Throttle and Servo Travel

On 12/27/2004 9:31 AM Ted shuffled out of his cave and grunted these great (and sometimes not so great) words of knowledge:

There are a couple of ways to go at this. The first way is with the servo arm. Adjust the point where the throttle control rod contacts the servo arm. Sometimes using a blank "wheel" and drilling your own hole is the solution for this. Also, don't forget that you have 2 locations on the throttle arm on the engine also.

The second way. If you can not get what you want/need after manually adjusting the control rod, use the "End Point Adjustment" in the transmitter itself. Just make sure you are on the correct model and don't forget to save the setting. You can go as much as 110% if needed (not recommended though ).

Too much travel. Move the control rod closer to the center on the servo or further out on the throttle arm. I usually set the radio at half then manually adjust the rod until the throttle is half open. Then see how it does at the ends. Too much travel, in on the servo or out on the throttle arm. Too little travel, out on the servo or in on the throttle arm. Get it as close as you can without using the endpoint adjustments on the radio. Then use the radio to get it just right.

John VB

Now I love computers as much as anyone, but they are not the foundation for a control system, they enhance it. You still need to do the mechanical linkage setup properly for the initial flights, to preserve servo resolution and to limit slop. I would also respectfully submit that if you have a computer radio and do have to compensate for a particular plane that you should readjust your linkages at the first convenience to minimize the amount of computer compensating you have to do.

It seems to work for me. Of course, I assume that some day the computer will crash because it was probably designed on a messydog system.

Walt:

This is the system that I have used many times in the past. It is a variant of calibrating pressure instrumentation:

1) Disconnect throttle cable at engine and at servo 2) Set carb to 50% open. By this I mean look at the notch in the carb barrel and set this to 1/2 throttle. 3) Loosen throttle arm (horn) and position so that arm is at 90 deg to crankcase mounting lug. If you were to look at the engine from the side with the motor upright the arm would be straight "up-and-down" i.e. 90 deg to the crankcase mounting lug 4) Set transmitter throttle to 50% and set trim to 50% 5) With transmitter and receiver turned on, manually set the throttle servo arm so that it is at 90 deg to the servo case. Do this by removing the servo arm screw and re-positioning the servo arm. This may not exactly be at 90 deg due to the location of the splines on the output shaft, but get it as close as possible. 6) Double check above steps. 7) Attach throttle cable 8) Adjust length of throttle cable/connectors so that throttle is 50% open with transmitter at 50%, the throttle cable will be close to 90 deg at the servo arm and throttle arm. 9) Now follow transmitter instructions for end point adjustments for throttle.

The key here is to have everything as close as possible to 90 deg at the

50% position.

Walt, I do my basic setup as "stearman" outlined. I do not change the end point adjustment in the transmitter, I leave it at 100% Instead I use a Rocket City (Nelson Products) adjustable servo arm for the applicable brand servo you are using. By adjusting the length of the servo arm you can mechanically adjust the throttle arm travel. This way you do not have to worry about the end point setting being accidently changed.

It has worked well for me for several years.

Thom