Is structual strength significantly compromised by a bulkhead box?
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By cutting a large chunk of box section away to make way for the t3, is the shell stiffness reduced by a significant amount? Also in an accident, will the bulkhead will just fold?

I'm at the initial planning stage of mine which I might turbo next summer. I can't afford aftermarket manifolds, t2 ect so the bulkhead box is my only way forward.

Just after opions on the matter really.

Cheers

Edited by minimole23 on 11th Jan, 2008.

Of course it is. How much however is hard to say. Many use rollcages in their trackday warriors, these obviously rectify this + more.

i think in a crash the bulkhead is gonna be the last of the problems...but i think the box's are made with thicker metal anyway so there'd be no real big strength lost...maybe lol
Moz

The cross member which the bulkhead box replaces part of is box section which is the strenghening for the bulkhead itself, when you fit the bulkhead box its concave on relation to this and youve obvioulsy removed the barcing box section that was there before so yeah it will definately be weaker!

The only way to reduce the rigidity lost by putting the bulkhead box in is to use really thick sheeting and combined with decent weld I dont think theres much else you can do!

With a steel front end though, surely a fairly hefty whack will in theory bend the subframe upwards? And not push it back towards the bulkhead? Ive got a flipfront, obviously wont take as big a hit so I might be having the engine as a passenger if I stack it badly lol!

Rich

Edited by richminiturbo. on 30th Oct, 2007.

i would say the bulkhead must be weaker even with a seam welded box and the subframe bracing kit.

BUT i've had a couple of turbo minis over the last 12 to 14years, and ive never had a bulkhead or subframe crack. the first turbo mini had the box section removed but the bulkhead intact and no subby bracing, then it got a seam welded bulkhead box and that was fine.

how they fair in a crash? i hope not to find out!

in mine , i have welded captive nuts on the subframe in 4 places along the engine side at the top ,then packed the space between the frame and the body with plates of steel ,then put a plate inside the car and bolted the whole thing ,plate, body, packing ,and sub ,all together in the 4 places with m8 ht bolts ,this prob makes it all a bit more rigid ,you could try that if your worried ?

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I've done a similar thing to Robert, with a packer and 3 off M10 HT capheads.

i can say that they definatley do weaken the structure, i have cut out my upper bulkhead as im fitting a large air box, with the lower bulkhead in one piece it was fine, but once cut out and the turbo box re welded (seam welded) in there is definate flex there.

its something im hoping with my cage and some bracing in the upper baulkhead i will be able to loose.

Well this is how I did mine and I dont think it'll be any worse than it was before the mod. Certainly worth spending a bit of time to get right.

Attachments:

86.94kb

It's all fun and games until someone gets hurt... Then it's hilarious!

Well this is how I did mine and I dont think it'll be any worse than it was before the mod. Certainly worth spending a bit of time to get right.

Attachments:

86.94kb

It's all fun and games until someone gets hurt... Then it's hilarious!

I would say that yes it does weaken it...

But, dont forget. You also have the shell tied together by that strong steel structure that is the front subrame, bolted at either side of the bulkhead box.
Get some solid or poly mounts for it, and it should remain pretty strong in there.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I have done some reasoning, and decided that as most turbo minis have them welded in so I will stop worrying and get on and chop the bulkhead when the time comes.

cheers.

Edited by minimole23 on 31st Oct, 2007.

PS- There is only one "a" in "bulkhead" :)

Removing that much of the crossmember will reduce its rigidity by at least 50% or more - that is torsional rigidity, for compressive strength it would be reduced by a far greater percentage - probably 80% or so. No matter how thick a gauge of metal you weld back in you will never regain the rigidity in this method - if you want to regain the strength you need to add section - box, tube etc across the dash rail area at least with large spreader plates tied into the crossmember at its ends and in the middle, to reform a "section" for the forces to react against.

wether this section of the mini was way over engineered in 59 I don't know, hence why it may not make a diffrence. If you were to do a torsional rigidity check on the mini shell with and without this section removed I think it would raise a few eyebrows as to how much the rgidity has changed

just my two penoths worth from a qualified chassis design engineer!

JK

If Carling made Mini engines
it would probably be like this one!

Taking out the box section from the bulkhead lowers its strength end of. It dosen't matter how you weld in yor box. You have replaced a box section with a pan type structure.

Hi,
A Mini involved in any serious acccident folds up to look like an explosion in an origami factory.
If you get hit side on the sills are more of a worry.
Full cage would be the only way to maximise your chances of staying intact!
Cheers,
Gavin :)

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Well thats cleared that up well.

What i'll do is weld the box in, mabie with some sort of bracing behind it, then do as per Robert mentioned and tie it in to the bulkhead.

Thanks all.

my idea to being back regidity was to make almost a strutbrace from each of big bolts at the top of the subframe wich if im not mistaken are part of the suspention. i was going to have a brace going from each of the mounts back into the car and then accros the back then bolted to the bulkhead box. no idea if this would work but im going to give it a go

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