TRM Bolt-in Roll Bar pictures

[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.

[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.

[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.

[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

[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:

[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.

[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...

[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.

[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:

[techno550]

A few notes. The bar is above where the down tubes meet the top of the rear wheel wells. probably around ~6 inches or so below the window line. How high is your cross tube/ harness bar there? Right around or just below the window line and how far in front of that rear point? what is the difference in angle?

The FIA cages generally don't have a bar in the main hoop for the harnesses. They usually don't like anything in the main hoop plane unless its a rally car. This includes a diagonal. They generally prefer the diagonal be in the plane with the downtubes.

for the belts

In the downwards direction, the shoulder straps must be directed
towards the rear and must be installed in such a way that they do
not make an angle of more than 45° to the horizontal from the
upper rim of the backrest, although it is recommended that this
angle should not exceed 10°.
The maximum angles in relation to the centre-line of the seat are
20° divergent or convergent.
If possible, the anchorage point originally mounted by the car
manufacturer on the C-pillar should be used.

That is from the FIA Sport / Technical Department, as of 29.03.2007. (FIA appendix J article 253. FIA world touring car champoinship safety equipment)

That same article then goes on to say

Anchorage points creating a higher angle to the horizontal must
not be used unless the seat meets the requirements of the FIA
standard.
In that case, the shoulder straps of 4-point safety harnesses may
be installed on the rear seat lap strap anchorage points originally
mounted by the car manufacturer.
For a 4-point harness, the shoulder straps must be installed
crosswise symmetrically about the centre-line of the front seat.
A safety harness must not be installed on a seat having no head
restraint or having a backrest with integrated head restraint (no
opening between backrest and head restraint).
The lap and crotch straps should pass not over the sides of the
seat but through the seat, in order to wrap and hold the pelvic
region over the greatest possible surface.
The lap straps must fit tightly in the bend between the pelvic crest
and the upper thigh. Under no conditions must they be worn over
the region of the abdomen.
Holes may be made in the series seat. Care must be taken that
the straps cannot be damaged through chafing against sharp
edges.
- If installation on the series anchorage points is impossible for the
shoulder and/or crotch straps, new anchorage points must be
installed on the shell or the chassis, as near as possible to the
centre-line of the rear wheels for the shoulder straps.
The shoulder straps may also be fixed to the safety cage or to a
reinforcement bar by means of a loop, and may also be fixed to
the top anchorage points of the rear belts, or be fixed or leaning on
a transversal reinforcement welded between the backstays of the
cage (see Drawing 253-66).

The drawing has the harness bar behind the B pillar bar in the downtubes, including if you are "silly" enough to put a diagonal in the main hoop plane. unfortunately, being here in the US, we are forced to have a diagonal in the main plane. At this point I generally revert to an X, but still put the harness bar rearward when possible.


so, I guess I'm trying to say... its not that low... and it should be back there.

[matt]

Lee, I see what you're saying about the angle... The angle is fine but the pictures make it hard to see. I've attached a pic that should clear things up a bit.

[Massive Lee]

That's the picture we've all been waiting for, Matt. :nice:

The shoulders usually being at the same height as the bend in the main hoop, then we can clearly see (now) that the angle fits the regulation. Nice work.

Lee

[155///MPH]

Seriously that brace is hardly "connecting the shock towers for reinforcement" as was stated earlier.

Not my car, or safety so go for it. I wouldn't feel comfortable with my belts being mounted that far back. That has no bearing on whether it is correct or not, but I wouldn't buy a roll bar designed like that.

[SpecE30DRVR]

Seriously that brace is hardly "connecting the shock towers for reinforcement" as was stated earlier.

Not my car, or safety so go for it. I wouldn't feel comfortable with my belts being mounted that far back. That has no bearing on whether it is correct or not, but I wouldn't buy a roll bar designed like that.

Mine is still farther back than I would like. I'm not sure if you could even get belts long enough to reach that far back. I would just run a bar through the X.

hard to see but you get the point

[whiltebeitel]

This sounds really good to me. Any ideas on a ball-park price range?