rancho Cordova CA 95742 AstroFlight Incorporated 13311 Beach Avenue Marina del Rey CA 90292 October1995 39 FOLLOW THE LEADER Galveston ra ie FAFE ORDER UNE 800-242-0489 0 L4gJ9U2LcwBg ONE OF THE MANY THINGS IN THIS WORLD THAT CANT BE BEAT SIG MANUFACTURING CO imports worlds fastest running production engine ROSS! engines performance tested race proven SIG carries engines airplane helicopter car boat also have full-time ROSS REPAIR CENTER youre talking performance youre talking ROSS! SIG-imported ROSS engines come full 3 year ROSSI WARRANTY against manufacturing defects ur E. SIG MANUFACTURING CO INC. Montezuma Iowa 50171 PH 515-623-5154 FAX 515-623-3922 Toll Free Orders 800-247-5008 Modelers Hot Line 800-524-7805 Rubber ft Engine Power Free Flight Display control Line Electric Power RJC Airplanes Penn Valley Hobby Center 837-A W Main St Lanadale PA 19448 215- 3680170
Edition: Model Aviation - 1995/10
Page Numbers: 36, 37, 39
Edition: Model Aviation - 1995/10
Page Numbers: 36, 37, 39
A S ginning Electric flier became very interested both propeller thrust propeller equations suggested predicting performance modeling done Idaho Falls Idaho elevation 4700 feetpredicting thrust Electric flight systems important wanted accurate measurements actual thrust particular system wanted know what thrust would available changed propeller rpm As first step designed built portable thrust-test stand portable test stand Im able measure propeller thrust anywhere comes handy will see second step testing suggested thrust equations explain own propeller thrust measurements tried applying equations found modeling liter ature None verified Some suggested equations predicted results almost 30% different static thrust measured equipment As result decided test general thrust equa tion full-scale propellers engineering text Engineering Fluid Mech anics John Roberson Clayton T Crowe biggest concern about using equation revolved around scale effect propellers Would shifting propeller diameters measured feet dia meters measured inches cause equation fail Roberson Crowe equation different other equations foundit included airdensity term test equation needed vary calculate air density measure rpm static thrust calculate static thrust coefficient Its easy change air density have trans portationjust change test location different elevation measured propeller thrust rpm portable test stand elevations ranging approximately 1400 feet locations 6800 feet Using same drive system propeller throughout testing process provided series measurements different air-density conditions discovered equation really works Lets look equation Roberson Crowe show development general thrust equation thrust propeller F 2 D4 Changing metric unit force ounces F f units ounces static thrust f grams per liter air density p rpm n meters inches/3937 propeller diameter D static thrust coefficient C[sub]t has no units Substituting F rewriting equation solve static thrust coefficient gives Ct l000f/pn2D4 Air density calculated using relationship p PI{ iXT -32 5/9] units inches mercury local station pressure P temperature degrees Fahrenheit T collected seven sets thrust measurements five elevations determine seven average values static thrust coefficient data set consisted measurements thrust rpm motor voltage motor current Table 1 contains typical data set location measurements made battery com binations possible process produced range values static thrust rpm data set plotted thrust rpm squared values data sets plotted values should produce straight line plotted points averaged single straight data line through origin graph After selected point data line gave convenient number thrust rpm squared calculation procedure smoothed data set increased reliability calculated value static thrust coefficient illustration consider data Idaho Falls example data set Convenient values rpm squared static thrust calculation rpm squared lOE7 static thrust ounces 36 Model Aviation cal data set thrust rpm measurements Location Idaho Falls Date/time May 171994 2000 hours Station pressure 2510 Hg Motor AstroFlight 15 geared Propeller Windsor 12 x 8 folding type Elevation 4740 feet Temperature 70 F Thrust ounces rpm Six cells 1733800 1603700 1563650 1563600 1473600 Seven cells 196 170 194 192 Eight cells 272 255 249 240 4100 3800 4050 4000 4700 4600 4600 4500 Fourteen cells 5386700 5136400 5056300 5486700 5306500 4966400 Motor Motor rpm2 amperes volts x 1OE-7 122 118 117 113 110 125 114 128 125 161 158 155 151 272 261 missed 290 280 270 69144 67137 66133 65130 64130 72168 66144 72164 72160 87221 86212 85212 84203 130 128 missed 136 133 130 449 410 397 449 423 410 Table 1 Calculated thrust versus rpm Windsor 12 x 8 80 70 60 Thrust ounces 50 40 30 20 10 0 12345678 Thousands rpm Note curves smooth quadratic Also note curves pass through origin ie zero rpm thrust zero Figure 1 T: r 50 Location