Stock Seat with 5 point harness

Re: Harness geometry and fit

As Hrant is going through birth pains with installation of his CT bar and 6 point harness, and rightly so, I have been poring over the FIA specifications on the shoulder belt mounting in my Formula Mazda race car as it is required for the HANS. I won't bore you with the details, I'll just say that the more you can understand how these belts work and the violent forces created in that awful sickening few moments when they do their job, the more care you will take to do the mounting right.

As I figure out how to keep the belts from slipping off the HANS during a multi-impact or off-angle crash, I keep the videos of the laboratory sled crash tests firmly in mind. They provide a vivid picture of how far the body moves before the belts really become loaded, how much they stretch and how much your head, arms and legs flail. The HANS site shows only a 28 g crash, but race belts are tested by SFI to a 60 g load and measured for elongation (20% max). Old Dale E died in a 43 g crash.

I didn't mean to get up on a soap box here, but re-reading these old posts about improper mounting of a single anti-sub strap (not wanting to cut the seat) just made me want to share my growing concern for function over form. Of course, if you just want to look cool and pick up chicks down at the In-n-Out Burger ........:cool: .nevermind, you're into a different sort of protection :wink:

OK, back to the garage...............
 
Re: Harness geometry and fit

92 white 0650 said:
...I keep the videos of the laboratory sled crash tests firmly in mind. They provide a vivid picture of how far the body moves before the belts really become loaded, how much they stretch and how much your head, arms and legs flail. The HANS site shows only a 28 g crash, but race belts are tested by SFI to a 60 g load and measured for elongation (20% max). Old Dale E died in a 43 g crash.
Click to expand...

Any chance these videos are online somewhere?
 
Re: Scary videos

Well, for some reason, I can't put my finger on the most representative of several I've seen. It'll come back to me, but in the meantime, maybe some others can chip in here. But here's one that Issace, the HANS competition, puts out. This one motivated me to go to work on moving my shoulder belt hard point spacing from 8" to 6".

www.isaacdirect.com/]

IIRC, the Wayne State University tests several years ago had videos, but a quick google is not giving me anything familiar.

Back to work............
 
There are some serious private discussions going on this subject with pics and articles being exchanged ...... I am in communication with Simpson and will follow up more once I find out more info from their tech. Texas is where their tech reside. They are very cautious when it comes to making any comments on harness belts and mounting. Bottom line is this, their belts are for dedicated race cars.

From what I have gathered thus far, unless one is willing to drill hole(s) through the frame right behind the hip in final track driving position (with proper reinforcement - a heavy duty washer will not do) at the purported 20 degree angle, where the sub belts get mounted on an NSX is truly a compromise. However, in all scenarios the sub belts should NOT be extended to come under and then over the front seat cushion. Either Ted's option of bringing them through the back and seat cushion should be used or through the seat.

Comptech's option of mounting the 6 point sub belts on the same bolt on the harness bar meets the separation of about 10" from the buckle but does not meet the 20 degree behind the chest/buckle - especially if you are not a tall driver or do not push your seat almost all the way to the back. For me, where the seat is about 2" from being full back, it would be more like 35-40 degrees. Also, having a separate bolt dedicated for the sub belt, mounted on the opposite side of the current mount is a better solution than having both loaded on the same bolt. There seems to be enough tread to put a bolt in that location.

Titaniumdave's bar offered by DaliRacing is another option. The bar goes between the front rails and helps to keep the location of the mount in constant position to the body albeit it is not 20 degrees behind the chest - as recommended - but more like straight down in a horizontal plane. This option works with a 5 point harness.

Stay tuned.
 
Hrant said:
There are some serious private discussions going on this subject with pics and articles being exchanged ...... I am in communication with Simpson and will follow up more once I find out more info from their tech. Texas is where their tech reside. They are very cautious when it comes to making any comments on harness belts and mounting. Bottom line is this, their belts are for dedicated race cars....................................................
....Comptech's option of mounting the 6 point sub belts on the same bolt on the harness bar meets the separation of about 10" from the buckle but does not meet the 20 degree behind the chest/buckle - especially if you are not a tall driver or do not push your seat almost all the way to the back. For me, where the seat is about 2" from being full back, it would be more like 35-40 degrees. Also, having a separate bolt dedicated for the sub belt, mounted on the opposite side of the current mount is a better solution than having both loaded on the same bolt. There seems to be enough tread to put a bolt in that location........................................Stay tuned.
Click to expand...

