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aeronca65t
03-16-2007, 12:52 PM
OK, here’s a question that I have regarding racing-type seat belts (safety harnesses).

Our club runs Time Trial events (intended mostly for street cars). We allow cars in our Time Trial events to have ordinary 3-point OEM* seat belts (most clubs running track day events in our area do the same thing).

Lately, we’ve been getting cars that come to our TT events with “race harnesses” (instead of the OEM belts) and often, the belts are improperly installed (especially the “bling-bling’ cars).
If the car still has the OEM belts, we make the driver wear those.
If the car only has the poorly installed race belts, we try to fix them or we turn the people away.

So we’re working on dealing with this issue in the form of a new rule.
One of our guys has said that he thinks that OEM 3-point belts are better at preventing “submarining” (sliding under the belts) than a 4-point race harness. He says we should allow the 3-point OEM or insist on 5-point belts (with an anti-submarine belt). 6-point and 7-point would be OK too….but no 4-point. He cannot find any supporting data, but thinks that someone has done a test on this.

I’m not sure I agree with dis-allowing the 4-point belts. As I see it, a 4-point belt that is properly installed is just as good as a 3-point OEM belt.
Do you guys have any opinions or sources of info on this?

Note: This does not apply to our RACE classes. In wheel-to-wheel racing, we require up-to-date SFI or FIA 5-point (minimum) race harnesses.

*OEM=”Original Equipment Manufacturer”

ChrisS
03-16-2007, 05:41 PM
Nial,

I've read an article that compared OEM 3 point and after market 4, 5, and 6 point harnesses. I'll try to find it.

Don't quote me on this but it had to do with the auto tensioning of the OEM belt and the fact that the hips were loaded in a crash where as the sternum is loaded in a 4 point harness due to the submarining. The three point let the torso move forward so that the body was "caught" by the lap belt and the shoulder belt prevented the torso from going too far. The forward action of the torso pulls on the shoulder stap, and thus the lap belt, ultimately putting more loading on the hips.

With a 4 point harness the torso is not loading the the lower straps in the same manner and actually pulls up on the buckle, unloading the hips and loading the sturnum more. The body then slides down until something restricts it like legs in the foot well or the neck getting hung up at the buckle.

Take this with a grain of salt since I'm doing it from memory. Again, I'll try to find the article(s).

WhatsThatNoise
03-16-2007, 05:44 PM
I’m not sure I agree with dis-allowing the 4-point belts. As I see it, a 4-point belt that is properly installed is just as good as a 3-point OEM belt.
Do you guys have any opinions or sources of info on this?

I'm with you on this one....
4 point trumps 3 point any day.
(I'm more concerned about rolling than a hard front hit)

BTW....You can add that 5th belt easy enough.
You don't have to buy a new harness.

aeronca65t
03-17-2007, 07:28 AM
Thanks Guys.
I think some drivers will show up at our TT events with 4-point and, like Dave, will feel that they're fine. And at this point, I'd agree with them.

Chris: If you can find an article with that info, it would be great. Right now we can't find any supporting data that shows a preference for 3 or 4 point.

In typical EMRA fashion, one of our guys has already decided an "interperatation" and has posted it on our website. So right now, we have a note posted that outlaws 4-point race belts in TTs.
That's fine if there is some supporting data. If not, we'll need to vote a change at our next board meeting.

tony barnhill
03-17-2007, 09:00 AM
So, I've just bought a 5-point...does that mean I'm okay?

aeronca65t
03-17-2007, 09:28 AM
Oh yeah. 5 point is fine for most orginazations in terms of track days, time trials and even wheel to wheel racing. Nowadays, if your belts are "SFI" labeled, they are good for 2 years. If they are "FIA" labeled, they are good for 5 years. I don't personally agree with this (I think they should all be good for 5 years) but this is the SCCA "belt date rule" and we follow it (so do many other groups).


Just be sure to mount the shoulder harness at no more than a 15 degree "drop" from you shoulders (ideal would be horizonal). We often see shoulder harnesses attached to the floor right behind the seat: no good. If we see that, we send folks home or try to have them re-route the belts.....we hate to send folks home, but a bad harness mount can be dangerous.

