TRM Bolt-in Roll Bar pictures

[matt]

Hey guys... my car got a little safety upgrade recently. :mrgreen:

We'll be selling these bars soon. I really like the design and it fits really well to the chassis and roof. The base plates are bent from 3/16" steel and follow the contours of the body really well. It also has a bar between the rear braces that will function as a rear shock tower bar and harness bar.

Pricing is TBD on these, but they will be available as fully assembled bars and weld-it-yourself kits. I may also have some cage "starter kits" soon with pre-bent main hoops and A-pillars, and probably some stamped and bent base plates. I will update this with pricing ASAP.

Pics follow. It's just tacked in, it'll be removed to make a jig before being finish welded on the jig. Sorry for the crappy camera phone pics.

[155///MPH]

It also has a bar between the rear braces that will function as a rear shock tower bar and harness bar.

???? Won't that make for some long harnesses?

[matt]

Yes, but no longer than bolting them to the rear seat belt mount like I think most people do. (shorter in fact) And it gets the angle right.

It's pretty common... http://e30m3performance.com/tech_art.../Mvc-a038f.jpg

[155///MPH]

Its not optimal though is it? I am under the impression that those belts should be as short as possible to minimize the belt stretch in the event of an impact. Less belt = less stretch.

I'm just saying you may want to offer some sort of conventional harness bar closer to the seats.

JP

[matt]

Less stretch = more energy transmitted to your body. Although I would guess the amount of stretch in harnesses is pretty low.

We can do a harness bar within the main hoop, no problem. For my own car, I prefer this way.

[155///MPH]

From the Schroth Harness Mounting Guide:

"SHOULDER BELT ROUTING

�� Shoulder belts must run from the shoulders horizontally or down, at no
more than a 20° angle.
�� In cases where the shoulder belts must be routed down to the chassis
floor, support by a roll cage bar or harness guide at the appropriate
height is essential to establish the horizontal shoulder strap routing off
the shoulder/HANS®. Most racing seats are not designed and tested to
carry shoulder belt crash loads from downward installation. Severe
injury or death could result. A 45° downward shoulder belt installation is
possible with seats that SCHROTH has positively tested to take a load
measured during a 50 kph [31 mph] and 28 G impact. Refer to the list
of SCHROTH approved racing seats in section “Bolts, Seats and Stuff”.
WARNING: 45° downward shoulder belt installation must never be
used with HANS®.
�� For the best restraint of the occupant’s upper torso, anchor points
should not be further back than 200 mm [8”] from back of user’s seat.
�� In the event that the anchor points are further towards the rear of the
vehicle [e.g. using a roll cage bar for wrap around attachment] the
distance between the strap anchorages will narrow or even cross over
as described in following graphs and formulas.
�� It is especially crucial to follow this strap routing when HANS® is in use."

The way you are doing it isn't wrong per se, but isn't what I would consider optimal given the choice.

Its a good read if you haven't gone through it.

http://www.schrothracing.com/docs/Competition_Instructions.pdf

[matt]

Wrong one... http://www.schrothracing.com/docs/Ra...structions.pdf

The link you posted applies to competition harneses designed to be used with HANS devices. Frankly, nobody with a HANS is buying a bolt-in roll bar. This bar is compatible with stock belts also.

I'm going to see about adding a more typical harness bar for production versions, but I am perfectly happy with the arrangement in my own car.

[155///MPH]

Whoops, my bad. I shouldn't have assumed you meant 6 points.

Roll bar looks to be of top notch design and execution like usual.

JP

[Massive Lee]

I hope I am not sounding rude, but please allow me to add my grain of salt as a BMW Club event organizer, instructor and tech inspector. Unless that hoop gets a harness bar at proper height, there is no way I would allow the car to set a wheel on the track unless the occupants agree to wear a regular three-point belt. The rear harness pick-up point appears to be too low for safety if it is between the two wheel wells. Maybe that pictures don't give justice to therear installation though. Under frontal impact, the harness will compress the driver's and passenger's spine if the rear pick-up point is too low.

The harness belt should be within the 20degree range. Even the drawing is not acurate BTW as most drivers are not that reclined.

[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

[e30sd]

puke

[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.

[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

[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.

[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.