TRM Spec e30 rollcage build photos

[matt]

In all honesty I haven't really seen any other e30 cages in person. I need to make it out to some nasa events more often. I just took a quick search around spece30.net and found some other examples. There are obviously plenty of other nice ones around (but I didn't feel the need to link to them). Bill told me a few of the tech inspectors said very nice things about the cage at his first race weekend a few weeks back.

No comment on the harness bars, I'll talk to Mike and see if I can get him to reply on that one.

Thanks, Lee. To be perfectly honest, I didn't design or install the cage. (I removed and refitted the dash though...)

[Axxe]

Nice looking cage. The welds look very well done.

To say this is the best SE30 cage only points out that you haven't seen that many cages in many of the cars that have joined Spec E30 this year.

with that said... this is a nice one.

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 agree with you on the harness bar. It's a glaring deficiency, since any significant side impact load will not be transmitted through the harness bar and thus increase the likely hood of large deformation.

[Charlie]

I agree with you on the harness bar. It's a glaring deficiency, since any significant side impact load will not be transmitted through the harness bar and thus increase the likely hood of large deformation.

Thirding this. The big "X" sort of made me go "wtf"? seems odd that you would have the impact travel at an angle. Really seems like it would deform a good bit.

Any reason you didn't go Nascar bars on the driver's side?

-Charlie

[techno550]

I agree with you on the harness bar. It's a glaring deficiency, since any significant side impact load will not be transmitted through the harness bar and thus increase the likely hood of large deformation.

The harness bar is at the appropriate height for the seats. (and thus the harnesses. Its called a harness bar for a reason, right?) Lower and it would hit the node for side impact protection... but not properly locate the harnesses for the driver. The point of the cage is to protect the driver, and all cages will have some sort of compromise. One solution could be the cross bar beeing lower and mounting the harnesses to a harness bar much farther back on one of the X's. The rules do not allow for such, so this was the best compromise as forced by the current rules.


That said, its not a required bar, and is not only legal as placed, but quite good.

another cage design to note would be

Thirding this. The big "X" sort of made me go "wtf"? seems odd that you would have the impact travel at an angle. Really seems like it would deform a good bit.

Any reason you didn't go Nascar bars on the driver's side?

-Charlie

Nascar bars are good "crush structure". that is their purpose in Nascar. Outwardly bent bars of that sort of magnitude will bend easily. They will bend in as far as they are out without any further stretching. This means the nascar bars can come into the car as far as they were sticking out... and thats generally a bad thing in someting as small as an E30. For side impact protection, the X is king.

[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.

[el bob]

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

[155///MPH]

What are you asking again?

[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.

[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.

[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.

[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.

[155///MPH]

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

[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.

[matt]

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

Good luck, Bill!

[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...