Tube Bending

N

Nitrohorse

New Member
#1
#1
How do you guys bend your tubing? I noticed that HF has a "pipe" bender on sale for 69.99. The owner's manual was laying along side of it and I decided to Evelyn Wood speed read it. There's a warning in broken English in the manual concering the possiblity that the bender may kink or split the pipe/tubing. I decided to then see how much a tubing bender costs and quickly decided that mortgaging the home is not worth owning one.

Anyhow, I would like to make a custom frame but I'm at a loss as to how I can bend the tubing without kinks or splitting the tube. I heard about filling the tube with sand and corking both ends, but the ability to duplicate a bend is kind of lost with out some tube dies or a jig table.

Thanks,
Larry
 
D

Darvin Jahnke

New Member
#2
#2
I just finished building a replica of a 59 Evans Special go kart. It is built to original specs and all bends including the steering and seat hoops were done with a cheap Harbor Freight bender. I was told by several people that it would be impossible without sophisticated hydraulic benders and dies. A little patience and ingenuity go a long way.
 
N

Nitrohorse

New Member
#3
#3
I think I'm going to buy the bender and take a shot at it. I came across a mini bike site where the author explained how to make plywood jigs and bend the pipe by hand. I guess it can work if you have unlimited access to primates because I don't think a human is going to muscle 1" tube around for any length of time.
 
Yellowhand

Yellowhand

#4
#4
...unlimited access to primates...I love that...

I'm about five minutes away from bending up a frame with this cheap HF model...

I was planning on posting some pics of what it will do, won't do, and what it can be made to do with some modifications...
 
x-90 rider

x-90 rider

#5
#5
I have 1 of those benders and we made some plastic blocks to replace the outer spools. The original spools left a lot of hard dents in the tubing. We made a pass down the plastic blocks with a ball mill that matched the tubing size.
 
N

Nitrohorse

New Member
#6
#6
Yellowhand said:
...unlimited access to primates...I love that...

I'm about five minutes away from bending up a frame with this cheap HF model...

I was planning on posting some pics of what it will do, won't do, and what it can be made to do with some modifications...
Click to expand...
Yellowhand, I'd certainly appreicate any photos or info you can share with us less fortunate, benderless folks. I posted on here about a month ago that I bought an MTD and have been working on it ever since. The frame is cracked back at the rear axle mount and the bottom of the frame near the engine mount has a 3-4" split in the tube right along what appears to be a seam. To be honest, at my age, I don't trust the structual integrity of the frame anymore. If I was in my teens, I'd ride it like the plastic coin operated pony outside of Kamrt and not give it a second thought.
At my current age...I stand in the garage and gaze at the frame, wondering how rusted and thin the tubing walls are. To make a long story short, I ordered many parts ($$$) for it and have a damn near new TC that I was going to use on it as well. I'm now at a point where either I weld up the splits and cracks and continue on with the build or look at making another frame or purchase a frame.
Tell me that I'm worrying too much and the welded frame will work.
Or be honest and tell me that I should cut my losses and look at an alternative frame..
Thanks,
Larry
 
Yellowhand

Yellowhand

#7
#7
I've seen some really badly broken frames, and have always tried to weld them back into shape...we don't really have a choice if it's an iconic relic from the 60's we're trying to restore...NOS frames don't exist, in most cases...

But, back to the bender for a minute...

This model was on sale at HF for $62...came with several dies labeled from 1/2" to 2-1/2" in 1/4" increments...

The die labeled 1/2" actually measured .873 and this length of 7/8" OD, .083 wall thickness steel tubing fit perfectly inside the die...

I wanted to find the most acute angle the bender would make without modifying the bender or the die, or even lubing the tubing while bending...

As can be seen from the pics, the bend is just reaching the point where the die would have begun crimping the metal, but the angle produced (without any mods to the bender) is more acute than needed to reproduce all the angles found in most vintage mini frames...

This bend took about one minute to complete, including clamping the bender to a workbench and installing the die...
 
Yellowhand

Yellowhand

#8
#8
x-90 rider said:
I have 1 of those benders and we made some plastic blocks to replace the outer spools. The original spools left a lot of hard dents in the tubing. We made a pass down the plastic blocks with a ball mill that matched the tubing size.
Click to expand...
The finish on the cast iron rollers and spools is really rough...they didn't do much finish work on them at the foundry, other than break off some flashing here and there...
 
N

Nitrohorse

New Member
#11
#11
Yellowhand, you convinced me to buy the bender. I have a few more questions regarding fabbing a frame. Do you use a length of tubing that is long enough to make a complete loop from and back to the front fork pivot tube?
Based on my rough estimates, I would guess that approximatley a continuous 15 foot section would be necessary for each frame rail? I'd have a hell of a time fitting that into the wife's SUV. I also noticed that some guys on here use 3/4" and brace and gusset the frames. I'm no engineer, so structual integrity to this farm boy is simply "bigger is better."

Finally, I notice a sweet looking engine on the reference bike in your photo. What is it and what's in it?
I just finished tweeking a clone engine with the billet rod, cam, valve springs, etc., that was going to replace the worn out H40 that was originally on the MTD. I saved the Tecumseh in the eventual reallity that I was going to rebuild it, but that is all on hold now until I figure out what I'm doing for a frame.
I may weld up the cracks and go from there. The MTD is a unique animal in that they use stamped rims and wheel hubs and there's not much you can do with them. The rear axle mount clearance is a paltry 7''.
 
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Yellowhand

Yellowhand

#12
#12
The Azusa frame in the pics has one piece sides, with the butt weld hidden under the engine plate...

I actually prefer the TACO style frame, with a one piece top tube and shorter side pieces...I need to tweak the bender a little to get the 180 degree bend behind the seat...
 
Yellowhand

Yellowhand

#16
#16
Nitro...

If you want to build a frame, it doesn't necessarily need to be continuous runs of round tubing...

I'm currently kicking around several ideas for alternate frame materials...

The 1" square tubing in the pic was heated and twisted over a cold steel mandrel...I'm thinking of weld-blending it into curved sections of round tubing to form a frame that looks like twisted round tubing...

The most unusual materials can make interesting minibike frames...the log chain and burglar bars in the third pic both became minibikes after some welding...
 
steven Durham

steven Durham

#17
#17
I have 1/2 and 3/4 inch pipe dies for my Pro Tools bender and there have been at least 5 handlebars made for trikes using 1/2 inch Stainless pipe . That is so close to the 7/8 inch tubing that even the twist throttles work just fine. On my bender you do not use any lube at all because of the following bar .
Steve :scooter:
 
N

Nitrohorse

New Member
#18
#18
I have to give you a 10 on creativity. You do some beautiful work!
I think I'm going to use the Taco style and go from there. It's off to Harbor Freight at lunch and then the scrap yard tonight after work.
 
M

Mikes Bikes

Member
#19
#19
Yellowhand said:
I wanted to find the most acute angle the bender would make without modifying the bender or the die, or even lubing the tubing while bending...

As can be seen from the pics, the bend is just reaching the point where the die would have begun crimping the metal, but the angle produced (without any mods to the bender) is more acute than needed to reproduce all the angles found in most vintage mini frames...
Click to expand...

Fill the tube with sand before bending. That'll help spread the force and keep it from kinking.
 
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