Geez Andrew I have been usurped before I've begun....

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225hp atw on 14psi. 1/4 Mile no idea. Take one 1971 Mini Clubman, one Starlet GT Halfcut, Simmer over a warm MIG Welder, and Voila Minstar! www.mpdesign.id.au

Matt/Andrew/All - what thickness is that tube? I've been planning to make my subframe out of RHS, but I'm changing my mind...

I used mild steel tube with a wall thickness of 2.5mm, Andrew used even thicker tube (4mm is that right Andy). Tube is technically stronger than RHS but if you used 4mm anything you'd be pretty right. The only thing is that tube is a little trickier to join up as you have to fishmouth all the joins. I did it mainly coz it looked trick...

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225hp atw on 14psi. 1/4 Mile no idea. Take one 1971 Mini Clubman, one Starlet GT Halfcut, Simmer over a warm MIG Welder, and Voila Minstar! www.mpdesign.id.au

what's a fishmouth join?

first thing I've gotta do is make that jig for the subframe - I only started making it back in December...

Hi skssgn and Minster,

Thanks for the accolades. The front spar will be a bolt-on bolt-off item because of the need for space to get the engine in and out with the turbo and catalytic converter in the way.

I used 38mm x 4mm round bar supplied from Orrcon. They can even supply MDS (Material Data Sheets) for this tube stating compression, tension, shear, ductility and maleability of the bar. The flat bar is 6mm plate. I used an entire 1m length of 100mm x 6mm flat bar.

I am not a personal lover of RHS, although it is easier to use (weld with). Section for section, round bar is stronger under load. That is why roll bars and space frames are all round bar. 4mm by the way is much easier to weld with as well - no issues with blow-through.

Fishmouth joins is where you cut the round bar on the end to suit the round bar profile of the other bar. Just imagine a right-angle join where the first bar is butt jointed in the middle of the second bar. It takes a bit of practice to get it right!

Matt - you are still the pioneer Old Son! Heres hoping is gets passed by Qld Transport.

Andrew

When joining pipe to pipe at an angle it is not just a mitre cut as it is with RHS (google TKY joints).
The profile shape is like that of an open fish mouth!
Although you can get CAD programs to work them out, it's easier to roll cardboard (weeties box) around the pipe and cut a template with scissors.
There are special Pipefitter's marking guides you can buy, but they cost $$$.

Also when buying your materials, specify structural TUBE, not pipe (that's for carrying stuff).
Structural tube is 350MPa yield strength, pipe is typically around 230MPa
so tube will be 50% stronger , allowing you to use a lighter wall thickness.
Most suppliers will also be able to give you a Mill or Batch Certificate so that you can prove to your engineer what type of material you used (though some won't ask).

Mike


Or you could bribe Andrew to make the templates off his completed subframe. afterthought

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Too many cars, and too little time.

Damn, too slow again

A curse on shared dial up accounts

Mike

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Too many cars, and too little time.

Well done Archangel007 impressive stuff. So what wall thickness is best 2.8 or 4 mm, thats a pretty big difference.

Minster,

4mm definately!

It welds easier, is stiffer, and overall will only add about 2kg in weight.
Also, I use thin-kerf (1mm) 4" angle grinder blades so the tube cuts no problem.

I think Matt would agree that if he had to do his over again, 4mm would be his choice.

Andrew

Ok then I will add that one to the list. It would be pretty expensive wouldnt it? Can you use a pipe bender when using this to create a subframe or is it not structually sound to do so?

it would have to be mandrel bent and that means made to order and that would probably mean it would be more expensive...

Yeah Andrew 4mm, still it seems to work pretty well so next time. Also most mandrel bending is on thin wall like steam pipe etc for exhaust, you would need a pretty strong mandrel and bender to do 4mm. I considered mandrel bent for some of the angles as this would make it stronger and plus the wow factor

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225hp atw on 14psi. 1/4 Mile no idea. Take one 1971 Mini Clubman, one Starlet GT Halfcut, Simmer over a warm MIG Welder, and Voila Minstar! www.mpdesign.id.au

Minster and MiniGT,

Mandrel bender would work OK but only to a certain degree - probably no more than about 20 degrees or so. Any more and you run the risk of kinking such a thick wall pipe even with a mandrel.

Like Matt said, would have to be one hell of a pipe-bender though!

Cost of my pipe for a 6m lenght from Orrcon was about $65.00 I think. I have about 2.5m left I think which I may use as a strut brace across the shock mounts in the boot, and then carbon fibre wrap it to give it some bling factor. Heavy though!!

Andrew

top chat & advice guys - I'm loving this thread... when I first discussed the plans with my engineer about a year ago, he was concerned about me using material that was too thick, and wouldn't crumple enough in an accident - has anyone come across this? or are they saying 'make it strooooong'

skssgn,

Mini's weren't designed with a crumple zone anyway.

I think its more important to keep the engine/gearbox rigid and in place under all loads than engineer in a crumple zone.

Matt/Brad - your thoughts??

Andrew