I have the lap belts attached on the "outside" of the mounting points on my Comptech harness bar and my dual sub mounted to the "inside" mounting points. With a race seat the sub works great, but the lap belts are not straight around my waist creating a troublesome stress riser and possible fraying point. This was not a problem with the stock seat as the lap belts did not have to snake through a guide.

The other option with a dual sub is to bolt the ends under the rear seat mounts. They were strong enough for Honda and the NTSB. You might need to massage the metal tabs to reduce stress risers.

As far as seat modifications, if you are willing to drive fast enough to need a racing harness, then you should be willing to make some sheet metal modifications to stay as safe as possible. JMHO
 
Gary, your points are all valid. The issue is not whether to cut/modify sheet metal or not but which one and where. I plan to drive without the seat cushion (already found a perfect 3/8" dense foam cushion), so having a 5th or 6th harness belt(s) through the seat is not an issue.

Al is already thinking along the lines of using a cross bar from both rear rail mounting points to see if he can then attach the sub belt there.

What size/grade bolt did you use with sub belt. We had a laugh finding grade 8 washers today, ...... the ones in the used package were clearly not grade 8.

As I said, its a compromise.
 
Re: Scary videos

I just remembered that the scary videos I'm thinking of were on the CD's sent with the HANS device and Schroth HANS specific belts. Unfortunately, they don't seem to have the same videos on their websites.

What's really interesting is to see the submarining action of a body sliding under 4 point belts. Just might be worse than 3 point belt performance. Either way, those videos will make you look at the 3 points belts with fear :eek: and trembling, especially when you're playing bumper cars on the freeway at 80.
 
akio, for the 5th point you can actually use a piece of thin channel strut (http://www.flexstrut.com/systems.htm) and bolt it underneath the seat. I like it that way since the 5th point is always consistent w/ my body positioning. And yes if you've ever seen the specs it'll handle well over 1k over vertical force.

x
 
Do I recall Titanium Dave made a brace that goes across the seat rails UNDER the seat, aligned with the 5th point so it pulls straight up, as is required for safety?

Not sure if he manufactured them or not, but it certainly looked like a possible safe alternative to the floor drilling. Dave??

I found the thread:

http://www.nsxprime.com/forums/showthread.php?t=50628

Regards,
LarryB
 
Re: Get a 6 point

Hey guys, a couple of things.

Larry, I gotta disagree with your statement in that old post you referenced where you said a 5 point keeps you planted in the seat better than a 6 point. Two reasons: On a superficial level, we can say the 6 point anti-sub belts do primarily just that (anti-submarining) but secondarily they keep the lap belts in place. Correctly positioned lap belts are what keep you down and planted in the seat. On a deeper level, the SAE engineer types and the racing community in general all agree that the 6 point is vastly superior to the 5 point in all aspects of safety performance as well as comfort. I won’t attempt to recite all the details, but it’s laid out pretty well on sites like
http://www.schroth.com/installation-instructions/en/index.html

I really am against 5 points when a 6 point could be just as easy to install.

VBNSX, please take another look at your channel idea. If by 1k you mean 1000 lbs (and that looks about right) that’s definitely the weak link in a system designed to support belts good for 2500 + lbs. You’ll find specific loads on page 17 of the site above.

It’s tough to get these things right, I know. I was just teasing Hrant by asking if he thought the ride down the slippery slope was only going to cost him money. With issues like this, it takes some blood sweat and tears to safely slide into the black hole of racing.
 
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Well Ted, the more I read up on this the more I am finding that none of the current "look good" options meet the basic requirements - except for where the shoulder belts mount.

Unless I am missing something, it appears to me that for a six point, both the lap belt and the sub belts do not meet the required angles on the Comptech bar - and most likely the others if the mounting points are similar; ie, on the bar. I have e-mailed Shad to get some feedback. DaliRacing offers Schroth as well, and Mark has been quite helpful in guiding me through this process especially regarding the pitfalls of where the lap and sub belts mount in relation to the body. I did not find any diagrams or mounting installation PDF files in SOS's website except for this: "The NSX is equipped with recessed mounting location that is compatible with 5-point harnesses. We recommend and supply hardware for a 5-point harness belt. 6-point belts will require additional modification to the floor pan to secure reinforcement points for sub belt mounting."

