TRM Spec e30 rollcage build photos

[whiltebeitel]

The NASCAR bars look really good. Most people stick them into the gutted door, not realizing that this sturcture is designed to collapse in as far as it sticks out. Yours sticks out very little, and should not pose a danger in a side impact.

[matt]

That is a nice seat mount.

[jhall1957]

Matt,
Here is better!

Done by a good ole NC boy.

Note the A pillar bar is way up in the dash and yes a dash bar up in there too!

Do these NASCAR bars look weak or bad to anyone?

No one even mentions using a "good" seat mounting point. How's this one look to you guys?

[matt]

A) This is a NASA car that will never be raced with the BMWCCA. It's still legal for both organizations.

B) BMWCCA rules... page 63. "At least one (1) diagonal brace shall be used..."

C) What do you mean by rear horizontal? Rear shock tower bar? Not needed based on a number of factors.

[winstontj]

FWIW: The only part I question is how the harness bar fails to connect in the center. With the horizontal bars as they are a side impact is going to transfer the load to the center at a point that is not triangulated. It seems to me, this is going to create a weak point in an area you'd want to be one of the strongest.

I'm just getting into D-Mod rules so I really shouldn't speak to SE30 but I also noticed the lack of rear horizontal...

IIRC rules say only one diag from driver's head to base of pax b pillar right?
Yours is a first one for me - nice welds though. Did the footings take more work than normal? They look very well done but small...

[matt]

This car will be racing at Barber this weekend if anyone wants to check it out in person.

Good luck, Bill!

[matt]

The cage was designed around the seats, so it fits perfectly.

The rear bulkhead was cut by a previous owner (probably for a subwoofer, judging by the wires running to the trunk) long before Bill bought the car. I should have mentioned that.

[155///MPH]

I believe that the partition was already cut out of the candidate car. I don't think TRM did it.

[UNHCLL]

Seating - Did you mock up the seating position before welding in the cage? Another very common mistake when building a cage. It gets built, and then "Oh lets fit a seat in there." This fails to account for where bars run in comparison to body parts (arms/legs/etc). I've seen some piss poor cages.

Welds - Very nice. Proper equipment, good beads, and appears to be nicely laid out.


I don't like how the builder sliced out 90% of the rear partition to make the cage though. That's a bit amatuer.

[matt]

We've got 5 points meeting against the main hoop. You've got 3 shown. When you're paying someone to do this, you do realize the difference in cost involved to get 5 points to meet at one node versus just 3 points? If you're doing the fabrication and have the time to do it that's great, but when you're paying someone's time, you're talking a difference of several hundreds of dollars.

Here's a better picture.. It's not easy or cheap getting these 5 points to meet in a single node.
http://www.vagworld.com/pics/gal/E30.../IMG_6144r.jpg

Like I said, a TRM cage is a few hundred dollars more expensive than the average for our part of the country. Things like that are why.

The rear down tubes were later Xed in (you can see them in the last picture) and they meet at the same node as the other 3.

This was intentional, as we kept the stock seat belt anchor point accessible. The car was driven on the street as well, and we opted to retain the factory seat belts for comfort. The B-Pillar hoop was intentionally spaced out. It was not due to poor design or engineering, but quite the opposite. We have exactly the room we designed to perfect fit and remove that seat belt anchor.

Point taken. That certainly sounds like a valid compromise.

[Mike@PureMS]

This is a node: a point where multiple tubes meet. This allows loads to be transmitted along the length of the tube to compress it instead of bending it. (Compare that to this cage, with poor nodes. (Tubes don't all meet at the same point.)

We've got 5 points meeting against the main hoop. You've got 3 shown. When you're paying someone to do this, you do realize the difference in cost involved to get 5 points to meet at one node versus just 3 points? If you're doing the fabrication and have the time to do it that's great, but when you're paying someone's time, you're talking a difference of several hundreds of dollars.

Here's a better picture.. It's not easy or cheap getting these 5 points to meet in a single node.

[Mike@PureMS]

Check out the close fit to the B-pillar. (Comparison here) Obviously closer to the chassis means farther from the driver, which makes a tight fitting cage safer.

This was intentional, as we kept the stock seat belt anchor point accessible. The car was driven on the street as well, and we opted to retain the factory seat belts for comfort. The B-Pillar hoop was intentionally spaced out. It was not due to poor design or engineering, but quite the opposite. We have exactly the room we designed to perfect fit and remove that seat belt anchor.

[155///MPH]

What are you asking again?

[el bob]

Somewhat OT, what about cages for E30 non-M street/drag strip cars looking to stay tech legal?

[Scott///M]

techno550,

I don't know that anyone was suggesting the harness bar be lowerd.

My thought was that the cage in question should have a piece to connect the 2 sides of the harness bar (just above the X ). All that's needed is a 8" piece. Without compleating the harness bar... there are off set points. And that leaves a weak point.

And as for the Spec E30 rules... the additional bar would be allowed as long as it's not creating an addition contact point. Which a bar in that location would not be doing.

However... to your point, this is a well designed cage. I think the comments made are only given to help make this an even safer design.