[YellowBird]

Has anyone had a problem with digital servos breaking control horns?

I have a weird problem. My Midwest Extra was built using 6-32 bolts as control horns (as per plans). I flew that plane for the last 3 years or so with no problems at all.

This year, I switched from Hitec 605 servos to Hitec 5925 servos on ailerons and elevators. I run a 5945 on the rudder.

This year I have broken three control horns in the ailerons! It's like there are gremlins in the wing cutting these things off.

The first time it happened, I was getting ready to take off for the second or third flight of the day and noticed the left aileron drooping. The bolt was broken off where it exits the ply block.

I went home and fixed it with another bolt. Putting the plane into the truck the next time out, the new bolt was broken again!

I replaced both sides with new Dubro bolts. Yesterday, the bolt broke again. This time in flight. I brought it around and landed, put it away and sat down to contemplate the universe, conspiring against my aileron horns....

I'm going to replace all the bolts with Dubro HD T-Horns, but just wondering it anyone out there has any thoughts on this....

[ronm]

There has been a history of this problem. (Ask me how I know )
6/32 bolts are not sufficient for this size of airplane.
With the extra speed and instant torque of your new servos, the bolts cannot take the load to instantly overcome inertia. You need to change to stronger horns, the new Dubro style or Rocket City seem to be the favourites. I think Hanger 9 has a decent one as well now. (It may be the same as rocket city)

[craigk]

I plan on using the Dubro hardware on my BME Edge
these are 8-32 bolts with the adjustable base for both ailerons and elevators.
I plan on using Hitec 5645s all round, on 4.8 volts.

[YellowBird]

Thanks for the info.

I already have the Lg Dubro T-horns in hand, so I'll use those.

I mentioned my servos as 5925's earlier. They are actually 5625's.

Another interesting point is that the failures all happened on the ailerons. The same setup is used on the elevators and haven't become an issue. It would seem that the loads on the ailerons may be higher than on the elevators, based on my experiences.

I'm replacing it all anyway. Enough said...

Regards,

Jamie

[nony]

I bent an 8-32 with a JR 8411 a couple of years ago....

[YellowBird]

How'd that turn out? I would imagine bending a horn could be a lot worse than breaking it clean off, since once it lets go completely the other surface has a better chance of getting the plane down safely, that is if you have two of the same surface

One aileron went into flutter during the last flight. Constant flutter. And while one of the other guys thought the lower than usual frequency flutter sounded awesome, I'd rather not hear it at all.

The loose control rod and the piece of broken bolt dangling from it did a nice job of punching some nasty dents into the underside of the aileron and TE too.

Hopefully the HD Dubro T Horns will not have these problems...

Regards,

Jamie

[nony]

It was a gradual bend...maybe 10 degrees or so, nothing that couldn't be trimmed out...it was the control horn for the canards on a super reaper jet...(no a fast jet by any means..)