Building a chassis (questions)

[fmjnax]

We've owned our kart for 2 weeks now and the whole time I have been thinking of increasing power. Now that I've got my head out of the clouds, I've realized that I need to work on the chassis first!

The kart is set up as a 2-seater, but there's no way in heck 2 people over the age of 5 can fit in there! It's also short! As a 6'3", 260 lb guy, I look like a a Shriner or a clown in one of their little cars. The driving is all set up on the left side (again, being that it was made as a 2-seater) so my left side is pressed hard against the frame. My thigh has a nasty bruise to boot! My knees are also up in the steering wheel, making it a big chore to drive.

Finally, my dad noticed that we have a bent axle (probably from my fat butt taking the thing off of a jump). I took a look at it closer and it is just the drive wheel/sprocket that is bent (the rest of the axle is straight). Either way, it looks like I will having to fix that anyway.

So anyway, I need to accomplish 3 tasks:
1 - Extend the wheelbase so that I have at least a little better leg room
2 - Shift the steering/pedals to the center
3 - Weld on a new axle (might even go live axle, instead of dead)

I was talking to my boss about it and he said just use that threaded pipe with elbow/T's so that there wouldn't be much/any welding. I'll admit, I've thought about it, so I'll ask what the feasibility is in that.

And now on more of the specific chassis; is there any sort of rule of thumb in regards to length/width ratio? I plan on keeping everything I currently have (so the 6" wheels with the 145/70-6 tires, the 5.5hp Intek, etc). Is there anything else I need to take into consideration?

 

[qtband]

Post a picture so we can see what you're working with. Do you have access to a welder?

 

[used2jeep]

Re: more legroom - Just moving the pedals and steering to the center (if you aren't thinking of keeping it as a 2 seater) and tilting the seat backward would give you a little bit more legroom. I found this out by playing with the power seat of a rental car not long ago. Increase the height of the front of the seat and you seem to get more room for your lower legs.

 

[fmjnax]

I'm currently at work so these are the only two pictures I have with me.

Yes, I have remote access to a stick welder. However, my boat trailer needs some welding done on it so I'm likely going to be biting the bullet any buying my own so that I don't have to run an hour back and forth to get some welding done. What I don't have access to is a mandrel or anything else to bend tubes.

 

[Doc Sprocket]

Do not use threaded pipe. I used to do a lot of pipe work, and I can tell you that it isn't strong enough. The problem is right at the threads. Pipe threads are tapered, unlike a bolt thread which is straight. As the pipe enters the fitting, the material (pipe) actually is getting thinner. At the exact spot where the pipe and fitting meet, there is a major weak spot which cannot tolerate any kind of shear load. The only way around this is to use pipe which is waaaay oversize for the job which will not only look dorky, but be heavy as he//.

As far as sizing considerations, consider the following-

*A longer kart will not steer as tightly.
*A heavier kart will not perform as well (all other things being equal).