TRM Bolt-in Roll Bar pictures

[matt]

The harness bar on my bar keeps the angle of the harnesses between horizontal and 20deg.

I don't think the FIA requires the horizontal bar within the main hoop like that cage has. North American sanctioning bodies have a lot of requirements that the FIA and european orgs don't have. It's pretty common to see cages with no harness bars, no back braces, no brace within the main hoop, and even a multi-piece main hoop. :ohsnap:

[Massive Lee]

I don't think it is so much the length of the shoulder belts but their angle. Most racecars will have the harness located about the same height as the shoulders, or BARELY lower. I might be wrong, but it looks like the tube between the rear inner fenders is way too low to keep a spinal compression from happening under a frontal collision. Then again, maybe the pictures don't do justice. I built a few rollbars on e30s and there are things I wouldn't do. Such as a low harness bar.

BTW Here's a project I am coaching. That's an e46 4-door done according the FIA's rulebook.

[techno550]

belt stretch is a good thing. allows the belts to absorb the energy and decelerate the occupant over more time. Slower decel means less energy transmitted to the driver.

If we want more modern examples from reputable builders, perhaps the DB9R? Prodrive 550? Bah, those guys don't know what they are doing though...

[matt]

Current NASA rules specify a 20deg or shallower angle and no minimum or maximum length to the shoulder belts.

Current BMWCCA rules specify a 20 degree angle and 12" or shorter between the seat back and the harness mount. Should be easy to do with the same bar mounted farther up the braces.

[matt]

The fact you are so quick to suddenly call the builder and have it changed also leads me to believe you had questions in the back of your mind to begin with. If you truly believed your product was superior/sufficient, then why change it?

Because I didn't have these bars developed to have nobody buy them because they have a non-traditional harness bar. (Even if it is based on unsupported comments from a bunch of internet engineers :roll:)

I didn't see any math in the rest of your post.

The manual for the Schroth competition belts makes it very clear that HANS performance is the reason they suggest such a close mounting position. And there is a chart in the same manual that shows that as long as you move the belts on the harness bar, potentially even crossing them over, you can make a longer belt work.

PS: I've been doing math and physics a lot longer than I've been doing DEs. :roll:

[UNHCLL]

Ok, I read this again more closely. Prove it. With math.

I'm serious. If you can't, I call bullshit. If you want to think it's not safe, be my guest. But if you're going to come in here and tell me that longer harness' are dangerous, you're going to need to prove it.

I'll get you started... standard 2" nylon harness webbing has a dynamic elongation of 12.5% at 3000lbs load. (Simpson website) How hard do you have to hit something to apply 3000lbs of force to your harness with your chest? And a little more help... 4 feet times 12.5% is 6".

PS: http://e30m3performance.com/tech_art.../int_rear2.jpg

http://e30m3performance.com/tech_art...46_cage-11.jpg

2 whole years of DE experience?
Damn.
Lets call Bernie Ecklestein and have you become the new head tech inspector for F1. You clearly know everything there is to know!

As stated, those photos are of old(er) race cars. Circa the same era as the E30 M3.

Also, the generally accepted "rule" is that harnesses stretch 14%... but hey, lets play the "make my math work" game...

Here are some quotes from the Schroth install manual:

"Shoulder belt mountings located more than 8 inches from the back of the user’s seat or angled upwards are not good restraint practice and are most strongly discouraged. If longer belts are used, the inside edges of the belts should be still closer together at their mounting points, even touching or crossing, but both belt and HANS® performance are severely compromised."
Page 23 - Schroth Competition Harness Installation Instructions

"For the best restraint of the occupants upper torso, attachment points should not be further back than 200mm (8") from the back of the users seat"
Page 21 - Schroth Competition Harness Installation Instructions

Direct Link: http://www.schrothracing.com/docs/Co...structions.pdf


I'm simply raising questions, because I don't like that you're promotion/claims aren't addressing all possible issues with the product. The fact you are so quick to suddenly call the builder and have it changed also leads me to believe you had questions in the back of your mind to begin with. If you truly believed your product was superior/sufficient, then why change it?

Kind Regards,
Chris

[Dave]

"doing the math" won't do you a damn bit of good if you are in the false grid and the steward doesn't like the looks of your setup.

I'd feel better having the harness bar on the main hoop knowing that is what the inspector will most likely expect to see. Its the out of the ordinary stuff that will catch his eye.

