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Throttle servo recommendations for 50cc

Old 03-28-2009, 09:46 PM
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Default Throttle servo recommendations for 50cc

Hi everyone

Currently putting together a 50CC extra, and have hitec 7955's all around. What is the recommended servo for the throttle? I am using a DA50 engine. Should I also go with a 7955 there as well? If not, do I need to stick with a metal geared servo? Thanks for your help

Andy
Old 03-28-2009, 10:12 PM
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Default RE: Throttle servo recommendations for 50cc

your best would be a digital servo, should be fast but does not have to be real powerful.
Old 03-28-2009, 10:12 PM
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Default RE: Throttle servo recommendations for 50cc

I am by no means an expert on this since I have just completed my first gasser but I think you would be fine with any standard digital servo. I used a Futaba 3152 for my throttle. I don't see where a metal geared servo would be needed for the throttle but digital would be preferred for a consistant idle.
Old 03-28-2009, 10:26 PM
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Default RE: Throttle servo recommendations for 50cc

I have read many times that the shock and vibration from a gasser can easily shatter the nylon gears.I 'd go with a metal one.
Old 03-28-2009, 10:30 PM
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Default RE: Throttle servo recommendations for 50cc

Just use a standard metal gear servo and you'll be fine. You won't gain an advantage using a digital servo on the throttle. I'm using Hitec 425s and no problems. Speed of the servo is greater than the engine's ability to react to the throttle movement.
Old 03-28-2009, 11:00 PM
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Default RE: Throttle servo recommendations for 50cc

My early experiences with non metal geared throttle servos for gassers has me using nothing but metal geared servos. Ruined several great flying days with stripped nylon geared throttle servos[]
Old 03-28-2009, 11:03 PM
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Default RE: Throttle servo recommendations for 50cc

I like the Hobbyco cs35. It's a rebadged Hitech 225 mg mini servo. http://www3.towerhobbies.com/cgi-bin...?&I=LXLN95&P=0
Good speed, very well made and slop free gears and a good price.
Old 03-28-2009, 11:03 PM
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Default RE: Throttle servo recommendations for 50cc

Well *****, I guess I need to get a metal gear servo for my throttle.
Old 03-28-2009, 11:11 PM
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Default RE: Throttle servo recommendations for 50cc

The plastic gear servos should work for a while. If thats what you have, use them. Heck we all use plastic horns on the throttle. Evan more important than MG servos is eliminating vibration. A strong solid engine mount is a great place to start.
Old 03-28-2009, 11:14 PM
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Default RE: Throttle servo recommendations for 50cc

Actually I got away with it for awhile. Took a little time for the vibration to take it's toll. Just wouldn't be that pleasant if she decides to let go in a low torque roll![X(] I was lucky, One gave up on base leg with ample altitude and the other on the ground during run- up.
Old 03-29-2009, 04:09 AM
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Default RE: Throttle servo recommendations for 50cc

Get another 7955. You want an accurate servo with good resolution. Seen/heard of two deadsticks more than likely due to inaccurate standard servos, one involved the loss of 35%er.
Old 03-29-2009, 10:41 AM
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Default RE: Throttle servo recommendations for 50cc

Well one other thought about throttle servos on gassers;

Since gassers are so sensitive coming right off idle, you have to pay attention to the geometry of the linkage setup and if you use a programmable Hitec it makes the setup also easier to compensate for limitations on what you can do with the actual hardware. While there are a few tricks you can use on radio setup depending on your tx, those should not be thought of as compensating for a poor mechanical/geometry setup of the servos/linkages anywhere on the model

If you've got an extra 7955 kicking around, you could easily use that but I've gone to a smaller Hitec digital with metal gears so I can also program them, works great.
Old 03-30-2009, 08:42 AM
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Default RE: Throttle servo recommendations for 50cc


ORIGINAL: Eagleburger

You want an accurate servo with good resolution. Seen/heard of two deadsticks more than likely due to inaccurate standard servos, one involved the loss of 35%er.
Curious! The throttle ratchet on most transmitters has a resolution of about 20. Any servo I've seen is a lot better than that.
Old 03-30-2009, 10:46 AM
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Default RE: Throttle servo recommendations for 50cc


ORIGINAL: RC_Fanatic


ORIGINAL: Eagleburger

You want an accurate servo with good resolution. Seen/heard of two deadsticks more than likely due to inaccurate standard servos, one involved the loss of 35%er.
Curious! The throttle ratchet on most transmitters has a resolution of about 20. Any servo I've seen is a lot better than that.