Then there is the issue of not having a roll bar, and not having a HANS device ........ :frown:

As I said, perhaps it's best that I revert back to cruising :eek: Just take the seat cushion off, lock the OEM lap belt and go for a ride with all the excuses of why not ....... :tongue: :biggrin:
 
Re: Diagram conflicts

I have found that conflicting information is the norm not only for adapting harnesses to street cars but even for applying FIA and SFI standards to race cars that are supposedly built or alterable to exactly comply with their specifications. I have several stories to tell about our Formula Mazdas, the most popular club formula car class in recent history. It's frustrating and each car owner/driver has to decide what configuration most nearly complies with the design of the system.

For me? I was very comfortable with the Comptech setup on my NSX back then. Now, I will admit the angle of the lap belts could be improved and the stock lap belt points do improve that "problem". Anyway, I believe the compromises of the CT 6 point system are very minor. That configuration, specifically the anti-sub belts, is very close to what we in the formula car world are comfortable with. Being the fastest and with open wheels, we are the most dangerous class in club racing and our tech gurus pay attention to the safety discussions and developments of F-1, CART, and Indy-Car. So, I'm looking at what they are doing and saying, not website diagrams.

So, I have given up trying to reconcile all the conflicting generic one-size-fits-all diagrams, and go to the heart of what the system is designed to accomplish. And, when we look at the whole system, the HANS or similar should be part of it.

Anyway, the good news is all this nashing of teeth keeps the detail oriented lawyer types off the track. :tongue:
 
Re: Get a 6 point

92 white 0650 said:
Hey guys, a couple of things.

Larry, I gotta disagree with your statement in that old post you referenced where you said a 5 point keeps you planted in the seat better than a 6 point. Two reasons: On a superficial level, we can say the 6 point anti-sub belts do primarily just that (anti-submarining) but secondarily they keep the lap belts in place. Correctly positioned lap belts are what keep you down and planted in the seat. On a deeper level, the SAE engineer types and the racing community in general all agree that the 6 point is vastly superior to the 5 point in all aspects of safety performance as well as comfort.
Click to expand...

After review of the article you point out, I understand what you are saying. I guess when I have seen these used with the stock seat in the NSX I always felt they allowed the driver to move upward, and thought it was a bad idea.

92 white 0650 said:
I really am against 5 points when a 6 point could be just as easy to install.
Click to expand...

Looking at the NSX for weekend track driving with stock seats do you have a recommendation as to lower mounting points for the 6 point? I have seen it used on the lower rear seat mounting bolts, due to practicality of installation, but if I follow the article you pointed out, not sure this is optimum. I guess my question is since you would always recommend 6 points, do you think it is a proper solution with the stock seat?

Frankly, I would prefer not to make a hole is a stock seat, so if so, your recommendation would solve multiple issues:).

Thanks,
LarryB
 
Re: Making a 6 point work

I guess my question is since you would always recommend 6 points, do you think it is a proper solution with the stock seat?
Click to expand...
Larry, I think a stock seat can work fine with proper 6 point installation/performance. And even though Shad refuses to leave me a bag of money under a certain tree on Monday nites for saying this, I think Comptech has the closest to a "slap it on and go" solution for the NSX. With the complete harness bar and anti-sub belts coming through the space between the seat cushion and backrest, the only drawback is that you can't move the seat back that last 2" (a problem if you're, what? 6-4 or taller). See my pics above posted ~ 2003

As I conceded to Hrant and based on your comment, perhaps the lap belts should be attached to the stock lap belt points and not all the way back on the bar. Now if a guy doesn't have a full bar (hard points down low), well, maybe that's a challenge. Using the rear seat attachment points with longer bolts should be a good structural hard point, but how the anti-sub belts are routed to that point may be a challenge. Similar to how the seat back cannot interfere with proper tensioning of the shoulder belts, we wouldn't want the seat cushion interfering with getting the anti-sub belts tight.
 
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Ted writes: As I conceded to Hrant and based on your comment, perhaps the lap belts should be attached to the stock lap belt points and not all the way back on the bar.

I think that would help especially if people are buying aftermarket seats that sit lower or in my case taking the seat cushion out. Because in these scenarios, the lap belt will be even at a lower angle - ie, more horizontal - than the OEM seat.

But based on the "recommended" and frankly correct mounting pics, the mounting of the lap belt bracket can't be flat with the plane of the floor; it has to be perpendicular so its pivots on the bolt without pressure. And that is a design issue that I am not capable of visualizing in 3D with any of the harness bars given that they all mount on the same tail end bolt of the rail.

