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Discussion Starter · #1 ·
This isn't Jeep related, but I know a lot of guys on this board know about metal bending so I figured it would be a good place to ask first.

Anyway, a buddy and I want to make offroad go-karts. I was intending to build the frames with pieces of 3/4" or 1" steel tubes and weld them together. My friend suggested bending the tubes to the shape we want because it will be stronger than welding pieces together. I have a welder. Neither of us has a metal bender (if that's what it's called or if such a tool even exists). So I'm wondering how metal is bent. The only idea I've had was to stick it in a vise, heat it with a torch, and bend.

Can anybody give some ideas on what kind of steel to use, and whether or not bending is better than welding? These aren't going to be slap-together pieces of junk, but rather tough machines with goodies like IFS, disc brakes, and motorcyle engines. Purchasing kit plans and frames is not an option (why buy when you can build, right?).

And if you were wondering, the karts will be towed to the off-road area by my trusty Jeep.

-Dorian
88 YJ w/ multi-speed wipers
 

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You will be wanting a hydrolic tubing bender. Check out places online like Harbour Freight, Northern Tool, etc... Wether these places have any quality products I don't know, but they do have pictures so you will know what you are looking for.

We were thinking about a project like this too...I would be interested in seeing what you come up with.


'79 CJ-7
 
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Discussion Starter · #3 ·
http://www.harborfreight.com

I found the bender:
http://www.harborfreight.com/cpi/taf/Displayitem.taf?itemnumber=32888

Look under shop equipment (at least i think it was there i saw it)
Price, about $ 80 for a bender handling 2" dia pipes (it comes with several
what-ever-they-are-called pieces to handle smaller tubes)

Warning !! I just discovered that pipe is measured ID, but tubing is measured OD !!!
This means that pipe bending dies *will not* fit tubes....
I have bought some *pipe* dies, and i measured them, and yes, they are nowhere near tube OD measurments. Not a problem for me, i will just machine the dies to match the tube sizes i'm going to use (at least i hope so....)

I'm going to build a similar bender, for my son's trike project.

I'm going to build a trike, based on moped (50ccm engine) parts, for my 7 year old son.
I will use the complete front fork, the engine, rear coil-shocks etc.

Then, building a custom frame w/40 deg rake, gas tank comes from an old norwegian moped, called "Tempo" (it looks very much like a small Harley fat-bob tank...)
The rear swing arm will be custom made, using fun-kart parts (from AZUSA)
Rear tires will be either 6" wide or some wild slicks 9.5" wide....
What else ?? total length will be like 60", seat height about 13". Width at the rear tires will be about 40".

Oh yes, i asked him to pull the clutch handle, but he wasn't strong enough...
Sooooo, i will build it with a (left side) foot clutch. Gear selection will then have to be "jockey shift" on the left side of the bike, between the tank and the seat. I will probably bend a custom "sizzy bar" as well.
The seat will be "U" shaped, and it should be large enough for two small "bikers"........

Regards,
PerJ (From Norway)

<[email protected]>
Using self-discipline, see http://www.eiffel.com/discipline
 
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Discussion Starter · #5 ·
Go to en electrical supply house. You will be looking for Rigid conduit or GRC (galvanized rigid conduit). Do not let them sell you IMC (intermediate metal conduit) because the wall thickness is less or EMT (electrical metallic tubing) it's even thinner than IMC. You want the Rigid. They will also be able to sell you a hand bender $40.00 max. It is not that difficult to bend with a little practice. The bender will produce wide-radius bends that do not squeeze the pipe in the middle (think tailpipe). Be careful when welding galvanized because the fumes are nasty. If you prefer a plumbing supply place can supply non-galvanized (black iron) pipe. LOL

 

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I know this isn't what you are looking for, but here is a field expedient repair we have used before when we didn't have a conduit or pipe bender:

Take the pipe/tube of at least 4 - 5 foot in length and pack it completely full of sand and tap a stopper of some sort into each end so that the sand doesn't fall out. Get a person on each end and bend the pipe/tube around a rounded object - a larger object for a wider bend, and a smaller object for a tighter bend. If you have had major back surgery or a history of hernias, I would recommend that you find two other people to help you! /wwwthreads_images/icons/crazy.gif Then you can cut it to length, weld it, whatever. It is important to have the sand packed tight though. It isn't perfect, but if you absolutely need a pipe bent with nothing else to do it with - this works well.
 
