Critique my rollcage

[molex]

Hey all

I've been thinking about this for some time, before I get back to the track I would like to invest a little in the safety aspect of my car. It's an EP82 Starlet, eventually would love to enter it in SS2000, probably 4age powered in the 1600cc class so weight is very important. Ideal weight for this thing would be about 700kg fueled up and ready to go. It's probably about 740kg currently, but with plenty more I could chop out.

Below is my first draft cage. This is MANZ specified 38.1x2.5mm ERW @ 2.19kg/m. Current design comes in at a fairly hefty 55kg and is dimensionally accurate (save for the legs through to the front strut towers, those are a guess)








Couple of questions for the brainy motorsport types:

Is the 'halo' bar (e.g the roof) and the A pillar design I've got legal under schedule A? I've read it until my head hurts and still can't figure it out. I've done it that way because it's primarily a lot easier to actually produce and because I've seen quite a number of serious porsches done in the same manner.

Secondly, elsewhere in the world the primary construction needs to be from the approved materials, e.g 38.1x2.5mm, however any additional bracing etc can be made from thinner material. From my interpretation of schedule A everything needs to be from this material?

Should I lose the double X and invest some weight in better supporting the A pillar?

[Truenotch]

As of January 1st your main hoop needs to be made of 44.5mm tube.

See here:
http://motorsport.org.nz/assets/Uploads ... mbined.pdf


And I think the front stays need to be one piece from the Main hoop to the front anchor point - not welded to the "halo" like yours is.

[molex]

Thanks for that, drawing has been revised.

Main hoop now 44.5mm, conventional A pillar back to main hoop, double X removed and replaced with single diagonal in main hoop, total weight 39.6kg

[Dell'Orto]

55kg in MS or moly?

[molex]

mild, not interested in CM for money and complexity reasons.

[Dell'Orto]

Fair enough...could get a little more weight ouf ot it hough haha

[Leon]

put harness bar(s) in between your diagonal and main hoop

Nice short harness bar free length between harness bar mount and drivers shoulder.

Maybe add a transverse bar between the lower end of the main hoop picking up on the transmission tunnel. Means if you get a massive shunt in the b-pillar area it reduces the chance of the bottom of the main hoop being bent in towards you (as it transfers the load to the opposite end of the main hoop.

Add 45 degree support bars between main hoop and your lateral bar.

Why are you putting a double diagonal in both your main hoop, and also in the rear stays? Might be a bit overkill perhaps?

Any reason why you're doing a roof bar and front legs rather than a pair of lateral bars and a windscreen bar?[/img]

[molex]

Maybe add a transverse bar between the lower end of the main hoop picking up on the transmission tunnel.

Why are you putting a double diagonal in both your main hoop, and also in the rear stays? Might be a bit overkill perhaps?

Any reason why you're doing a roof bar and front legs rather than a pair of lateral bars and a windscreen bar?[/img]

By picking up on, do you mean dodge the tunnel or blast through it and weld together?

Double diagonal is goneburgers, roof bar and front legs was done because I thought it would be easier to build. More I thought about it the more I didn't like the idea.






It's now got a diagonal on the backstays and a diagonal on the main hoop going to opposite corners


New total weight is 43.6

[Truenotch]

Looks good. I'd put the bars that connect the bottom of the rear stays to the main hoop back in. They make a big difference to structural rigidity.

[Boost_4_Life]

id also put a couple of small diagonal braces probably at the corners of the windscreen maybe? Just to help strengthen that top corner, cos if you roll, you're always likely to pound that corner above the front windscreen

[molex]

Looks good. I'd put the bars that connect the bottom of the rear stays to the main hoop back in. They make a big difference to structural rigidity.

They were initially added as it made a lot of sense but it was one of the few bars I didn't actually measure up on the car. After having another look I would have to chop through the floor in a pretty substantial way to get those two nodes connected. Could connect up the harness bar/upper side intrusion with the rear struts though?

[pc]

I'd loose the bar between the rear struts so that it's easier to pack gear into the car, loose the diagonal across the main hoop for weight saving, put a horizontal bar across the base of the main hoop for more protection in case of side impact on the b-pillar.
Also i'd put a diagonal across the roof for a bit more support on the top of the driver's A pillar.
...and a plate/gusset on the intersection of the side impact cross thingie to tie the two bars together better.
I wouldn't want the little 45 degree bars going from the main hoop to the roof intruding on head space.

[DexGT]

I cant find the pics of my cage atm , so I'll try to get some tomorrow , but it has the bar across the base of the main hoop , and bars from the base of the main hoop to the rear suspension towers . My GT has a factory bar under the dash that is made of similar tube to roll cage tube , it's straight and solidly mounted so I left it there, the steering column etc mounts off it too.
I would leave the bar between the rear struts as it strengthens the car , just get the front drops stitched to the 'A' pillars and they will be plenty strong.