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Old 12-15-2008, 10:14 AM
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Seat belt mounting points in glass car

I would like to ask what is the perferred method to anchor seat belts in a glass 33 body. The floor is probably 1/4 to 3/8 thick with some mat glassed in. Is it safe to just use a large washer under the floor, or do I need to weld in a piece of steel tubing across the frame under the floor to tie into? Thanks for any advice provided.

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Old 12-15-2008, 12:55 PM
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Hi: I'm, going to move your thread to General Rodding Tech. You'll get better answers there.

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Old 12-15-2008, 01:08 PM
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I had the same concerns about my glass 34. To answer your question, no it is not good enough to mount the seat belts through the glass floor even with larger washers. What I did was weld some 1/4" thick tabs onto the inner frame rails for the front mounts, then for the back mounts I welded a 1-1/2" piece of square tube between the frame rails.

Vince
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Old 12-16-2008, 01:38 PM
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thanks

Thanks for the advise, I will install some tubing to anchor thru. rod
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Old 12-16-2008, 02:11 PM
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Just remeber if you take a hard hit you can pull 10g's pretty easy and then momentarily you will weigh 10 times your body weight..The seat belts and other safety items need to withstand that sort of force..

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Old 12-16-2008, 02:30 PM
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California Law says that seat belt points have to be capable of withstanding 1000lbs between them at a 45 degree angle. Most guidelines are higher, I think Europe says 5000lbs. That means you should be able to lift your car on the mounts! Sounds a little excessive.

Does anyone anyone know whether it is legal to place the mounts in fiberglass?
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Old 12-16-2008, 03:56 PM
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Quote:
Originally Posted by scrimshaw
. Does anyone anyone know whether it is legal to place the mounts in fiberglass?
Legal is what you feel you can get away with. I would not want to rely on seat belts anchored in fiberglass.

Vince
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Old 12-16-2008, 05:26 PM
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I agree. I wouldn't want to trust my lift to seat belts anchored in fiberglass either.

I'm building a glass Deuce and actually welded in 1/8" plate (with gussets) today for seat belt anchors. They are shown in the red circles in the pic below.



Haven't had a chance yet to dress the welds.... I'll get to that tomorrow.


Last edited by Centerline; 12-16-2008 at 06:10 PM.
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Old 12-17-2008, 05:48 AM
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Very nice looking job, I think those will be strong enough to lift the whole car!

While it might be easier to weld on the chassis on the floor what about the shoulder strap?

Not quite sure what you mean "whatever I can get away with". Aren't the seat belt mounts looked at when the vehicle is inspected?

As for not trusting fiberglass as a mounting point we regularly bed chainplates that would take a pull of 10 tons or more so I wouldn't have a problem as long as I was the one doing the work .
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Old 12-17-2008, 08:07 AM
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Quote:
Originally Posted by scrimshaw
Not quite sure what you mean "whatever I can get away with". Aren't the seat belt mounts looked at when the vehicle is inspected?.
That depends on how your car is registered, it may or may not require the use of seatbelts. My 34 does not have shoulder straps, only lap belts.

Quote:
Originally Posted by scrimshaw
As for not trusting fiberglass as a mounting point we regularly bed chainplates that would take a pull of 10 tons or more so I wouldn't have a problem as long as I was the one doing the work .
Sure you probably could apply enough fiberglass to provide a decent (mayby) attachment point for seat belts, but who would want that big hump on the floorboard

Vince
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Old 12-17-2008, 08:55 AM
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I got hit head on in about 1961 at about 30 mph in my 54 Olds. I had the seat belt (they were not cool back then) mounted to a 3 x 24" x 1/4 plate under the floor. I weighed about 210 back then. The impact buckled the floor about 9 inches. It was enough that I still hit the steering wheel hard enough to bend it over at the top. Had it not been for the seat belt I probably would have been seriously injured.

I see 3 point seat belts mounted to the wood reinforced B posts and fiberglass floors all the time in the "glass" streetrod. There is less wood there than in a baseball bat. Often times there is just a through bolt maybe 3/8 through the wood. Can you imagine what would happen if you drilled a 3/8 hole through the trademark on a baseball bat???

'Centerline' has some nice mounts. I'm using roll bar mounts on my car with 4 point belts.
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Old 12-17-2008, 12:06 PM
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Quote:
Originally Posted by scrimshaw
...Aren't the seat belt mounts looked at when the vehicle is inspected?
Just to follow up a bit on what Vince said, a lot depends on the state you are in and the way your car is titled as to what safety standards you must comply with. In Wisconsin, for example, my Roadster is titled as a 1931 so it must meet the safety standards which were in force in the original year of manufacture...1931. So under a safety inspection I'm not even required to have belts, turn signals, two brake lights, backup lights, parking lights, safety glass, etc.

So in the end, I think we need to build using the highest standards we can...rather than just meeting the state's safety requirements, whatever they may be.

Just one small side note on anchor points for 3-point belts. I believe those would require a seat manufactured for a frame mount OR the shoulder strap needs to be attached to an anchor point at shoulder height of slightly higher. One alternative in a glass car or open top car would be a roll bar. That's one of the main reasons I put a roll bar in my roadster. It also means details like the seat belts need to be considered rather early on in a build so that appropriate mounting points can be welded in early.

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Old 12-17-2008, 02:57 PM
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Well, being a tech inspector, I'll give you the blurb from the Rulebook....
"In all cars with fiberglass floors, a crossmember (minimum 2" X 2" X 0.083" wall square steel tubing) must be installed between frame rails for proper driver's seat belt installation."

Common sense would tell you that this also applies to wood floors.

Also, resist any temptation to mount shoulder belts to the floor if you're using aftermarket 2" or 3" belts. Shoulder belts should be mounted in the line of pull, even with, to a max of 4" below the shoulders. This will require more fabrication of steel mounting structure. Mounting belts to the floor and bringing them up over the seat in back will result in an improper "line of pull", resulting in the compression of your spinal vertebrae in a crash. You won't like the results.
http://www.sfifoundation.com/
On the left of the page, click "Articles", then click "Seat belts". Pay particular attention to the loss of strength chart over a period of time. That is an eye-opener
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Old 12-18-2008, 04:16 AM
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Thank you guys for some useful info.
Tech guy - I have been looking for specific details like that but hadn't found anything from this country. Seems like all the seat-belt info in the internet is from other countries.
Cboy - I wish I could take the advice on a state by state basis but I have been through 3 states since I started building, don't know where I will be when I finish, and I will be building to the highest standard I can but a roadster always has some difficulties with some issues like seat belts and roll bars (I do not want to add one). I hope the wife doesn't get too upset when I have to move to a different state to get it legal!

Apologies to 'rod' for hijacking the thread.
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Old 12-18-2008, 07:20 AM
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Quote:
Originally Posted by scrimshaw
...I wish I could take the advice on a state by state basis but I have been through 3 states since I started building, don't know where I will be when I finish...
Ahhhh, that does make your build a bit more challenging eh?
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