I built a Sig Kadet way back when I was 15. Finally, while flying it in low clouds, and high winds, I lost it, never to be seen again.

Well, I now own several airplanes. I have:

1.) Great Planes PT - 40
2.) Avistar
3.) Some other kind of 3 channel trainer. I don't know what name.
And,

I bought several other planes, that others had crashed. I got them for parts.

AND

the one item in common, is that the throttle servo was hooked up direct! No springs!

On my kadet, I put springs on the push rod that worked the throttle. This kept the servo from running continously, when at full throttle, or idle.

WHY do so many R/C ers not realize that a throttle servo, running, and with the throttle arm on the carburator bottomed out, will cause the airborn pack to discharge needlessly fast, and it is not good for the servo! Besides, in a crash, it is more prone to strip out the gears, if it is bottomed out already!

My question is WHY is this issue mostly neglected? Is there something I don't know, and have left out of my equasion?

Thank you!

Nate

Nate While servo savers are popular with RC cars, the majority of airplanes seldom use them anymore simply because they are not needed with modern radios. You see even the simple entry computer radios today all have near infinate end point adjustment and there is no excuse to have a stalled throttle servo open or closed.

John

Natertater, you are not setting up the mechanical portion correct if the servo is being jammed. You need to properly attach the pushrod on both ends. If the throttle is trying to move beyond it mechanical limits, cut the throw by moving the attach point on the throttle farther out or move the attach point of the push rod on the servo inward; just the opposite if you need more throw. Fortuneately, most modern transmitters also have a way of adjusting the servo throw from one extreem to the other called "end point adjustment" or "ATV" or some other conotation depending on brand of transmitter. In most cases, using the spring to control over ride is not the best way to do it.

Nate,
If you set up your endpoints properly there is no binding of the servo,or drain on the battery.

Are you saying that there is enough give and play in the rubber servo mounts, and the linkage to allow for any minor deviation in end points of throttle arm? And, by careful adjustment of trim, there should be no problem?

Somehow, it just seams that there needs to be some kind of fuse in the linkage between the throttle arm, and the servo motor. Relying on PRECISE adjustment appears to be your answer. Even some change in the idle adjustment could affect this.

Thanks for all your responses. And, I want to get a plane ready to fly!

On one of these planes I put some fuel line on the throttle rod, and drilled out the hole it goes in, so that the rubber fuel line acted as a spring. I have seen an airplane that probably had NEVER run at full throttle, because the person that set it up never realized that it was confugured (sic) wrong!

Nate

Hi!
No, No ! you must have missunderstood the whole thing...the throttle servo must be set up so that it doesn't push against the throttle more than is necessary, that means the throw of the servo must be adjusted properly. This is easy with todays servos as end point adjustment is done electronicaly. Even before modern computer transmitters came along it was easy...you just matched the right lenght of the servo arm to the right lenght on of the throttle arm so that the throttle opened and closed precisely the way you wanted. No spring is needed!
Regards!
Jan K
Sweden

OK, but I don't seem to be able to adjust the throw, electronicly, on the older radio set. I can change the holes, to get it close, but it still seems too, (how shall I say it) prone to leaving the servo running.

I have been to a local (40 miles away) flying field, where the throttle servo probably runs when it is set at idle, on 10% or more of the planes!

What do you think of bending the throttle rod, perpendicular, go 1", then 180", and back down, to place a "springy" place in the throttle rod?

This would tend to leave throttle response crisp, but also allow just a little give. Then I could use the servo holes, and throttle arm holes on the motor to adjust it JUST right.

Does this sound good?

This would possibly be just right for cushioning in event of an un-planned earth attacking event!

I'm not prone to crashing, but there are always things that go wrong!

Do you also use NmHydride batteries in the TX & RX?

I like them in other applications.

Nate

If you can't find a throttle servo arm with holes at a radius that takes care of your problem and provides precise nonbinding endpoints.... drill a hole at that radius, in an existing servo arm.

Good luck,
Dave Olson