Understanding Control Horns

[Tom Strom]

Sometimes, the older I get, the less I understand.  I am having trouble setting up my new control system.  I often hear people talk about a one to one system.  Controls should be one to one.  What does that really mean?  I have a new airplane I am getting ready to put the flap horn on.  Full body enclosed system.  I have several issues.  Picture #1 will show flap and elevator control horns.  Elevator control horn has one hole, 1.11", or 28.20 mm, center of wire to center of hole.  Flap control horn has three holes.  Bottom hole is 0.755", or 19.19mm from center of wire to center bottom hole.  Middle hole is 0.98", or 24.98mm, and third hole, or top hole, is 1.177", or 29.90mm from center of wire to center of hole.  Which flap hole from bellcrank to flap, and which hole from flap to elevator.
My main issue is when I put my ball link on top hole from bellcrank, There is not enough room for use of the middle hole.  It is halfway covered by the ball link on one side, and the retaining nut on the other.  I tried to use the ball and socket that some use, (ball bolts to horn, and socket then attaches to ball) and the same issue.  Middle hole is covered.  And I know enough not to use the bottom hole.  Can I use the top hole on the flap horn to control flaps and elevator?  I have room inside fuse to attach both to top hole, just not sure about the geometry of the thing.  Sorry to be so long winded, but I am really confused.  Easy to do at my age.

Thanks in advance for not calling me what you are probably thinking.

Tom Sr.

[Steve Helmick]

Tom, you have email.   

[Dennis Toth]

Tom,
Steve may have sent you this information, if so I post this as general setup tip. With the ball links if you have the large 1/4 scale size you can put one on either side of the horn, second option is to use smaller ball link (2/56 size) and drill the end to take a 4/40 connector. Third option is to use just music wire from the bellcrank to the flap horn and ball links from the flaps to the elevator.

"One to one" refers to getting the same degree of deflection (say 35 deg) from both the flap and elevator. This is accomplished by setting the distance from the horn center of rotation (normally the wire) to be the same for both the flap and elevator horns (i.e. 5/8") on the flap to elevator pushrod connection. If you want more elevator deflection with less flap you use a hole that is higher on the flap and lower on the elevator (3/4" flap to 5/8" on the elevator.

Hope this helps.

Best,           DennisT

[Frank Imbriaco]

Check the Dubro  website. They have a smaller head design 4-40 thread ball link. I've used it in 2M R/C pattern applications so it is pretty robust. It uses a  smaller ,brass , semi-radiused ball that will still require washers on either side as insurance that it won't pop out. But, those washers can be smaller  in diameter which will help with your clearance problem.

Hope this helps.

[Frank Imbriaco]

Just checked. It's Dubro Cat. No. 2161   " 4-40 Ball Links with Hardware"  . Apparently, Tower doesn't stock them or they're out of production. I've had good response from Du-Bro when I contact them directly.
If they're discontinued, some hobby shop must have them as N.O.S.

Good Luck

[Steve Helmick]

Tom called this AM. I found that the subject build is a UHP Impact ARC...and he's not happy with any of it, due to many warped surfaces out of the box, including wing, stab, elevators and one flap. And he hasn't been able to get any response from UHP. Also said there was no instructions booklet to 'splain the details. It didn't take a lot of convincing to get him to order up new horns from Tom Morris, since he used Morris hardware in his eVector 40 ARC. The Impact is also going to be an electron burner.    Steve

[Chris Cox]

Tom

Looks like you are getting lots of help with your question.  My question to you is, where were you this weekend?  Your absence at the Portland Fireballs "Spring Tune-Up" was noticed.

[Doug Moon]

In that second picture where it shows the ball link is covering half the hole you can use a ball link stand off to get the clearance you need.
A ball link stand off is a small aluminum cone shaped washer that moves the ball link out away from the mounting surface it is up against.  I know when I ordered links from Tom Morris his always came with them.

1. 4/40 bolt through the top hole in the horn, and slide the stand off on the other side.  The side where eventually the ball link will be. You want the wider part cone down against the horn.
2. 4/40 bolt through the 2nd hole on the horn going the other direction. Slide on the ball link and tighten as normal.
3. Slide on ball link on the top 4/40 bolt and it should lay up against the stand off and clear the head of the bolt in the second hole. You would need to tighten the ball link on the lower hole before you add the ball link on the top hole as your wrench wont get in there once the upper link is in place.  A ball end wrench might get in there but I just tightened mine prior to the installation of the top one.

I have done this in the past and it worked just fine. I actually added a couple of #4 washers between the stand off and the horn just to make sure it would be clear.

The owner of UHP has been out of town, in his case that always means out of the country, for about 3 weeks now.  Should be back around soon. He should be able to help you if needed.

 

[Tom Strom]

Thanks for posting all the replies. 
Chris, mom had her hip replaced a week ago, and I do not want to go too far from her until she is a little more mobile.  She is doing very well.  Sometimes life gets in the way, but that's OK.
Doug, good advice.  I use the Hanger 9 4-40 ball links on all my customers airplanes as well as mine.  (R/C)  I have used the standoffs for years.  Just thought it might make the pivot point a little wobbly.  Also, I was told by someone else UHP owner is not always available, so thanks for the confirmation on that.  I will keep marching on, and see what happens.  Again, thanks to all who responded.

Tom Sr.