Track car seam welding - a necessity or a hobbyist's rite of passage?

I'd been thinking about a thread on this for a while, but a conversation earlier bumped it up the list...

As title, why do we do it? In some ways, I'm as guilty as the rest for some box-tick modifying, and the process of shell preparation sits up there with the best of them as a manly thing to be doing about the garage. Full of good karma, as well as an experience to tick off in its own right.

But is that why we do it? Has it really got shell stiffness benefits you're going to see a laptime advantage from? Does it need to be done end-to-end? Resale value, future use.. just what is/are the reasons?

VW Cup racers aren't always seam welded... and race/track car shells get nothing of the sort of grief that rally car shells get....

Discuss!

 

I'm not so sure on this. A lot of time goes into completing a job like this but how much shell stiffness is gained? Will it really knock a couple of seconds off a lap? A full multipoint or even 6 point cage would probably do more I suspect. Also, modern cars have exceptional shell stiffness to old stuff so possibly just loads of weight added via the mig?

Gurds

 

on a mk1 you need all the help you can get,

back to torsional stiffness, when is enough, enough?

I know on BMW production cars, they haven't got any stiffer since the E39s as that was all that was needed, and any extra stiffness was more weight for little discernable gain.

i think i'd rather crash something seam welded

 

I should have said in post 1 that for debate's sake, if a car is seam welded, it's implicit that a cage has been fitted.

That cage could be a 6-point bolt in, or it could be a multi point weld-in with all the structural beefing up that implies. The VW Cup cars I mentioned all have the latter.

 

I think once you've added a full multipoint cage the gain in torsional rigidity from seam welding will be negligible to all but the people chasing the last few milliseconds. So probably not worth it.

However if your regs don't allow you to have a cage going through the bulkhead to the strut tops then the next best option is to seam weld the chassis legs at the front at least.

I think the weight argument is fairly negligible, driver could lose 2kg and that will be about the same as the amount of wire fed in to seam weld a car.

But while you have the car stripped out why not do it as it's much easier than doing it before, than after the cage has been put in. You also have the added safety which comes with a stiffer shell as prof says.

 

On a track you're needlessly adding weight by seam welding (IMHO) - as said, a rally car gets more stick, more of a pounding and I have seen stock seams split after an intense event (usually with people buying a car for the one event, spending some time prepping, welding in plates for a bolt in cage, complete the event and then bin the shell and move on to the next)

I know why we do it to our cars, but a track car may need it if it's spending some time on the kerbs - other than that, it seems pointless.

On a side note, I was looking at keeping my car legal for the stock hatch rounds and their regs explicitly prohibit seam welding (or did in 2009 when i started my project - I doubt it would have changed)

 

I seam welded my quattro and wouldn't do it again if I built another. The first point was that it was bloody hard to do as I just could not get the seams cleaned up properly. The welder hated it untill the heat burn't off what was inbetween the seams. The second point I came to think about much later after doing it was that any sort of protection that was between the seam was now gone!

The final point is that with a modern multi point cage they are almost a spaceframe now. I cant see the turret tops moving at all with a proper weld in cage?

 

Mine isn't seam welded just because i don't think i'll see any benefit over the cage i'm fitting, plus its more time the car will be in bits.

Me and a few mates re-shelled a 106 cup car a year or so ago (which wasn't seam welded at all) and we/they seam welded the new shell and spent about a week of evenings and a few weekends doing the whole thing. not worth it i don't think.

Like hamish has mentioned, getting the seams clean is the worst bit, wire wheel on a grinder and a mini blow torch are good ways of cleaning it out. nightmare!!!

 

It is nice when you're in the paddock and looking over cars, the anoraks seem to get excited over cars that are fully seam welded up

If you're not caging a car, it does stiffen the lower tub and there's a benefit there

 

I think it's all about working to the set of regs you're governed by. So, for example, if you're only allowed a bolt in cage, but you're allowed to seam weld then that's the way to go - for example some of the classic touring car series stipulate this.

Also, if you're allowed a weld-in cage, but not allowed to brace to the suspension turrets, then there's a good case for seam welding the front end. As Prof says though, it all depends on what you're starting with.

I've heard of cars racing in 'one make' series that have tended to do better in the wet races through not being seam welded, and having a bit more compliance in the chassis. I guess if you have infinite choice or suspension components and set-up facilities, you could probably get round this, but for the budget conscious clubman, maybe you can go too stiff to have an all-rounder set up that works with limited adjustment options.

 

Racing and regs is one thing, but I think this is aimed at the track day enthusiast rather than competetive racing & championships.

