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Building Tips and technical articles. => Building techniques => Topic started by: Tim Wescott on April 20, 2011, 11:50:08 AM
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Has someone put together a page of line attachment methods for control line? I know of:
- "When we were kids", "plain ol'", etc. -- i.e. just loop the leadouts through the bell crank and have at it. It works well for beginners because the plane will crash long before anything wears out.
- "Brickhaus's Doghouse" -- brass tubing over the leadout loops, protecting the leadouts from the B.C., and the B.C. from the leadouts
- The two-layer bellcrank thingie, where you have two thin sheets of hard stuff (aluminum is what I've seen) sandwiching end-grain balsa or other soft, light material. The leadouts get little teardrop-shaped bushings that ride on 4-40 or similar sized bolts that go through the hard stuff.
- "Button" style -- I know about this from glancing in the rule books, but couldn't sketch one if my life depended on it.
Are there others? The middle two ones both seem to depend on keeping the leadouts stationary with respect to a bushing, which then provides a nice bearing surface for the bellcrank (or pin). They both look like great trades for work committed vs. longevity gained. The 'button' style is used by combat fliers who don't use leadouts, per se, at all. The "plain ol'" style is a good way to get a plane in the air quickly, and to save money on materials costs in kits.
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Tim,
I use a method similar to the Brett Superbellcrank. I lay up a carbon fiber bellcrank with a sort of horseshoe sort of end on them. The I make up the teardrop shaped ends out of PC board and use a 4/40 shoulder bolt through the bellcrank.
I've also used a more, ah, robust method. I machined some aluminum horseshoes, ran the leadouts into the end and secured them in closed loop pull through method with a bobbin in the middle sort of like a guitar string end. Then the forks went over the thinner, solid bellcrank with a 4-40 shoulder bolt through the forks and bellcrank. Worked extremely well, but it was a lot of work to make the end pieces so I went to my current setup.
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Randy:
Got pictures?
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Tim,
At home somewhere. I scout around later.
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Tim,
At home somewhere. I scout around later.
Well, hurry up about it. We're all waiting.
The last few planes I built all used a bellcrank/leadout setup from Tom Morris products. Leadouts go through brass tubing then the tubes get bent through the BC in a "U". I guess it's close to the Brickhaus style. Looks pretty bulletproof to me.
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hey, I had to find it. I don't have a pic of the second type (a victim of a previous hard drive crash).
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Oddly, the NoblARFs have a rather cute little wire dingus that connects the BC to the LO's. It could be easily improved...and who knows about the quality of the materials they used? What I envisioned (before the NoblARFs hit the market) was 1/16" wire with a pigtail aimed toward the LO guide. An eyelet and copper wire would fix the "clip" and LO into a unit. This would prevent flexing of the cable and prevent the clip from hanging up on ribs and stuff.
H^^ Steve
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Randy...I must say ( a picture is worth a thousand words ) .... NICE WORKMANSHIP ON THAT WING !!!!!
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Randy,
Fantastic wing structure and craftsmanship! The way I build, I would have started that wing ~5-6 times...after being stumped on j1. When it comes to finesse, I am an elephant in a Yadro shop HB~> That is why combat is so easy to me. Line up 10-15 planes and build. Don't have to be pretty. But I droll when I see you guys and your masterpieces. Makes me want to do the challenge more so than Combat ( no creativity, just flying) Kudos BW@
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For info on button attachment, go to my post in Carrier about attaching lines to bellcranks. No reason you couldn't do the same thing with leadouts..
Bill Bischoff
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hi Tim,
It seems that most either use a method like Tom Morris, or like Brett's. The most I have seen were the "Morris" type. It is sufficient for anything that will last say, oh, 200 years...........
Solid .032 run through the nylon bellcranks do not wear after about 500 flights. (that's the most I personally know of). There was absolutely no evidence of either wearing at that point.
The major problem was in the old unbushed Perfect, Veco, Fox, and early Brodak bellcranks where stranded wire was run through them. The wire would either saw through the aluminum, or the aluminum edge would wear the strands, either way causing a catastrophic failure. The new molded BCs have almost eliminated that, and running stranded wires through the brass does eliminate it.
The problem these days is terminations causing stress risers which fatigue and break the wire.
Big Bear