Planning for my Roll Cage

[Sid_RallyX_82]

I'm currently stripping my next daily for paint and as I'm doing so, I can't help but examine the chassis, looking for weight I can cut out(like the rear seat brackets, roof trusses, etc) and wonder if I can design a cage for my rally car that will minimize the negative effects it will have on the car(such as improper chassis stiffening and excessive weight) while still being safe in a crash. In one of my head-on accidents, I noticed that the front lower rails will collapse the footwells, so I definitely want strong longitudinal braces and a system that will disperse force on impact. Also, the roof is quite weak, so I'll need to strengthen it, but I would like to avoid using oversized upper rails. Today I found that the dashboard is a fair bit heavier than I thought it would be. Should I delete it and integrate a new one into my design? While I'm talking about that area, in terms of chassis flex, does the firewall need any help? Or should I ensure that section can let the body flex around it?

Thank you all for your knowledge, wisdom, and experience

[Sid_RallyX_82]

Starting a list of areas holding significant weight that can be quickly lightened. Gonna try to keep it in order of most weight that can be cut quickly. May repost this from time to time with a new edit

Rear seats ~30#
Dash board ~30# (kept, but lightened ~20#
Window glass ~30# (replaced with Lexan or other polyglass ~15#)
Front seats ~25# (replaced with lightweight bucket seats ~10-15#)
A/c compressor and P/s pump ~20#
Spare tire, emergency equipment, etc. ~20#
Rear bumper, pad, and cover ~20# (kept, but lightened <10#)
Seat belts and motors ~20#
A/c evaporator, heater core, ventilation ducting, etc. ~20#?
Rear seat bracket, roof trusses, and miscellaneous metal brackets, tabs, mounts, plating, etc. ~20#
Interior panels, headliner, carpet, etc. ~15#
Speakers and audio equipment (when not in conjunction with interior panels and dash) ~15#

Looks like I may be able to strip out about 200# before putting it all back in as cage tubing

[ryanprins13]

I am not sure how you would design a roll cage that could flex when your racing and not flex when you crash.
Can you build it so the cage part just around you is stronger and everything else is a little um, more flexable?
What if you just make the cage stiff and put time into figuring out how to make the suspension more flexable?
There is a thread somewhere here with weights of all different parts on the car. I think your estimating over on some and under on others. But if you weigh each part as you take it out, add to that thread and weigh your cage that would be cool.

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[Sid_RallyX_82]

I did find a thread with weights and some of it is just by my trusty hand scale, but either way, I'm not too concerned if I'm off by 4 pounds, I just want to know what to strip first. I need to find a way to make the cage strong while not applying its strength to the chassis, so the car can flex around it. I need to strip as much weight as possible so I can drop into the lowest weight bracket I can, so I can use the lightest tubing I will be allowed. If I can do that, maybe the cage will end up being strong but flexible

[Sid_RallyX_82]

So I can find this later:
FIA Article 253.8.3

http://www.fia.com/file/54650/download/17461?token=mQiBfplj

[Sid_RallyX_82]

Starting a list of areas holding significant weight that can be quickly lightened. Gonna try to keep it in order of most weight that can be cut quickly. May repost this from time to time with a new edit

Rear seats ~30#
Dash board ~30# (kept, but lightened ~20#
**edit: Door and Quarter panel side crash braces look to be ~30#. I'll r&r them with something stronger(heavier)
Window glass ~30# (replaced with Lexan or other polyglass ~15#)
Front seats ~25# (replaced with lightweight bucket seats ~10-15#)
A/c compressor and P/s pump ~20#
Spare tire, emergency equipment, etc. ~20#
Rear bumper, pad, and cover ~20# (kept, but lightened <10#)
Seat belts and motors ~20#
A/c evaporator, heater core, ventilation ducting, etc. ~20#?
Rear seat bracket, roof trusses, and miscellaneous metal brackets, tabs, mounts, plating, etc. ~20#
Interior panels, headliner, carpet, etc. ~15#
Speakers and audio equipment (when not in conjunction with interior panels and dash) ~15#

Looks like I may be able to strip out about 200# before putting it all back in as cage tubing