Pietenpol-List: Re: Bell crank tubing

[matronics]

Original Posted By: "w b evans"
Subject: Pietenpol-List: Re: Bell crank tubingI used that same size streamline tubing for my bellcrank, flattened the ends by heating the tubing with a torch and flattening in a vice when it was red hot. It helps to take a couple of pieces of angle iron, cut it at the angle inabout 2 inches and bend the free piece into a nice curve. Put two of these between the jaws of your vice and it'll keep the sharp edge of the vice jaws fromcutting into your tubing and gives a nice easy bend from the round tubing to the flattened section. I think Tony Bengilis has a description and pic of thisin one of his books on aircraft construction. And I did edge weld the ends.One advantage of the streamline tubing is that, though it looks pretty massive, you are going to drill a big hole in it for the axle shaft, so you needsome width there to carry the loads around the shaft, and to give something toweld the shaft to.Regarding the attachment of the two elevator cables to each end of the bellcrank, standard shackles don't have enough room for two cable eye, with thimbles, at least I didn't using 1/8" cable. I ended up taking two pieces of .090steel, about 3/4" by 1 1/2", putting about a 20 degree bend in them and puttingone on each side of the bellcrank, with the bends pointing outboard in each case with a pivot pin through, and attaching my cables to those. If you have trouble visualizing this, I can email you a pic of my set up.Oh, and while we're on the subject, think about making up some pulley brackets and using pulleys where the elevator cables and the rudder cables makethat bend at the rear seat back. I wasn't satisfied to just drill holes in the bottom seat support for that, but to each his own.Matt PaxtonYou wrote:Do you happen to remember what size you use for the cabane struts. Did you flattenthe ends on it for use on the bell crank. The plans show you should flattenthe ends. The streamlined tubing I have is 1.685 x 0.714 0.049 thickness.Is this to big? or does the geometry of the control cables (two into one attachmentpoint)require this much strength?Speaking of flattened ends, when you pinch the ends for the rudder bar and thebell crank do you need to weld the ends closed after you flatten them?Chris Sacramento, CA________________________________________________________________________________

[matronics]

Original Posted By:
Matt,Just an added 2 cents,,,You can use just one cable eye in the center of a long cable. The cablesplits from the single eye and one goes left and one goes right.I know a guy who flew a Piet that someone else built, and he told me that afriend and friends wife was flying it and the weld at the bellcrank/shaftbroke with a very unhappy ending. He kept pushing me to put a "safety" tubeinside the normal one just in case.But that's another story.waltNX140DL22 1/2 down, and 2 1/2 to go----- Original Message -----