Four-point elevons????? 1

[kitarusapien]

On my experimental tailless biplanar aircraft, I am getting ready to affix the elevators, drag rudders and ailerons with standard cabling and control stick, but not by choice! Now, initially, I wanted to make use of a computer-controlled/actuatored elevon system, just like on an R/C flying wing(except having four wings and thus four elevons; BTW, I have a six foot model of my ship using exactly that with a Futaba computer radio and four servos....works good, lasts long time), mixing the elevator action with the correct aileron action. Unfortunately, no one has been able/willing to show me how to do it on a 1500lb scale(something about power requirements, internal potentiometers for proper actuator control and speed of the actuators themselves), so my next stupid question is "Can it be done with cables and/or pushrods?" I built a vertical pyramid using pushrods to emulate what I thought was a pretty good "torque-tube-straight-to-the-stick" system, but with the wing bridges traveling through the fuselage, and the main gear tucking tight into the same area, I've hit a BIG snag, so I'm all ears........THANKS!!!!

 

[GregLocock]

Mechanical mixers were well known for RC planes in the seventies. I suggest you try and get hold of plans or mags showing delta winged models, or V tails.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[kitarusapien]

Been there, done that...they all have sliding servo trays which, at least to my eye, are not applicable to a scaled up, true mechanical version since my ship would not have servos. But, I'm still open to thoughts, if you'd like to eaborate further.

 

[GregLocock]

So replace the elevator sero with a pushrod, and the aileron servo with a pulley operated by a cable, and take the drive off via pushrods.

Having said that I'm sure some were based on bellcranks, not sliding elements.



Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[kitarusapien]

I wish I could find one of the bellcrank configs. I must be looking in the wrong places. I just keep finding the same sliding tray units. I will, however, try to rig up the method you just stated on my model......might work just peachy! Thanks!

 

[GregLocock]

It's a bellcrank on a bellcrank, as I remember

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[magnograil]

Greg has the right idea. Imagine two bellcranks side by side. One set of push/pull rods connects to the centre of each, the other connects to one end of each. The outputs are the opposite ends. Which input is elevator and which is aileron depends upon the throws available/required. If the middle points are elevator, they pivot about the lower aileron inputs giving an increase in output travel by the 2:1 length ratio. Holding the elevator points fixed and differentially moving the aileron (lower points) pivots the links about the elevator points giving a 1:1 ratio. The relative lengths are arbitrary. The whole system has to be supported by slider blocks on either the elevator or aileron pushrods.

 

[kitarusapien]

I'm working on that form on my model now, thank you.

 

[karlbamforth]

Try looking at flaperons, used on a lot of kitplanes such as the Kitfox etc.
A simple extension of range in the flap part of the system to give upward travel would change the system from flaperon to elevon. Obviously some redesign would be required but it should be a good starting point.
I believe that a number of these systems are pushrod operated.

Ranger

 

[gwolf]

kitarusapien,

I hate to piss on your bonfire but I thing that what you are attempting is really dangerous for a human flyable plane. Here are many reasons why I think this:

1) If it is a good idea to include mechanical mixing chanels on a plane then why don't we see any current examples? The trend is that you either control it using a simple mechanical system and use the pilot as the mixer, or you use a FADEC - it is one of the main differences between 20 year old Airbus and Boeing aircraft

2) Complex mechanisms mounted within flexible airframes JAM as Spaceship one found out nearly to their cost.

3) Even if you do what you percieve (and maybe is) a good job you will find it very hard to get an airworthyness certificate.

I suggest that you become a better pilot and enjoy learning yourself how to mix using your own mind and please keep the mechanisms simple and robust.

I don't usually post such negative comments but I really think you are about to kill yourself.

Kindest regards,

Gwolf.