Rollcage/ROPS Mounting Points

[Altrezia]

Hi guys,

I also posted this on Ten Tenths, so please feel free to ignore if you've read it there or whatever. I don't normally cross post but I'm feeling a bit gutted / worried at the moment!

I bought an old E30 BMW to race in the PBMWC championship in 2014 - and while the car needs quite a bit of work to get it up to spec, I thought the core of the car was solid - the cage and what-not. The car was raced until 2009, and has been sat in a garage since.

However, after re-reading the blue book, I think I may have hit a stumbling block. The points where my bolt-in cage mount to the shell are supposed to be 120cm2 (K 1.3.2.), but the top area of the mointing only point matches that of my roll cage's feet - 78mm x 100mm (78cm2).

So; am I being an idiot, or do I have a serious thing to 'fix' on the car? - Does the rule include any folded metal that is also welded on, or is it just the top face used for mounting the cage on?

Here is a picture as an example, it is the front most mounting point of my cage:
http://dorkish.com/albums/Cars/BMW%20E30%20Racecar...

And here is one behind the seat:
http://dorkish.com/albums/Cars/BMW%20E30%20Racecar...

(please ignore the genral poor state - I know the car needs paint and a tidy up)

Any thoughts/help would be greatly appreciated, and if there is anyone local to me who is 'in the know' with regards to scrutineering I would happily pay for your time to check over the car for anything else I may have missed.

Cheers,
Alex

[Altrezia]

Bit more info - someone on another forum has said that the cage looks like a Safety devices B006 (http://www.safetydevices.com/motorsport/products/roll-cage/BMW+3+Series+E30+-1982-1991/40/) which is FIA homologated, and as such doesn't need to comply with all in Blue Book.

I think I'll give SD a call and see what they say.

[ollie854]

Those mounts look very similar to that I have in my MG ZR race car, that too is a safety devices cage and I have never had an issue from scrutineers.

[Altrezia]

Yep, I *think* they are the mounts that come with the cage.

Found this on the cage too: http://dorkish.com/albums/Cars/BMW%20E30%20Racecar...

Proving it's homologation status.

Hopefully a quick call to SD will clear it up

[Philip S]

The mounting feet will be to the correct spec. as it's a homologated cage, but the weld- in reinforcing plates for the main hoop and the front legs should be 120 sq.cm., the rear stay plates should be 80 sq.cm. if my memory is right, Your plates look slightly under size but reasonably well fitted, If the car has raced before? I guess it has satisfied the scutineers in the past. Probably best to get it checked out by a scutineer .

[Altrezia]

Yes, the car has raced before - up until 2009 when it had it's last race.

Have the rules on 'feet' changed since then?

[velocemitch]

Not changed since then no, the welded in pad should be at least 120sqcm, which personally as a structural engineer I find a bit daft. The way your main hoops are mounted you would not benefit from having any extra area as it could only be added at the front of the base plate. The action way the forces would distribute through the base plate into the mounting plate would be totally unaffected by that extra area.

I found the same with mine when I was making up the mounting plates, the area of the plate is comfortably within that specified by the blue book, but most of it is wasted as the force can't get to it without introducing glut stiffeners between the tube and the base plate. It's basic structural mechanics which is obviously lost on the MSA rule makers.

I suppose it depends on the type of race series and how keen scrutineer is, but it's not unsafe, just slightly outside the rules.

[Altrezia]

velocemitch said:

Not changed since then no, the welded in pad should be at least 120sqcm, which personally as a structural engineer I find a bit daft. The way your main hoops are mounted you would not benefit from having any extra area as it could only be added at the front of the base plate. The action way the forces would distribute through the base plate into the mounting plate would be totally unaffected by that extra area.

I found the same with mine when I was making up the mounting plates, the area of the plate is comfortably within that specified by the blue book, but most of it is wasted as the force can't get to it without introducing glut stiffeners between the tube and the base plate. It's basic structural mechanics which is obviously lost on the MSA rule makers.

I suppose it depends on the type of race series and how keen scrutineer is, but it's not unsafe, just slightly outside the rules.

Thanks mate - all good to know.

I'm racing the car in the same series it used to be raced in, which I think has the same scrutineers, so I might be OK

[PhillipM]

velocemitch said:

It's basic structural mechanics which is obviously lost on the MSA rule makers.

It's to stop it tearing the floor out under the tube, not to stop it distorting the floor. Stiffeners aren't necessary for that job.

[velocemitch]

PhillipM said:

velocemitch said:

It's basic structural mechanics which is obviously lost on the MSA rule makers.

It's to stop it tearing the floor out under the tube, not to stop it distorting the floor. Stiffeners aren't necessary for that job.

Perhaps, but it's still a very arbitrary figure which can't possibly be relevant to all floor designs.