13 replies to this topic

[Jellevandok]

Hi there,

I'm rebuilding my Mini for trackday's. I've been told that to make the car more stiff I should weld the subframes aside from the spotwelding. Before I just start at it, I wondered if someone knows where to weld en what not. I don't want my car to fall apart @ the first corner...

Jelle
(The Netherlands)

[il-barba]

i think what you really need are solid subframe mounts, that attaches the subframe solidly to the body

[Retro_10s]

One of the first and easiest things to do is to make sure all the joins on the subframe are fully seam welded - for instance around the tops of the towers etc, just make sure all the joins have a good continuous weld on them

And as mentioned above - it would be worth mounting the subframe using solid tower mounts and floor mounts. This stiffens up the front end a lot - Retain the standard engine mounts and make sure all the engine steadies are in good condition.

[Jellevandok]

It was my plan indeed to use the poly mounts, teardrops etc for the subframemounts. Aside from that I will weld the frames (or have it done by someone with the skill;)

[jaydee]

If you want to fit solid lower mounts weld a steel plate to the floor where each mounting fasten to, this to avoid that the stiffened mounts crack the floor.

[Cooperman]

You don't need to weld the subframesw, just bolt the front one in with solid mounts. The one over-engineered item in the entire car is the front subframe. In over 45 years of rallying Minis I've never seen a front subframe split its seams, even on the roughest tracks. The one wek area on the front frame is the 'ear' onto which the tie bars fix at the forward end. These can be supported by a 3 mm or 4 mm triangular steel plate welded in place.
The rear sub-frame is also over strength unless it is rusty. It really needs no modification unless it's to be used on really rough and unsurfaced roads when the lower faces can be plated with 2 mm steel sheet to resist wearing away by stones and rocks.

[MRA]

You don't need to weld the subframesw, just bolt the front one in with solid mounts. The one over-engineered item in the entire car is the front subframe. In over 45 years of rallying Minis I've never seen a front subframe split its seams, even on the roughest tracks. The one wek area on the front frame is the 'ear' onto which the tie bars fix at the forward end. These can be supported by a 3 mm or 4 mm triangular steel plate welded in place.
The rear sub-frame is also over strength unless it is rusty. It really needs no modification unless it's to be used on really rough and unsurfaced roads when the lower faces can be plated with 2 mm steel sheet to resist wearing away by stones and rocks.

Agreed, as we manufacture and fit a 285mm disc kit and have done some pretty extensive research on the front subframe, the "ears" MUST be welded up as a decent brake setup can rip them off

However we are not just talking of damage to the subframe.... welding up all the seams stiffens the subframe and does aid on track, not so much on rough surfaces but on smooth race circuits you can feel the subframe twisting also add another seat cross member to stiffen the shell

Regards Martin

[Wil_h]

My personal opinion is that seam welding the subframe does nothing other than add weight. When a subframe flexes it not the joints that move, its the whole thing. If you want to stop it flexing you need more triangulation.

[MRA]

Hi Will,

Yes triangulation, however take a look at the front subframe and you will see that a compromise for more triangulation is to seam weld it up

Regards Martin

[daveeeeee]

Martin have you had noticable success with a second crossmember? I'm very interested in the idea Do you mean layering another on top, or adding a second behind it?

[MRA]

About 15" behind the current one, it takes a little bit of "fettling" and the panels are not cheap, but it does help stiffen the shell up by a noticeable anount

Regards Martin

[daveeeeee]

Thanks

[Wil_h]

Hi Will,

Yes triangulation, however take a look at the front subframe and you will see that a compromise for more triangulation is to seam weld it up

Regards Martin

I have run some seams on what I have found to be the weaker joints of the frame, but these are more for an increase in life rather than reducing any flexing. Seam welding mainly comes from rally cars where the shells take a massive pounding and fall appart, the seams reduce failures.

I will have a look at my subframe and see if I can spot what you mean, always keen to make improvements.

[MRA]

If you have a subframe out of your car.......

use a paint pen to mark the welds, if its a spot or seam weld paint the weld with say red paint, when done stand back and take a xareful look at your handywork, you will see that you can either carve chunks out of your subframe to make it lighter (not recomended) or weld it up to make it stiffer and stronger.

Also when I said seam weld in my last post I meant the subframe, however seam welding the shell does help, it enabled me to walk away from a ptentially fatel head-on crash with a 38 tonne milk float (EDIT: Tanker) on the A5 near Hinckley Leicestershire...... I could even open the doors.... estimated impact speed was about 40mph

Regards Martin

Edited by mra-minis.co.uk, 12 May 2009 - 08:14 AM.