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Ideal Harness Mounting Questions

Ok I’ve searched this as much as I can, here and on any other forum I can find. Can’t find a consensus.

I’m looking to install my new seat and harness as safely as possible. I’m willing to do some fab work and break out my welder if needed.

Priorities:

-Separate harness mounting from seat mounts to distribute load.

-Design and execute in accordance with most of the stricter standards which state not to place any mounts into sheet metal.

So other than building a cage with nodes that terminate where you will incorporate harness mounts how does one execute sub mounts and especially the trans tunnel lap belt mount without building them off of or through sheet metal? Seems that I have no choice, so then how to execute as strong as possible.

My current thought is to make the biggest 1/8” plates I can fit in a given area, hopefully 6”x6” or bigger per mounting area, round corners and radius edges and weld in. Then weld on or through-bolt double shear harness mounts. I think for subs this should be sufficient since they see much lower loads than lap belts. But how about for lap belts?

Option two would be these or something like these:

https://www.izzyscustomcages.com/product-page/double-shear-racing-harness-mount

My other idea for the trans tunnel lap belt would be to build a plinth/box as you would for a cage tube end and weld on a double shear tab. Not sure there’s enough space to do this though even if it were the best idea.

So anyone whose spent time lying in bed trying to figure this stuff out please chime in!

P.s. the below link is one of the better compendiums of info on harness mounting I’ve found so far.

 
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362
sfo
Ok I’ve searched this as much as I can, here and on any other forum I can find. Can’t find a consensus.

I’m looking to install my new seat and harness as safely as possible. I’m willing to do some fab work and break out my welder if needed.

Priorities:

-Separate harness mounting from seat mounts to distribute load.

-Design and execute in accordance with most of the stricter standards which state not to place any mounts into sheet metal.

So other than building a cage with nodes that terminate where you will incorporate harness mounts how does one execute sub mounts and especially the trans tunnel lap belt mount without building them off of or through sheet metal? Seems that I have no choice, so then how to execute as strong as possible.

My current thought is to make the biggest 1/8” plates I can fit in a given area, hopefully 6”x6” or bigger per mounting area, round corners and radius edges and weld in. Then weld on or through-bolt double shear harness mounts. I think for subs this should be sufficient since they see much lower loads than lap belts. But how about for lap belts?

Option two would be these or something like these:

https://www.izzyscustomcages.com/product-page/double-shear-racing-harness-mount

My other idea for the trans tunnel lap belt would be to build a plinth/box as you would for a cage tube end and weld on a double shear tab. Not sure there’s enough space to do this though even if it were the best idea.

So anyone whose spent time lying in bed trying to figure this stuff out please chime in!

P.s. the below link is one of the better compendiums of info on harness mounting I’ve found so far.

I have built a number of racecars welding my own cages bending tube etc. I have also done several dual use cars over my time too.

How safe do you want to be? You can do do 4point hoop w/bolt-in door bar and slide in containment elements, 4point hoop w/bolt-in door bar, 4 point hoop, truss, harness bar, or connections to rear seat anchor points. Everything has compromises.

Will you wear HANS?

How much interior will you remove?

Will you cut some interior? If your interior is black I got a bunch or interior parts you can cut or save for when you sell the car.

What do you believe? Are you anti harness bar without a rollover hoop? Are you anti-rollover hoop without wearing a helmet?

What are your beliefs about containment?

Are you willing to modify to run sidenets?

I'm not an engineer but here is really rough in head calc. 50G crash is totally survivable. 100G in racecars happen in pro racing all the time. 50 x 250lb guy = 12500lbs / 6 point anchor = 2000lb per anchor. Add in a fudge factor double it for 4000lb per anchor. I want that as minimum pounds with no anchor point deformation. 100G's by the way is 4000lbs. So while 100Gs is less likely at our amateur speeds it is still quite possible. What is 4000lbs? The weight of your S550 is almost 4000lbs with driver and fluids. So would never would jack your car from the sheet metal floor under your seat so don't use the sheetmetal floor for your anchor points either.
 
Thanks for your thoughts and questions Bob.

My goal is as much safety as I can stand for a dual purpose car. For me now that includes:

4pt rollbar (CMS Motorsport)
Containment seat (OMP HTE-R)
6PT harness
HANS

Not planning on door bars or nets for now.

Im not averse to cutting interior panels and carpet. Most rear panels are out and will stay out.

This said, what would you do for anchors that need to go where there’s mostly just sheet metal?
 
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find an SCCA rule book, they give standards, recommendations and illustrations

