Harness: sub belt attachment?

[jpnovak]

I just finished re-installing the cage in the ST. Now its time to bolt up the harnesses. I will be mounting the shoulder straps around the cross bar built in to the cage. The hip straps will be mounted via M12 nuts welded to my seat brackets (factory mounting points for a 71).

My question is about sub belt attachment. I marked the floor directly under the sub belt hole in the seat. I plan to mount the belt so that the belt is 1" behind this mark. I will be sharing track time with my father who is shorter and this gives a good comprimise for both seating positions.

I have a question about afixing the mount to the floor. I am looking at a permanent installation. Clipping to an eyebolt will not work since I don't have enough clearance under my seats. The belt comes with a bolt in clip. I am under the impression this should be mounted in a manner that places shear stress on the bolt. Both options below will have proper backing plates on the bottom of the floor.

Mounting option #1 - bolted to the floor:


If I bolt this mount directly to the floor the bracket could pull upwards and bend, comprimising strength.

Mounting option #2 - U-bolt

I found these grade8 u-bolts made for making custom cable setups. This arrangement should allow for correct shear position and allow a little angle play in the setup.




Let's hear your suggestions for mounting this up. One better than the other? Other options?

Thanks

[nostatic]

u-bolt. you don't want to be pulling perpendicular to the mount direction. If you go back a ways we had a long discussion about sub belts, although it was mor focused on "non-ideal" mountings as opposed to yours.

[jpnovak]

I read that thread. I did not see anything about actual mounting hardware. Looks like the U-bolts are going in.

[givory]

.... for me, I think the big issue with the u-bolt shown is making sure there's a damn good backing plate under those nuts ... is there enough thread on the bolts to do that?
Gavin

[nostatic]

Gavin has a very good point. At the very least you need to big arse fender washers. At most a nice big backing plate. The u-bolt shown would never work.

[nein14-6]

One bit of advise, try not to put the attachment directly through the floorboard. I was warned that if you go off course and hit something, that something could catch on that attachment and do some terrible things to my anatomy. Later, I actually saw this exact thing happen to a friend of mine from high-siding his 911 on gator strips while going off track, luckily he was not hurt. On my 914, I was able to mount the sub belt on the cross member that fits under the seat of a 914.

[John Rogers]

I'd say find a race prep shop nearby and see how they do it.

[Todd Simpson]

nevermind...I was going to recommend an eye bolt then I reread your post.

[jpnovak]

here is an update. I called a few places and found that as long as I use a large backer plate, either the eyebolt or the U bolt will work. Here is my solution.

I took the U-bolt and cut off one side of the support. I then drilled the floor and mounted it. You can see in the picture that it allows the belt to lie flat forward similar to a direct bolt through the floor.



The best thing about this arrangement is that I have an orthoganal pull up to 90 deg from the floor.



The U-bolt is more than long enough to go through the floor and the 1/8x2x3" plate I made underneath. In fact, I had to trim more than 1/2" of excess threads that stick out the bottom.

[Zeke]

I was going to say your u-bolt had more threads availble than shown in the first pic. Looks good to me. I will use your method. Only trouble is that the hardware variety u-bolt might not pass some people's tech. It has to be a forged part for the serious tech guys.

[Dave at Pelican Parts]

And double-nutted... Self-locking can work, but it's a lot easier to see two nuts on the fastener than to check that the single nut there is self-locking.

--DD

[jpnovak]

Milt, I understand about the cast/forged. The support section is likely cast. I think this should be fine since it would not load in the event I need the harness. The load will be carried by teh U-bolt itself (which is a Grade8) and the backing plate/floor.

I used Loctite instead of either a double nut (clearance) or a self locking. They are marked to spec as well.

[Dave at Pelican Parts]

As long as it passes inspection, that's cool. But the local (N. Calif) inspectors specfically want to see either safety wire or a double nut. (There are specific "jam nuts" which are thinner than standard ones, which can make clearance less of a problem sometimes.)

But like I said, as long as it passes tech all is well.

--DD