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5 Point Harness lap belt mounting

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5 Point Harness lap belt mounting

Postby redfire106 » Tue Apr 20, 2021 10:18 pm

Hey Guys, I don't post often but I've gotten plenty of help putting my car together from browsing all of the knowledge on this site!

I'm finally getting ready to install my autopower roll bar and 5 point harness for track days and autox and I couldn't find the info I needed from searching here or on hondatech.

I have an 89 CRX Si with door mounted belts and I see people talking about welding in nuts for the lower lap belts, but from what I've read it seems like people weld in both nuts on the driver side without using a backing plate of some sort. I bought 2 Schroth backing plates that I plan on having a friend weld in. The plate on the exhaust tunnel is easy, drill a hole and weld it in place. I'm stuck on how one goes about getting the backing plate into the driver door sill area. I can't seem to find any info on this. I was thinking maybe I should just cut a hole in the door sill area under the side skirt to have the plate welded in. Then once I put the side skirt back on no one will see it. Has anyone thought of doing it this way? Or maybe have a suggestion on a better way that I'm not seeing. Any advice in this area would be greatly appreciated before I go and start cutting holes in the frame.
TIA

Link to the plates I bought
https://www.pegasusautoracing.com/produ ... ecID=29945
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Re: 5 Point Harness lap belt mounting

Postby nihkon » Wed Apr 21, 2021 1:21 am

On my previous CRX, I converted from door-mounted seat belts to pillar-mounted seat belts. Not the exact situation you're in, but similar enough.

I used home-made versions of the plates you linked to. But instead of mounting them on the opposite side of the sheet metal, we drilled a hole just large enough for the weld-nut to be inserted into, then welded the perimeter of the plate on the inside/interior face of the sheet metal.

I'm no engineer, but I think with a plate that's welded on all 4 edges....if doesn't really matter which side of the sheet metal it's welded to, particularly in the case of the door sill and the exhaust tunnel, where the forces from the belts are being applied somewhat parallel to the sheet metal.

For the crotch belt anchors, it's easy enough to get access underneath the car to weld the plates on the outside. So I'd probably opt for that.
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Re: 5 Point Harness lap belt mounting

Postby AttackCRX » Wed Apr 21, 2021 7:46 am

It's actually much simpler than that. Since the Autopower bar comes with backing plates for under the car, I used one of the bolts on the left side (floor) pad of the rollbar and mounted my lap belt to it. On the right side, all I did was use the factory hole for the OEM seat rail into the floor. This is in a '91HF with a PCI seat bracket. Zero welding required and the only holes I had to drill were for the rollbar.

:-)b
1991 HF - '97 B18C1
1989 Si - gone
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Re: 5 Point Harness lap belt mounting

Postby redfire106 » Thu Apr 22, 2021 1:48 pm

Thanks for the responses folks. as an aspiring mechanical engineer, I'm concerned about welding the plate to the outside of the rail even though its mounted such that it will be loaded in shear. The weld beads don't seem like the best for distribution of the load, Even though there's more bead holding the plate in. For the second suggestion, have you ever had the car inspected at a sanctioned event? I wanted to make sure that the mounting will be safe and will pass a tech inspection at a track day.
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Re: 5 Point Harness lap belt mounting

Postby AttackCRX » Thu Apr 22, 2021 2:40 pm

redfire106 wrote:For the second suggestion, have you ever had the car inspected at a sanctioned event? I wanted to make sure that the mounting will be safe and will pass a tech inspection at a track day.



I have, and will be doing so again on May 13th. Both are HPDE events. The ONLY thing they looked for was the expiration date on the harness. I wanted to mount/install everything correctly for MY safely, ie. correct harness angle and what not.

The car's end goal setup will be multiple HPDE events a year, so tech inspection will be a reoccurring procedure. No corners were cut and like I said, safety is the main goal.
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Re: 5 Point Harness lap belt mounting

Postby redfire106 » Fri Apr 23, 2021 6:36 pm

That's definitely reassuring. Did you have to use a longer bolt for the side that mounts to the seat bracket? And I noticed the rollbar comes with grade 5 hardware. did you end up replacing the one used to mount the belt with a higher grade one?
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Re: 5 Point Harness lap belt mounting

Postby AttackCRX » Sat Apr 24, 2021 6:00 am

redfire106 wrote:That's definitely reassuring. Did you have to use a longer bolt for the side that mounts to the seat bracket?


Neither side of the lap belt is attached to the seat bracket. One side (right) went to the unused OEM seat rail hole into the floor, and the left side went to the roll bar pad on the floor.


redfire106 wrote: And I noticed the rollbar comes with grade 5 hardware. did you end up replacing the one used to mount the belt with a higher grade one?


I used what came with the harness itself and the roll bar, the only bolt I upgraded was for the crotch belt. It was my original plan to upgrade the harness bolts but the supplied hardware was more than substantial.
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Re: 5 Point Harness lap belt mounting

Postby incomplete » Thu Apr 29, 2021 1:41 pm

quick tips for an annoying job:

* quintruple-check everything. measure, mock up, have a buddy help when you're in the seat
* use oem mounting points if possible for eyelets
* if you can't, drill holes and use grade 10 bolts with big-ass thick steel washers
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Re: 5 Point Harness lap belt mounting

Postby incomplete » Thu Apr 29, 2021 1:43 pm

incomplete wrote:quick tips for an annoying job:

* quintruple-check everything. measure, mock up, have a buddy help when you're in the seat
* use oem mounting points if possible for eyelets
* if you can't, drill holes and use grade 10 bolts with big-ass thick steel washers


i'll try and swing by the racecar this afternoon and take some pics of how we mounted our 6-point.

oh yeah, final tip: don't get cheap harnesses. i <3 schroth, and they're worth every penny.
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