AIRBORNE AUXILIARY DC OTORS U Ken Cashion THE BASIC DESIGN Radio Control components has remained constant number years operating specifications may occasionally improved sizes individual components may vary operation has remained unchanged actual movement control surfaces spoilers flaps landing gear etc still begins rotation servo output shaft generally limited 45O mechanical reactions rotation have become cleverly adapted produce multitude push-pull pullpull pivoting levers sliding servos similar functions airframe response movement transmitter stick switch still limited tion shaft linear servo rarely seen today Modern transmitters permit variations servos will respond control sticks yet still limitation 45-degree rotation November 1998 issue Model Aviation Richard Carignan presented very good article Case 180Degree Servos demonstrating other options sometimes needed article could called Case 360-Degree Servos occasions designer would like have another power source changes aircraft structures necessarily just movement control surfaces modified servo can drive rack-and-pinons winches pulleys particular lead screws As Scale models get larger scale landing gear structure operation expected popular pneumatic systems presented another power source powerful airborne bidirectional variable-speed DC motor limits its resulting movement user-defined has applications modified servos have used RC sailboats sail-tending winches Some used modified standard-sized servo tend 600 square inches sail winds would ground model aircraft Operation The servo selected demonstrating modification RCD Hitec Standard HS-300 servo typical large enough permit good photography though much smaller servos could modified same manner Futaba S3003 servo can easily modified HS 300 Carignan article would useful acquiring details disassembling servo Most modification involves output gear servo feedback potentiometer pot pot consists rear insulated wafer body threads shaft Inside rear wafer electrically resistive element forming near-full arc electrical terminal end Also rear wafer third center terminal connected small conducting spring makes contact rotating clement wiper mounted shaft running through body output gear shaft rotation shaft moves wiper different positions resistive element thereby changes resistance between center terminal two end terminals resistance between end terminals remains fixed generally 5K ohms modification variable 5K ohm resistive element eliminated two fixed resistors added keep center terminal voltage constant control stick moved neutral servo starts rotate rotation continues until limit switch interrupts current motor control stick returned neutral limit switch opens motor can no longer rotate 100 Model Aviation os author Graphic Design Jill Ann Cavanaugh direction however diode across switch permits reverse current drive motor opposite direction reversing current occurs control stick moved past neutral opposite direction As soon motor starts rotating opposite direction limit switch closes again permitting motor again rotate either direction Another switch diode limits rotation other end travel farther control stick moved faster motor rotates Modification The modification difficult user has moderate soldering skills following steps adhered Editors note reminder modifications servos will almost certainly void manfacturers warranties items 1 Remove servo horn 2 Remove four screws servo bottom 3 Remove top carefully keep gear clusters place 4 Remove bottom 5 Note rotation-limit stops inside upper case stop output gear Step 10 stop gear will removed permit 360-degree rotation gear 6 Remove spacer top output gear remove output gear prying lightly between case gear bottom center screwdriver Caution damage output gear teeth during operation gear light press-fit feedback pot shaft 7 Remove gear-clusters obvious sequence taking care protect gear teeth best remove center gear pulling lightly gears shaft Set gears aside sequence removed tops gears facing up 8j necessary remove gear grease gears will handled very little 9 At point shaft can rotated hand Determine has built-in limit stop Hitec does 10 Remove limit stop gear Caution very careful gears during operation Make sure stop material remains interfere adjacent gears II Pivot bottom circuit board free case end away motor 12 Record color location three wires soldered pot same two wires motor 13 Remove pot removing nut washer top servo Some Futaba servos have pot clipped some servos have pot element secured small screws 14 Unsolder wires pot 15 Unsolder wires motor 16 To free pot wafer uncrimp three tabs securing pot wafer back pot body 17 On pot body locate three-fingered wiper use needle-nose pliers break off wiper shaft structure 18 Identify resistive element wafer knife pry under element break section free pot electrically disconnects pot terminals can used support resistors will added later 19 Now rotation-stop inside pot body must removed easiest way to rotate shaft until free access indentation metal frame pot body Lay outer edge pot over hard surface use small punch tap flatten indentation pot shaft will have easy 3600 rotation 20 A small drop light machine oil point pin may placed inside pot shaft remove shaft 21 Place rear wafer back pot body test free full rotation should rotate easily 22 Confirm wafer properly aligned body reassemble pot crimping three back place compress assembly 23 Solder two 22K -watt resistors