Primarily used for autocross. 3 point belts on street.
Its not installed in the picture, but the race seat is an aluminium butlerbuilt with harness pass through.
The new roll bar presents challenges to mounting the shoulder straps. Not enough sound metal left around the package tray for eyebolts, except at the very rear under the top area.
My thought was to wrap the harness straps around the vertical parts of the tube, crossed behind the seat, with a couple of stop collars to keep them from going down the tube and creating a spine compressor.
Ive never seen this done. There may be a reason for that, and im not smart enough to figure it out.
Picture of the roll bar in question with street seats:
Whats left of the rear package tray under the carpet and top
The twist in the strap is a bad idea. Clamp a cross tube in place behind the verticals as discussed previously.
In reply to TurnerX19 :
Problem is, i cant. Not enough space to the seatbelt towers. This was my workaround thought while the problem rolls around in my head some more.
Don49
Dork
8/10/19 12:13 p.m.
Can you weld a tube across the hoop of the roll bar? Set it at the height of the opening in the butler seat.
I fail to see the interfearance in your photos. Maybe go all the way across the car from seat belt tower to tower?
The vertical outside tube to seatbelt tower only has 1/8 inch of clearance.
Putting it on the angled rear legs across the width of the car interferes with the glass window at proper angle.
Brainstorm!
Can i use SQUARE tubing? I can get a 1/4-20 bolt in the gap. Barely. Drill through the square tube and build a clamp!
Why not add a horizontal tube across the back between the two supports that run from the hoops back? You should be able to set it in there at a height to get your proper 0-20 degree downward shoulder strap angle. In this thread you can see that is how NickD's rollbar has it integrated - https://grassrootsmotorsports.com/forum/grm/harness-bar-for-blackbird-gt3-rollbar/156495/page1/
Square tubing doesn't sound great as the edges could cause stress on the webbing compared to a round tube, having said that the edges of the adjusters/clip in or bolt in brackets of a harness probably have an even sharper edge on them than that.
Adam
not my greatest work. But a functional solution i believe.
I like this less and less. It'll get me though next weekend, but NOT the permanent solution. Im just not sure what is.
Don49
Dork
8/10/19 5:03 p.m.
You're halfway there. Make notched plates, weld to the upright and weld the round tube to the plates.
I need to mount the aluminum seat again and see what the angles look for the harnesses. IF the angles are good in a place where a welded horizontal bar between the rear downtubes will clear the rear window, thats thw way to go. If not, 1x1 square tube welded to the vertical posts on the backside of the hoop and a tab for the bolt on ends....
In reply to Dusterbd13-michael :
I would say that if this is the functional solution for now.. fully weld the muffler clamp saddles to the temporary crossbar..
Maybe there were just tack welds in the pic?
Greg
They were just tacks. Fully welded now, but....
Any engineering types able to say whether or not 1x1x1/8 square tube on a 12 inch span is a bad idea?