[matt]

If weighed 150 lb, and you placed two straps in pure tension and subjected it to a dynamic load, you'd need 40G.

But if you consider that the shoulder harnesses are really only constraining the torso and head, the mass would be lower and the force would have to be higher.

[FredK]

I'll get you started... standard 2" nylon harness webbing has a dynamic elongation of 12.5% at 3000lbs load. How hard do you have to hit something to apply 3000lbs of force to your harness with your chest?

If weighed 150 lb, and you placed two straps in pure tension and subjected it to a dynamic load, you'd need 40G.

[155///MPH]

Those pics are irrelevant. The first is from a VERY early E36 DTM car, ~92. The second pic is a body in white E46; i.e. an unfinished cage. Neither car is legal to race in any series in NA as is. If you'd like to put your life in the hands of 20 year old safety standards, be my guest.

As for the harnesses, there is nothing per the rules that defines what is legal and illegal in regard to harness length. However, many of the top series (Rally, DTM, WTCC, etc.) are moving to shorter harnesses. There was even an article about it in the last Race Car Engineering regarding the Rally initiative to improve safety. Shorter harness length was on the short list. Do a little research, its all out there.

[joshh]

I don't see the problem. Many Porsche drivers have even longer harnesses. If it were completely unsafe to do they wouldn't sell harnesses that mount that way.
You could however add another bar that is a harness bar but attaches to both sides of the main hoop. It would just stick out the back a few inches because you have cross braces in place of where the harness bar might go.

Looks good though.

[matt]

That has a huge harness length, equaling greater potential stretch in the event of an accident. While your theory that this might help reduce impact on the body... the steering wheel and windshield, (which you will contact) will make up for your alleged "stretch" benefit.

Ok, I read this again more closely. Prove it. With math.

I'm serious. If you can't, I call bullshit. If you want to think it's not safe, be my guest. But if you're going to come in here and tell me that longer harness' are dangerous, you're going to need to prove it.

I'll get you started... standard 2" nylon harness webbing has a dynamic elongation of 12.5% at 3000lbs load. (Simpson website) How hard do you have to hit something to apply 3000lbs of force to your harness with your chest? And a little more help... 4 feet times 12.5% is 6".

PS: http://e30m3performance.com/tech_art.../int_rear2.jpg

http://e30m3performance.com/tech_articles/cage_symposium/e46-1/e46_cage-11.jpg

[matt]

Ugh... this wasn't supposed to be about the harness bars. Everyone ALWAYS bitches about the harness bars. Go look at any FIA certified cage and show me the harness bars.

I guess since you guys bitched, I'll call the fabricator and have him add them. Or just move the existing bar farther up the braces.

I've run two years of DEs and autocrosses with Rallye belts hooked up to the stock lower rear seat belt mounting location. Never failed tech, never had an instructor complain.

A bolt in roll bar is still a compromise. I would guess there will be people who will use this with stock belts. I am using mine with stock seats.

[e30sd]

puke

[UNHCLL]

The base plates look nice.
The rear "harness" bar is not my forte... sorry. That has a huge harness length, equaling greater potential stretch in the event of an accident. While your theory that this might help reduce impact on the body... the steering wheel and windshield, (which you will contact) will make up for your alleged "stretch" benefit.

Also, the theory that it's going to help brace the rear shock towers... pretty far fetched assumption. It's far forward from any actual pivot points that could move. Add to that that it's been proven that the e30 chassis, in most cases does not require additional bracing in the rear, and it's added weight.

Also, your little bit about harness connections, lets review that.
You're claiming JP's link is incorrect.. because it speaks to HANS users.
1) I know many HANS drivers who have solely bolt in rollbars
2) JP's link is for competition harnesses. Perhaps one of the best options/styles Schroth offers.
3) You're link is for Rallye belts - perhaps the most compromising belt setup offered from Schroth.

Schroth makes great products. However, the Rallye belt, IMHO is for someone who is using stock seats, and maintaining a full interior. It's a system designed with compromises to allow for versatility of use for the vehicle.
Competition belts, are designed for cars, that aren't compromising.

By adding a rollbar, be it welded or bolted, you've crossed that threshold. Unless you have no regard for passengers safety, you'll never have passengers in the back seat. So why buy the "compromise" Rallye harness setup?


And I have to agree with Lee.
I would never, let a car with that harness attachment setup cross the false grid for a DE. IMHO that harness location is way to low.


Good luck,
Chris