outside terminal rear pot wafer Resistors Radio Shack RS #271-1325 Keep resistors flat against pot wafer facilitate reassembly Unmodified servo top removed Rotation limit stop output drive gear blackened photo will removed Servo pot gear clusters removed Note stop has now removed output gear September 1999 101 Unmodified servo bottom removed showing circuit board motor top feedback pot Unmodified wafer top pot body Note indented edge pot body right internal rotation stop will removed 24 Solder other ends 22K resistors together solder wire attached pot center terminal junction 25 Solder other two pot wires respective terminals operation will make voltage center wire approximately what would have pot centered except rotation pot shaft no longer changes voltage did before modification 26 Solder multicolored wire two ends two wires motor terminals four wires should long enough other ends comfortably clear sides servo 27 Study article electrical drawing mark drawing wire colors being used wiring error point may damage servo and/or receiver 28 Attach four wires servo proper pins female interface connectors Four-wire connectors such Deans Power Plugs shown can used two twowire connectors whichever best serves design application female connector can cemented directly outside servo case short leads entering servo through holes immediately adjacent connector pins designer confident enough about aircraft installation layout 29 Solder two diodes two limit switches Different switch types may used providing double-pole switches shown RS #275-0 16 would serve majority applications switches can also purchased rollers ends levers diodes RS #2761101 Observe polarity diodes position switch 30 Solder two wires switch indicated drawing again noting color codes Attach other ends wires proper pins male interface connectors 31 Reinstall pot servo case noting physical key-ways guides used mate pot case 32 Determine limit-switch harness will exit servo remove small area mating lip servo bottom notch should large enough crimp wires servo reassembled 33 Before putting servo bottom place confirm spliced wire joints insulated no wires compressed between circuit board motor Lay out wires no crimping between circuit board components resistors added pot small protrusion inside bottom servo bottom presses against bottom center motor should no wires obstructing 34 Trial fit bottom place moderate pressure 102 Model Aviation ion resistive element wafer broken free center Three fingered wiper broken center element Wafer recrimped pot body resistors added wafer original Pot circuit board reinstalled Leads added motor terminals leads place Motor leads spliced external connector four leads attached four-pin female connector necessary get good fit servo sides bottom install four screws fit before disassembly remove bottom determine area resistance reposition wires Now time impatience will fit perfectly little pressure wires positioned properly 35 Reinstall gear clusters reverse order removed 36 Inspect gear clusters confirm free debris teeth faces proper alignment 37 Press servo top cover place should no resistance achieving proper fit 38 Secure four screws holding servo together Testing servo analyzer useful Plug modified servo receiver channel has mechanical centering transmitter such rudder Apply power receiver transmitter stick can moved both directions servo output changing directions small amount stick movement will result slow rotation holding stick extreme position press switch determine switch stops rotation servo stops rotating continue hold limit switch reverse direction control stick As stick passes neutral motor will start rotate Test both limit switches manner control stick neutral servo should rotate does position trim stop rotation Conclusion In early days Radio Control servos made discrete components timing capacitor resistor replaced circuit board broaden null point making neutral area wider SMT Surface Mount Technology used modern servos replacing components no longer easy option however transmitters have exponential stick adjustment accomplishes same thing Using old standard transmitter receiver modified servo positive stable though narrow neutral applications 36OO servo will take some time before designer will stop thinking just 450 terms will full potential powerful airborne bidirectional variable-speed DC motors fully realized * Ken Cashion 157 Tennyson Cove Picayune MS 39466 E-mo ii kcash ion @darasynccom Leader Small AhloIl Technology MASTER AIRSCREW MASTER AIRSCREW has propellers foryour flying needs popular sizes best prices Superefficient airfoil sections create greater thrust lower rpms resulting quieter operation Available 8 distinctive styles both glassfilled nylon strength durability beechwood maple great looks Both materials offer superior performance 55x4 55x45$129 6x3 6x35 6x4 1 29 7x3456139 8x34567149 12x6 12x8$289 13x6 13x8399 14x6 14x8559 7x4 7x5$149 8x4 8x5 8x6 8x6159 9x5 9x6 9x7179 10x510x610x710x8. 209 12x6 12x8$400 13x6 13x8500 14x6 14x8600 16x6 16x8 16x10.. 1050 16x6 16x8 16x10.. $795 18x6 18x8 18xl0.. 1325 9x4568$210 10x5678240 11x67810270 12x689345 13x6810420 14x6810555 10x6 10x8$415 11x711x9425 12x8 12x10445 13x8 13x10465 9x45678 95x6$169 1Ox4567R9 1 99 11x45678910219 11x75139 15x8 15x10$289 16x6 16x8399 11x6 11x7 11x8$229 12x6 12x8299 13x6 13x8 13x10429 14x8 14x10599 18x8 18x10$1600 20x820x101800 20x820x102100 20x6 20x8 20x10. $1525 16x6810$950 18x68101500 20x68101700 22x810121925 24x810122100 U 10x7$795U 11x711x88953 12x6995A 13x8 Windsor Propeller Co Inc 3219 Monier Circle Rancho Cordova CA 95742 Ph 9166318385 wwwmasterairscrewcom K1Ws1IlI September 1999 103
