Aileron Servo Sizing
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Aileron Servo Sizing
I'm thinking of putting twin aileron servos in my Goldberg Cub so I can try flaperon mix on landing.
Using two standard-size servos seems like overkill and a lot of weight when the load is split over the two servos. But I've never heard of anyone trusting S3101/Hitec HS-81 mini/micro type servos in gas-powered aileron service, even on a sedate model like a .60-size Cub. Most of the references to mini's are regarding electrics and park flyers.
What's people's experience with servo sizes? Are gas fliers just stuck in a standard-size rut, or are mini servos to weak to drive an gassie's aileron?
Using two standard-size servos seems like overkill and a lot of weight when the load is split over the two servos. But I've never heard of anyone trusting S3101/Hitec HS-81 mini/micro type servos in gas-powered aileron service, even on a sedate model like a .60-size Cub. Most of the references to mini's are regarding electrics and park flyers.
What's people's experience with servo sizes? Are gas fliers just stuck in a standard-size rut, or are mini servos to weak to drive an gassie's aileron?
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RE: Aileron Servo Sizing
If it were me I'd stay with standard size servo's. Price difference is about the same and even though the servo load will be light, the extra assurance that the servo provides is an increase in safety. Long term thought is that the servo's could always be transfered to another airplane down the road
Cheers,
Cheers,
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RE: Aileron Servo Sizing
I have a Sig Kavalier that had one Futaba 3004 servo in the wing center connecting to torque rods. That servo has 42 oz of torque, I think. I put in 2 of the Hitechs side by side, one for each torque rod. So, that gave me more power per aileron than the single Futaba standard servo. It is ridiculously easy to do and I actually saved about .1 oz in weight. Plus, I have stronger servo power to the ailerons and can set aileron differential if I need to....or flaperons. I only had to shave off less than 1/8 inch of the bay for both servos to fit.
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RE: Aileron Servo Sizing
ORIGINAL: Balsacutter
I've never heard of anyone trusting S3101/Hitec HS-81 mini/micro type servos in gas-powered aileron service, even on a sedate model like a .60-size Cub.
I've never heard of anyone trusting S3101/Hitec HS-81 mini/micro type servos in gas-powered aileron service, even on a sedate model like a .60-size Cub.
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RE: Aileron Servo Sizing
ORIGINAL: blw
I have to agree. I think the HS 81 puts out only 36 oz of torque. I am building my first 60 sized plane and I'm settling for around 60 something oz for each servo.
I have to agree. I think the HS 81 puts out only 36 oz of torque. I am building my first 60 sized plane and I'm settling for around 60 something oz for each servo.
Edit: forgot to add speed data: 0.14s @ 4.8volt, 0.11s @ 6.0volt
Lighter, smaller AND stronger then a standard servo.
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RE: Aileron Servo Sizing
Altough the Hitec Hs-225 servo is more powerful than a standard, the gear train is weaker. Its a great servo and probably much more than needed in a 60 size Cub. I used standard servos in my 1/4 Cub and it did great until I got cocky. Beautiful flying bird!
Carl
Carl
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RE: Aileron Servo Sizing
ORIGINAL: carlbecker
Altough the Hitec Hs-225 servo is more powerful than a standard, the gear train is weaker. Its a great servo and probably much more than needed in a 60 size Cub. I used standard servos in my 1/4 Cub and it did great until I got cocky. Beautiful flying bird!
Carl
Altough the Hitec Hs-225 servo is more powerful than a standard, the gear train is weaker. Its a great servo and probably much more than needed in a 60 size Cub. I used standard servos in my 1/4 Cub and it did great until I got cocky. Beautiful flying bird!
Carl
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RE: Aileron Servo Sizing
Don't forget that on a cub with scale ailerons, if you use them as flaps you will *increase* the risk of tip stall. If its semi-scale and has full span stip ailerons then I wouldnt worry.
The HS-225 servos should do ok. I've stipped the plastic gear version on 40 size 3D ships and wont use them in that application anymore, but on up to 40 size sport planes with smaller surfaces and throws they do great.
The HS-225 servos should do ok. I've stipped the plastic gear version on 40 size 3D ships and wont use them in that application anymore, but on up to 40 size sport planes with smaller surfaces and throws they do great.
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RE: Aileron Servo Sizing
John, this servo torque calculator is an answer to a design issue I've been pursing for some time, so thank you so much. Is this your work?
Manufacturers catalogs detail servo power, and offer some choices in quality of materials (bearings, gear material, etc.) but very little application data. I think we're often selecting them based on guesswork or conservative experience, or just following what everyone else does like sheep. (Until they strip a gear and crash, of course!)
I wanted some rational engineering estimates of the power required to move control surfaces, and now I have it. Now I can select the servos based on the need.
(And then go do a figure "9" due to dumb thumbs. :-))))
What a great hobby!
- Balsacutter
Manufacturers catalogs detail servo power, and offer some choices in quality of materials (bearings, gear material, etc.) but very little application data. I think we're often selecting them based on guesswork or conservative experience, or just following what everyone else does like sheep. (Until they strip a gear and crash, of course!)
I wanted some rational engineering estimates of the power required to move control surfaces, and now I have it. Now I can select the servos based on the need.
(And then go do a figure "9" due to dumb thumbs. :-))))
What a great hobby!
- Balsacutter
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RE: Aileron Servo Sizing
That is a great calculator, John. Thank you. It's interesting how it shows that as servo arm throw is increases, so does the mechanical advantage. A linkage set up so that 50° of servo travel gives an intended surface throw of 15° requires less torque than a linkage where the servo only travels 40° to provide the same surface deflection. As others have explained, keeping your EPA as close to 100% is to your advantage.