Cage Building Question

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Chet
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Cage Building Question

Postby Chet » Mon Nov 04, 2013 10:15 pm

So im looking into caging my e30 and i have come across two approaches to mounting the back stays. I was wondering what some of the clubs members might think about these two approaches

Approach one seems to be landing the backstays on the trunk floor just above where the spring seats to the unibody.


The other approach seems more traditional by mounting to the shock tower. That picture is also showing another common e30 cage mount copied from DTM cars which i intend to duplicate but may recreate as a bolt on rear shock tower brace to make the car more adaptable to multiple sanctioning body rules.


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Pitcru
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Re: Cage Building Question

Postby Pitcru » Tue Nov 05, 2013 7:11 am

Chet, I would op to go with option 2 - Shock tower mounted. There tends to be more structure and that area should already be setup to take more load. It will certainly help out stiffening the entire chassis suspension wise. Good luck!

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eg8tuner
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Re: Cage Building Question

Postby eg8tuner » Tue Nov 05, 2013 11:57 am

I also recommend the tower version. i just feel that it would need less beefing up to work properly. but i know very little about e30 chassis
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Chet
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Re: Cage Building Question

Postby Chet » Tue Nov 05, 2013 1:00 pm

One picture i found was from a cage builder advertising his work, he felt so strongly about where the back stays were placed he made a point of marking the photo claiming the shock tower was the place to locate the back stays not the floor as the customer had requested. The argument i have heard is that the load is transmitted thru the spring and there for mounting the stay to the floor above the spring helps to transmit load better than to the shock tower. Of coarse these cars often get converted to a coilover and when that happens the original shock towers are often rebuilt and then cages are always mounted to the towers at that point. If they ran spec e30 races more close by i would go down to check out some cages and see what the winners are doing. I could also copy the DTM style cage designs but those cars are rear coilover and i'm not going to convert to that, at least not yet. So i have to wonder weather the floor or the shock tower is the best place to go. I really don't want to go to both. It seems overdone and cluttered at that point.
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Re: Cage Building Question

Postby saabman » Tue Nov 05, 2013 1:15 pm

I think a lot depends on what forces you are trying to control. The main hoop (b pillar ) and windshield hoop (a pillar) are the main rollover crush preventers. The rear braces would seem to be more in sheer than compression. The angularity that one of your earlier post shows is a not in a traditional attachment to the b pillar hoop. It seems too far in board. The location shown in the pic about goes to the outside of the b hoop and probably does well in sheer with a backing pad behind the mount pad. Many cages are built just the way that picture sows.
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SoloSE-R
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Re: Cage Building Question

Postby SoloSE-R » Tue Nov 05, 2013 3:37 pm

Just curious why you would be adding a cage? I would presume that the car is no longer going to be driven on the street after this? Also be aware that a car with a welded-in cage would not be legal for SCCA stock/ST/SP/SM classes except for vehicles competing under specific classifications for log-booked, GCR legal road race cars.
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Chet
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Re: Cage Building Question

Postby Chet » Tue Nov 05, 2013 5:01 pm

Im thinking about caging the car so i can run it in LeMons or Chump car racing as well as the occasional autocross. I figure i don't loose much in vehicle value with this move and despite the fact that my car doesn't really fit the rules of either series when it comes to value i'm thinking it will be just as much fun to race and loose on penalty laps until i get the car worked back into their price range.

This difficult part is balancing all the different race series rules of which most important will be the cage.
Im going to try and make the car legal for LeMons, Chump, Spec E30, and maybe scca road race classes. Im not sure if it will be doable yet but i'm going to work on it in the off season.
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