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Do you guys have by any chance any photos how you have done it in your cars? What to avoid, what too look for when welding? Do you use MIG or TIG? Any tips are welcome!
cheers,
Pete

Well, it is a big job and you need one of these things if you want to do it fully. I made the rottisserie to start with. If you have a hoist to use at your leisure, that's almost as good but not quiet.
You need to pressure clean everything first. Strip off the body protection materials with a heat gun and scraper. If you have a mobile sand blaster, you can blast off the paint tracks along the seams to get a clean weld going. Otherwise, a small angle grinder will get the job done too.

When welding, just do short runs along the seams about 10mm long and the same length apart.

I used a MIG.

I have done strokes of 40 [mm] welding and 40 [mm] apart, with a mig welder.
If you have the chance (not everywhere applicable on the transaxle chassis) use plug / slot welds, without making slots in the upper plate.
The upper two sketches in this picure





The advantage of this weld:
due to the material shrinkage of cooling weld, the two plates will build up a pre tension between them. So even outside the welds the plates build up a friction force. Making the welded construction almost as stiff as a real beam.

Sweet unit, MD!

Thanks.
A very useful tool. Its on castors so you can roll the shell anywhere like onto a flat bed truck for transportation to other work sites like, the paint shop, pressure cleaning bays etc. While at the paint shop, its useful to paint the whole underside of the chassis and the interiors for ackward angles. Also great for welding flow where it would normally need to flow "up-hill" which is otherwise tricky to get right unless you are a skilled welder. Handy when building the roll cage too.

Thanks for the tips. I understand that welding everywhere is unnecessary. Or is it?
Areas like engine bay, shock mounts, seem straightforward to me but what about floorpan? Weld Only around members or other particular areas?

Pete, I'm no expert at this but fortunately you cannot overdo it in a sense other than put on extra weight !!

I just followed existing weld lines like subframes front and rear. Sill sections, cross members.

What is important to do is put a re-inforcement plate inside the front sway bar mount and stiffen that whole section up as it will flex instead of the bar and eventually tear right out-particularly with big bars.

If you plan to use coil overs , it's also wise to plate up the shock towers up front.

Hey MD , is what they call '' put another shrimp barbi '' in OZ. You could set up your playstation in there attached to accelerometers on your rotissiere.

kevin wrote:Hey MD , is what they call '' put another shrimp barbi '' in OZ.

Yanks have got a lot to answer for when it comes to that saying .
Ozzies don't call them Shrimp, we call them Prawns. But I am speaking from a non-Queenslander point of view. Banana Benders like MD probably call them something else again

'fetta on a spit???

Faaark, the amount of humble pie a guys has eat just to help out a Polish mate.
Pete, I hope you're sucking this up..BTW the advice is going to cost you two bottles of your bootleg firewater I know you got stashed away in the shed.

Duk..'fetta on a spit. Good one son.
Kevin. Get stuffed. I hope all your chickens grow up to be Emus and eat you out of house and home..

Last weekend I've been in (2400km round trip hehe) Zandvoort, Holland to see alfas racing big style. Awesome event. Of course I was there to taka a few peeks how people prep their alfas. What I noticed, few cars had their chassies seam welded, the cages themselves were not too complex or extensive in design, the only logical assumption is that transaxle chassis is superb in terms of stiffness? Just food for thought.

Pete,

From the firewall back I would agree.

From the firewall forward I would not agree as the chassis rails tend to flex and crack including the inner guards and welds fracture inside the engine bay. The bigger the torsion bars you use, the more the front flexes and fails in places. The sway bar mounts also rip out too. The stronger the cage is behind the firewall, the worse the condition evolves in the front particularly the rally cars when they get a pounding.

I have just finished doing repairs on my next racer just for these reasons.

I have always thought of, at least the 75 body stiffness, in terms of a wet dishrag. It's incredibly compliant and will twist like hell given the chance.
For the records, the load from the front wheels will go into the car at the LCA mounting points.

A cage will certainly help but there is a trade-off, weight. So make it stiff but don't just add pipes, think carefully where they will help and where they are just weight. Making a scale model in wire or similar (straws and hot-glue) is usually very interesting.

Good Luck.

@MD,

here in Holland most racers don't use bigger torsionbars, they are quite rare over here. The RS stuff is made over here and is extensively used.

Also the 75 was not a very rare car over here and if it got written-off it was easy to replace with another shell. All that extra effort in the shell would be lost then and i'm guessing they don't think it's worth the work. Would be interesting to have a few racers from all over the world on a track to compare them.

@ PieterQ,

Good to hear you were over here at the SSAR! It was a nice weekend apart from the horrible weather. I will never forget the sound of the 33 Stradale...

I've been at the SSAR the last ten years and i can't recall worse weather than this year, almost every other year we had beautiful weather. This year i went on Sunday and that was the worst day, heavy rain in the afternoon soaked us to the bone and kept us wet until we got home (150 km later).

Front rail strengthening;