Noel

Hey Guys,

I just picked up a used DAS-Sport rollbar for my 1980 SC. I plan to use the stock "Sport" seats with a six-point harness with an H-strap. My question is about the harness guides I have seen on some of these bars. Are these necessary if I use an H-Strap harness? Should I worry about the harness sliding around on the rollbar (I will be attaching the harnesses to the roll-bar)?

Thanks,

Noel

Bill Gregory

You should check that the group you plan to run with allows that configuation. Some PCA regions will not allow harnesses with stock seats, rather, require harnesses to be used with seats with holes in the seat to ensure the harness can't slide up the seat headrest.

Also, FWIW.....having had two DAS rollbars (81SC and 964), I was not entirely comfortable about attaching the shoulder harness to the cross bar, and instead ran them over the bar to clip into the rear seat harness mountings at the base of the rear seats. In an accident, I'd rather the pressure be put on the bar (that the shoulder straps went over), rather than pulling on the bar (with shoulder straps anchored to the cross bar), as the DAS bar is secured by two bolts in back. Maybe the harness stretches and breaks before the bolts give, however, that's how I used harnesses with the DAS bar. I run a cage now.

JBH

How do you get the 2 sub belts up through stock seats? I agree with Bill, from a safety perspective, this is not a good arrangement. If your serious about tracking your car, this is not the place to make compromises.

I assume your rear fold down seatbacks are gone, so might as well use that area for mounting the eye hooks to secure the shoulder straps. If you make the seat change and use the described mounting points, I don't think you need guides for you belts.

RedlineMan

This stuff is a real sticky wicket.

If you are to mount belts directly to a bar of any sort, it should be of roll cage grade tubing (minimum 1.5x0.95, but preferably 1.75x0.95). A simple harness bar of the larger spec would do. If it is not to this spec, it should be triangulated in its mounting, like the B-K 944 bar. This greatly increases strength.

I understand Bills reluctance to use the bar for belt mounting. It only bolts in place with an 8mm bolt in the rear. I do not feel this offers enough shear strength to make me comfortable either. I'd want at least the 11mm (7/16-20)seat belt bolt, which is somewhere in excess of 35k PSI shear if I remember right. If they'd designed it to mouint in the rear belt hole, and/also picked up the b-pillar belt mount point, I'd feel a LOT better about it.

However, looping belts over from a rear belt mount point on long paths has a serious drawback in that it allows far too much potential belt stretch. Like I said, a sticky wicket!

If forced to choose, I'd use Bill's method WITH THAT BAR DESIGN, but I'd make sure I had a set of Simpson Platinum Nylon belts. They reduce elongation (stretch) considerably!

RedlineMan

Jeff -

You can either run it over the front or back of the seat. To the rear is actually more effective in some respects, but you'll get your bell rung if you hit anything. Run it over the front, and make it REALLY TIGHT. It is not an ideal setup because of the long and obstructed path, but it is better than nothing and does offer a fair amount of lap belt retention... if you make it TIGHT. It should CRUSH the front seat foam significantly.

Did I mention that you need to make it REALLY TIGHT?

Noel

Thanks guys.
I do realize the compromises of using a stock seat, however, with me only running four events (Sometimes three) a year, I can't come to terms with swapping out seats. I guess if I run with the CT region, I will have to run my old three points. Is this really safer? Perhaps, my three points with the harness on top would be the answer? I've heard of others doing this.
The rear seat belt mounting point for the belts is a good idea, but with a 1980 car, there were no rear seat belts. John, I've read some of your past posts about you not being a fan of using eyebolts through sheet metal with large washers on the back. What do you see as my alternative in my situation? Also, I hear you about the small bolt and lack of shear strength with regard to mounting the shoulder harnesses directly to the bar. However, part of the load of the harness (While under a deceleration load) would be shared with the front mounting points as well as the roof of the car, as the bar is wedged against the roof. As I look at the situation (as a non-engineer mind you), it does not appear that the bar would simply tip forward in the event that both rear bolts were to snap. I'm curious what you guys think about this logic (if you care to call it logical).

I was also planning to mount the sub-belts to the lap belt mounting points (Factory points), then sitting on the sub-belts, similar to a climbers harness.

Thanks again. I really value your advice.

Bill Gregory

Noel,

I've also seen where people have run eyes through the rear firewall, with appropriate additional plate steel backing in the engine compartment.

RedlineMan

Hey Noel;

It's a slippery slope indeed. It's very hard to push your limits and grow as a driver while maintaining a pace in keeping with the level of your safety equipment. It's also hard to justify a really good setup for only a few events a year.

