Well, I guess I'm the odd man out here. You guys can make this all about ProStunt if you want to, but for an "early in your career, and actual young builder of the model" it is better to get the thing built in a workman-like manner and maybe start another one with what you learn from the first.
1. There's no real need to upgrade the bellcrank to maximus Zootness. The SIG piece works. Just get the control ratios right.
2. Properly made stranded leadouts going thru a nylon bellcrank is plenty good for a thousand flights. That's right, bare cable on chamfered, rounded holes in the nylon. It is already a low friction combination. I have yet to see a nylon bellcrank damaged by this method. We are not talking about a 65 oz. plane here with a BullRoarer .60 on it. Terminate the leadouts to the bellcrank in much the same way the rulebook says to terminate the ends of your flying lines. Just use a single loop thru the bellcrank. The loop in the wire should be made by gently wrapping it around an appropriate-size dowel or rod. Make it a teardrop shape. Wrap with fine copper wire, not heavy gauge stuff. (I use 32 to 36AWG and it works well. Coat the copper wire with epoxy. Keep it off the leadout wires! All of this minimizes the fatigue flexing and concentrated bending, so the cable with handle it. Never grab the leadout wire (or lines for that matter) with pliers. That's going to cause damage where a failure may now occur. Don't make it complicated, just pay attention to craftsmanship.
3. The plastic horns out there seem to work fine for your basic "40-sized" planes. One method that works well is to take the left/right pair that DuBro(?) sells and use them back-to-back. See the picture attached. Other methods also work.
4. I wouldn't use a clevis, but that's me. And certainly don't use the threaded brass coupler shaft that you solder onto a wire pushrod. That's going to be short-lived. If you decide that it will be a clevis on this one, use the long pre-thread end rods in the hobby rack. They come in lots of lengths. All that said about not preferring the hobby clevisis for control line models, I've used a lot of them on control line racing planes, and within certain limits, they work. And quite a few on "up to .40-size stunt planes." Those are not expected to be the most reliable, but in most cases, that is how the plane was set up when I got it. The best of the breed in my opinion are the Sullivan gold ones with the 4-40 threads. I wouldn't use the smaller threaded ones on anything but a half-A, and on those, I still use the 4-40s.
5. It is really important that the control system is absolutely free. This means that things must line up, be the right angles. no dragging on planking, no dragging on plywood bellcrank mounts. Take as much time and mocking things up as you need to to get there.
6. There's nothing wrong with a 3/32 music wire pushrod on a plane like this. But you will need a pushrod guide in the middle of the flap-to-elevator pushrod. If you look at the geometry, you will see that while each end of the pushrod translates up and down as these move in an arc about the hinges, the center of the pushrod will hardly move up and down at all. That's the sweet spot. Use a large cotter pin that is a loose slip fit to the pushrod. Clip the ends to shorten it. Mark your center point and drill a close-fit hole in the fuselage. A drop of CyA and you're done. Or use epoxy if you got a loose fit when you drilled the hole. Just be sure you degrease the cotter pin with either. No carbon tube needed.
7. Make sure your flap pushrod termination does not interfere with your elevator pushrod termination on the flap horn. Several times I have thought I got just the right geometry, only to find out that the pushrods interfered at the flap horn before I got to my desired travel limits.
8. If you want 1:1 controls, that means that the horn holes used must be the same on both the elevator and the flaps. You want less flaps, then move in on the elevator horn, and vice-versa. The hole that the bellcrank-to-flap pushrod goes into has nothing to do with this. That said, the farther out on the flap horn that the flap pushrod goes, the lower the loads in it, the lower the wear, and most importantly here the less angular slop in the controls for the given fits of pushrod diameter and horn holes. Start with the tightest fit that is absolutely free.
9. If you want to use rod ends they work, but you may have some trouble keeping them tight and trouble-free if you use plastic horns. Big washers help. Don't just put the big wrench to it and crush the plastic. That is going to make things (much) less reliable. In the example picture of my PTwainer, a PT-19 treatment of the Twister, I made a simple aluminum sheet elevator horn. I use red LocTite on the screw threads on the pivot screw. I do the same on the pivot ball if you go with the "hooded" ball ends.
10. I would avoid the old "truism" that the control system needs "slop" to stop hunting. You can go read endless posts about this, but quite honestly, I have tried this on two hunters and it didn't help at all. Getting the rubbing out of the system when the leadouts were under tension fixed one plane; the other one has resisted all efforts to date. It may need a new stab to fix it.
Of course, if the weather outside is unflyable, and the plane is the immediate precursor to a ProStunt SouperZoot--well, use both hands to grab, then shake your wallet and have a ball. It is a hobby of experimentation. Just don't believe that titanium pushrod ends in a carbon fiber tube will make you fly better. Not really. Just like a thousand-dollar tennis racket would ever make me a tournament winner....
If the build crew already knows all this, then my apologies for not asking questions before running my mouth keyboard.....
Best of luck and have fun building!
Dave
Topic: Need Help on Pushrod Hardware (Read 2996 times)