DarkAngel996

If harness bar was only needed because of harness, why not get
https://www.schrothracing.com/produc...sche-harnesses, PORSCHE BELT FOR CARBON SEATS 4 point harness which is designed for our seats and is street legal in US?

PCA also have the following line:
https://www.pca.org/driver-education-minimum-standards

KingSize.Hamster

Personally ... I think it's a matter of design. If the bar/cage is just bolted on to sheet metal or even those holes meant for seat belts, I would be quite skeptical.

There is a reason why cars equipped with factory roll cage (or those ready for retrofit) have reinforcements at the mounting points.

Bill Lehman

I have a background in steel fabrication and structural steel design. Back in the day I designed and built a bolt in roll bar for my race car that met the SCCA rules of the day. I later improved the design and built a new welded bar. The Cayman has a pretty strong roof structure and I believe it would stand up to most roll overs. When I added seats and harnesses to my 987 Cayman I went with an RSS harness bar without a hoop. I run in Instructor group and one day one of my PCA racer buddies suggested that I'm running lap times close to their race cars but they are using full cages. I installed a Hargesheimer unit which used the existing Boxster roll bar attachment points which were in all 987 Caymans. While waiting for delivery of my GT4 I looked at all available bolt in harness bars with and without hoops. If I went with a straight harness bar, I like the RSS design. I decided to go with some roll over protection. Among those then available (We seem to be getting new vendors), I choose the Cantrell. From a design point, the BBi is very similar. There are other very good designs including Speed Sport, BGB, and GMG. None will offer the protection of a full welded cage but I think all will add some degree of roll over protection.

d00d

This is an interesting option.
Know how this mounts on a GT4 without a harness bar?
Can't locate any pictures of that.
If there are rear seats and belt attachment points, the shoulder straps can attach through the front seat pass through openings to those, not at an appropriate HANS angle though.

Bill Lehman

The Schroth 4 point needs seats with holes for harnesses and a harness bar for attaching the shoulder harness. I'm thinking about this for the passenger side, have 6 point for driver.

pegdrag

Gentlemen

Thank you...I think this is an important discussion. Having people with experience and expertise comment is useful.

I suspect there is no testing and will never be testing on these bars for this car. I also suspect that most of the people who manufacture these bars don't have a lot of data about what is good or not. The bar may (or may not) meet "spec" for one or more racing groups. That may not help us with best points for attachment, strength, etc.

To state the obvious, bad stuff sometimes happens and having the best safety gear matters.

I cross posted to the 993 group as well and the comments there are helpful as well. The general sense there among the "real racers" is that a well designed and well built bolt in is better than nothing, but a welded-in bar is better. Most of us aren't going weld a bar into the car for a variety of reasons (cost, resale, not "really" racing, defacing the car).

Be interesting to see the cage in the clubsports and the attachment points, etc. Can't duplicate that, of course, but we assume Porsche knows how to do it.

HelpMeHelpU

Bill, You have been around PCA/DE, etc. a LOT longer than I have (really no comparison), but I heard/read somewhere that PCA requires same level of safety for passenger and driver and driver can't be more (...under the theory that six point is safer than four). Ever hear of this? Thoughts? (BTW, I was thinking of doing same for new GT4, especially since Porsche didn't cut hole in passenger LWBS, until I read what I mentioned.)

Crazy Eddie

Those were the rules out here on the left coast when I was doing DE events back in the early 90' s

Bill Lehman

Delete

Manifold

Some thoughts on validation options:

- Crash testing in real cars would be best, but would be very expensive, especially considering that you'd need multiple tests to cover a variety of crash scenarios.

- Short of full crash testing, static or dynamic testing of roll bar/cage assemblies can be performed, but this would also require numerous tests to simulate various crash scenarios, would be expensive, and it would still be missing the interaction with the car.

- Structural analysis software can be used for analysis and design. This allows cost-effective simulation of a variety of crash scenarios, and enables fine-tuning of the design. This is a pretty good option, but I don't know how many manufacturers of these bars/cages do this (and do it competently).

- A qualified structural/mechanical engineer should be able to do a decent job of designing a roll bar/cage based on judgment and some hand calculations. As noted in the PCA regulations, key considerations are the overall configuration of the system (triangulation, etc.), tubing diameter and thickness, type of steel used, quality of welds between the tubes, and strength at connections to the car. Welded connections aren't necessarily better than bolted, since it depends on the specifics of the connections (bolted connections are widely used in large structures such as bridges and buildings).

dntlvet

Interesting... the more we know, the certainty with regard to safety is less.

