I plan to build a cargo bike for a customer in the coming monthes, and I’m gonna need to produce 16 bends of 22mm 4130 tubing (handelbar style), they could be in 1.5mm thickness or 0.9 (preferable for the project, but unsure for bending ability).
I’m now in between trying to buy a JD style bender or building something by myself (I have access to a lathe, and a mill, and a 3d printer, and laser-cut so it could be a mixed of all those processes). So before diving any further,
I wanted to write there, seeing if someone have any advice/ experience with tube bending with that diameter (and thickness), because from what I understood, JD benders will work well with 1.5 but maybe not at all with 0.9 …
Radius of bend and angle will drive a lot of the decision making. Tighter radius and more angle will mean you’ll need better fitting dies and bender support. 0.9mm wall is pretty strong and with careful design you’d end up with a pretty good frame. I once built a walking cargo trailer that carried a 400kg rock for 500km using 31.8 X 0.9mm wall.
True,
I forgot to mention, the 16 bends are all the same : 90degree, which is quite a lot.
Also about Radius, If I make the die (turned or printed with steel reinforcement) I can choose it. I guess going under 90mm would be too much, I was thinking about 100mm (close to 5d). When you did that trailer did you bend tubing ? if yes what tool did you use ?
Turning a 200mm diameter die will be a bit of a challenge but should be doable on my lathe, the chuck is 170mm already and I have reverse jaws.
I kept to straight sections. After I finished it another fabricator added a bent tube support for when it’s parked. I’ve made a bending die for my chainstays on eeh mountain bikes but I’m only using a haydraulic press not a bender, so I get a little deformation in the bent area. It’s only slight and you have to look for it but I’m only bending at 170mm radius through 8 degrees. I cut that die on the mill with a rotary table.
I made an error iy was 160kg not 400kg but here is a video about the story…..
Johnny came to me on the referal from another friend and I got to design a really cool trailer. I unfortunately didn’t get to walk with them as my mum was in her last days at the start of their journey with the stone. It is one of my life higlights to be involved.
Wall thickness of the tubes you are bending makes a big difference, something you should consider A smaller wall thickness will require a larger radius die.
Developing a process for making nice bends on thin wall tubing can be difficult, time consuming and expensive. If you are willing to experiment and make your own dies, I would suggest a purchasing a Diacro #2. Make the die’s the largest your lathe/mill will accommodate and try.
I have a DiAcro #3 and it’s been fun. Would love to see more of your dies/ followers and radii/ diameters you’ve gotten away with. So far, I’ve only made a 19mm x 150clr, and it puts out a really nice bend. Just takes me a long time to make dies. lol
We have one, but the max angle on the r4.5” 22.2 die is a bit further than 45°, so to do 90° you need to do two bends back to back, and it leaves a small bump halfway. It would be easy to make all the bends identical tho
I picked up a #3 with a stand for a song. He had a #1 and I should have bought that too. Still working to fit it into the shop and then I’ll get out the rotary table. I had one of the online cnc places make a die for rack making but bigger dies would be very expensive. You should do a thread with learnings. Or a YT vid.
I could have bought a #3 years ago before I bought the #2 I use today. I still regret not buying the #3, it was loaded with tooling. The #3 is a huge heavy beast and I could not see myself needing that kind of capacity at the time.
Most of the tooling I have for my diacro #2 is home made by myself. Diacro tooling is fairly easy to reproduce. The largest diameter tubing I’ve bent with it is 1.25” x .035 tubing (7” radius).
I am pretty busy right now but I’ll try to post some more info about my Diacro mods and tooling.
You are going to love your Diacro. It has so many uses in a shop. The only down side the diacro benders is cost. The benders themselves are cheap but tooling is super expensive.
