Thread: ORGS build up
View Single Post
Old 02-06-2011, 03:27 PM   #130
x3300 OP
geoff
 
Joined: Mar 2005
Location: San Jose, CA
Oddometer: 170
Tube Bender

Rotary draw bending of tubes has little cross section distortion at the bend, and I thought that it would give the appearance I wanted in the subframe and rear luggage racks. Here's a nice diagram I found that shows several tube bending methods.

http://stuff.gotdns.org/bike/orgs-build-up/39-tube-bender/bend-types.jpg

I decided to make my own bender so that I would then have the capability to make a bender for any size tube or bend radius I might find I need. A minimal design would need a bending die with an integrated clamp die, a pressure die, and a frame.

I found a large block of mild steel at the scrap yard I thought I could use to make a double 1/2" & 3/4" bending die for a 1 1/2" radius. I cut the block down to a square and drilled a hole in the center so I could bolt it to the left over stock I had used to make my lower shock bearing mount. Here's the piece in the lathe almost ready to be turned down.

http://stuff.gotdns.org/bike/orgs-build-up/39-tube-bender/turning-bend-die.jpg

Once I got the OD turned down I cut grooves of 1/2" and 3/4". I didn't have any full radius cutting tools so I just ground a few left and right hand turning tools to have the proper radius. I had five tools in all to do the grooves, a common center one and left and right radius ones.

Here's the final cutting of the 3/4" groove. After the block was bolted to the mount I drilled a center hole in the bolt so I could support the right side with the center seen in this photo.

http://stuff.gotdns.org/bike/orgs-build-up/39-tube-bender/groove-cutting.jpg

Here's the finished bending die with my mount and center drilled bolt.

http://stuff.gotdns.org/bike/orgs-build-up/39-tube-bender/bend-die.jpg

To simplify the design I decided to weld the clamp die and a handle directly to the bending die. I cut a clamping strap from a thick wall rectangle tube and welded it to the bending die.

http://stuff.gotdns.org/bike/orgs-build-up/39-tube-bender/bender-done.jpg

I found some 1" square stock to use for the pressure dies. To mill the slots I bought a 1/2" and a 3/4" ball end mill. Here's the milling of the 3/4" die.

http://stuff.gotdns.org/bike/orgs-build-up/39-tube-bender/milling-pressure-die.jpg

Here's a view of the 1/2" die with a section of tube and the cutter.

http://stuff.gotdns.org/bike/orgs-build-up/39-tube-bender/pressure-die.jpg

I had some rectangle stock left over from my swingarm fixture that used for the frame. I cut these slots to allow adjustment of the pressure die position.

http://stuff.gotdns.org/bike/orgs-build-up/39-tube-bender/milling-slots.jpg

Here are all the finished parts ready for assembly.

http://stuff.gotdns.org/bike/orgs-build-up/39-tube-bender/bender-parts.jpg

And the bender in action. I used some c-clamps to clamp it to this sturdy frame. I put some grease on the pressure die to lubricate it. It doesn't take much to bend 1/2" thin wall tube. 3/4" takes considerably more effort.

http://stuff.gotdns.org/bike/orgs-build-up/39-tube-bender/bender-in-action.jpg

After doing some test bends I decided to re-work the bending die, clamp and handle. The final version has the handle between the bending die and the frame, the 3/4" grove as the inner groove, and the handle welded to the other side of the clamp die.

Here's a close-up of some bends I could make.

http://stuff.gotdns.org/bike/orgs-build-up/39-tube-bender/bends.jpg

-x3300

x3300 screwed with this post 02-06-2011 at 03:32 PM Reason: Minor text update.
x3300 is offline   Reply With Quote