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Building Tips and technical articles. => Building techniques => Topic started by: Leester on June 12, 2006, 02:43:32 PM
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Being a little gun shy I thought I'd run this by the Hangar crew first. I am putting in a suspended bell crank, my mounts are as pictured. They span the center four ribs with the straight side up against the spars. Each rib is notched to accept the mounts at 1/8" depth where shown on the mount. I will epoxy the mount to each rib and the spar. Do I need anymore support? Of course there is sheeting covering the center section. Thanks
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That will work just fine! Also add a piece of 1/16 plywood 1X1 inch (Epoxy) top and bottom of sheeting after sheeting is on the wing. It captures it. I always solder a washer on top and bottom of the 1/8 wire.
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and NEVER use JB weld on the bellcrank, the vibration will crack it and the bellcrank will get loose
Randy
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Randy: Do you solder? or wheel collars?
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I will try to explain. 1/8 rod first you put fuel line on ,then a 1/8 wheel collar then a washer then bell crank then the washer then the collar then the fuel line. Use the fuel line to center it between the bearers.
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Robert: Understood y1 y1 y1 y1 y1 j1 j1 j1 j1
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Leester,
That is almost a direct copy of what I and many others do. Put the ply plate flush with the top of the spar of course you'll have to notch the ribs so that the top of the plate is even with the top of the ribs and then when you sheet the center section of the wing the ply will also get attached to the sheeting both top and bottom. Another benefit of doing it this way is that you get a glue joint along the top spar and the bottom spar about 6 inches long on each spar and the joint is in shear which is the strongest way to do it. And a side benefit is that the center section of the wing is strengthened by the bellcrank mount. In the picture below the center sheeting will butt up against the leading edge sheeting and go over the top of the ply mounting plate with glue or epoxy. You will be styling.
:!
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Nice. I will steel.
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Yep, the picture that Greg posted is the best method of mounting a bellcrank I have used, so far. I will try Al Rabe's new method shortly on a built up plane.
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A club member recommended providing a fixed end to the bellcrank arc. A bump or bumper to define the end of the up/down movement. I usually do this with 1/8" ply tabs that make endstops for the crank. One for each end usually attached to the outboard rib backing up the crank. (IS any of this clear. I don't have digital camera.) This also helps define the middle of the arc as the point at which the pushrod is centered. Seems to me this is useful in equalizing the geometry for up and down movement. Important in setting up a model so that it turns inside and outside at a similar rate.