[F-Minus]

Can anybody with experience using this stuff recommend how much past the bend I should put it?

Obviously enough to support the dies... but a diameter beyond that? Two?

I'm trying to bend a 1.500 x .035 DT and would like about 35°.

My friend has a Pines mandrel bender, but does not have the ID mandrel for .035 wall, but he said we could try the Cerrobend.

Thanks!
=stan

 

[Walt]

I don't think you are going to have much luck getting 35 degrees of bend even with the cerrobend. But I'd go a diameter or so.

Remember it's SUPER carcinogenic if you weld with any of it still in there.

-Walt

 

[Clockwork Bikes]

I had to buy my bending vendor an internal mandral but I think it was less than $200. These are 1.25" x .058" chromoly at r.3".

https://flic.kr/p/28966469154

 

[F-Minus]

Well, Walt you were right! Snapped like a twig at 10° or less. The die is 4.125" CLR (!) :blush:.

I followed instructions found in this PDF:

https://www.canadametal.com/wp-content/uploads/2016/08/bending-using-legend-products.pdf

I made a PVC tube with hose fitting at the bottom to quench the filled tube etc.

The bender is a Transfluid and my friend suggested I could try making a plug mandrel for it. I suspect it won't bend even with he mandrel because of the tight radius.

I have an old Mittler Brother 90° bender with 6" CLR die that I might try with my other piece of Cerrobend filled tube...

 

[m-gineering]

Can anybody with experience using this stuff recommend how much past the bend I should put it?

Obviously enough to support the dies... but a diameter beyond that? Two?

I'm trying to bend a 1.500 x .035 DT and would like about 35°.

My friend has a Pines mandrel bender, but does not have the ID mandrel for .035 wall, but he said we could try the Cerrobend.

Thanks!
=stan

You haven't mentioned your bendradius. If you're elongating the tube more than the tube can handle you're not going to get there without heattreatment in whatever form. Calculate outside radius/ mean radius, and compare this with the tubing specs

 

[F-Minus]

M-gineering, I found out later it was 4.125" CLR, which explains why it broke.

I did some research and math like you suggested and found the following:

Plymouth Tubes publishes a minimum elongation for this 4130 tube at 15%.

Doing the math for percent elongation = (change in length)/(original length)

Plugging in the formulas for arc length, the minimum radius (Rmin) can be found as a function of tube diameter (d) and percent elongation (%El):

Rmin = d / (2 * %El)

So for my tube of d=1.500 and %El = 0.15 the minimum radius is found to be 5.0"

 

[Walt]

Here's the thing - you also need to ride the bike. Even if you can just *barely* safely bend around a 5" radius, how confident are you going to be in the tube going forward?

I'd get something with a long enough butt and cut/weld it to get your angle.

-Walt

 

[F-Minus]

Walt, I agree. Not trying to say this tube should be bent at 5" CLR, just getting an idea of the how to interpret the specs. I think there is more to analyzing the tube stress during bending than just looking at elongation.

I also agree, I'll cut and miter this tube. I'll post some photos when I get things figured out a little more, this is an unusual design using rod ends instead of a headtube.