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Alternative servo linkage

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Roy Hill 311/09/2019 20:49:47
138 forum posts
97 photos

Here I am asking for advice twice in one day! Many moons ago, RCM&E published a thread on an alternative method of connecting the servo to the control surface entirely within the wing. It operated on removing the arm from the servo and replacing it with a 'top hat' which, via a threaded rod, moved the control surface in a sliding tube in the control surface. I have tried all day, without success, to find it. Can some-one help before I start to beat my sorry head against the wall? Roy.

Denis Watkins11/09/2019 21:01:34
4055 forum posts
75 photos

Spangenberg Roy, is an alternative

But threaded servo blocks are still sold



Edited By Denis Watkins on 11/09/2019 21:03:44

Chris Bott - Moderator11/09/2019 21:49:23
6707 forum posts
1392 photos
1 articles

Try this thread for some pointers to info on RDS (Rotary Drive System)

Foxfan11/09/2019 22:43:27
883 forum posts
7 photos

That is in some ways very much like a system I invented for VW to drive a Palm computer out of a Passat's dashboard. They wanted "slow start, slow finish"..."technics" as they liked to call it, but in the position of control surface drive it gives an automatic exponential as the surface will start to move slowly and then speed up, then slow down again, simply by virtue of the geometry of the linkage. I got the grand title of "designated designer" for the VW patent, but not a penny piece in royalties as they said it was too expensive to make<G>

But I like the use of a similar action in a wing.


Doc Marten11/09/2019 22:56:10
396 forum posts
4 photos

RDS is way the scale guys do it. It takes up no more space than the thickness of the servo and is a direct drive system so delivers plenty of torque, it has to be set up accurately though, with the bend right on the hinge line.

Edited By Doc Marten on 11/09/2019 22:56:41

Martin Harris11/09/2019 23:03:35
9084 forum posts
224 photos

I came up with this solution as a retro fit when it became apparent that my Tony Nijhuis Hawk would need tail weight. It drives the rudder (normally fixed) from below. It's worked well with little or no slop but I don't know that I would recommend it as an aileron or elevator system without a bit more engineering. It might give food for thought?


Roy Hill 312/09/2019 08:46:00
138 forum posts
97 photos

Thank you all very much for the rapid response. I knew that somewhere out there, some-one would know the answer. Chris Bottt, moderator supremo, pointed out the one which I was trying to find. RDS will work just fine, Thank you!

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