Edition: Model Aviation - 1999/09
Page Numbers: 100, 101, 102, 103
Edition: Model Aviation - 1999/09
Page Numbers: 100, 101, 102, 103
AIRBORNE AUXILIARY DC OTORS U Ken Cashion THE BASIC DESIGN Radio Control components has remained constant number years operating specifications may occasionally improved sizes individual components may vary operation has remained unchanged actual movement control surfaces spoilers flaps landing gear etc still begins rotation servo output shaft generally limited 45O mechanical reactions rotation have become cleverly adapted produce multitude push-pull pullpull pivoting levers sliding servos similar functions airframe response movement transmitter stick switch still limited tion shaft linear servo rarely seen today Modern transmitters permit variations servos will respond control sticks yet still limitation 45-degree rotation November 1998 issue Model Aviation Richard Carignan presented very good article Case 180Degree Servos demonstrating other options sometimes needed article could called Case 360-Degree Servos occasions designer would like have another power source changes aircraft structures necessarily just movement control surfaces modified servo can drive rack-and-pinons winches pulleys particular lead screws As Scale models get larger scale landing gear structure operation expected popular pneumatic systems presented another power source powerful airborne bidirectional variable-speed DC motor limits its resulting movement user-defined has applications modified servos have used RC sailboats sail-tending winches Some used modified standard-sized servo tend 600 square inches sail winds would ground model aircraft Operation The servo selected demonstrating modification RCD Hitec Standard HS-300 servo typical large enough permit good photography though much smaller servos could modified same manner Futaba S3003 servo can easily modified HS 300 Carignan article would useful acquiring details disassembling servo Most modification involves output gear servo feedback potentiometer pot pot consists rear insulated wafer body threads shaft Inside rear wafer electrically resistive element forming near-full arc electrical terminal end Also rear wafer third center terminal connected small conducting spring makes contact rotating clement wiper mounted shaft running through body output gear shaft rotation shaft moves wiper different positions resistive element thereby changes resistance between center terminal two end terminals resistance between end terminals remains fixed generally 5K ohms modification variable 5K ohm resistive element eliminated two fixed resistors added keep center terminal voltage constant control stick moved neutral servo starts rotate rotation continues until limit switch interrupts current motor control stick returned neutral limit switch opens motor can no longer rotate 100 Model Aviation os author Graphic Design Jill Ann Cavanaugh direction however diode across switch permits reverse current drive motor opposite direction reversing current occurs control stick moved past neutral opposite direction As soon motor starts rotating opposite direction limit switch closes again permitting motor again rotate either direction Another switch diode limits rotation other end travel farther control stick moved faster motor rotates Modification The modification difficult user has moderate soldering skills following steps adhered Editors note reminder modifications servos will almost certainly void manfacturers warranties items 1 Remove servo horn 2 Remove four screws servo bottom 3 Remove top carefully keep gear clusters place 4 Remove bottom 5 Note rotation-limit stops inside upper case stop output gear Step 10 stop gear will removed permit 360-degree rotation gear 6 Remove spacer top output gear remove output gear prying lightly between case gear bottom center screwdriver Caution damage output gear teeth during operation gear light press-fit feedback pot shaft 7 Remove gear-clusters obvious sequence taking care protect gear teeth best remove center gear pulling lightly gears shaft Set gears aside sequence removed tops gears facing up 8j necessary remove gear grease gears will handled very little 9 At point shaft can rotated hand Determine has built-in limit stop Hitec does 10 Remove limit stop gear Caution very careful gears during operation Make sure stop material remains interfere adjacent gears II Pivot bottom circuit board free case end away motor 12 Record color location three wires soldered pot same two wires motor 13 Remove pot removing nut washer top servo Some Futaba servos have pot clipped some servos have pot element secured small screws 14 Unsolder wires pot 15 Unsolder wires motor 16 To free pot wafer uncrimp three tabs securing pot wafer back pot body 17 On pot body locate three-fingered wiper use needle-nose pliers break off wiper shaft structure 18 Identify resistive element wafer knife pry under element break section free pot electrically disconnects pot terminals can used support resistors will added later 19 Now rotation-stop inside pot body must removed easiest way to rotate shaft until free access indentation metal frame pot body Lay outer edge pot over hard surface use small punch tap flatten