Hi
I've spent a frustrating morning tacking the lower chassis together and (you guessed it) after I'd turned it over and done the bottom it wouldn't lie flat.
Ive made some adjustments to it an now it is nearly flat but I need some advice about how flat is "flat enough".
It is not twisted but has a gap of 1mm under the D1 and D2 tubes.
Opinions please.
Thanks
Dave

I had the same thing, put one end up on a piece of 3x2 and jump on it and it'll flatten out. I wouldn't worry about 1mm, personally I wouldn't worry about 3mm or you'll never finish it

i didnt tack the bottom mine until everything else was done.....ie it was on the board a long time.....lol

Thanks for the advice.

Cheers
Dave

theres a few possible causes besides welding distortion, if your board was a mere mm out then the chassis would be 2mm out. Just tack it as best you can and make sure that the suspension brackets are correct to the board, not the chassis.

As long as it isn't twisted, you will be fine, clamp it back down (shouldn't really remove it until all the triangulation has been tacked in), and finish the chassis.

If the chassis does end up bowing up at the front, it is not a problem, it will only add to you much needed castor angle!

How did you get on jumping on your chassis?

I have done the same thing earlier this week and have read meany's advice too late!

Jumping on it sounds serious - that I might add more bends, in different places, than are already there.

I'm liking the idea of clamping it to the board until it's finished until the rest of the chassis braces everything in place.

I am still at the striving for perfection stage!

You won't bend any tubes, just the tack welded joints. If you go too far, just turn it over and jump on the other side.

hmmm what will the neighbours think?

mad man furiously jumping on a few pieces of metal, swearing when they bend too far

nah only kidding, the idea of jumping on it actualy sounds like quite a good idea so long as you dont take it too far otherwise fatigue will set in .....

Matt

JoelP is correct, no spaceframe is going to be "correct" in space, as welding will warp it. And no point trying to make it. As long as all suspension points are correct in x,y,and z it is better than any production car, imho.

That did the trick anyway. I'm sure any fatigue I've introduced will be undone when the tubes are fully welded.

What do you guys use for clamping the tubes to the board? loads and loads of G-clamps?

Small blocks of wood screwed everywhere to hold the chassis in place then longer bits between the shorter bits to hold it down.

http://bitsablade.co.uk/displayimage.php?album=11&pos=94

Pat...

When a weld cools it shrinks.

You can limit distortion by welding to a sequence, weld on the top, weld on the bottom.
Move to the other side, and same again, and of course, clamping down helps.

It is a job to get it perfect, well in fact you can't. near enough is the best any of us can hope for.

You can however make this shrinkage work for you.
Clamp the chassis back down, and run a nice hot weld where you need the shrinkage.
Allow to cool, and hey presto, back to flat.
(If you reweld a fillet, grind the build up off first so you don't end up with a huge weld.)


Paul G

Thanks a lot guys, that's very helpfull.

Used to be the way to do the corner weights on Karts, put a block under the relevant point and twist the chassis slightly by standing at the right place!
ATB
Phil