As for the subs in a 6 point, Ted's arrangement of passing them through the back and seat cushion by sitting on them is the correct set up, but where they mount on the bar is does not appear to me to be correct - albeit one of those compromises that we all make. The recommended angle is 20 degrees from the plane of the chest and and buckle. Mounting the sub belts on Comptech's bar appears to be 45+ degrees, and with lower seats or no seat cushion even more! True, the subs main function is to prevent the lap belts from pulling up, but they must have the right "range" of angle to do their job by forcing the belt to stay down. I can compromise beyond 20 degrees, but doubling or exceeding that range seems to me to defeat the entire purpose of a sub.

YMMV.
 
Dave, since my focus has been primarily on the 6 point, I took a third look at your set up ..... we are all looking at the weakest point(s) in all these discussions so we all appreciate the solutions and risks involved. Please accept the comments in that vein.

If I am correct from the visual of your pics, the attachment of the sub appears to be almost straight with the plane of the chest/buckle. As I mentioned above, this looks like a better solution than the subs on a harness bar albeit this would not work with a 6 point. And for those trying to maximize head room by taking the seat cushion out, there would be no cutting of the cushion - just tuck it under the seat or put the seat cushion over when not tracking. [The same latter scenario can be used for the 6 point coming through the back and under the seat cushion - albeit two esthetically parallel black harness belts will appear in the lower rear corners of the seat. And in a tan car that would be striking LOL!]

The weakest point appears to be where the bracket mounts to the under seat plate. See yellow arrow. I am assuming your bar ought to be pretty hard not to bend on a heavy pull - though theoretically speaking it could break at both welded ends if the welds are weak. See red arrow.

I know we don't have the luxury of laboratory testing, but have you given any thought if the mounting area (yellow arrow) might bend upward and the bracket shear off the (thin) bolt that you are supplying? I have not looked under the seat, how thick is the mounting plate under the seat and how vulnerable is it to bending? How securely or firmly is the plate connected to the seat structure? If you can bend it with plyers by using some elbow force then that wouldn't be much help. TIA.
 

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Hrant,

Reviewing your comments makes me wonder if we could use Dave's bar at the rear portion of the seat rail to mount the 6 points, to keep within the mounting guidelines in the reference by Ted.

Although this would also require holes in the lower seat shell and cushion.

Thoughts??

Regards,
LarryB
 
I have a silly question...

Why are the angles / mounting positions/locations different between 6-pt and 5pt? The shoulder belts, lap belts, and buckle (for lack of a better term) are identical...the only difference is whether the anti-sub belt has one (5-pt) or two (6-pt) straps (thus 1 or two anchor points). It doesn't make sense to me that the physics would be so different between the two as to warrant such different mounting locations (roughly in line with chest line for 5-pt, straight down or slightly back from crotch for 6pt).

I would think one would get roughly the same protection from a 6-pt sub mounted in line with chest line as one would get with a 5-pt sub mounted in the same location. I can see how there would be a comfort issue going the other way (mounting 5-pt sub where 6-pt is described in this thread)...but I don't see the issue with mounting a 6-pt like one would mount a 5-pt.

Is it that people using 6-pt harnesses usually have a different goal (they could get same protection as 5-pt mounting it like a 5-pt...but want some additional/different functionality)? What's the purpose of the different locations?

Thanks.
 
Re: 5 pt vs 6 pt

Why are the angles / mounting positions/locations different between 6-pt and 5pt?
Click to expand...
I should probably wait for Hrant to come back from his latest class on harness design and technology, :rolleyes: but I will offer this weak superficial answer. Basically the 5 point only holds the lap belts down and hopefully tight across the pelvic cradle which prevents anti-submarining to a moderate degree. The 6 point anti-sub belts are wrapped around the inner thighs and primarily hold the pelvis back in a much more efficient manner than the lap belts can. The 6 pt belts also have a secondary function of holding the lap belts down and in place. The 6 pt is a more efficient design.

Incidentally, they have recently come out with a 7 point. I'll wait for Hrant to explain the subtle nuances of that but I'd guess it's just a 5 point belt added on to a 6 pt harness. I don't know and didn't sleep in a Holiday Inn Express last night, but it would seem they would be especially desirable in say, an open desert Dakar type race where the belts get continual vertical stress which subjects them to gradual loosening which also affects driver comfort over a long period.

