Fitting the Roll Hoops - 3 - The Plan

Right then, here's the plan:

The GD method of cutting the top holes involves drilling pilot holes, using a plumb bob and adjusting as necessary. It is not possible for me to get the body level in both planes when the whole car is up on axle stands. So a different method is required.I bought some M12 studding - checking it was straight - and cut some lengths. These have been bolted to the roll hoop mounting holes. I will then mark the underside of the body and drill a small pilot hole from underneath. Using the pilot hole I will then cut a hole from the top big enough to expose the end of the studding. One piece of studding has had a 6mm hole drilled in the end of it to take the mandrel from the hole cutter.

I will then cut a 51mm dia hole above each piece of studding. This is the exact same size of the roll hoop legs. By turning the roll hoops through 180 degrees the back leg can go down into the cockpit and can therefore be conveniently ignored whilst the two main legs are positioned.

I doubt if the two holes thus drilled will match up exactly to the roll bars so I will open the holes out as required until the hoop legs can be passed through. The holes will be further enlarged until the fixing bolts through the chassis can be installed.

I will be left with an odd shaped hole but by then scribing round the leg with a washer a concentric hole can be marked and opened out. This last bit is how GD do it:What can go wrong?:

1: Studding not square to chassis - this a risk I'll have to take as there is nothing square in the boot that I can check against. I've checked the studding bolted to a piece of MDF and it is as near as damn it square when tightened up.

2: Roll Hoop legs not parallel - checked this with a home made tool shown below - less than 1mm out over the embedded length:3: End up opening the holes out so much that the grommets don't fit properly. I cut some holes in the piece of bonnet I cut out for the scoop:
I found that I could go up to a 64mm dia hole and the grommet would still fit nicely. So that gives a difference from the roll hoop of 13mm. Therefore the accuracy of marking the centres on top of the body using the studding has to be within 6.5mm or the resulting holes would be too big for the grommets to fit.

Now the only way that this error could occur would be down the studding not being square. For it to be out by 6.5mm over a 300mm length would be pretty drastic - and hopefully obvious!!

I wouldn't say that I am 100% confident at the minute but I'm going to sleep on it before cutting commences tomorrow.

If you think this plan is fatally flawed then you best leave a message quick!

P.S. The third back leg needs a slightly different plan as the fixing bracket is free to rotate - more on that later