indentation pot shaft will have easy 3600 rotation 20 A small drop light machine oil point pin may placed inside pot shaft remove shaft 21 Place rear wafer back pot body test free full rotation should rotate easily 22 Confirm wafer properly aligned body reassemble pot crimping three back place compress assembly 23 Solder two 22K -watt resistors outside terminal rear pot wafer Resistors Radio Shack RS #271-1325 Keep resistors flat against pot wafer facilitate reassembly Unmodified servo top removed Rotation limit stop output drive gear blackened photo will removed Servo pot gear clusters removed Note stop has now removed output gear September 1999 101 Unmodified servo bottom removed showing circuit board motor top feedback pot Unmodified wafer top pot body Note indented edge pot body right internal rotation stop will removed 24 Solder other ends 22K resistors together solder wire attached pot center terminal junction 25 Solder other two pot wires respective terminals operation will make voltage center wire approximately what would have pot centered except rotation pot shaft no longer changes voltage did before modification 26 Solder multicolored wire two ends two wires motor terminals four wires should long enough other ends comfortably clear sides servo 27 Study article electrical drawing mark drawing wire colors being used wiring error point may damage servo and/or receiver 28 Attach four wires servo proper pins female interface connectors Four-wire connectors such Deans Power Plugs shown can used two twowire connectors whichever best serves design application female connector can cemented directly outside servo case short leads entering servo through holes immediately adjacent connector pins designer confident enough about aircraft installation layout 29 Solder two diodes two limit switches Different switch types may used providing double-pole switches shown RS #275-0 16 would serve majority applications switches can also purchased rollers ends levers diodes RS #2761101 Observe polarity diodes position switch 30 Solder two wires switch indicated drawing again noting color codes Attach other ends wires proper pins male interface connectors 31 Reinstall pot servo case noting physical key-ways guides used mate pot case 32 Determine limit-switch harness will exit servo remove small area mating lip servo bottom notch should large enough crimp wires servo reassembled 33 Before putting servo bottom place confirm spliced wire joints insulated no wires compressed between circuit board motor Lay out wires no crimping between circuit board components resistors added pot small protrusion inside bottom servo bottom presses against bottom center motor should no wires obstructing 34 Trial fit bottom place moderate pressure 102 Model Aviation ion resistive element wafer broken free center Three fingered wiper broken center element Wafer recrimped pot body resistors added wafer original Pot circuit board reinstalled Leads added motor terminals leads place Motor leads spliced external connector four leads attached four-pin female connector necessary get good fit servo sides bottom install four screws fit before disassembly remove bottom determine area resistance reposition wires Now time impatience will fit perfectly little pressure wires positioned properly 35 Reinstall gear clusters reverse order removed 36 Inspect gear clusters confirm free debris teeth faces proper alignment 37 Press servo top cover place should no resistance achieving proper fit 38 Secure four screws holding servo together Testing servo analyzer useful Plug modified servo receiver channel has mechanical centering transmitter such rudder Apply power receiver transmitter stick can moved both directions servo output changing directions small amount stick movement will result slow rotation holding stick extreme position press switch determine switch stops rotation servo stops rotating continue hold limit switch reverse direction control stick As stick passes neutral motor will start rotate Test both limit switches manner control stick neutral servo should rotate does position trim stop rotation Conclusion In early days Radio Control servos made discrete components timing capacitor resistor replaced circuit board broaden null point making neutral area wider SMT Surface Mount Technology used modern servos replacing components no longer easy option however transmitters have exponential stick adjustment accomplishes same thing Using old standard transmitter receiver modified servo positive stable though narrow neutral applications 36OO servo will take some time before designer will stop thinking just 450 terms will full potential powerful airborne bidirectional variable-speed DC motors fully realized * Ken Cashion 157 Tennyson Cove Picayune MS 39466 E-mo ii kcash ion @darasynccom Leader Small AhloIl Technology MASTER AIRSCREW MASTER AIRSCREW has propellers foryour flying needs popular sizes best prices Superefficient airfoil sections create greater thrust lower rpms resulting quieter operation Available 8 distinctive styles both glassfilled nylon strength durability beechwood maple great looks Both materials offer superior performance 55x4 55x45$129 6x3 6x35 6x4 1 29 7x3456139 8x34567149 12x6 12x8$289 13x6 13x8399 14x6 14x8559 7x4 7x5$149 8x4 8x5 8x6 8x6159 9x5 9x6 9x7179 10x510x610x710x8. 209 12x6 12x8$400 13x6 13x8500 14x6 14x8600 16x6 16x8 16x10.. 1050 16x6 16x8 16x10.. $795 18x6 18x8 18xl0.. 1325 9x4568$210 10x5678240 11x67810270 12x689345 13x6810420 14x6810555 10x6 10x8$415 11x711x9425 12x8 12x10445 13x8 13x10465 9x45678 95x6$169 1Ox4567R9 1 99 11x45678910219 11x75139 15x8 15x10$289 16x6 16x8399 11x6 11x7 11x8$229 12x6 12x8299 13x6 13x8 13x10429 14x8 14x10599 18x8 18x10$1600 20x820x101800 20x820x102100 20x6 20x8 20x10. $1525 16x6810$950 18x68101500 20x68101700 22x810121925 24x810122100 U 10x7$795U 11x711x88953 12x6995A 13x8 Windsor Propeller Co Inc 3219 Monier Circle Rancho Cordova CA 95742 Ph 9166318385 wwwmasterairscrewcom K1Ws1IlI September 1999 103
