Positioning frame tubes

[Tilman]

Heyho everyone,

we have got a big problem with our frame construction ...

This year we do not have access to laser-cut frame tubes so we ground them to profile by hand, so they are everything but accurate and our welding fixture is crap, too. (I will not explain why, there are multiple reasons. We know our mistakes very well.)

Now we are looking for a cheap, easy and quick method to position our frame tubes, but we have no idea how to do this.
Building a new welding fixture using laser-cut steel sheets is one option, but the guys that did the first welding fixture think it will take too long to build this.
The second method is to buy square aluminium profiles and build a rig, but we do not have the money to buy them and no sponsor of us has got such profiles ...

Could you please tell me how you positioned your frame tubes? Please provide a photo, if possible. This would be great ...

Thanks in advance,

Tilman

Yes, we know, we are *very* late, this is the biggest mistake we ever made this year ...

[Tilman]

Heyho everyone,

we have got a big problem with our frame construction ...

This year we do not have access to laser-cut frame tubes so we ground them to profile by hand, so they are everything but accurate and our welding fixture is crap, too. (I will not explain why, there are multiple reasons. We know our mistakes very well.)

Now we are looking for a cheap, easy and quick method to position our frame tubes, but we have no idea how to do this.
Building a new welding fixture using laser-cut steel sheets is one option, but the guys that did the first welding fixture think it will take too long to build this.
The second method is to buy square aluminium profiles and build a rig, but we do not have the money to buy them and no sponsor of us has got such profiles ...

Could you please tell me how you positioned your frame tubes? Please provide a photo, if possible. This would be great ...

Thanks in advance,

Tilman

Yes, we know, we are *very* late, this is the biggest mistake we ever made this year ...

[Auerbach]

I've built a frame using MDF jigs (medium density fiber board) on a 4x8' wooden table and it turned out nicely. We only used the profiles developed in CAD for the important stuff(roll hoops, suspension pick up points) and then constrain said important stuff with jigs and hand grind the remaining tubes to connect the dots. Not the most scientific, but it meets your goals of cheap, easy and quick.

For my roadster project, I used the same concept but used CNC plasma cut steel plates for jigs. It worked well but does take a little time to design, cut, assemble and weld all the plates. I'll dig for a photo of both...

[Bazanaius]

we used ply wood cut on the water jet (mdf tends to expand on the jet), about 12mm thick if I recall.

As Auerbach did, we found we just cadded jigs for the front box, rear box (ensuring jigs set both bits at correct relative height) and then knocked something up to hold the main hoop in the right place. the two boxes could be welded independantly then positioned and the connecting bars welded in place. Takes a bit of time to ensure the connecting bars are correct and everything is straight, but works quite well with little distortion.

B

[Mikey Antonakakis]

We used a table made of MDF or something last year, with jigs for individual tubes made of some type of wood. The MDF does swell a lot when it gets wet, so be careful not to spill drinks on it. I think ideally we'd have a much bigger workshop, with a lot more time and money, so we could have a gigantic steel table that weighs several hundred pounds and jigs machined out of aluminum or something.

[fixitmattman]

Man this is basic welding and fitting skills right here. No fancy jig required.

[Benn]

we build our car in 3 parts then join it together. the rear diff box and the front pickup area are built on steel plates. the plates have difference sets of holes so we build the front and rear of them first, and then join the front and rear on top of the plate. the safety cell was built on some pieces of mdf screwed together, then the diffbox, safety cell and front of the car are connected on a chassis jig, its just some pfc thats been welded then milled flat.
http://i29.tinypic.com/2j4pkzn.jpg