Post By Ries
Hot VS Cold pipe/tube bending
Are there major differences in the quality of bend.Case:I want to build a motorcycle frame and no bend is greater than 40*, what would be the strength factors here understanding that too much heat and distortion is damage?Thanks,Ron
there are lots of other factors to consider.
what alloy is the steel? wall thickness? radius of bend? weld technique?
Some steels are very forgiving of heat, but many high strength tubing alloys will change radically when heated, depending on how they cool, as well. Some steels, with higher carbon contents, may want to be annealed after heating, then re-heat treated, to achieve specified strength.
If you are using plumbing pipe for your frame, sure, go right ahead and do it all hot.
The angle of the bend is one thing, but the radius of the bend is a totally different thing- long gentle bends are much easier to do and much less likely to cause cracks or stress than tight radius bends of the same angle.
I had a good friend who was a real guru- and he did a lot of bending at black heat. Just heating steel up to 500 to 800 degrees makes it bend much much easier, but is less likely to radically change the material.
Commercial motorcycles are engineered to be made from the lightest possible material for the application- but that means precise bending, welding, and heat treating, depending on the bike. If you over-engineer to account for homebrew techniques, your frame may not be quite as elegant as one that has been stress tested to destruction a few dozen times.
Thanks for the reply Ries..I will be using DOM 1.125 X .120 A513 Type 5 steel tube,my bends will mostly be 4-6" radius and I will TIG weld all joints.My question was directed at the "black bend" as you described where just enough heat to bend without turning the steel cherry red.
My reasoning here is the difficulty in being able to find a bender suitable to do the job and my wanting to build this thing from the ground up.Buying a bender is out of the question simply because I am not doing anything radically different than what is already available so I would be better suited to use the funds to buy a frame.
A JD2 bender, which is probably the best manual tube bender out there, is only 300 bucks.
I am pretty sure that includes one set of dies.
thats so cheap, I think you are crazy not to buy one. You will spend a lot of time jigging to bend without a bender, and get inconsistent results. Buy a JD2, and sell it when you are done, you can probably get 250 for it, and you will come out far ahead in time, money, and accuracy, and save a LOT of aggravation.
I dont know what a frame costs these days, but my guess is that its a lot more than what it would cost you to own a JD2 for six months and then sell it.
I think you are right! thanks for the link..Ron
You will not be happy with the results of bending that material trying to use heat and DIY machinations.
Keep an eye on craigslist, people buy these benders, and similar benders all the time and never use them, wind up selling them for cheap.
I have a Pro-tools 105HD and the only regret I have is not being able to borrow dies from my JD-2 owning friends.
You could also find someone with a bender and have them bend what you want the way you want it and skip the learning curve.
In all due respect fangars ole boy,if I wanted someone else to do it I would just buy a frame! Its the learrnin curve that I am lookin for!