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Discussion Starter · #9 ·
I think you will find that water pipe and Rigid conduit is the same thing.
In my training I was told that the conduit was 10 Ft to get around a union
pipe fitter thing. Soooooo if the pipe is 22 Ft its a pipe fitter union job and
if its 10 ft its a IBEW union job.
BTW PerJ cool trike . A friend of mine did this with a Honda 50 mini trail.
use the two wheels on the back and lenghened the front forks and used a small
motor cycle tire and wheel on the front. Don't remember how he cut the frame
but you sat on the rear axle on a seat. Give it a low rider raked look. /wwwthreads_images/icons/smile.gif
 
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Discussion Starter · #10 ·
I'm going to use the front fork and front wheel as is. It comes from a small moped. The fork is about 24" end-to-end and the front wheel is about 20"..

Since this is for my 6-7 year old son, the ride height will be about 12-13".
From the drawings, it looks so low and short, that i doubt that i will be able to ride ont it...

Sooo to get it low enough, i have to rake the front fork about 40 deg (from vertical). I should perhaps have raked it out even more, but then the telescopic shocks stops working. Instead, the fork just bounces up/down, not in/out....

The rear swing arm will be about 30" wide at the rear axle, and about 10" at the
point where it is mounted to the frame. To get it to move up/down, i'm going to mount it to the frame, using 2 male heim joints. The male /stud part is threaded into the tube ends of the swing arm, and a bolt through the head of the heim joint, into a tapped cross tube in the frame. This gives me the added benefit, that if the swing arm is slightly out of alignment, i can adjust the heim joint in/out of the swing arm, to align it correctly.

To dampen the swing arm, i will use the 2 original coil-over shocks from the moped, mounted at the rear of the seat frame (which is only 10" wide), and down to the swing arm where the rear axle bearings are mounted. Seen from behind they will sit at an angle, going down and out to the monting point.
Much like an ordinary trike ...

The biggest decision at the moment, is if i'm going to use a live axle with 2 driven wheels, or let one of the rear wheels be un-driven /freewheeling...

I'm about finished with the general layout drawings, hopefully start building in a couple of weeks....

The biggest problem was getting a nice gas tank, i got the one i wanted, it looks very much like a Harley fatbob tank...

Regards,
PerJ (From Norway)

<[email protected]>
Using self-discipline, see http://www.eiffel.com/discipline
 
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Discussion Starter · #11 ·
PerJ Sounds like your going to have some happy little ones. Sounds way cool.
You probably already have it aced, but if I remember right the swing arm pivot point has To be as close to and same level as the output shaft of your motor so the chain does Not tighten or loosen as much as the swing arm goes up and down.
Just a thought./wwwthreads_images/icons/smile.gif
 
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Discussion Starter · #12 ·
Yeah, i know...
When i started drawing, my original idea was to make a rigid frame...
But then i started to look at these two small chrome coil-over shocks in the back of the donor moped... So then i thought, what the heck..., i'll try and use them as well..
I then started drawing, but soon realized that my geometry re. the chain tension wouldn't work (because of the wrong pivot point for the swing arm)
Sooooo, i had to do the rear-end & the swing arm drawings one more time....

It won't be perfect, but i figure that for the 2" movment of the swing arm, it will be "close enough"...

Will see, when it's finished....

Regards,
PerJ (From Norway)

<[email protected]>
Using self-discipline, see http://www.eiffel.com/discipline
 
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