conditions values static thrust coefficient Windsor 12 x 8 folding propeller Elevation Thrust Locationfeetcoeff Test conditions Coeur DAlene231 8*0123 est 450F P 275 Ha outdoors calm Grana average OT measurea vaiues static tnrust coefficient Windsor 12 x 8 folding propeller 0125 rcent * Airport elevation Tests performed close airport property est These station pressure air temperature values directly measured estimated extrapolation National Weather Service information Table 2 Portable static thrust test stand calibrated spring scale thrust measurementPhoto author Graphic Daaign Bill Thorabro October1995 37 Dillon MT5240*0125 700F P est 242 Hg indoors combination value rpm 6324 tests discussed propeller diameter 12375 inches 031441 12375/3937 meters air density data set 10066 grams per liter Therefore static thrust coefficient data set 1000488 C t 1 006663242 03 144 1 Ct 124 averaged thrust coefficient values seven data sets listed Table 2 Now validity test Does static thrust coefficient remain constant air density other parameters change measured thrust coefficient values different elevations very consistent Measurement error could account differences 5% Note values static thrust coefficient within 3% average value Therefore results well within range experimental error So what does show First Roberson Crowe s general thrust equation valid location elevation model-scale propellers Second portable static-thrust test stand assembled can used provide repeatable 3% values static thrust coefficient Third units chose static thrust coefficient Windsor 12 x 8 folding propeller 0125 coefficient can now used calculate expected performance under wide range air density conditions rpm used compare expected static thrust performance propeller other propellers different type Note density value becomes difficult calculate propeller tip speeds exceed Mach 03 4References Roberson John Crowe Clayton T Engineering Fluid Mechanics Houghton Mifflin Company 1975 pp 444-447 Manufacturers Windsor Propeller Company 3219 Monier Circle Rancho Cordova CA 95742 AstroFlight Incorporated 13311 Beach Avenue Marina del Rey CA 90292 October1995 39 FOLLOW THE LEADER Galveston ra ie FAFE ORDER UNE 800-242-0489 0 L4gJ9U2LcwBg ONE OF THE MANY THINGS IN THIS WORLD THAT CANT BE BEAT SIG MANUFACTURING CO imports worlds fastest running production engine ROSS! engines performance tested race proven SIG carries engines airplane helicopter car boat also have full-time ROSS REPAIR CENTER youre talking performance youre talking ROSS! SIG-imported ROSS engines come full 3 year ROSSI WARRANTY against manufacturing defects ur E. SIG MANUFACTURING CO INC. Montezuma Iowa 50171 PH 515-623-5154 FAX 515-623-3922 Toll Free Orders 800-247-5008 Modelers Hot Line 800-524-7805 Rubber ft Engine Power Free Flight Display control Line Electric Power RJC Airplanes Penn Valley Hobby Center 837-A W Main St Lanadale PA 19448 215- 3680170
Edition: Model Aviation - 1995/10
Page Numbers: 36, 37, 39
A S ginning Electric flier became very interested both propeller thrust propeller equations suggested predicting performance modeling done Idaho Falls Idaho elevation 4700 feetpredicting thrust Electric flight systems important wanted accurate measurements actual thrust particular system wanted know what thrust would available changed propeller rpm As first step designed built portable thrust-test stand portable test stand Im able measure propeller thrust anywhere comes handy will see second step testing suggested thrust equations explain own propeller thrust measurements tried applying equations found modeling liter ature None verified Some suggested equations predicted results almost 30% different static thrust measured equipment As result decided test general thrust equa tion full-scale propellers engineering text Engineering Fluid Mech anics John Roberson Clayton T Crowe biggest concern about using equation revolved around scale effect propellers Would shifting propeller diameters measured feet dia meters measured inches cause equation fail Roberson Crowe equation different other equations foundit included airdensity term test equation needed vary calculate air density measure rpm static thrust calculate static thrust coefficient Its easy change air density have trans portationjust change test location different elevation measured propeller thrust rpm portable test stand elevations ranging approximately 1400 feet locations 6800 feet Using same drive system propeller throughout testing process provided series measurements different air-density conditions discovered equation really works Lets look equation Roberson Crowe show development general thrust equation thrust propeller F 2 D4 Changing metric unit force ounces F f units ounces static thrust f grams per liter air density p rpm n meters inches/3937 propeller diameter D static thrust coefficient C[sub]t has no units Substituting F