Gurds

 

Indeed, racing and regs: you've got to be as close to the rules as possible to be competitive, but definitely, unquestionably not over them!

I've left the provision for "future use" in post 1, so where a car is going to evolve into a competition car, that's a clear basis to plan ahead.

But otherwise this is a thread to scrutinise preparation in a regulation-free environment, aka the 'Open class' !

 

I can't believe the response, considering the number of previous threads about seam welding!

http://www.clubgti.com/forum/showthread.php?t=196308
http://www.clubgti.com/forum/showthread.php?t=228296
http://www.clubgti.com/forum/showthread.php?t=183451
http://www.clubgti.com/forum/showthread.php?t=153544
http://www.clubgti.com/forum/showthread.php?t=122624
http://www.clubgti.com/forum/showthread.php?t=104284
http://www.clubgti.com/forum/showthread.php?t=70191
http://www.clubgti.com/forum/showthread.php?t=9673
http://www.clubgti.com/forum/showthread.php?t=2498

 

I think it's about what you're planning to do with the car - I can't speak for everyone else, but for me, seam welding the lower half of the car (between front and rear suspension pillars) gives a nice sturdy platform to work from. I'd say tha seam welding is the starting point for a track car that doesn't include a roll cage that will provide the same rigid references for the suspension. But I'd also say don't seam weld everything - you still want some flex/give in the shell in some areas or you'll get cracks appearing. Tieing the roll cage into the suspension pickup points will eliminate those stresses that lead to cracking.

So my 2p:

Seam welding adds strength - if you're tracking the car and WON'T be fitting a rollcage, there's a benefit, if you're rallying it then definitely do it regardless of cage or not (road rally cars are often not caged). But when you seam weld, weld the lower half of the car and only go between suspenion pickup points - that way you retain front and rear crash structures, and still retain a degree of flex in the shell so you don't promote cracking

 

Agree with this.

I would certainly think twice about doing it again, for the reasons given above. If I did, it would be on a dipped shell without any sealer or waxoyl left in the seams. On a dipped shell there is more chance that you would get decent welds.

For the hobbyist the welds can look untidy due to the sealer melting and can lead to corrosion later on.

Also, if you are going that far you will have done a million other things, so how do you gauge any results?

 

Hope this isn't about my car as to be honest I don't have a clear answer.

My car was already stripped, engine was out, trim was out, it's going to have full paint inside and out with lots of other modification so while it was apart it was a case of why not? Also allows the guy who's building my car some publicity and if this thread is as a result of the seam welding on my car then fantastic! If it isn't then apologies for being a little big headed!

And really that's the only reason I've got for doing it, it's stripped, it's going to be painted and abused on track so anything that helps protect the integrity of the shell for the next few years is a bonus, the fact it looks a bit trick aesthetically is an added bonus to me, car's never going to be for sale unless I go bankrupt so why the hell not!

Very much a case of because I can, I will.

 

i think that when you race a car on the track or drive a car on the street seam welding could be very important i have seen some parts of the chassis getting cracks because of large amounts of bhp's under the bonnet ,some people don't realise what that can do to a chassis.Don't they use different type of chassis on rally courses with or without seamwelding,depending on the surface where they are racing?
As for on the track i think seamwelding plus a multi point cage will give you benefit especially in corners,i'm not sure in the wet

 

Not at all, just a very general topic teed up by one of those random convos which focused on the box ticking modifying. Dobbed myself in in post 1 as you see!

 

I think it was very much a box ticking thing for me too Chris, there's no reason why it's been done, it just seemed worthwhile seeing as it was going to be a full resto and colour change.

 

I've been reading this tread and any including seam welding.

I'm doing it at the moment on my own MKI golf car, well not long started. I'm in two minds. One side is a MKI is a flexible chassis. I know of one rallycross car that frequently broke windscreens with a 6point welded in cage. A pillar was weled to the cage with gusset to try and stop this.
My car will be race track only and the track widened. I think I'm going to do the front chassis anyway as it will have the track widened and the extra force that comes with that. It will have a welded cage that will come off the a hoop to the front turrets and maybe braced front the turret to a bar that will run across the bulkhead over say where the heater hole is.

I was all set to do a lot of seam welding when I got a call from a friend to tell me taht with his MKII the seam welding over the winter could have made the car worse and too stiff. He has changed the springs for softer ones and it improved but I'm concerned as to what a MKI with a lot of seam welding would be like in the wet too.

In short I'm going to do the front chassis and turrets but I'm not sure where to stop!!!