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Old December 8th 2009, 09:05
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evilC evilC is offline
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Location: UK Where Leics is more
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The roll cage can provide a good deal of stiffness to the chassis and can link the body more fully to the chassis that will further stiffen things. People often forget that the body can contribute and rely solely on the cage.
If you weld tabs onto the cage at about 1/2 way up the door frame and bolt to door frame and similarly at the top of the cage where the bend occurs. Also, the same for the front legs of the cage to the door fame and A pillar.
Cross link the front legs at the base of the dash and if feasible at the top of the dash.
There should be a cross tube at about mid seat back height but that would affect the rear seat availability. If so, then put a cross tube immediately in front of the seat frame, which can be also bolted to the tranny tunnel.
Diagonal cross tubes across the car is a bit of a must to stop the cage lozenging but this again buggers the rear seat access. If making it removeable is a hassle then consider putting bracing gussets at the bends at the top of the cage and at the cross tubes. The principle here is to get stiff joints/changes in direction if its not possible to triangulate.
Door bars are well worth having but full on door bars are a real pain except in a competition only car. Here keep the bars within the side profile shape of the seat and if that means fairly low down use gussets to add a little extra.
If you can take a pair of tubes through the front bulkhead to link to the top of the Macpherson strut that will also have a strut brace (right?).
Provide some good boxed sections onto the heater channels and the plate legs down onto the floor pans.
I've mentioned gusset braces and these can be formed by bending some 16g over a pice of tube the same size as the cage and then weld to both members. Its a strong but smooth stiffener.

Clive
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