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Dual elevator servos?

Old 01-11-2015, 04:02 PM
  #101  
Lucky Dog
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Originally Posted by radfordc
You seem to be saying that dual servos only work if they're mounted at the tail? Mount your servos at the front of the plane and run the pull/pull cables back to the tail. One servo driving the left elevator and the other driving the right.
Exactly. On a split elevator, it's easy to set-up. A full flying elevator (like on a scale Eindecker), a bit more of a challenge.
Old 01-11-2015, 04:07 PM
  #102  
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Originally Posted by radfordc
You seem to be saying that dual servos only work if they're mounted at the tail? Mount your servos at the front of the plane and run the pull/pull cables back to the tail. One servo driving the left elevator and the other driving the right.
You're right that I hadn't thought of mounting dual elevators up front (with dual cable systems). That could, indeed, be a handy solution on some WWI models, for example, on types that had an external control horn in the front, like the DH1a.
Old 01-11-2015, 04:10 PM
  #103  
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Stegl, it's also interesting to see your servos mounted in the stab halves themselves. Never seen that before. I suppose on most models adding weight in that location makes that impractical.
Old 01-11-2015, 04:14 PM
  #104  
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Originally Posted by Lucky Dog
A full flying elevator (like on a scale Eindecker), a bit more of a challenge.
Not least of which because you'd have to cut the central "spar" in half so that each half could rotating independently. I have to admit that idea raises my scale hackles.
Old 01-11-2015, 04:39 PM
  #105  
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I put dual elevator servos in my Super Scout. Just used a Y harness on them and used the opposite side of a control horn on one side. Only thing you have to watch out for is that the angle of the control linkage rod is such that the travel will be the same on both sides, although I doubt a mm of difference would be cause for concern. Keep it simple!
Old 01-11-2015, 07:09 PM
  #106  
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Here is a way to have the redundancy of dual servos while driving only one link to the tail.
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Old 01-11-2015, 07:52 PM
  #107  
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Reminds me of the old mechanical v-tail and elevon mixers.
Old 01-12-2015, 12:35 AM
  #108  
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Originally Posted by abufletcher
Stegl, it's also interesting to see your servos mounted in the stab halves themselves. Never seen that before. I suppose on most models adding weight in that location makes that impractical.
By using the right servo with low weight this is very practical. The cost was higher but by running each servo wire into a separate receiver port kinda makes for a bit of redundancy in case one should pack it in. Not that I was concerned in that area as the servos used are pretty high quality. Application outweighs the cost for me.
The took the weight of the added weight in the tail and subtracted the weight of a metal cross link and a pushrod and added weight was not a whole lot more...

Last edited by stegl; 01-12-2015 at 12:42 AM.
Old 01-16-2015, 09:14 AM
  #109  
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Originally Posted by radfordc
Here is a way to have the redundancy of dual servos while driving only one link to the tail.
I may be wrong, but if one servo stalls, it's not going to help correct?
Old 01-16-2015, 09:54 AM
  #110  
radfordc
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Depends on where the failed servo stops. If it stops a center the other servo will provide about 1/2 the normal control movement. If it stops at the end of its travel the other servo can only counteract the problem by maintaining the control surface in it's neutral position.
Old 01-16-2015, 01:21 PM
  #111  
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I guess we could put it this way..... if using only one servo you are totally hooped; if using two independent servos you may only be half hooped or you may have a chance that survival may work and if we look at all the negatives then better to hang up our hobby and spend all our time on the internet with all our what-if's ....
Old 01-16-2015, 01:26 PM
  #112  
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Depends on where the failed servo stops. If it stops a center the other servo will provide about 1/2 the normal control movement. If it stops at the end of its travel the other servo can only counteract the problem by maintaining the control surface in it's neutral position.
And, that's what counts!

Servos rarely fail anyway but when I had an aileron servo fail on a dual servo setup it was enough to save the model.
It took full opposite aileron on the good servo to maintain control & get the model safely down.

Radfordc's linkage method results in reduced movement evenly to both elevators. One drawback of dual servo to elevator
halves is unwanted roll when one fails, not too big a problem with many models but a real problem on some. - John.
Old 12-08-2023, 10:23 AM
  #113  
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Just thought I would get someone to help me with setting up 4 aileron servos on a biplane. I do not want to use Y's. I am using an Airtronics SD-10G transmitter. I tried to use the "Procedure to obtain DUAL AILERONS in each wing of a BIPLANE" originally written by Jack R Albrecht, Airtronics Technical Su[pport and revised on 29 June 2010. Everything Jack wrote about this procedure worked up to the point of activating the Snap Roll Function. At that point, only the lower wing aileron servos worked while performing a snap roll. I have tried just about everything I know to do to get ALL 4 wing servos to activate in the performance of a snap roll and so far have not been successful. Failing to get helpful information, my next step will be to use 2 Smart-Fly Equalizer II units. Any suggestions would be appreciated. Thanks in advance.

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