Help! I may be out of control!

Started by Wingnutz, October 25, 2012, 09:10:52 AM

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Wingnutz

Attached pics show aileron control horn and linkage on an HK ARF which I'm working on. #127 tries to show how the pushrod is way off 90 deg to hinge line. #128 tries to show how a line extended through the holes in the control horn misses the hinge line by 1/4-3/8". (all four horns on this model)
I've googled control horn geometry but am still not sure if the geometryshown is my pics is cause for alarm and a possible remounting of horns and shortening of pushrods.
BTW, with both ailerons y-harnessed to one channel of my Orange rX, the receiver browns out. (Doesn't happen with either aileron alone) With the ailerons connected to separate channels, no problems.
Any advice appreciated.
DOWN WITH GRAVITY! UP WITH LEVITY!

Papa

I think it may be built in differential, less down than up??

Jack.
A motto to live by:
"What other people think of me is none of my business"

Ededge2002

if you angled the servo horn on the servo you could re gain some of the travel...  that and a little radio adjustment and no one would know the horns were put on by a 6year old.   

  do it like this i think...     servo horn  /_____\ surface horn  that should fix some of it then use the end points to get equal travel.
Yea 400W/lb should about do it.. But wouldn't a nice round 500 be better?

gordonbw

If you simply move the pushrod z-bend to the opposite side of the servo horn, the angle of your pushrod should be pretty close to 90 degrees to hinge line.  :P

Wingnutz

Gordon,
Did as you suggested and the pushrod is closer to 90 deg. to the hinge line.  Also managed to solve the brownout problem with a(nother)new ESC. Kind of cuts into the savings of buying HK! I'll see if they respond to a "replacement request" (chuckle)
DOWN WITH GRAVITY! UP WITH LEVITY!

Ededge2002

The troubles with the hinge line and the pivot of the pushrod?
Yea 400W/lb should about do it.. But wouldn't a nice round 500 be better?

Wingnutz

Jack, I like your explanation about differential. However, to my eye, and confirmed by measurement the opposite is happening and there's more down movement than up which makes no sense to me.
Ed, Perhaps I'm worried about non-problems but I'd be more comfortable if the push-rod made a right angle with the hinge line. This doesn't happen on the ailerons on this model but does on the elevator and rudder...and on almost every other model I own. I'm concerned if the pushrod doesn't meet the hinge line at 90 deg, push-rod,control horn and servo arm will bind as the servo moves them.
Also, when the pushrod is located in the outermost hole of the control horn, control horn length is noticeably longer than the servo arm length...seems to me this will cause binding too?
Thanks to you both for trying to get me under control.
Regardless of my paranoia about the aileron geometry, putting a different ESC in the model solved the problem. I'm now negotiating with HK for a replacement ESC. I am not holding my breath.
DOWN WITH GRAVITY! UP WITH LEVITY!

Ededge2002

#7
Im sorry if I came off incorrectly.  What im trying to say is that the surface horn connection is far behind the hinge line and this will give you the differential your experiencing.   tilting the horn on the servo the same degree away will eliminate some of the troubles.  Having more down travel is not a good thing.  It can lead to stalls of that wing along with increased roll coupling.
Yea 400W/lb should about do it.. But wouldn't a nice round 500 be better?