Since i fear the projects i'm working on right now are going to require a fair bit of tube-bending, i've decided to embark on building a bender.

Now, i'll probably do a pro-tools style HMP bender, or else a got-trikes style bender.

http://www.pirate4x4.com/forum/showthread.php?t=376183 (got-trikes)

http://favoriteprojects.com/how_to_buil ... bender.htm (hmp)

I'm leaning towards the trikes style bender right now, especially using one of those handy princess auto long-stroke air-hydraulic cylinders.

The tenative plan is to browse mcmaster-carr until i find the following:

A 1" hardenned shaft
A few brass bushings for this said shaft.

Now, i'll be spending probably 500+$ on the dies to do 1.5 and 1.75" tubing by the time you factor in shipping. Probably another 250$ or so in materials including the ram too. So it won't be cheap.

Now, the slightly-tricky part. The frame.

Most people have decent access to milling machines or else eye-ball it and end up with issues in binding/such.

I am planning to get it water-cut out of 3/8" plate (it's going to be effing heavy) and have it able to just about bolt-together (aside from the few things that need to be welded like the mounting points for the cylinder and such).

This will give me decent tolerances and quite a bit to work with.

Now, i have never played with brass bushings before, this is the question:

Can anyone tell me how they might work in this type of setup? I know the force is going to be much less than the yield strength of the brass bushing, BUT i don't know much more about how brass works in itself as a bushing, how it wears, what type of tolerances i'll need for 5000+psi on it. Can anyone shed some light here?

The whole thing is spurred on by the shops here wanting about 80$/bend at the cheapest, ontop of no liability if they mess up on the rather expensive material. I've tried to find some local car guys with a bender, but to no avail. I figure that in the grand scheme of things, if i do more than fifteen bends with it, it'll have broken even assuming i can make it all for less than 1k.

I'd go with a hardened steel bushing and a high pressure lubricant (possibly with graphite and molybdenum bisulphide).

For what it's worth, my Hossfeld is is made of material quite a bit thicker than 3/8 plate.

I don't think the brass will last very long under such loads.

Cheers,

Richard

Regardless, it's a pretty cool bender. I've got a pipe bender for NPS pipe, but it doesn't make very nice bends on, say, exhaust pipe.

kk, it looks like i'm gonna build a trikes-style bender. can get the parts run off on a local plasma table for some beer and use the P/A air cylinder.

saweeet.

BTW, you can probably get off-the-shelf alloy steel bushings by using hardened steel drill guide bushings from a place like Fastenal. Another possibility is to get bearing races, we do that at work for the larger sizes (1.25" and up).

RT

I looked pretty hard at that kit - I know you're a student, but if it were me, I'd go with the kit and weld it up. I've learned the hard way that my time is worth something. Sure there is only $100 of materials, but for $200 some one else can drill holes and cut stuff to length etc for me at this point.

yep, i've worked it out, the materials and time on the plasma table will end up running me about 220$ on the dot. add in the dies, cylinder and a couple hardened shafts and it's only around 800$ to do all i need. The welding is the small part of it.

Screw putting in the time it would take to make a bender that could take a bunch of tweaking to make work how i want it to.