H-86 build: Shop built tubing bender

[jrbirdman47]

Been trying to come up with a way to make consistent bends for the tail surfaces, this is my experiment: Wood is 3/4' oak, jigged to a router to cut half round slots in the edges of appropriate depth and sizes, (3/8", 1/2", 5/8"). Holes in the sides are for squeeze clamps to hold the tube in place. Angle iron forms the handle and are probably stouter than required, but it's what I had on hand. Got about $60 in it, not counting the router bits, but I found carbide bits online quite cheap. Really hoping the wheel rolling around the fixed part will lessen stresses on the tube. Will be trying it out soon and will make comments as to performance.

[Kamcoman77]

Very nice. Your version should work just fine. A similar bender was built by the YouTube guy (Jeremy) building a Double Eagle. He bent 4130 tubing with his since the Double Eagle did not use aluminum tubes.

[jrbirdman47]

I looked at the videos you referenced and decided to modify the thing. I simply inverted it so that the tubing is pulled through the bender instead of having the smaller wheel roll around the tube. First try is on the 3/8" rudder trailing edge. While the first try was successful, I did learn a couple of things: First, because of the spring back inherent in the tube, to get a 6" radius bend I would be better served to use maybe a 5" radius wheel in the bender. As it is, getting the 6" bend requires tweaking by hand for those bends approaching 90 degrees, but it is possible. Second, I accidentally flattened a spot on a side of the roller wheel during construction, but I wasn't concerned about it because the wheel will not make a complete revolution for the bends. I learned that when finished, I had to rotate the smaller wheel so this this flat spot was along the tubing and that this is the only way to remove the tubing since the two wheels fit together to the diameter of the tubing.(Sometimes you screw up in reverse!) The tubing has to be set to a specific place ahead of the bend to get it to bend exactly where you want and I'm still learning where that spot is. Over all I think the design works well enough and isn't expensive. 3 days worth of work and rework and still further modifications to get to this point, but now I can crank out the tail feathers for both planes pretty quickly.

[jrbirdman47]

Finished 3/8" tube for rudder trailing edge

[Kamcoman77]

Your bends look very nice. As you mentioned, one good thing about your bender, once you figure out where to place the tube to get a bend exactly where you want it, you can duplicate things with zero error. I did all mine by hand using a spring over the tubing, but I'm only building one plane.

[jrbirdman47]

Update to above: Practiced bending the two rudder trailing edges to learn the idiosyncrasies of the beast. (Reasoning that they didn't have to be identical to anything so if I messed up......) Learned that I have to mark the tubing 1 inch prior to where I want the bend to begin in order to get the correct placement of the bend. Learned to bend the "small end" first as it is easier to tweak the larger bend into the final dimension. Also, due to some mysterious witchery, after the initial bend is made I have to clamp the first bend at a slight angle to the left in order to get a second bend that will allow the entire thing to lay flat on the bench when finished, otherwise there is a slight twist. So after practicing on the rudder trailing edges I boldly went where I'd never been before and bent all 4 elevator trailing edges applying the aforementioned knowledge gained, and voila! 4 identical pieces! Now I will change out the dies for 1/2 inch tubing and try bending the rudder leading edges. I will be interested to see if the 1 inch "lead" that I discovered holds true for the 5/8" and 1/2" tubing as well. I did not use sand to fill the 3/8" tubing as I figured it would bend pretty easily, but not so sure about the larger diameter tubing, so what do y'all think? Input appreciated! I think now that all the effort put into the bender was worth it for the ease of making identical parts. Unfortunately, after I'm done it will be a large paperweight. (Of course all those jigs made for making wing parts are already gathering dust, so it will join them I suppose) Sure felt good to work on something besides wood for a change too.

[jrbirdman47]

two rudder and four elevator trailing edges complete!

[jrbirdman47]

I got brave about bending the 1/2 inch tubing without filling it with sand. I had enough length that if I kinked the first bend I could still use the remaining length and just fill the tube before bending again. The bender worked just as well as with the 3/8 inch tubing, just a bit more effort on the lever, so I'll probably be glad that handle is so long when I bend the 5/8 " stuff. Can't see any evidence of stressing the tubing so far, but on such a large radius there may not be that much stretching/ compression.

[jrbirdman47]

Got braver still and bent the 5/8 inch horizontal stab leading edges without sand. The bender handled these just as well as with the other sizes. Also, the "lead" for the bend remained the same regardless of the tubing size, at about 1 inch. So now I have this really nice paperweight........

[Kamcoman77]

Beautiful bends. Maybe somebody will offer to buy the bender from you.

[Wescraft]

Jbirdman, i'd love to know how you made your bender in better detail.

[jrbirdman47]

Hi Wescraft- I used 1 1/2 inch angle iron for the frame, mostly because I had some. Could likely get by with 1 inch. I decided to used a 6 inch radius on all bends so I wouldn't have to make several benders in each size specified per the plans. (3/8, 1/2, 3/4, etc)

The wood parts are all oak using a board wide enough to make that 6 inch wheel. The only way to make the upper wheel was to "splice" two pieces, using dowels to strengthen and maintain alignment. Once cured I made a jig from pine boards to mount a router and cut the radius after removing as much excess as possible with a jig saw. Mounted the work piece flat on the pine to rout the circumference of both upper and lower pieces. Then placed a pine board 90 degrees to the base piece to mount the oak for routing the 1/2 tubing diameter groove in the circumference.

Once the wood is complete the dimensions for the steel frame becomes obvious and is welded and drilled accordingly. Though bolts for the "axles" are all 1/2 inch and large area washers are used between the wood and frame.

If you are interested, I can ship this one to you cheaper than you can build one and it would probably be there before you could build it. See the thread at the bottom of the forum page called "Jigs and Tools for Loan" for details.

Rick

[jrbirdman47]

Pic is the jig with the vertical plate installed, made of pine. Bolt/ wing nut is in the hole used for the lower wheel axle and the piece can be rotated to cut the circumferential groove at 1/2 tube diameter. You can see the axle hole above that one for the upper wheel cut.

The circumference is cut prior to this on the horizontal plate before installing the vertical plate using the same method.