Servo modification to a screwjack

[Dave the Bucc pi]

Does anyone have a link to doing the this ? I want to use a screw jack system for a models flaps and u/c.

[bryguy17]

well, ive never heard of doing that in particular, but my best suggestion would be to go check out the driveshaft attachements that servocity.com sells. you can probably hack some threaded rod onto those adapters and just add the right sized nut. good luck with the project though

[Sparky Paul]

Don Incoll modified a servo to drive a screwjack for a 90 change in wing incidence on a VTOL.

[Dave the Bucc pi]

Cheers Paul, thats ideal.

[ps2727]

I've tinkered with such a device but haven't finished it yet. For heavy loads such as a landing gear I think I'll need thrust bearings which is what the assembly in the middle is all about. Much room for experimentation here. Glad to see others are thinking along these lines.
Don's solution is very nice.
Paul

[shanghai_fool]

I've been working on this same thing for over a year and still have the need for a screwjack servo. I used 1 like the above with a Fut 3001 on my VTOL but its too big and heavy. I'm looking for a smaller servo that has a complete gear on the output shaft. Most of the smaller ones only have gears halfway around.

Anybody taken apart any servos and got a look at the output shaft gear?

This thing has lots of applications besides retracts. i.e. folding wings on my Corsair, fowler flaps, almost anything where air is now used. The idea has plenty of torque and slow movement. Can be used with extrernal pot or microswitches.

So far, the only one I found is GWS Naro. Any others?

Donald


Donald

[Kyle D.]

What about something like this. An electric actuator thats programable for speed and delay.http://lado-tech.com/

[shanghai_fool]

What about something like this. An electric actuator thats programable for speed and delay.http://lado-tech.com/

I emailed them but never got an answer. I will try and call them when I get to the states.

They are pretty expensive but may be small enough to do the job.

[jeffsr01]

Why not use a long stroke air cylinder. I got mine from Robart. Used them for fowler type flap extension on a Top Flite Giant P-47 (No longer have it, sold to a friend). Use two pneumatic valves and lightweight servos for activation of the flaps. Worked great, and was not a money pit...

[shanghai_fool]

I did try the air cylinder but was unhappy with the action. The air cylinder is fine for loads that are constant but for movement where the load changes or there is ANY binding, it is jerky and unrealistic. It has to build up pressure to overcome the friction, then it jerks to equilibrium. The motor drives are fairly constant and easier to control the speed of actuation.

[jeffsr01]

I used a restrictor on the exhaust side of the cylinder, soo.. when was activated the piston was working against a buffer of air which prevented jerky, inertially driven motions, voila!! scale looking flap deployment. BTW, I used restrictors on the intake side as well so as to give scale movement to flap retractment. :) :D Your call my friend, you can search for the holy grail or wait for Uncle Fred to leave you a pot of $$$$$. You sound like you have engineering intuition. I always used the KISS principle. Simpler and less expensive..Best wishes for a successful solution.. :o BWT, a jackscrew mechanism can be made with an inexpensive motor,threaded rod,jackscrew nut, simple linkage and 2 limit switches, one for forward and one for back. Have to bre attached to a DPDT switch which is positioned by one servo which has enough torque to produce full movement of the switch.. :cool:

[awmeade]

Gents - try here : http://www.smservices.net/acatalog/Large_Model_Units.html
About 2/3rd of the way down there is a screw jack controller. You can then use any sort of electric motor you want with a suitable coupling to the screw. Just microswitches then to sort out on the limit of "up" and "down" or what have you.

Hope this helps.
Andy