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tdskip
11-24-2008, 11:45 AM
Hi guys - I scored a shelf mounted roll bar for my TR6 at a swap meet this weekend for cheap ($35).

Any do/don't considerations to be aware of?

Thanks!

Trick6
11-24-2008, 12:16 PM
Can you post a photo so that we know what we are commenting on? Does this one bolt to the floor or goes thru to the frame?

tdskip
11-24-2008, 12:50 PM
Will try to get pictures up later - this one bolts to the shelf floor only.

Brosky
11-24-2008, 12:53 PM
Does it look like this?

tdskip
11-24-2008, 12:58 PM
Paul - yep, that is it.

DNK
11-24-2008, 02:05 PM
See Bill's post of a couple of days ago.

vagt6
11-24-2008, 02:22 PM
If that "shelf mounted" bar is simply attached to the sheet metal behind your seats, and not securely fastened/welded to structural metal (i.e., your frame/chassis), it can be a hazard in a crash.

In other words, it could mangle/kill you and your passenger(s) in a crash or rollover, performing the exact opposite of its intended purpose.

It may look nice, but it's potentially very dangerous.

tdskip
11-24-2008, 03:27 PM
Ah - found Bill's thread.

It looks like the shelf mounted roll bars need substantial support in order to serve their purpose.

Would plates welded to the bottom of the rear shelf fix that? Paul is that what you did?

trfourtune
11-24-2008, 04:12 PM
what you want to do is build up from the frame itself to a plate under the shelf with 3/16" plate (min) for the verticals(imho). you will need 3 vertical sides and the top plate(under the shelf with 0" clearance. You should add spacers to fill in the contours of the shelf for both the roll bars and the reinforcing underneath so you don't squish the shelf metal flat,it will distort the shelf shape (or not, i would). I would say a vertical up the shelf frontfrom the frame,one behind the shock and one along the inside rail with holes for the shock and bolts as required.the top plate thickness will be determined by the span of the top plate. any additional vertical members that can be added up to the top plate from the frame makes it better. Any angular plates that can be run from the top of the frame to your vertical plates the better.
never weld across the frame! weld only at the frame corners parallel to the frame rails.Design your brackets so you do not weld across the frame.do not overheat the frame.support the car from the frame and also support the frame on both sides of the member that you will weld to. You don't want to end up with a bent frame.
If you weld with the car standing on its wheels you will bend the frame.

PeterK
11-24-2008, 07:51 PM
Here's a photo of a rear frame mounting for a rollbar.

Note the stiffener on the bottom mounting plate. For strengthening the shelf mounted rollbar, you might be able to fabricate an entension from the rollbar legs under the shelf to somewher on the rear chassis legs (like this one). Square tube is relatively easy to work with. No need to weld it to the frame with this method.

(this is a TR4 race car with spring blocks to lower the rear height).

tdskip
11-24-2008, 07:54 PM
Thanks for the info guys.

Peter - that picture is a huge help.

I can see why a frame mounted roll bar really stiffens the car up.

One question - is the bottom extension there bolted on to the top part or is this a case of the roll bar passing through the shelf in one piece?

Thanks!

Brosky
11-24-2008, 08:32 PM
No doubt, that is one of the best ways to do it. I'm sure there are others, along with a cage, but whatever goes directly to the frame would be best.