Edition: Model Aviation - 1999/09
Page Numbers: 100, 101, 102, 103
AIRBORNE AUXILIARY DC OTORS U Ken Cashion THE BASIC DESIGN Radio Control components has remained constant number years operating specifications may occasionally improved sizes individual components may vary operation has remained unchanged actual movement control surfaces spoilers flaps landing gear etc still begins rotation servo output shaft generally limited 45O mechanical reactions rotation have become cleverly adapted produce multitude push-pull pullpull pivoting levers sliding servos similar functions airframe response movement transmitter stick switch still limited tion shaft linear servo rarely seen today Modern transmitters permit variations servos will respond control sticks yet still limitation 45-degree rotation November 1998 issue Model Aviation Richard Carignan presented very good article Case 180Degree Servos demonstrating other options sometimes needed article could called Case 360-Degree Servos occasions designer would like have another power source changes aircraft structures necessarily just movement control surfaces modified servo can drive rack-and-pinons winches pulleys particular lead screws As Scale models get larger scale landing gear structure operation expected popular pneumatic systems presented another power source powerful airborne bidirectional variable-speed DC motor limits its resulting movement user-defined has applications modified servos have used RC sailboats sail-tending winches Some used modified standard-sized servo tend 600 square inches sail winds would ground model aircraft Operation The servo selected demonstrating modification RCD Hitec Standard HS-300 servo typical large enough permit good photography though much smaller servos could modified same manner Futaba S3003 servo can easily modified HS 300 Carignan article would useful acquiring details disassembling servo Most modification involves output gear servo feedback potentiometer pot pot consists rear insulated wafer body threads shaft Inside rear wafer electrically resistive element forming near-full arc electrical terminal end Also rear wafer third center terminal connected small conducting spring makes contact rotating clement wiper mounted shaft running through body output gear shaft rotation shaft moves wiper different positions resistive element thereby changes resistance between center terminal two end terminals resistance between end terminals remains fixed generally 5K ohms modification variable 5K ohm resistive element eliminated two fixed resistors added keep center terminal voltage constant control stick moved neutral servo starts rotate rotation continues until limit switch interrupts current motor control stick returned neutral limit switch opens motor can no longer rotate 100 Model Aviation os author Graphic Design Jill Ann Cavanaugh direction however diode across switch permits reverse current drive motor opposite direction reversing current occurs control stick moved past neutral opposite direction As soon motor starts rotating opposite direction limit switch closes again permitting motor again rotate either direction Another switch diode limits rotation other end travel farther control stick moved faster motor rotates Modification The modification difficult user has moderate soldering skills following steps adhered Editors note reminder modifications servos will almost certainly void manfacturers warranties items 1 Remove servo horn 2 Remove four screws servo bottom 3 Remove top carefully keep gear clusters place 4 Remove bottom 5 Note rotation-limit stops inside upper case stop output gear Step 10 stop gear will removed permit 360-degree rotation gear 6 Remove spacer top output gear remove output gear prying lightly between case gear bottom center screwdriver Caution damage output gear teeth during operation gear light press-fit feedback pot shaft 7 Remove gear-clusters obvious sequence taking care protect gear teeth best remove center gear pulling lightly gears shaft Set gears aside sequence removed tops gears facing up 8j necessary remove gear grease gears will handled very little 9 At point shaft can rotated hand Determine has built-in limit stop Hitec does 10 Remove limit stop gear Caution very careful gears during operation Make sure stop material remains interfere adjacent gears II Pivot bottom circuit board free case end away motor 12 Record color location three wires soldered pot same two wires motor 13 Remove pot removing nut washer top servo Some Futaba servos have pot clipped some servos have pot element secured small screws 14 Unsolder wires pot 15 Unsolder wires motor 16 To free pot wafer uncrimp three tabs securing pot wafer back pot body 17 On pot body locate three-fingered wiper use needle-nose pliers break off wiper shaft structure 18 Identify resistive element wafer knife pry under element break section free pot