throttle return spring ?
 

I noticed the throttle on my tt36 goes to full with no control arm, this just seems wrong, if the link were to pop off it would be bye bye birdie. does anyone run a throttle return spring ?

RE: throttle return spring ?
 

a return spring will burn out your servo, what type of radio do you have you should be able to set your failsafe setting to zero throttle

RE: throttle return spring ?
 

The failsafe in the radio won't help as he is talking about the link on the throttle arm coming off. Obviously it makes no difference what the servo does if it's no longer connected to anything.

You could put a light spring on the throttle without a problem if you're worried about this. The load on the throttle servo is minimal so a light spring won't hurt. Just don't put a big honking spring on it. Personally I don't think it's necessary. In 20 years of flying helicopters and fixed wing I've never had a throttle linkage come off.

Regards,

Mike

RE: throttle return spring ?
 

I was thinking about a thin rubberband or something like a pen spring (but a puller not a pusher)I know the chances of the link coming off are slim but if it can happen it will happen to me. LOL

RE: throttle return spring ?
 

I agree with chopper. It is a better practice to keep a visual inspection on your links (at least once each time before heading to the field). If the ball links start getting sloppy, or if you are able to easily pop the link off with your finger, replace the plastic. You'll want to keep the links good and tight anyway as it will add to the overall handling of the bird.

Just my .02, I change my plastic ends yearly, as it only cost me about $9 to do the whole bird.

RE: throttle return spring ?
 

I'm still new to this wonderful hobbie, but, if your pushrod to your throttle accidently comes off and the engine goes to full throttle, can't you still have control of your pitch and land your roaring bird down safely? Just a thought

RE: throttle return spring ?
 

You're right. I never thought of that. The rotor speed would be off the charts with full throttle and very little load on the engine. It might damage something screaming like that and it might be hard to control. But you wouldn't lose it.

Mike

RE: throttle return spring ?
 

A return spring is a good idea to save your engine because the link will usually pop off in a crash. Fail safe or any radio input won't help you there.
I can't see the head staying together at full throttle with no pitch and I wouldn't want to be anywhere around it while trying to bring it in!
It needs to be a light and linear coil spring around the throttle shaft like most autos have, not a screen-door tension spring pulling on the arm.
I got some springs from an old junked VCR that should work but have yet to get them rigged up.

Kirk

RE: throttle return spring ?
 

My OS 46 FX-H is set up this way as well. There is a spring in the carb that pulls it to full throttle.

Who's idea is this? On any model application this just seems dangerous. Be it a plank, a car or a heli. When the linkage comes off the engine should return to idle, at least IMHO.

I personally find this very unsafe, as the linkage is likely to break or come off during a crash.

Is it possible to modify the carb to take out this spring?

RE: throttle return spring ?
 

The spring is in there to keep the throttle barrel against the the guide pin as it rolls open. If it was removed, the barrel and low needle would float in and out making the engine lean and rich accordingly. The fact that this spring moves the throttle open on it's own is the nature of the beast but don't remove the spring.
This is why an external return spring is a good idea, but it must not interfere with the internal springs ability to keep the barrel out against the guide pin.
I believe this is one of the biggest reasons guys have problems with engine tuning-- because of an improperly set up throttle linkage.
If the servo linkage pushes the barrel in as it is rolled open or closed, it changes the mixture curve and the engine will never run consistently. It's not such an issue with helis as both ends usually have ball links so there is no side loading unless the canopy or something is rubbing the rod, but it is very important on an airplane where the rod usually rubs the firewall and can push in on the barrel if the rod isn't bent correctly.

Kirk