5 point/sub belt harness mount on stock seats

[titaniumdave]

I have been working on this idea for quite a while, how to attach a 5th point/sub belt to the stock seat. I like the convenience of the electric seat, the bolster support is good enough for most use and the comfort is fantastic for road trips! I pull the bottom seat cusion when I am on the track to give me clearance for my helmet, so I have been looking for an option to securely mount a 5 point harness that does not interfer with any of the things I like about the stock set up.

Here is what I came up with:

I used the 2 bolts which mount the rails to the bottom of the seat to attach a chromoly tube with end plates welded on, used longer bolts and locking nuts to secure the tube in place. All stock electrics clear and the connectors will fit between the tube and the seat bottom.

I needed to make a hole in the aluminum seat bottom, which I did by drilling 3 1" holes with a hole saw, and grinding between the holes. The slotted hole had sharp edges I put a finishing plastic moulding on, bought from the local trailer supply store.

The install took about a hour, including taking the seat out. Very clean and the sub belt can lay under the seat front when not in use. The location is perfect for the gap in a Dali seat cusion, putting just enough forward angle to the sub belt to keep the waist belt on my hips and protect the family jewels during hard braking.

I will see about producing these for market if there is interest.

Dave

 

[VBNSX]

isn't there a bolt on spot underneath the seat? Under the carpet or some junk? I could be completely way off considering I have never checked but I could've sworn I read something about that to some extent...
x

 

[MiamieNeSeX]

As your set up is better than none, I would feel more comfortable attaching the belt to the car itself and not the seat. I believe MarkB has a 5 point harness installed on his stock seats.
http://home.kc.rr.com/mbartlett4/Interior pics.htm
Armando

 

[titaniumdave]

isn't there a bolt on spot underneath the seat? Under the carpet or some junk? I could be completely way off considering I have never checked but I could've sworn I read something about that to some extent...
x

You can use a 6 point and bolt to the front seat mount bolts, I think the angle is a bit to far forward, especially if you are running the seat farther back. I like the idea of having the sub belt in a consistant position comapared to the waist belt, the only way to do this is have it move with the seat.

 

[titaniumdave]

As your set up is better than none, I would feel more comfortable attaching the belt to the car itself and not the seat. I believe MarkB has a 5 point harness installed on his stock seats.
http://home.kc.rr.com/mbartlett4/Interior pics.htm
Armando

The angle of the sub belt is very important, the belt keep the waist belt on the pevlis making sure the force of an impact is carried there. As shown in this PDF:
http://www.gforce.com/pdf/harnessinstall.pdf

The angle of the sub belt should be forward, or in the case of a front impact a significant amout of the force will be put into the crotch of the driver as the sub belt holds the driver in place, not just holding the waist belt down on the pelvis. Mark's install seems like it would be a real ball buster in an accident

The area on the seat rails where I have attached is quite well reinforced, making contact at 4 points on the steel rails, the load is applied against the frame with very little load on the bolts. One needs to remeber the point of a sub belt is to maintain the position of the waist belts, the mount I have used runs all the way across the bottom of the seat with a heavy tube of cromoly, it is stronger and stiffer than any other portion of the seat. The tube would have to be pulled through the seat rails, the bottom of the seat and the legs of a driver before the waist belt could move off the pelvis. My goal is not to make a race set up, the seat would be replaced first for any one who wants to race, this is to increase safety for an enthusiast who wants to keep the stock feel of the interior while keeping their butt planted during hard track runs, plus make them safer if they should have an accident while on the track.

Here are the shots of the seat re-installed. This shows a Dali seat cushion, but the stock seat bottom could be used with a slot cut in the front most fold of the cushion.

 

[MiamieNeSeX]

I would guess with the "crotch" belt so far forward you are prone to "Submarining".

Armando

 

[titaniumdave]

I would guess with the "crotch" belt so far forward you are prone to "Submarining".

Armando

Pulls at about 10 degrees forward, like recommended on the Gforce PDF. As I have stated, a sub belt does not prevent your body from 'submarining', it keep the waist belt on your pelvis so load is carried by your pelvis in an accident, not your guts. Your pelvis can take 5000 lbs. of force with out damage, your internal organs can only take 800 lbs., once again numbers off the Gforce website.

 

[VBNSX]

Interesting dilemma...

Either get the safety and firmness of a harness but then if you don't get a rollbar, you're screwed b/c of the whole roof caving in/not being able to move your head... versus

No harness but if you roll over you can have the ability to move within the event of a roll...

Personally I just do the whole pull the seat belt slide seat into belt ordeal... can get REAL tight.. :tongue:

It kinda seems like you sacrifice one for the other...

x

 

[titaniumdave]

Interesting dilemma...

Either get the safety and firmness of a harness but then if you don't get a rollbar, you're screwed b/c of the whole roof caving in/not being able to move your head... versus

No harness but if you roll over you can have the ability to move within the event of a roll...

Personally I just do the whole pull the seat belt slide seat into belt ordeal... can get REAL tight.. :tongue:

It kinda seems like you sacrifice one for the other...

x

I only wear the harness when on the track, the chances are pretty slim of getting my car upside down on the track while doing an HPDE day, so I am comfortable with the harness and no roll bar. A coupe NSX has pretty damn good rollover protection anyway.

Having done the slide the seat forward with the belt locked for 3 years, I am amazed with the increased control I have being harnessed in and not having to brace my self. First time I have not had a bruise on my left knee, plus, all of a sudden I can left foot brake with complete control :biggrin: , yahoo, trail braking!

 

[titaniumdave]

Thanks for the input on this project. I have finalized a design and am going to build a small batch of these, PM me if you are interested. First batch will be $56 each with hardware. I will post something on the vendors section once I have finished parts and pictures.

 

[Jeff A]

Here's what I did with a harness bar and simpson 5-points. Works for me, and now with this discussion it's perhaps the best way to do it?

 

[Larry Bastanza]

Jeff,

I beleive that is 6 point. The main difference is that with this arrangement you can move upward in the seat. The 5 point will keep your entire body planted down in the seat.

Dave,

I have done alot of thinking about something like this, I had some alternative ideas, but yours is quite simple, I like that. Do you have any idea how much load that it can take? I know the harnesses are rated at 5500 pounds. Do you think that if you had a strap connected, could you lift the car from that point? That would be maybe a 1500lb static test(if you could lift that side of the car). I have little doubt your bar can take it, wondering about the seat rail.

Regards,
LarryB

 

[titaniumdave]

Jeff,

Dave,

I have done alot of thinking about something like this, I had some alternative ideas, but yours is quite simple, I like that. Do you have any idea how much load that it can take? I know the harnesses are rated at 5500 pounds. Do you think that if you had a strap connected, could you lift the car from that point? That would be maybe a 1500lb static test(if you could lift that side of the car). I have little doubt your bar can take it, wondering about the seat rail.

Regards,
LarryB

I am sure you could lift the car whole from this point , the seat rails will distort but not fail. I think this is a better failure mode. The distortion of the rails will absorb energy, rather than having your body have to take the whole load. I have personal experince from my accident last fall when I hit a wall on the track at 70 MPH, much of the force came from the right rear quarter which hit first. The seat back bolster held my torso securely and bent with me absorbing a significant amount of the blow, allowing me to walk away with no more injury that some bruises on my ribs. One of the great features of the multi part seat design of the NSX is it can move and distort in an accident, fantastic way to disipate energy.

I will stick my engine hoist in and actually see what I can do as far as lifting the car, now I am interested in the result :wink: . Will post pics of what happens :biggrin: .