electrically disconnects pot terminals can used support resistors will added later 19 Now rotation-stop inside pot body must removed easiest way to rotate shaft until free access indentation metal frame pot body Lay outer edge pot over hard surface use small punch tap flatten indentation pot shaft will have easy 3600 rotation 20 A small drop light machine oil point pin may placed inside pot shaft remove shaft 21 Place rear wafer back pot body test free full rotation should rotate easily 22 Confirm wafer properly aligned body reassemble pot crimping three back place compress assembly 23 Solder two 22K -watt resistors outside terminal rear pot wafer Resistors Radio Shack RS #271-1325 Keep resistors flat against pot wafer facilitate reassembly Unmodified servo top removed Rotation limit stop output drive gear blackened photo will removed Servo pot gear clusters removed Note stop has now removed output gear September 1999 101 Unmodified servo bottom removed showing circuit board motor top feedback pot Unmodified wafer top pot body Note indented edge pot body right internal rotation stop will removed 24 Solder other ends 22K resistors together solder wire attached pot center terminal junction 25 Solder other two pot wires respective terminals operation will make voltage center wire approximately what would have pot centered except rotation pot shaft no longer changes voltage did before modification 26 Solder multicolored wire two ends two wires motor terminals four wires should long enough other ends comfortably clear sides servo 27 Study article electrical drawing mark drawing wire colors being used wiring error point may damage servo and/or receiver 28 Attach four wires servo proper pins female interface connectors Four-wire connectors such Deans Power Plugs shown can used two twowire connectors whichever best serves design application female connector can cemented directly outside servo case short leads entering servo through holes immediately adjacent connector pins designer confident enough about aircraft installation layout 29 Solder two diodes two limit switches Different switch types may used providing double-pole switches shown RS #275-0 16 would serve majority applications switches can also purchased rollers ends levers diodes RS #2761101 Observe polarity diodes position switch 30 Solder two wires switch indicated drawing again noting color codes Attach other ends wires proper pins male interface connectors 31 Reinstall pot servo case noting physical key-ways guides used mate pot case 32 Determine limit-switch harness will exit servo remove small area mating lip servo bottom notch should large enough crimp wires servo reassembled 33 Before putting servo bottom place confirm spliced wire joints insulated no wires compressed between circuit board motor Lay out wires no crimping between circuit board components resistors added pot small protrusion inside bottom servo bottom presses against bottom center motor should no wires obstructing 34 Trial fit bottom place moderate pressure 102 Model Aviation ion resistive element wafer broken free center Three fingered wiper broken center element Wafer recrimped pot body resistors added wafer original Pot circuit board reinstalled Leads added motor terminals leads place Motor leads spliced external connector four leads attached four-pin female connector necessary get good fit servo sides bottom install four screws fit before disassembly remove bottom determine area resistance reposition wires Now time impatience will fit perfectly little pressure wires positioned properly 35 Reinstall gear clusters reverse order removed 36 Inspect gear clusters confirm free debris teeth faces proper alignment 37 Press servo top cover place should no resistance achieving proper fit 38 Secure four screws holding servo together Testing servo analyzer useful Plug modified servo receiver channel has mechanical centering transmitter such rudder Apply power receiver transmitter stick can moved both directions servo output changing directions small amount stick movement will result slow rotation holding stick extreme position press switch determine switch stops rotation servo stops rotating continue hold limit switch reverse direction control stick As stick passes neutral motor will start rotate Test both limit switches manner control stick neutral servo should rotate does position trim stop rotation Conclusion In early days Radio Control servos made discrete components timing capacitor resistor replaced circuit board broaden null point making neutral area wider SMT Surface Mount Technology used modern servos replacing components no longer easy option however transmitters have exponential stick adjustment accomplishes same thing Using old standard transmitter receiver modified servo positive stable though narrow neutral applications 36OO servo will take some time before designer will stop thinking just 450 terms will full potential powerful airborne bidirectional variable-speed DC motors fully realized * Ken Cashion 157 Tennyson Cove Picayune MS 39466 E-mo ii kcash ion @darasynccom Leader Small AhloIl Technology MASTER AIRSCREW MASTER AIRSCREW has propellers foryour flying needs popular sizes best prices Superefficient airfoil sections create greater thrust lower rpms resulting quieter operation Available 8 distinctive styles both glassfilled nylon strength durability beechwood maple great looks Both materials offer superior performance 55x4 55x45$129 6x3 6x35 6x4 1 29 7x3456139 8x34567149 12x6 12x8$289 13x6 13x8399 14x6 14x8559 7x4 7x5$149 8x4 8x5 8x6 8x6159 9x5 9x6 9x7179 10x510x610x710x8. 