Oh, look, here comes Hrant with an arm load of text books now !!!:tongue:
 
ROTFWL .......... yeah what Ted said :biggrin:

Larry, regarding your comment, intuitively we have thought about that. But my questions to Dave would apply whether it is the front or the back. What are the weakest links ........ ?

Perhaps a more "functional" approach to resolve the angle issues, albeit conceptual at this point since I am not tinkering with the seats out, would be to have a flat 2" wide and 1/4" thick metal plate that goes across between the back rails and secured by the rail bolts. Then the sub belt(s) for either the 5 point or 6 point can be mounted on the plate with two holes and bolts - and if necessary the bolts go through the frame for extra structural support. Now if there is room to extend the plate ends 1" beyond the rail, couldn't that become the mounting point of lap belts with a vertical mount welded to the edge?

The downside of this approach are:

(a) it raises the back rail by 1/4" (if that is the appropriate strength required - I just tossed a number) hence you may need to put a washer on the front rail mountings as well and get longer bolts perhaps. Unless it can be designed such that the plate rests on top of the rail mounting seat. I am assuming the plate has to go under the rail and the rail rests on top with matching the mounting holes.
(b) putting two holes into the frame to secure the plate further if needed - not an option that most want to follow - and some may think the plate becomes moot if you are already drilling
(c) not sure if it resolves the lap belt angle issue but seems it would
(d) if one is height challenged and needs to push the seat forward, this approach may not resolve the angles.

I think the engineers amongst us, and not the ever questioning analysts, should take the challenge henceforth :wink:

Edit: Dave, thanks for the post below. Your bar seems to be solid enough. Where did you mount the lap belts? See picture of what the thinking is for a six point. Not sure if it is feasible or not.
 

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Hrant,
My bar is 7/8 x .065" Cromoly tubing with a 1/4 x 3/4" flat bar running continuously through it. Welds are to keep every thing in place and help spread load. All hardware is grade 8.

Loads will be applied in a more or less vertical direction, pulling the bar up and through the seat and seat rails. The rail contacts the bar a few millimeters from the tube/flat bar interface effectively acting like a fulcrum and transferring most of the load into shear across the flat stock. That is until the seat and rails fail. At that point your pelvis is broken:frown: .

From what I have read, a 5 and 6 point harness perform the same function as long as they are installed correctly, keeping the lap belt on the pelvis. The 6 point has the advantage of not putting pressure on the groin if you are involved in an accident. Personally I would never use a sub belt which goes back under my butt. The sub belt should go down and forward, on a line behind a projection from the front of the chest.
http://www.daliracing.com/v666-5/info/restraint-info/restinfo.html
Dave
 
Re: 5 pt vs 6 pt.

We've all got our opinions, but here's the SCCA's

SCCA General Competition Rules and Specifications

Para. 20.1 ".... A five point harness is considered a minimum restraint system. Six or 7 point systems are highly recommended in all cars including automobiles where the driver is seated in an upright position."
Personally I would never use a sub belt which goes back under my butt.
Click to expand...
Para 6. The double leg straps of the 6 pt or 7 pt system may be attached to the floor as above for the 5 pt system or be attached to the seat belt so that the driver sits on them, passing them up between his legs and attaching either to the single release common ......."

Every formula car driver I know or see sits on the sub straps. Just my observation.
 
Thanks for the input & clarification. To close the loop (for me), here is what I now understand/think:

1. One can mount 6-point straps as a 5-point strap would generally be mounted (similar angle - forward of groin, roughly in-line with chest line) and will get the same benefit/performance as a 5-point but with a little more comfort (and maybe more mounting options).

2. Mounting a 6-point as documentation generally prescribes for 6-points (behind groin, which often involves sitting on the straps) would offer better performance/efficiency in a crash. This is common / preferred among sanctioned open-wheel (i.e. Formula Mazda) drivers. 5-point strap should not be mounted here.

3. In either case it is desireable to use a straight path for the strap(s) as bends & slack are bad. Forces of a wreck will take slack/bends out, likely/possibly resulting in belts that were in correct position (with slack/bends) being out of position at the moment they're most needed. (Exception is that a 6-point strap, mounted so the driver is sitting on it, will obviously curve around under the driver's legs/butt, so it's bent...but between driver and mount it should not bend / have slack.)

4. In either case (5/6/7-point attached forward of groin vs. 6/7-pt attached behind), guidelines for mounting degrees/angles should be followed.

Does that sound about right?
 

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