rewriting equation solve static thrust coefficient gives Ct l000f/pn2D4 Air density calculated using relationship p PI{ iXT -32 5/9] units inches mercury local station pressure P temperature degrees Fahrenheit T collected seven sets thrust measurements five elevations determine seven average values static thrust coefficient data set consisted measurements thrust rpm motor voltage motor current Table 1 contains typical data set location measurements made battery com binations possible process produced range values static thrust rpm data set plotted thrust rpm squared values data sets plotted values should produce straight line plotted points averaged single straight data line through origin graph After selected point data line gave convenient number thrust rpm squared calculation procedure smoothed data set increased reliability calculated value static thrust coefficient illustration consider data Idaho Falls example data set Convenient values rpm squared static thrust calculation rpm squared lOE7 static thrust ounces 36 Model Aviation cal data set thrust rpm measurements Location Idaho Falls Date/time May 171994 2000 hours Station pressure 2510 Hg Motor AstroFlight 15 geared Propeller Windsor 12 x 8 folding type Elevation 4740 feet Temperature 70 F Thrust ounces rpm Six cells 1733800 1603700 1563650 1563600 1473600 Seven cells 196 170 194 192 Eight cells 272 255 249 240 4100 3800 4050 4000 4700 4600 4600 4500 Fourteen cells 5386700 5136400 5056300 5486700 5306500 4966400 Motor Motor rpm2 amperes volts x 1OE-7 122 118 117 113 110 125 114 128 125 161 158 155 151 272 261 missed 290 280 270 69144 67137 66133 65130 64130 72168 66144 72164 72160 87221 86212 85212 84203 130 128 missed 136 133 130 449 410 397 449 423 410 Table 1 Calculated thrust versus rpm Windsor 12 x 8 80 70 60 Thrust ounces 50 40 30 20 10 0 12345678 Thousands rpm Note curves smooth quadratic Also note curves pass through origin ie zero rpm thrust zero Figure 1 T: r 50 Location conditions values static thrust coefficient Windsor 12 x 8 folding propeller Elevation Thrust Locationfeetcoeff Test conditions Coeur DAlene231 8*0123 est 450F P 275 Ha outdoors calm Grana average OT measurea vaiues static tnrust coefficient Windsor 12 x 8 folding propeller 0125 rcent * Airport elevation Tests performed close airport property est These station pressure air temperature values directly measured estimated extrapolation National Weather Service information Table 2 Portable static thrust test stand calibrated spring scale thrust measurementPhoto author Graphic Daaign Bill Thorabro October1995 37 Dillon MT5240*0125 700F P est 242 Hg indoors combination value rpm 6324 tests discussed propeller diameter 12375 inches 031441 12375/3937 meters air density data set 10066 grams per liter Therefore static thrust coefficient data set 1000488 C t 1 006663242 03 144 1 Ct 124 averaged thrust coefficient values seven data sets listed Table 2 Now validity test Does static thrust coefficient remain constant air density other parameters change measured thrust coefficient values different elevations very consistent Measurement error could account differences 5% Note values static thrust coefficient within 3% average value Therefore results well within range experimental error So what does show First Roberson Crowe s general thrust equation valid location elevation model-scale propellers Second portable static-thrust test stand assembled can used provide repeatable 3% values static thrust coefficient Third units chose static thrust coefficient Windsor 12 x 8 folding propeller 0125 coefficient can now used calculate expected performance under wide range air density conditions rpm used compare expected static thrust performance propeller other propellers different type Note density value becomes difficult calculate propeller tip speeds exceed Mach 03 4References Roberson John Crowe Clayton T Engineering Fluid Mechanics Houghton Mifflin Company 1975 pp 444-447 Manufacturers Windsor Propeller Company 3219 Monier Circle Rancho Cordova CA 95742 AstroFlight Incorporated 13311 Beach Avenue Marina del Rey CA 90292 October1995 39 FOLLOW THE LEADER Galveston ra ie FAFE ORDER UNE 800-242-0489 0 L4gJ9U2LcwBg ONE OF THE MANY THINGS IN THIS WORLD THAT CANT BE BEAT SIG MANUFACTURING CO imports worlds fastest running production engine ROSS! engines performance tested race proven SIG carries engines airplane helicopter car boat also have full-time ROSS REPAIR CENTER youre talking performance youre talking ROSS! SIG-imported ROSS engines come full 3 year ROSSI WARRANTY against manufacturing defects ur E. SIG MANUFACTURING CO INC. Montezuma Iowa 50171 PH 515-623-5154 FAX 515-623-3922 Toll Free Orders 800-247-5008 Modelers Hot Line 800-524-7805 Rubber ft Engine Power Free Flight Display control Line Electric Power RJC Airplanes Penn Valley Hobby Center 837-A W Main St Lanadale PA 19448 215- 3680170