209 12x6 12x8$400 13x6 13x8500 14x6 14x8600 16x6 16x8 16x10.. 1050 16x6 16x8 16x10.. $795 18x6 18x8 18xl0.. 1325 9x4568$210 10x5678240 11x67810270 12x689345 13x6810420 14x6810555 10x6 10x8$415 11x711x9425 12x8 12x10445 13x8 13x10465 9x45678 95x6$169 1Ox4567R9 1 99 11x45678910219 11x75139 15x8 15x10$289 16x6 16x8399 11x6 11x7 11x8$229 12x6 12x8299 13x6 13x8 13x10429 14x8 14x10599 18x8 18x10$1600 20x820x101800 20x820x102100 20x6 20x8 20x10. $1525 16x6810$950 18x68101500 20x68101700 22x810121925 24x810122100 U 10x7$795U 11x711x88953 12x6995A 13x8 Windsor Propeller Co Inc 3219 Monier Circle Rancho Cordova CA 95742 Ph 9166318385 wwwmasterairscrewcom K1Ws1IlI September 1999 103
Edition: Model Aviation - 1999/09
Page Numbers: 100, 101, 102, 103
AIRBORNE AUXILIARY DC OTORS U Ken Cashion THE BASIC DESIGN Radio Control components has remained constant number years operating specifications may occasionally improved sizes individual components may vary operation has remained unchanged actual movement control surfaces spoilers flaps landing gear etc still begins rotation servo output shaft generally limited 45O mechanical reactions rotation have become cleverly adapted produce multitude push-pull pullpull pivoting levers sliding servos similar functions airframe response movement transmitter stick switch still limited tion shaft linear servo rarely seen today Modern transmitters permit variations servos will respond control sticks yet still limitation 45-degree rotation November 1998 issue Model Aviation Richard Carignan presented very good article Case 180Degree Servos demonstrating other options sometimes needed article could called Case 360-Degree Servos occasions designer would like have another power source changes aircraft structures necessarily just movement control surfaces modified servo can drive rack-and-pinons winches pulleys particular lead screws As Scale models get larger scale landing gear structure operation expected popular pneumatic systems presented another power source powerful airborne bidirectional variable-speed DC motor limits its resulting movement user-defined has applications modified servos have used RC sailboats sail-tending winches Some used modified standard-sized servo tend 600 square inches sail winds would ground model aircraft Operation The servo selected demonstrating modification RCD Hitec Standard HS-300 servo typical large enough permit good photography though much smaller servos could modified same manner Futaba S3003 servo can easily modified HS 300 Carignan article would useful acquiring details disassembling servo Most modification involves output gear servo feedback potentiometer pot pot consists rear insulated wafer body threads shaft Inside rear wafer electrically resistive element forming near-full arc electrical terminal end Also rear wafer third center terminal connected small conducting spring makes contact rotating clement wiper mounted shaft running through body output gear shaft rotation shaft moves wiper different positions resistive element thereby changes resistance between center terminal two end terminals resistance between end terminals remains fixed generally 5K ohms modification variable 5K ohm resistive element eliminated two fixed resistors added keep center terminal voltage constant control stick moved neutral servo starts rotate rotation continues until limit switch interrupts current motor control stick returned neutral limit switch opens motor can no longer rotate 100 Model Aviation os author Graphic Design Jill Ann Cavanaugh direction however diode across switch permits reverse current drive motor opposite direction reversing current occurs control stick moved past neutral opposite direction As soon motor starts rotating opposite direction limit switch closes again permitting motor again rotate either direction Another switch diode limits rotation other end travel farther control stick moved faster motor rotates Modification The modification difficult user has moderate soldering skills following steps adhered Editors note reminder modifications servos will almost certainly void manfacturers warranties items 1 Remove servo horn 2 Remove four screws servo bottom 3 Remove top carefully keep gear clusters place 4 Remove bottom 5 Note rotation-limit stops inside upper case stop output gear Step 10 stop gear will removed permit 360-degree rotation gear 6 Remove spacer top output gear remove output gear prying lightly between case gear bottom center screwdriver Caution damage output gear teeth during operation gear light press-fit feedback pot shaft 7 Remove gear-clusters obvious sequence taking care protect gear teeth best remove center gear pulling lightly gears shaft Set gears aside sequence removed tops gears facing up 8j necessary remove gear grease gears will handled very little 9 At point shaft can rotated hand Determine has built-in limit stop Hitec does 10 Remove limit stop gear Caution very careful gears during operation Make sure stop material remains interfere adjacent gears II Pivot bottom circuit board free case end away motor 12 Record color location three wires soldered pot same two wires motor 13 Remove pot removing nut washer top servo Some Futaba servos have pot clipped some servos have pot element secured small screws 14 Unsolder wires pot 15 