Seat belts All drivers in SCCA sanctioned speed events shall utilize either a 5, 6, or 7 point restraint harness meeting the following specifications.7 point restraint harness is recommended. Arm restraints are required on all open cars including open Targa tops, sunroofs and T-tops. Arm restraints shall not be worn in a manner which limits the ability of the driver to provide visible signals to other competitors while on track. The shoulder harness shall be the over the shoulder type. There shall be a single release common to the seat belt and shoulder harness. When mounting belts and harnesses it is recommended that they be kept as short as reasonably possible to minimize stretch when loaded in an accident. The shoulder harness shall be mounted behind the driver and supported above a line drawn downward from the shoulder point at an angle of 20 degrees with the horizontal. The seat itself, or anything added only to the seat shall not be considered a suitable guide. Guides must be a part of the roll cage or a part of the car structure. Only separate shoulder straps are permitted. (“Y” type shoulder straps are not allowed.) “H” type configuration is allowed. The single anti-submarine strap of the 5 point system shall be attached to the floor structure and have a metal to metal connection with the single release common to the seat belt and shoulder harness. The double leg straps of the 6 point or 7 point system may be attached to the floor as above for the 5 point 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 to the seat belt and shoulder harness or attaching to the shoulder harness straps. Each seat (lap) and shoulder belt of the harness (5, 6, or 7 points) shall have an individual mounting point (i.e. 2 for seat belt and 2 for shoulder belt minimum). 6 or 7 point system anti-submarine straps may share a mounting point with one or both seat (lap) belt(s). The minimum acceptable bolts used in the mounting of all belts and harnesses is SAE Grade 5/Metric 8.8. Mounting hardware, including eye bolts, as provided by the belt manufacturer, may also be used for mounting belts and harnesses. Where possible, seat belt, shoulder harness, and anti-submarine strap(s) should be mounted to the roll structure or frame of the car. Where this is not possible, large diameter mounting washers or equivalent should be used to spread the load. All driver restraint systems shall meet one of the following: SFI specification 16.1, 16.5, or FIA specification 8853/98, 8853-2016 or 8854/98. Restraint systems meeting SFI 16.1 or 16.5 shall bear a dated SFI Spec label. The certification indicated by this label shall expire on December 31st of the 5th year after the date of manufacture as indicated by the label. If for example the manufacture date is 2014 the fifth year after the date of manufacture is 2019. Restraint systems homologated to FIA specification 8853/98 and 8854/98 will have a label containing the type of harness designation (‘C-###.T/98 or D-###.T/98) and date of expiration which is the last day of the year marked. All straps in this FIA restraint system will have these labels.

crow-safety-harness-installation.jpg
 
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362
sfo
Thanks for your thoughts and questions Bob.

My goal is as much safety as I can stand for a dual purpose car. For me now that includes:

4pt rollbar (CMS Motorsport)
Containment seat (OMP HTE-R)
6PT harness
HANS

Not planning on door bars or nets for now.

Im not averse to cutting interior panels and carpet. Most rear panels are out and will stay out.

This said, what would you do for anchors that need to go where there’s mostly just sheet metal?

This one?



If you are willing to weld to the 4 point I would convert the 4 point and weld a seat truss from 1" DOM tubing fabing up a seat mount to bolt into the 4 existing seat floor anchors. This way no welding on the car. Those seat anchor points are designed by FORD and should be fine. Then mount the seat" fixed" to the seat mount. Now you can weld the double shear tabs at exactly the right 45 degrees to your hip when belted in or you can weld eyes. You can also weld in the 1" bar for the subs under the sub hole. Much more work must be done if you use a slider. If seat is fixed mounted you can also weld on a back brace to the 4point Your seat is an FIA 5 year seat so it has no integrated back brace mounting and is only certified for 5 years. I stable weld made back brace does wonders in a rear end crash. I can attest to that having been taken out from the rear twice and flipped over once racing over the years. I'm in 90275 and I'll be racing SCCA next week at BRP. I do not know where you are in cali but I can show you ideas if you want to come by and draw them out on your car if you need more fab tips.

These are not finshed pics of fabrication I did on my 2019 mustang GT but give you some ideas. You can do the same thing welding onto the 4 point and bolting into the stock seat anchor locations. You want more surface area back brace than this for plastic seat. I have a full containment aluminum seat mounted 6 places to cage. I'm from school of containment is everything.


20200118_112428.jpg20200118_112418.jpg
 
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362
sfo
Then of course you can always do this that 90% of dual use guys do. Kludge it.




 
Yeah that’s the roll bar. I don’t think building a seat truss off of it is viable as it sits up on the “saddle” beam that’s the front of the rear seat area. It’s pretty far up there.

So I guess another way to ask this question is despite the fact that I want to divorce harness from seat mounts, can I reasonably expect to build stronger harness mounts in beefed up sheet metal than anchoring the harness to the seat bracket? The more I think about this the less confident I am.

I wonder what loads Ford designed the seat anchor points to withstand given that the seat belt buckle is part of the seat?
 
533
362
sfo
Yeah that’s the roll bar. I don’t think building a seat truss off of it is viable as it sits up on the “saddle” beam that’s the front of the rear seat area. It’s pretty far up there.

So I guess another way to ask this question is despite the fact that I want to divorce harness from seat mounts, can I reasonably expect to build stronger harness mounts in beefed up sheet metal than anchoring the harness to the seat bracket? The more I think about this the less confident I am.

I wonder what loads Ford designed the seat anchor points to withstand given that the seat belt buckle is part of the seat?

You can if you use same diameter tube as rollover hoop weld onto the rollover hoop bar by saddle anchor down to seat truss bolted to the outboard rear seat anchor point and fab something similar from the X point or copy that to the passenger side run a bar low and parallel to the saddle and then you can to weld in board seat truss side bolting to inboard rear seat anchor.

A crash engineer told me once streetcar survivability is about 50g or 45mph pulse. So those anchor points of ford should be ok.

If you divorce and do not do a truss to the 4 point you will have to weld on the car. At that point weld the 4 point too.
 
Great thanks for the info Bob. More to think about.

Also you had asked about sliders, which I’m not using. Been contemplating a seat back brace too, seems they help a lot.
 
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362
sfo
Great thanks for the info Bob. More to think about.

Also you had asked about sliders, which I’m not using. Been contemplating a seat back brace too, seems they help a lot.

Yeah once seat is 5+ year old. The fia seats have an expiry date. Back brace is thought to extend that but there is no real testing of that. FIA does not allow drilling and rigid mounting of FIA 5 year seats because they were not designed and tested that way past 5 years. Metal seats deform but have no expiry date. You can drill and weld on them to do things like get the harness holes in the perfect spot for your body. But they must be supported at more places because they can deform. You want to support it so it can't do that. I see the seat as the most important part of the safety system which everything else is built around.
 

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