15 replies to this topic

[jackclancy]

Hi guys,

My shock mount areas have pretty bad rusting. I’m torn between repairing, or just replacing the entire bulkhead crossmember. Inside the crossmember looks pretty rusty to be honest.

The RH mount looks repairable, the LH looks to be trickier. I think if I cut out a large amount of the LH side and then put some new plates in that protrude below the crossmember it would be fine.

Would be easier to repair for sure, just not sure about all the rust inside the crossmember. Considering the car is gonna be a very boosted racer!

Any thoughts?

[jackclancy]

Extra pic

[stuart bowes]

looks to me like you'd want to replace the whole inner wing(s) to be honest, it's a bit of a patchwork isn't it

 

at which point, might as well put a new crossmember in (he says, as though it's a quick easy job lol)

Edited by stuart bowes, 12 February 2025 - 12:56 PM.

[Ethel]

I'd be tempted, looks like you're half way there anyway. How much do you value your time? Looks there's more than a week's work in botching repairing the existing one.

 

You'll have to decide before you go much further, so there's enough left to jig up for locating a new one.

[DeadSquare]

To get you on to the grid:-

 

The shock mount isn't a structural part of the body, so from your competition point of view, there isn't a safety aspect.

 

@ Ethel inadvertently mention botched.  You are wanting to get the vertical loads from the shocks, into the body, so how about carefully shaping, fitting, Isoponing and screwing a piece of hard wood (Oak) into the cross-member with the grain from front to rear, then painting it and screwing the shock mounts to it in addition to the factory mounts.

 

I don't wish to be pessimistic, but even though the cars are all meant to be travelling in the same direction, accidents do happen, at which point, you could re-evaluate the state of the 'tin-worm' in your shell.

 

If I thought that a "modification" was safe, I worked on the principal that, it was my car and my life, and what the scrutineer doesn't see, his heart doesn't grieve over.

[sonikk4]

I'm going to disagree with Deadsquare here as the shock mounts are incorporated into the tower mount area (part of the crossmember) so yes structural especially as that whole area is compromised. Although two tapped mounting blocks and a couple of half arsed spot welds holding those blocks in place is not exactly saftey inspiring to be honest. But it works.

 

Having replaced all of the tin at both ends on Paddys crossmember and considering the loads there and looking at your corrosion i would replace the inner wing halves and the full crossmember. New gussets as well, make your own.

 

I understand its more of a track orinetated car and as you say boosted (and i would assume caged) but do it properly the first time, get the strength back in there and happy racing.

[jackclancy]

Thanks for all the responses. Yea I think I am just gonna go ahead and change out the crossmember and inner wings. Better to just do it properly at this stage and get strength in there as I am looking at about 200bhp when finished so want it to be structurally sound! 

 

Oh and yes it will be caged!

[weef]

It's like opening a can of worms when you start cutting out the crossmember, take lots of measurements and work from a fixed datum just go easy when you cut it out.

Looking at your pictures its probably the only option for a succesful repair, and not really before time as it does look like a red indian.

[stuart bowes]

I imagine you'd also want to weld some lengths of box section on the inside to brace things up, with that sort of job

[jackclancy]

I imagine you'd also want to weld some lengths of box section on the inside to brace things up, with that sort of job

 

As in inside the crossmember?

 

There is always the option of an entirely new bulkhead too I suppose....

[stuart bowes]

I was thinking more generally along the lines of, one vertical either side from the floor up to the window rail maybe, then from there to the inside of the bulkhead in a couple of places, with a triangulation or two, I dunno

 

I've not done it myself I'm sure others can advise if it's necessary or not, that's just how I saw it in my mind when thinking how would I do it.  maybe it's overkill and not necessary

Edited by stuart bowes, 13 February 2025 - 11:08 PM.

[Ethel]

How about building a jig so you can fit it with the subframe? I'm seeing a couple of  4by2's clamped or bolted  to the floor with another making a crossbar that bolts in place of the front mountings.

 

p.s. the "botched" was just me imagining it as my job 

[DeadSquare]

@ Ethel.  I'd like to think that you were actually meaning "Bodged", not botched,

 

A Bodge was a rough measure of about half a Peck, and a Peck was a gallon scoop of something dry like peas or corn.

 

If circumstances were getting hard, people resorted to "Half measures", and made do with a Bodge instead of a Peck, as sometimes happened on an unexpectedly long sea voyage.

 

The voyage might have been lengthened by something breaking and being repaired by what ever was to hand, called a "Jury-Rig", and so the Bodge and the Jury-Rig often went hand-in-hand and to Land-lubbers, and came to mean the same thing, ie; making the best repair under the circumstances.

 

It is a quirk of the English language, that something jerry-built, that was done wrong, badly or has failed, is described as botched.

[Blumeanie]

@ Ethel.  I'd like to think that you were actually meaning "Bodged", not botched,

 

A Bodge was a rough measure of about half a Peck, and a Peck was a gallon scoop of something dry like peas or corn.

 

If circumstances were getting hard, people resorted to "Half measures", and made do with a Bodge instead of a Peck, as sometimes happened on an unexpectedly long sea voyage.

 

The voyage might have been lengthened by something breaking and being repaired by what ever was to hand, called a "Jury-Rig", and so the Bodge and the Jury-Rig often went hand-in-hand and to Land-lubbers, and came to mean the same thing, ie; making the best repair under the circumstances.

 

It is a quirk of the English language, that something jerry-built, that was done wrong, badly or has failed, is described as botched.

 

Ha! I love it!

 

I believe it to be true that the only use left for 'Peck' these days is when one says: "Peter piper picked a peck of pickled peppers..."

I believe it to be true that the only use left for 'Peck' is when one says: Peter piper picked a peck of pickled peppers...

[Cooperman]

You can get bulkhead cross member end repair pieces from M-Machine. For additional strength it would be easy to make up a doubler channel to go inside the join area, plug welded in place, to increase the strength. The new inner wings will weld to the flanges on the ends of the repair pieces.

I would do a dummy fit of the sub-frame to obtain accurate alignment of the end pieces, then remove the sub-frame for final welding in place. 

For a competition car, it can be a good idea to reinforce the cross-member ends locally to better get the vertical (shear) loads from the damper brackets into the structure.