Posted this over at corner-carvers.com but no response yet ...
Anybody here wanna have a whack at it?

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I am having some clearance problems with my relocated seat belt attachment,
and I hope some of the engineers here can help. The mount points for the standard
seat-belts are on sliding bolts that aren't long enough to mount the bar and the
seatbelt simultaneously. Plus, when I did attempt to mount them together, the
belt jammed slightly because the bar prevented it from swing back far enough.

So, I drilled a new hole in the bar mount (10 mm) and got some 1 1/2 in grade 8
bolts. That helped, but the bar still infringes. So I need to move the belt mounting
inboard enough to clear the bar and allow the movement. The mounting is on a
shoulder in the stock position and rotates to accommodate different height people.

On the new mount (2" 10 mm) I have a 1" brass sleeve that moves the mount point
inboard.

My question is how strong does this mounting have to be? I used the search here,
but didn't see a lot of relevant info for this situation. I also Googled and found that
the shear strength of the 1/2" bolt is about 940 lbs at the thread root (1470 full bolt).

This has me concerned but the original mounting is also in single shear,
so I just need to not degradate beyond whatever that piece of engineering calls for.

Thanks in advance for any help ...

Cliff

F150 Lightning

The red is the original seatbelt mounting point.
The yellow is the clearance problem (can't swing back).
The blue is where I need a longer bolt.

 

Cliff:
I have one of Stan's harness bars also and I am also trying to find a functional way to mount stock belts. I am going to try to have a new piece fabricated to hold the belt. Looking at your picture (yellow arrow), If this mounting piece were more of a C shape instead of a triangle, the belt could swivel down closer to the harness bar and the belt slot would be more horizontal instead of diagonal which forces the belt fabric to bunch up. Using your picture as an example, I would think that a good machine shop could make a new bracket out of flat stock and cut the belt slot and mounting hole. The plastic fold over bolt cover should still fit. Let me know if you think this is a workable solution.

Rick

 

I certainly hope you are installing new racing seatbelts aswell?

I assume that your rollbar is functional and you are adding it to comply with drag racing rules??

If so, aftermarket racing belts are requirred!

My rollbar clears the stock seatbelts anyway.

 

Nope, don't need to ... actually using five or six point belts with only a harness bar is pretty dangerous.
Actually, no ... it's not a rollbar. It's a camera mount ... < grin >
And I spend a LOT more time on track than those mere 12 second races !!!
Harnesses are not required for any HPDE that I know of.
Good ... Does it have a rear 30 degree support? (Couldn't resist ..)

 

I dunno, Rick ... I was hoping not to have to change out the
stocker since it slides and locks so well ... I'm getting desperate though.

So after my latest changes I have the attachment hanging out
about an inch farther inboard from where that picture shows it,
and it now at least slides nice ... Do you think the 1 inch will
change the shear load enough to make it unsafe?

Cliff

 

why not buy a bracket to weld on for the seat belt? Its what we use in my race cars to mount the belts. It could easily be added to the bar to make the belt angle safe and not shear or dump.

 

First of all, I dont know you or your truck, I had no idea that you were talking about a "harness bar", your post only says bar...I assumed it meant rollbar.

Second, if attaching a five or sixpoint harness to a harness bar is dangerous....why the heck do they call it a "harness bar"??

Third, what 12 second races? Rollbars aren't required for 12 second racers!

Fourth, you mentioned nothing about HPDE in your post, and I said IF you were drag racing, which apparently you don't or you're not fast enough to worry about it!

BTW, glad you missed the part in that post that 30 degrees were NOT required on rear bars!!

 

 

Can you not mount the slider on the other side of the bar?I know they[factory] use a bolt head about half as thick as the standard head thickness.Since it is in tension and should have a stand off[spacer] or maybe even try it without the spacer ?Stan

 

Stan, if I use the same mount point for the seatbelt as the bar,
the lower part of the bar mount (square part) interferes with
the smooth running of the belt. That's why I tried to move it
forward and inboard.

Not sure how I'm gonna solve it. welding a new piece would
result in the same jamming thing I think ...

 

Fomocofan, let me make it clear that I am not starting anything with you (I lost about 10 IQ points in our last pointless battle). I am responding because this in an important issue that merits explanation.

I believe that Cliff is referring to the school of thought that says that using five- or six-point belts in a car without a rollbar can be dangerous because the belts do not allow the driver to duck down. Without a rollbar, the roof can cave in on you.

I do not have an opinion on the matter either way -- I'm just trying to explain.

 

Tim, read what he said before you go explaining anything to me for him!!

He said using a 5 or 6 point belt with only a harness bar would be dangerous!!

Your explanation of using a harness w/o a rollbar has nothing to do with what he said!

I guess maybe you did loose a few IQ points there bud!

 

I just confirmed this with my engineering manager. (we are seating engineers) You'll want a M12 w/a grade 9.8 (or higher)
And keep the brackets to a 3mm minimum thickness.


Rich

 

"Only a harness bar" as opposed to a mounting the belts to the cross-bracing on a roll bar or roll cage.



The argument was well stated on a BMW board:

"In short, harnesses do not allow one to submarine (stock belts do) in the event of a roll over and as a result, without a cage, the roof would collapse while you're held tightly in your seat...

I have always been aware of this but I have no issues running them w/o a cage. Around here, a harness bar is referred to as the bar of death when not used in conjunction with a cage. As a result, lots of guys who were running a harness bar w/o a cage have taken them out and are no longer wearing harnesses."

Fomoco, I will not respond to your personal attacks. And I don't care whether you understand the issue. I responded the the above only to make sure that the issue was properly framed for the others.

And again, I take no position on the matter. I'm just putting it out there for consideration and discussion.

 

Rich, I'm still unclear on what bolt and bracket you are referring to.

As a seating engineer, can you explain in detail how you would solve this dilemma? My harness bar is on ice until I can figure this issue out. Damn if I'm wearing camlock 5 points to the 7-11.