One of the Reasons I use a Heli TX.
Old 03-30-2009, 11:26 AM
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Default RE: Throttle servo recommendations for 50cc

That ratcheting can be removed in 5 minutes...but I like mine.
Old 03-30-2009, 11:54 AM
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Default RE: Throttle servo recommendations for 50cc


ORIGINAL: Eagleburger

Get another 7955. You want an accurate servo with good resolution. Seen/heard of two deadsticks more than likely due to inaccurate standard servos, one involved the loss of 35%er.
Sounds a bit of an overkill to me. As mentioned before, any good metal geard standard servo will do. What I always use, in conjunction with metal geared servos, is a Sullivan nylon pushrod. Only the ends have metal clevises. The nylon pushrod acts as a shock absorber and reduce the vibration on the servo gears. The minimal differences in expansion due to temperature changes are negligible and can be corrected with the trim on your radio. Never lost a throttle servo on any of my gassers.
Old 03-30-2009, 12:17 PM
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Default RE: Throttle servo recommendations for 50cc

I prefer a servo that is extremely accurate in centering. Having a servo that will repeat the idle position every time is more important to me than a fast servo. Most servos will actually travel faster than a gas engine can respond anyway. Accuracy is WAY more important than speed IMO.

I use nylon geared servos all the time. Never had any problems. But I also use sullivan graphite pushrods and mount my servos at least 12" away from the engine compartment. I still follow the old rules of installation when it comes to the ignition box. (12" rule) By using the longer pushrod I believe it gives some vibration isolation.

Consider which will provide more isolation from the vibration....... a servo mounted 5" from the engine and a metal pushrod with ball links on both ends..... or...... a servo mounted at the back of the wing saddle and a 30" long pushrod with ball links on both ends....

Thats just what I do. I'm sure anybody could point out some flaws in my setup. It's probably not the "best" way to do it, but it does work.
Old 03-30-2009, 12:32 PM
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Default RE: Throttle servo recommendations for 50cc


ORIGINAL: Zeeb

it makes the setup also easier to compensate for limitations on what you can do with the actual hardware.

Like what??
Old 03-30-2009, 12:46 PM
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Default RE: Throttle servo recommendations for 50cc


ORIGINAL: exeter_acres


ORIGINAL: Zeeb

it makes the setup also easier to compensate for limitations on what you can do with the actual hardware.

Like what??
Well I went as long as I could on the carb arm and as short as I could on the servo arm, then setup the thing so that the idle was with the servo near it's rear most position. This allows the intial movement of the throttle servo to be less linear and thereby less speed opening the carb butterfly. Then I went in and set the travel limits using the servo programmer so my tx uses ATV's on that throttle servo in the neighborhood of 135% ATV (I'm using JR which goes to 150% so there's some room for adjustments) and it really seems to have given me a much better control of lower RPM range of the engine. That's nice for taxiing and throttle blips on landing for descent control.

I suppose one might accomplish something with a throttle curve in the tx, but that doesn't allow you to use the higher ATV settings and better resolution.

JMHO, YMMV....
Old 03-30-2009, 12:55 PM
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Default RE: Throttle servo recommendations for 50cc


ORIGINAL: Zeeb


ORIGINAL: exeter_acres


ORIGINAL: Zeeb

it makes the setup also easier to compensate for limitations on what you can do with the actual hardware.

Like what??


I suppose one might accomplish something with a throttle curve in the tx, but that doesn't allow you to use the higher ATV settings and better resolution.

JMHO, YMMV....

Why not?
Old 03-30-2009, 05:07 PM
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Default RE: Throttle servo recommendations for 50cc


ORIGINAL: Rcpilot

I prefer a servo that is extremely accurate in centering. Having a servo that will repeat the idle position every time is more important to me than a fast servo. Most servos will actually travel faster than a gas engine can respond anyway. Accuracy is WAY more important than speed IMO.

I use nylon geared servos all the time. Never had any problems. But I also use sullivan graphite pushrods and mount my servos at least 12" away from the engine compartment. I still follow the old rules of installation when it comes to the ignition box. (12" rule) By using the longer pushrod I believe it gives some vibration isolation.

Consider which will provide more isolation from the vibration....... a servo mounted 5" from the engine and a metal pushrod with ball links on both ends..... or...... a servo mounted at the back of the wing saddle and a 30" long pushrod with ball links on both ends....

Thats just what I do. I'm sure anybody could point out some flaws in my setup. It's probably not the "best" way to do it, but it does work.

Good advice, especially the bold typefaced.

I use digitals with plastic gears, nyrods, servo mounted on or near gear plate and never had a problem. Usually with mini servos to boot. just started to use 7955 on my two latest and they are the best of both worlds.

Old 03-31-2009, 11:33 AM
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Default RE: Throttle servo recommendations for 50cc


ORIGINAL: exeter_acres


ORIGINAL: Zeeb


ORIGINAL: exeter_acres


ORIGINAL: Zeeb

it makes the setup also easier to compensate for limitations on what you can do with the actual hardware.

Like what??


I suppose one might accomplish something with a throttle curve in the tx, but that doesn't allow you to use the higher ATV settings and better resolution.

JMHO, YMMV....

Why not?
Now you're just trolling....

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