Jenner

This is correct (at least in my region of CVR) for novice drivers.

Here is what it says on the CVR tech form:
http://cvrpca.org/docs/de/CVR_Tech_Form_2016.pdf
Seat Belts: Factory or better installation in both seats; must be securely mounted; belts not frayed; equal restraints for passenger and driver.
4 point harnesses prohibited except Schroth Quick Fit.
5-, 6- and 7-point harnesses must use seat with factory routing holes.
Harness webbing must be replaced every five years.

(personally I think 4 point Quick Fit should be updated to say ASM as well)

And from the CVR DE guide:
http://cvrpca.org/docs/de/CVR_DE_GUIDE_2016.pdf
For purposes of instruction only, CVR approved Instructors may ride in a
student’s car (and vice versa, at the discretion of the instructor) provided both occupants are registered for the event and the same type of restraint system (seats, seat belts, roll bars, cages, etc.) is available to both

I can give you some examples of how this works in real life with the GT4 at CVR events:

I'm in black (advanced solo) so I don't have an instructor with me very often. I installed a RSS harness bar with hoops, 6 point belts and sub belt bar for just me. When I do take an instructor out with me we both wear the 3 points.
For the number of times I have a passenger it wasn't worth the cost of another set of belts, cutting the a hole in the passenger CF seat and getting an upholstery shop to do the passenger seat cushions.

A good friend of mine did the same thing to his GT4 but he is in green (novice). I told him I thought it was silly since he would rarely get to use his 6 point belts since he would always have an instructor for the next year or so and the life of the belts would be counting down to replacement. To my shock his instructors have allowed him to use his belts while they used the 3 points at several track days so far.

So while the rules state one thing and they will give you a hard time about it at the track side tech inspection it seems that the final say is with the instructor.

HTH!

matttheboatman

Great discussion. Thank you DA for pointing the 4 point option from Schroth.

I am in the process of trying to make an informed decision on restraints for my income GT4.

So, in the decision making process we all know that a welded in full roll cage is best for the track, but incompatible with street driving. And, all other solutions involve a compromise which each of us must weigh in making our decision.

So, the next level down from full cage is a Harness bars with hoops which will provide some degree of roll over protection as is necessitated by being strap'ed into the seat in a fixed upright position. The negative compromises are a) possible failure during a severe event, and b) possible increased risk due to unprotected head impact while driving on the street.

A horizontal bar, or shoulder strap attachment points mitigate the possible street driving unprotected head impact with a hoop. But, the compromise is zero assistance in a rollover situation.

Hmmm. Care to weigh in on the following questions?

1. What is the likelihood that in the case of a severe roll over, the 981 would fail at the A pillars and crush?

2. How does the Schroth 4 point system prevent a driver from submarining under the strap?

3. Is it accurate to say that any 4 or 6 point harness is safer than std seat belt during an impact or is the harness simply to improve track performance?

Jenner

1. Not sure who can say....even if Porsche tested this and you had data, you won't be going the exact same speed at the exact same angle etc etc etc. The 981 is VERY strong and has a very strong A pillar and roof design but ANYTHING can happen.

2. The Schroth 4 point belts ONLY prevent submarining if they have ASM:


That yellow square section on the belt above stitched specially to "blow out" under G forces.
On the drivers side the belt with ASM is to be installed on your right shoulder, on the passenger side it is the left shoulder (ie always the inside shoulder) in order to work correctly. When you have an impact it "pops" allowing the drivers upper body energy to go forward and over the hip belts rather than going under them.
More info here:
http://www.schroth.com/en/segments/r...hroth-asm.html

Video:


I ran ASM belts with the factory seats in a Nissan GT-R. It's a compromise, but the ONLY way to do 4 points without at least roll hoops IMHO. Also saves you from having to purchase and install the sub belt bar and lets you run HNR.

3. I would say that 4 (or 6) is safer because you can now wear a HNR. Yes technically you can buy a HNR that attaches to your body and allows you to wear it with 3 point belts but you don't get held in the seat as well by the 3 point belts. Being fixed in the seat with 4/6 harnesses allows you to feel more info from the car as well as concentrate on driving instead of holding yourself in place. That to me is also a "safety" feature.

ShakeNBake

+1 I share the same opinion, but without the experience to back it up (...I did help fabricate the cage in our chump car....but that was more of a lesson in what not to do).