Manual 3 roller tube bender

[Undies]

Can anyone provide any advice (plans) on making a "large radius" manual 3 roller tube bender

Have been trying to buy one but live in New Zealand which makes freight costs very high.
I suspect I will need to buy the dies from somewhere (or get them CNCed.)

What kind of compression do I need to achieve on the middle roller?

Thanks

[Rody]

Undies,

Fabricating your own tooling is both an excellent investment in knowledge/experience as it is an opportunity to save some cash.

Here's a pic of the tubing roller I fabricated kinda on the fly, drawn out on the back of a parts receipt, so no plans to share. Only had to purchase the mounted spindle bearings and the pump for about 75 bucks, the rest was done in house.
Roll bender.jpg
Insure that you overbuild the frame to resist the downward pressure exerted by the hydraulics and incorporate some lateral adjustable holes to increase the center distance between the lower rollers to change the variation in the arc achieved.

If you have access to a lathe, dies can be made with a little time and patience, if not, contracting for custom cnc machined sets is an option.

Here is a blog post that shows more including the acheived results for a cruiser application

Groovy Cycleworks 330-988-0537: A little bending fun...Steve's retro 29er

Have fun and good luck,

rody

[edoz]

Swag offroad makes dies for the Harbor Freight version. I have a lathe and will probably pony up and buy their dies. I'll make the roller though.

[ThomD]

3 roller designs are good particularly if you have long enough tubes to run smooth curves over a section that you can use. Benders will also bump in amazingly nice curves.

One thing you can do to make a roller if you have a horizontal mill is to set rollers on the mill table, and the third roller in the head. Then you can use the table adjust to make the curve. Should be fine for the light tubes we have.

[edelbikes]

Here's a cheap one I made, based on the same principle as the Groovy, have a look in my flickr gallery, there's some details on how I made it and the dies (and the radius cutter to make the dies ;-) )
It works very well, and costed me around 50 euros (including dies). The only issue with aluminum dies is that it leaves a super-dirty deposit on the tubes ! :

Roll bender par Edelbikes, sur Flickr


Roll-bender dies... par Edelbikes, sur Flickr

[Willie1]

I have a newbie question on the tubes used for bending. Are these straight guage tubes or can a .9.6.9 tube be radius bent? How thin can one go with gentle curves before the tube is not structurally sound?

[EricKeller]

people bend butted seat tubes for tire clearance on mtb frames. It's pretty hard to avoid end effects. Most bent tubes are straight gauge.

[edelbikes]

To give you an example, this one is Verus in 9/6/9. With harder heat-treated stuff I found it hard to avoid artifacts in the butting transitions.

Peinture fraiche ! par Edelbikes, sur Flickr