Brass horn arms for 35 size ships

[Dennis Toth]

Guys,
Has anyone made control horns arms using K&S 5/64" x 3/16"  brass strip for the control arm brazed to steel wire? The brass seems strong enough for a small 35 size ship as long as a clevis type connector is used so there is no bending moment. Any down side to this?

Best,         DennisT

[Don Hutchinson AMA5402]

I have used the 1/16th by 1/4 K&S brass on every model I have built. I have never had a problem with them failing. Note: I use long horns so the bearing pressure is kept low. 1" for elevators and 1&1/4" for the flaps. The T-6 Joe Gilbert is flying was built that way and he says there are probably about 1000 flights on it and still going strong.

[Tim Wescott]

Brazing brass is a trick and a half, unless you're using low-temperature rod.  Regular brass melts at the same time as the rod -- I've never been able to get a non-ferrous metal to do anything for me but just turn liquid suddenly and dribble on the floor.

Assuming that you're using silver solder or sil-braze you should be OK, but I'm not so sure about the clevis idea.

[Randy Cuberly]

What is the perceived advantage of using brass over steel?  Given the brazing problems mentioned by Tim I fail to see any real advantage to using brass for the control horn.  I'm not saying it won't work, it is very likely strong enough if the horn levers are kept long as Don mentioned and the width of the horn arm (not the thickness) is kept wide enough to allow at least.080 inch from the edge of the part to the edge of the bearing hole ( the compressive strength of the brass is much less than steel).   I just don't see any real advantage to doing so!

Randy Cuberly

[Randy Cuberly]

The brass is easier to form than steel.

Not enough to make it a big advantage in my opinion.  If hand filing there is some advantage but not that much.  If milling there really is none.  There is really none in drilling.

Randy Cuberly

[Dennis Toth]

Randy,
I agree the steel would be the first choice if available. I asked about the Brass because it is readily available at the LHS. I have looked for the same size of strip steel, I can't find a source? If you know of one please let us know.

Don,
What did you use to attach the brass arm to the wire - silver braze or silver solder?


Best,       DennisT

[Allan Perret]

I have used the 1/16th by 1/4 K&S brass on every model I have built. I have never had a problem with them failing. Note: I use long horns so the bearing pressure is kept low. 1" for elevators and 1&1/4" for the flaps. The T-6 Joe Gilbert is flying was built that way and he says there are probably about 1000 flights on it and still going strong.

Hey Don:  What is your method of making the arm to wire connection ?

I don't get the "bearing pressure" comment.  For any given control surface deflection and load, the torque that is seen at the arm/wire connection would be the same, right ?   A longer arm would just mean there is less force on the pushrod..

[Dave_Trible]

Dennis Dubro packages these nickel plated steel straps #202 that are great for horn uprights and braze well.  I've used then for years on everything large and small.  Most any Dubro dealer should have them.

Dave

[Dennis Toth]

Dave,
Thanks for the info on Dubro, I just looked in my stock box and I have the strips you are referring to. Great tip.

Thanks,           DennisT

[Don Hutchinson AMA5402]

Allen- You got it, less pressure at the pushrod end. How do I attach the wire to the horn? I put a ~1/2' length of 1/8" sq. brass tubing on the 3/32 horn wire and solder it well with Stabrite solder. I drill a 1/8"hole in the horn and file it out square and a tight fit and Stabrite that joint too. Works for me, I know others will frown on such method but this way I can make all my own control parts exactly the way I want them, including my bellcranks.

[RogerGreene]

I use a BernzOmatic FAT BOY MAPP GAS and Lincoln Electric Flux Coated Bronze 3/32" rods to weld the brass horn to 1/8" wire for the control horn assembly. I haven't had a problem.

[Randy Cuberly]

Allen- You got it, less pressure at the pushrod end. How do I attach the wire to the horn? I put a ~1/2' length of 1/8" sq. brass tubing on the 3/32 horn wire and solder it well with Stabrite solder. I drill a 1/8"hole in the horn and file it out square and a tight fit and Stabrite that joint too. Works for me, I know others will frown on such method but this way I can make all my own control parts exactly the way I want them, including my bellcranks.

Actually Don, I think that' a great method if you must use brass.  Jim Hoffman from Phoenix used to make horns simisar to the for big airplanes.  Worked very well and no failures.  It does seem a little labor intensive though!

Randy Cuberly