Unsolder wires motor 16 To free pot wafer uncrimp three tabs securing pot wafer back pot body 17 On pot body locate three-fingered wiper use needle-nose pliers break off wiper shaft structure 18 Identify resistive element wafer knife pry under element break section free pot electrically disconnects pot terminals can used support resistors will added later 19 Now rotation-stop inside pot body must removed easiest way to rotate shaft until free access indentation metal frame pot body Lay outer edge pot over hard surface use small punch tap flatten indentation pot shaft will have easy 3600 rotation 20 A small drop light machine oil point pin may placed inside pot shaft remove shaft 21 Place rear wafer back pot body test free full rotation should rotate easily 22 Confirm wafer properly aligned body reassemble pot crimping three back place compress assembly 23 Solder two 22K -watt resistors outside terminal rear pot wafer Resistors Radio Shack RS #271-1325 Keep resistors flat against pot wafer facilitate reassembly Unmodified servo top removed Rotation limit stop output drive gear blackened photo will removed Servo pot gear clusters removed Note stop has now removed output gear September 1999 101 Unmodified servo bottom removed showing circuit board motor top feedback pot Unmodified wafer top pot body Note indented edge pot body right internal rotation stop will removed 24 Solder other ends 22K resistors together solder wire attached pot center terminal junction 25 Solder other two pot wires respective terminals operation will make voltage center wire approximately what would have pot centered except rotation pot shaft no longer changes voltage did before modification 26 Solder multicolored wire two ends two wires motor terminals four wires should long enough other ends comfortably clear sides servo 27 Study article electrical drawing mark drawing wire colors being used wiring error point may damage servo and/or receiver 28 Attach four wires servo proper pins female interface connectors Four-wire connectors such Deans Power Plugs shown can used two twowire connectors whichever best serves design application female connector can cemented directly outside servo case short leads entering servo through holes immediately adjacent connector pins designer confident enough about aircraft installation layout 29 Solder two diodes two limit switches Different switch types may used providing double-pole switches shown RS #275-0 16 would serve majority applications switches can also purchased rollers ends levers diodes RS #2761101 Observe polarity diodes position switch 30 Solder two wires switch indicated drawing again noting color codes Attach other ends wires proper pins male interface connectors 31 Reinstall pot servo case noting physical key-ways guides used mate pot case 32 Determine limit-switch harness will exit servo remove small area mating lip servo bottom notch should large enough crimp wires servo reassembled 33 Before putting servo bottom place confirm spliced wire joints insulated no wires compressed between circuit board motor Lay out wires no crimping between circuit board components resistors added pot small protrusion inside bottom servo bottom presses against bottom center motor should no wires obstructing 34 Trial fit bottom place moderate pressure 102 Model Aviation ion resistive element wafer broken free center Three fingered wiper broken center element Wafer recrimped pot body resistors added wafer original Pot circuit board reinstalled Leads added motor terminals leads place Motor leads spliced external connector four leads attached four-pin female connector necessary get good fit servo sides bottom install four screws fit before disassembly remove bottom determine area resistance reposition wires Now time impatience will fit perfectly little pressure wires positioned properly 35 Reinstall gear clusters reverse order removed 36 Inspect gear clusters confirm free debris teeth faces proper alignment 37 Press servo top cover place should no resistance achieving proper fit 38 Secure four screws holding servo together Testing servo analyzer useful Plug modified servo receiver channel has mechanical centering transmitter such rudder Apply power receiver transmitter stick can moved both directions servo output changing directions small amount stick movement will result slow rotation holding stick extreme position press switch determine switch stops rotation servo stops rotating continue hold limit switch reverse direction control stick As stick passes neutral motor will start rotate Test both limit switches manner control stick neutral servo should rotate does position trim stop rotation Conclusion In early days Radio Control servos made discrete components timing capacitor resistor replaced circuit board broaden null point making neutral area wider SMT Surface Mount Technology used modern servos replacing components no longer easy option however transmitters have exponential stick adjustment accomplishes same thing Using old standard transmitter receiver modified servo positive stable though narrow neutral applications 36OO servo will take some time before designer will stop thinking just 450 terms will full potential powerful airborne bidirectional variable-speed DC motors fully realized * Ken Cashion 157 Tennyson Cove Picayune MS 39466 E-mo ii kcash ion @darasynccom Leader Small AhloIl Technology MASTER 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