I'm not a fan of eye bolts because they increase leverage on the mount point as they become positioned more toward perpendicular with the load path. Straight pull linear paths are fine, though. Also, the belt mount clips associated with eye bolts have been known to mysteriously come adrift on the track. Not good!

Any forward movement in the belt bar is to be avoided. I assume the main hoop must not be quite vertical, and you think it might jam into the roof if it pivoted forward on its bottom mounts. I bet it would move much farther than you think, and you'd be smacking the steering wheel or dash. That creates a serious whiplash effect too as it moves, then stops. You MUST have quick and decisive retention to be at your safest. Nope, I'm with Bill. I don't like it.

I don't like groups like CVR coming up with rules like that either. They see an incident, and the evidence seems to indicate it is a universal problem, when in fact it was an isolated occurence. They then make a rule like this - that in effect limits the ultimate safety of many more people - to avoid this isolated set of circumstances. This is not sound or objective reasoning, and is based on conjecture, not fact or statistical significance.

I guess I am coming around to the H-strap thing. They are indeed a compromise, with their own set of problems. They cannot be quickly or easily adjusted for different occupant's seat positions. However, they seem to be a better idea than nothing at all. I do agree that belts can be pulled off of drivers shoulders in an offset hit, and I think the H eliminates a lot of that. Since most people do not have their necks right against the head rest, putting the H in FRONT of the head rest would be even better. A tad uncomfortable, but might be worth it.

It would be easy to say that wearing both belts would give you the advantages of both, but that is not based on data, just supposition. Some groups don't allow that as a solution anyhow.

If I were to risk the long belt paths and mount the belts to the rear firewall, I would do it with a MINIMUM 4"x 3/16 thick square backing plate. I would also put it as near the upper rear deck as possible to take advantage of its shear strength. A lower mounting would be in linear tension in an unsupported thin panel, and would not take much of load before it pulled through.

Noel, here is what I would do. I would have someone fabricate tabs from the main hoop over to the upper pivot for the lap belt in the b-pillar, and bolt it right in. Then I would mount my belts right to the belt bar. This pic is of my bolt-in roll bar for 996s, but you can get an idea of what I am talking about looking at the belt pivot and the main hoop. It would be a natural solution to take some of the load off of the rear mount bolts, and would eliminate my concern about their frailty.

JBH

John:

That is an impressive roll bar - I assume you fabricated that yourself. Where are your shoulder harnesses attached? What is the platform in between the two rear bar mounting points?

I hadn't thought about the belt stretch issue - it seems like the OEM rear belt mounting points (if you have them) are the best place. Without going directly to the bar, I don't see any location closer. I am surprised a 1980 SC did not come with rear belts.

I would think just about any harness, properly done, would be safer than a three point belt. After using a harness, I don't feel very comfortable wearing a conventional seat belt even for highway driving.

RedlineMan

Jeff;

Yes I built the bar myself, and have a jig to produce more. It's kinda what I do, ya know?

The 996 is an exceedingly difficult car to build anything like this for. Not space, architecture, or existing-bolt-point friendly.

If you look closer at the horizontal bar, you will see the belt positioning loops the customer asked for. The rear shelf that is normally hidden under the removeable carpet panel between the rear shock towers houses a bunch of relays and computers, heaven knows for what. Probably ABS, cruise, PSM, some such things...

This bar resides in a customer 996 in Minnesota.

I agree. My feeling is that a well thought out harness system - despite the compromises inherent in a dual use car - is better than a 3-point. The trick is to study deeply and carefully to make the best choices possible. That really takes a lot of intense thought and research.

Noel

Thanks again for the replies guys. You have given me a lot to consider.

BTW, I just got off the phone with a Tech at DAS-SPORT and they recommend attaching the shoulder harnesses directly to the rollbar. This was how the bar was designed, according to them.

Decisions, decisions....

JCP911S

2 cents here. I am not a fan of 5 points and stock seats. THe shoulder straps are not properly fit...even with an "H" strap, and the sub belt is probably worse than useless if it is wrapped around the front of the seat. In an impact your body will tend to push into the seat cushion putting the lap belt across your abdomen... not the hips.... bad news. Also, in a hard rear collision, the seat will quite probably break and you could hit the rollbar with your head or neck.

I am not in a position to say that the 3-points are "safer" but they have passed crash testing and the 5-points haven't. IMHO i'd use the 3 points until I got a dedicated race seat.

Also, check out some of the Schroth harnesses.... no personal experience, but they claim to make 4-points that are safe with stock seats..... who knows, but they certainly have some credibility as a manufacturer... probably better than wishing and hoping