Compact's- is seam welding needed??

[compacthope]

Can i ask do any of you think seam welding etc is needed on a compact im looking to build for a tarmac rally car??
Im hopefully putting in a M3 engine/box up front and it will be used in the STRC next year,and the odd trip over Otterburn too!!
I've seen links on here where some of you have double skinned the turret tops on some cars and beefed up the rear diff mounts- are there any other areas i should look at??

Pics will be added of the donor car when i start the build in the next 2 weeks of so- weather permitting

[is-si]

I can only comment on what we did to our E30 . . . . a while back
We just fitted a clubby bolt in cage at first, (we just wanted to get out and have a go with the car 1st)
but we added fixing points to the body, up all the pillars. We added gussets to the inner wings/chassis, and made sure all the front was well stitched with welds. A while later we added some stiffeners/gussets under the inner wings, that boxed up a lot of corners. Didnt do much at all to the back.
we've had no movement so far...
having said that i think the E30 shell is a better job than an E36 one, pressings and steel thicknesses seem better (i may be mistaken)

[slippy]

Anymore for anymore on this as we may have a very cheap donor car available so would be interested to see what people do re shell prep

[M3 Compact]

i think the E30 shell is a better job than an E36 one, pressings and steel thicknesses seem better

I think you're probably right. The overall strength and rigidity of the compact shell is good imo, but some of the 'bolt-on' areas could be more durable.

We did a fairly minimal amount of 'preventative work' on my first compact, as it was only ever intended to be a 'stop-gap'.

The bolt-in cage was tagged in several places and fastened up to the front bulkhead (not through to the turrets), not a huge amount of stitching and it used a single diff lug mounting.

The weakness were exposed very quickly...

The rear diff mounting box section parted company with the 'boot' floor very readily.

The fully floating front turrets bent the bolt-on strut brace like a banana on the first event. The turrets deformed badly and were literally pulling off the inner wings after a few roughish events.

Passenger side rear of the front turret was the worst (in front of the OE fuse box), I could get my finger in the gap between the turret & inner wing.

No probs at all with the wishbone rear mountings, rear beam mounting area, chassis rails, tunnel or door gaps etc. I use some substantial tank guards to brace the beam.

Steering rack mountings on the X-member are rubbish and need strengthening. X-member generally ain't too s**t hot imo. Engine mounting area is also a bit poxy.

If I was building another compact from scratch, I'd either use a 'World Cup' type X-member arrangement, or chassis mount the engine.

If you're using a pedal box with bulkhead mounted cylinders, the bulkhead would benefit from strengthening - mine was flexing a tad.

[m3heaven]

M3Compact wrote:

X-member generally ain't too s**t hot imo. Engine mounting area is also a bit poxy.

Agreed. The metal work should be double skinned where the engine mounts are fitted. Standard road going E36 M3 subframes (axle support, x-member) suffer from cracks and elongated holes.

[is-si]

as you say r.h. front x-member tabs suffer stress fractures too with age, even with a 4 pot on them.

[compacthope]

Thanks- thats all good stuff to know

I've been in touch with Custom Cages today and sorted out a club cage with some extra tubing for X bars etc...It comes in at about £450 plus vat which is pretty good i think

They show a compact on their website having a full multipoint cage being fitted...if you look over the pics it shows the front turrets basically welded onto the inner wing rails via the cage and a gusset. I think i'll go down that route, seem weld the front end and beef up the rear diff area. Im sure i've seen on here a pic showing a double pick up E36 rear cased axle set up?? Maybe while im building from sctratch, it will be worth spending some extra hours sorting the areas where problems arise!!

[granthughes]

We used liquid nitrogen to freeze and break off all of the sound deadening and glue. Removed around 50 lbs of s**t from the bottom of the car. Then seam welded. Holy s**t there are a ton of seams on the compact. It took two sessions to do the seam welding on the BMW Compact whereas on my Merkur (Ford Sierra) gravel car, it took about half of the time. That said, there are alot of seams on these cars and I'd definitely recommend seam welding.
There's a few pics of doing so on my Merkur here:
http://www.rallyanarchy.com/phorum/read ... #msg-36349