Please help with retract servo setup.
 

Here’s the question. How do you change the limits on a ‘Retract’ servo? I have 3 HS-75s and the travel is too much for the retract lever. The end point adjustment on my JR6000 Tx does nothing to limit the travel. I know the EPA is working because if I connect a HS-81 to the same channel, I can limit its motion. Even if I connect to the inner-most hole on the servo wheel, it’s too much travel. I’ve never set up retracts before. Would using a bell crank with different ratios on the input & output levers work? Thanks for any help.
Rick

RE: Please help with retract servo setup.
 

I've setup a few with the same problem you are faced with, In hope I can explain how I fix this problem.

I do not know how to change the limits of a retract servo, but here's how I have fixed the problem. I use the small round servo wheel to start with since most retract servos turn a little more than that 180 +/- degrees if I'm correct.

I start with the conection to the servo at say 9&3 o'clock, in line with the retract arm, and if this is not enough move them to to 10 & 4 o'clock and let the connecting rods turn over each other when the servo is cylced. I hope I explained this and I hope it helps.

Flyrcs

RE: Please help with retract servo setup.
 

I agree with Flyrcs.

Basically, what he is saying is that the retract swing must be controlled mechanically, not electrically, when using a retract servo.

In addition to his technique for changing the servo arm position, you can often change the retract swing moment. If you can access the elbow section of the retract, there is usually a linkage hole choice that can be changed to increase or decrease the throw range.

Good luck!

RE: Please help with retract servo setup.
 

Thank you for your replies. They are a big help. I should have given some more info, as the retracts are going on a P-38, 1 servo per retract, so having to deal with two pushrods on 1 servo is eliminated. I think I need to reposition the servo to be more inline with the pushrod. Then I can apply some of your techniques for determining the amount of travel needed. Any other tips or comments are greatly appreciated. Thanks again.
Rick

RE: Please help with retract servo setup.
 

Rick which P38?
You know there are small air systems out there if it's one of the smaller Lightnings, only need one servo total to operate all three retracts. Air up and spring down, so if there is a malfunciton the gear automaticly drops. I've used the GP10's retrofitted to air in my PZ Mustang, and some other small units from SouthEast models in my 52" P38.
Oh one other thing, nose gear takes a pounding unless you fly off pavement, make sure it beefed up enough to handle it.

RE: Please help with retract servo setup.
 

GG,
Thanks for the info. The P-38 is the Raidentech 52". It's actually my bro-in-laws, but we're both going to school on this one as it's the first with retracts. My bro-in-law doesn't have access to a computer so I'm the link to these forums. Everyone has been very helpful! Thank you all. He has said a few times that maybe an air system would be the way to go. You mentioned some smaller systems. I'll check them out. Might eliminate a bunch of headaches. There's not a lot of room for all of these servos. Also, which do you think would weigh more, a small air system or the mechanical 3 servo system? The HS-75s are a bit porky. Thanks!
RICk

RE: Please help with retract servo setup.
 

i need a little help, does anybody know if you can use a y connector to connect two retract servos for a tricycle mechanical retracts. so that all three gears will work at the same time. i would like to use one channel for the retracts. any help would be appreciated.

RE: Please help with retract servo setup.
 

Max - Yes that should work fine.