[edit] I'm adding a picture of the harness bar I added to my car to raise the shoulder harness mount to a safe angle

https://img.photobucket.com/albums/v170/aeronca65t/Cars/lizard2.jpg

Bugeye58
03-17-2007, 10:45 AM
Nial, just one very minor point. Shoulder harnesses should ideally be installed at 90* to the angle of your spine in the normally seated position. If you have a 20* layback seat, the correct angle would be 20* from horizontal.
Sorry to be pedantic, but I guess it's just the tech inspector in me. I don't want to see anyone hurt due to improper belt installation.
Jeff

aeronca65t
03-17-2007, 02:40 PM
Jeff:

You're 100% correct.

My comment was a more generalized remark for street vehicles (like our Time Trial cars).

Baz
03-17-2007, 08:41 PM
Nial, do you happen to have specs handy for that harness bar please?

WhatsThatNoise
03-18-2007, 02:40 PM
Nial, do you happen to have specs handy for that harness bar please?
Can't find anything in the GCR about it other than it is recommended....(rather odd???)

9.4.4E Talks about seat back bracing being on the main hoop or the 'cross bracing'.

9.4.6C Talks about required bracing being the same size as main hoop material.

9.4.4A figure 11 seems to indicate that the bar itself is optional.

You can't go wrong if you make it out of the same tubing as the main hoop. (Most people do)

AngliaGT
03-18-2007, 03:39 PM
There was an article awhile back in
Stock Car Racing Magazine.
That was the thing that sunk in the most -
- having the shoulder belts go back as straight
as possible from the contact point of the driver's
shoulder.
Also,use the proper grade (or better)bolts for
mounting the harness.When we put the belts in the
SSC Fiesta,a friend,who got me the roll bar for
the car,also supplied the bolts for the belts.
A couple of years later,while cleaning the garage,
I tossed the belts accross the garage.When they hit
the floor,one of the bolts broke in two.I thought to
myself - "Hmmmm.... that's interesting".Never again.
Also in the same magazine was an article on
Smoky Yunick.I was tickled to find that his daily-
- driver was a Ford Fiesta!

- Doug

Baz
03-18-2007, 05:09 PM
This bar isn't going anywhere, it's solid. The Simpson eyebolts are 3/8", grade 8, so I used the same, also used a 4" pair of steel reinforcing bars under the wheel arches with oversized washers.
It's right at 90* from the spine position, and about 10*-15* from the shoulder.
Thanks for the inspiration!
https://image2.frappr.com/pix2/i/20070318/b/f/7/bf703929fdf0010958c9f5ab4c2a9e240_large.jpg

tony barnhill
03-18-2007, 05:44 PM
Nial - do you have a photo of how the back of your seat is braced to the roll cage?

WhatsThatNoise
03-18-2007, 05:45 PM
That might work for track days.(not sure)

You know you are allowed to wrap belts around the tube.
(And it is stronger...No holes)

Eric
03-20-2007, 01:34 PM
My experience with track day organizations is that their requirements are very different. In my Miata, I've been required to run 5 points rather than OE 3 points and I've been forbidden to run 5 points and required to run OE 3 points.

The problem with 4 points is not submarining per se (at least in cars with a relatively upright seating position), but the lap belt riding up in a collision. With a 4 point, as your torso moves forward in a collision, it tends to pull the lap belt upward off your pelvis and onto your squishy bits. A 5 point prevents this, and a 3 point auto-tightens your lap belt to prevent this.

My understanding is also that it isn't recommended to use a harness without a race seat. If the shoulder straps are routed around the sides of a stock seat (esp tall modern seats), there's nothing to keep them from coming off your shoulders as you rag doll from side to side in an accident. A racing seat (with the slots for the shoulder straps) will prevent this. Also, a stock seat won't allow proper routing of the crotch strap/straps to allow them to do their job.

One more consideration is headroom. If you're not running a roll bar that keeps your helmeted head 2" below the top of the bar, harnesses aren't recommended. In a roll over, a 3 point belt will allow you to be displaced to the side should headroom suddenly decrease. A harness won't allow that, meaning your noggin is suddenly be supporting the car, something it wasn't engineered to do.

For mounting info, see https://www.gforce.com/pdf/harnessinstall.pdf

An alternative (should your seat allow proper positioning of the shoulder straps) are the Schroth ASM 4 point belts. They are engineered to allow lateral displacement, minimizing the lap belt rise that other 4 points cause. See https://www.schrothracing.com/products/streetlegal , especially the Rallye line.

ChrisS
03-26-2007, 02:24 PM
Nial,

You have an email.

aeronca65t
03-26-2007, 04:14 PM
Thanks, Chris!

(And I'll try to post a picture of my seat mounts and harness when I get a chance. Right now, the darn car is buried in my shop under a tarp, old race tires and assorted junk.)