Hey all

I'm assembling a Brodak (plastic 4 inch) bellcrank with .027 steel leadout cable.  This is the first time I have attempted to run the cable through an annealed 1/16 brass tube.  I can't get the cable  to go through the .035 hole.  What is the trick?  Or do you go up to 3/32 size tube?

Also, regarding wrapping, once through the tube and in place, is it a simple single wrap about a 1/2 inch long and then a small amount of epoxy on it?

I have searched and not found exactly what I'm asking here.

Thanks!

David     

That works OK for.  Maybe you need to de-burr the hole with a #11 blade and get a good clean cut on the .027 7-strand cable.

Once the brass tube is bent into the horse shoe shape it is almost enough to secure the cable all by itself.  For sure, it does a good job of minimizing stress on the wrapping and solder/ crimped termination.

Do you use cable cutters or simple wire cutters?  If wire cutters are a bit dull they will flatten the cut and make it too large to fit.  A drop of CA on the ends will hold the strands together and you can sand/file it smooth. As to the wrapping AFTER you bend the loop I just bend it over like a normal eyelet and lightly wrap. Then shrink wrap the joint.

Ken

 A single wrap as you described is asking for trouble. It's either lazy, ignorant of proper procedures, or foolish.

 After doing your first wrap, fold the tag end of the leadout wire back towards the bellcrank, and wrap the fine wire back towards the bellcrank. Wrap up to the end of the brass tubing. give it a pull test before you install it, then cover it with shrink tubing. In the AMA Control Line General rules, this is shown in figure #3. To go back with the second wrap only takes a minute or two. Fixing your crashed airplane when the leadout lets loose will take a bit longer. A very experienced local modeler, who is no longer with us, had this happen more than once, because he didn't think the second wrap was necessary or worth the trouble.

Thank all three of you.  I appreciate it.

My cutting technique was the problem regarding getting the .027 cable thru the hole.  That's resolved.

Bill - thanks - I will double wrap as you described.

I'm glad you asked when you didn't know. Kinda' why we're all here. 

I believe you have to drill the holes in the belcrank slightly bigger too or at least champher the holes. You don't want any binding there. If you double wrap it, like you should as Bill suggests, there's no need for glue or heat shrink tubing. There's a certain size drill shank you can use to bend the tubing after the wire is in place. I'll have to check my notes.

MM

Quote from: Motorman on June 25, 2026, 03:09:05 PMI believe you have to drill the holes in the belcrank slightly bigger too or at least champher the holes. You don't want any binding there. If you double wrap it, like you should as Bill suggests, there's no need for glue or heat shrink tubing. There's a certain size drill shank you can use to bend the tubing after the wire is in place. I'll have to check my notes.

MM

Good points about the drill shank and camper.  The bend is done BEFORE putting it into the bellcrank holes.  He is tight the shrink wrap is unnecessary for strength. I use it to keep everything in place.

Ken

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The leadouts on the bellcrank end turned out good. 

Now I need advice on which control horns to use in both the flaps and elevator.  I suspect most of you fabricate your own, but I would like to buy off the shelf if possible.  Plans show a 3"x 1/8 on flaps.  Only one I can find is a Brodak that has the upright tilted forward (differential) Thoughts on this? I'm concerned about hole placement not being correct.

Plans show elevator to be a 2 1/2 x 3/32. Brodak has one of these and it has 3 adjustment holes.  Go for it?

Also, what about going 3/32 on flap horn to make it easier to tweak?

Thank you in advance for your response.

David