View Full Version : Please help with retract servo setup

10-11-2006, 02:39 PM
Hereís the question. How do you change the limits on a ĎRetractí 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, itís too much travel. Iíve never set up retracts before. Would using a bell crank with different ratios on the input & output levers work? Thanks for any help.

flypaper 2
10-11-2006, 11:54 PM
Is this a true retract servo, or do you want to retract them with a regular servo?

10-12-2006, 05:54 AM
flypaper 2,
They're 'Retract' servos. What I've been able to find out, and please educate me if I'm in error, is that these type of servos have a set amount of travel that is not adjustable. It's usually around 170deg stop to stop. They're being used on a P-38, so 1 servo per retract. TIA for any tips or comments.

flypaper 2
10-12-2006, 09:40 AM
Your right Rick. They go the full 180 degrees with no stoping in between. They also shut off the driving electronics at the end so there is no electrical drain. Measure the mechanical stroke of the retract mechanism from lock to lock. It may be ,say, 1 in. Measure half that distance from the centre of the servo wheel or arm out and drill a hole for the pushrod, in this case 1/2 in. Now that hole will travel the 1 in. when it does 180 degrees. Hope this makes sense. I use a Z bend at the servo end and an adjustable link at the retract end for fine tuning.