I'm not a cage expert so the only observations I can make relate to the cage that John (Hoonatic Racing) was kind enough to install in our E30 -
If you haven't trial fitted your seat yet, now would be a good time. Get your seat in place and temporarily stick some approved roll-cage padding around the halo at the door and down the A-pillar bar. Now get your drivers to sit in the seat with their racing helmet on and check for head clearance at the halo and hand clearance next to the steering wheel at the various seat positions required by your drivers. I think the rules say 2 inches all round, but check the rules for yourself and make sure you are compliant. Don't take my word for it, I'm frequently wrong
If there is a clearance issue, first port of call is lowering your seat. Don't forget you will have to install harness mounting furniture under the seat so it can't be totally flat to the floor; that and they still have to be able to see over the dash! If that doesn't solve the problem then you're stuck with altering your cage.
You might have to undo your welds at the top of the main uprights and the A-pillars and move your halo forward...and possibly upward for head / hand clearance. If you have a sunroof, it is helpful to remove the slide runners and slide mechanism, which will give you perhaps another inch of headroom for the roll-cage bars.
If, by moving stuff about to get clearance, you find that your tubes are now not tall enough to go from the floor to the roof, there is a thread on here somewhere that shows a method of using plinths to connect tubes to floors....it's solid and makes it easy to meet the new minimum weld length rules
Half-assed information and only just coherent, but thats as good as I get. Good luck and Merry Christmas!
Steven
Edited for dodgy spelling and to say : keep in touch with John (Evil Genius) he will guide you in the right direction. Follow his instructions and you'll be racing safely in no time.
Pulp Friction #333 - Overall & Class 'A' winners of the 2012 North Dallas Hooptie
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