944 Cage Help
12-19-2007, 08:59 PM
#34
Rennlist Member
Getting in and out of this car is a dream compared to most I have driven....I am very satisfied with how the cage turned out...Raced the car all season and visibility is a big plus too. Mark is the master!
Last edited by bgiere; 12-19-2007 at 08:59 PM. Reason: sp
12-31-2007, 10:55 PM
#35
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Location: Morris County, NJ
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All the pics really help out. I cut the whole back of my cage out including the horizontal bars in the same plane as the main hoop. After many hours of grinding I now have a clean slate to start the new cage. I have fabricated the single piece diagonal and the two short horizontal pieces for the harnesses. They are tacked in place. bgiere, I want to do my rear braces very similar to yours. Do you have a close-up pic of the attachment of the rear brace to the floor of the car? That is a small area and I want to make sure I get in the required 9 square inches of plate. The attached pics are the current status. The wrapping paper rolls from Christmas make good mock-up bars. The white cardboard is what I considering for a template for the plates.
01-01-2008, 03:48 AM
#36
Very similar door bar and through dash setup to my cage, the only difference being that the door bars in mine are canted out into the door panel space to make for more elbow room for the driver. Ingress/egress is a piece of cake with this setup. Yours has much more meat in the rear. The double diagonals look extra beefy. Nice work!
Do you happen to know what paint and application method was used? I'm transferring my cage to a new body, which is turning out to be trickier than building a new cage!!
Do you happen to know what paint and application method was used? I'm transferring my cage to a new body, which is turning out to be trickier than building a new cage!!
01-01-2008, 11:59 AM
#37
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Looks pretty good, Steve;
- Make sure you tie in just at the beginning of the rear floor plane, like you pictured on the passenger side. Without the welded in tranmission x-member, that is closer to the existing stress point (or node) in the Series II floor/rail. Another point on this is that it also picks up near the suspension point.
If you look underneath, Porsche put the shock mount point there. It has the greatest section height (and strength) at the "dogleg" or kick-up bend in the rail. Makes sense to mount there, eh? If a 944 is blasted hard in the ***, it will buckle just aft this point. Tony can likely confirm.
- The rail is narrow there, but I wouldn't get too hung up on plating for strength. You will be near the inside vertical wall of the rail, and so be utilizing its inherent strength in compression. A much stronger spot than out in the horizonatal center of the rail surface (like the main hoop). If you need to fudge the shape of the plate to make it fit a square inch statute, go ahead. In that light, I'd always opt for sliding the plate surface down over the inside of the rail (where the rear seat back pivot hole is) rather than up onto the redundant fenderwell or floor that has no real structural role to begin with.
I'd be more concerned with the puny main hoop plates.
- Make sure you tie in just at the beginning of the rear floor plane, like you pictured on the passenger side. Without the welded in tranmission x-member, that is closer to the existing stress point (or node) in the Series II floor/rail. Another point on this is that it also picks up near the suspension point.
If you look underneath, Porsche put the shock mount point there. It has the greatest section height (and strength) at the "dogleg" or kick-up bend in the rail. Makes sense to mount there, eh? If a 944 is blasted hard in the ***, it will buckle just aft this point. Tony can likely confirm.
- The rail is narrow there, but I wouldn't get too hung up on plating for strength. You will be near the inside vertical wall of the rail, and so be utilizing its inherent strength in compression. A much stronger spot than out in the horizonatal center of the rail surface (like the main hoop). If you need to fudge the shape of the plate to make it fit a square inch statute, go ahead. In that light, I'd always opt for sliding the plate surface down over the inside of the rail (where the rear seat back pivot hole is) rather than up onto the redundant fenderwell or floor that has no real structural role to begin with.
I'd be more concerned with the puny main hoop plates.
01-04-2008, 02:58 PM
#38
Rennlist Member
Thread Starter
Ok, the car is heading for the shop next week and I am mostly decided on what I want. I am still struggling with what to do in the rear, however. I understand the arguments about retaining the crumble zone but I am concerned about the tank rupturing in a big hit. I had a bad backward hit at the Glen years ago (roll bar only at the time) and my tank leaked but not catastrophically. A good friend, who may chime in here, had a very bad rear hit at Mid O this year and he feels that his rear bars, which did have the bends in them and did extend into the hatch area saved his tank from rupturing. His cage was a DAS sport design which is an apparent copy of the old Matter Factory turbo cup car cages. So it looks like a trade off not matter what I do? John I am most interested in any additional thoughts that you may have on this as well as anyone else.
Thanks again, this thread has been very helpful
Thanks again, this thread has been very helpful
01-21-2008, 02:21 PM
#39
Rennlist Member
Thread Starter
Ok, my cage is underway. I am now trying to figure out a good way to tie the seat mount into the cage structure. I know this is preferred and most pro cars have it. Has anyone done this well on a non tube frame car? My current set-up is: seat mounts mount to a sheet of 1/4 aluminum, sheet mounted to factory holes. I have some ideas to create a platform from the rear of the cage to suspend a plate above the floor but I dont think it will be better than what I have? Any ideas folks?
01-21-2008, 09:45 PM
#41
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Hey;
The main goal of building the cage is cockpit preservation. Next is stiffening, and getting the same structure to do both is certainly attainable. In the case of a 944, I don't see protecting the tank as something that easily coincides with the above. If you feel you need something there, that is fine, but I would not compromise the first two (particualrly the first) to get it. I feel that giving up a rear stay that SUBSTANTIALLY braces the main hoop, and counters suspension forces at the same time, is not a good compromise.
If you were relying on that very long tube - from the main hoop all the way back to under the tail lamps - to brace much of anything, I think you'd be kidding yourself. Not only would it provide very little bracing for the main hoop (it's main purpose), but it would only counter suspension forces very indirectly. Even if it did not have the bend at the end (like the DAS kit), I think you would be amazed at how little force it would take to cause a tube that long and unsupported to fail completely.
As for seat mounting, that is pretty tough. The setup you have now still relies on the floor pan with its factory holes, and arguably renders them less effective than if they were directly utilized as they were originally. Having points where the seat bolts to the plate that are remote from the points where the plate bolts to the floor likely enters funky offset loads into the fasteners and mounts. The closer these two sets of points are, the better - obviously - but I'm not sure that it is ideal in any event.
As you say, without a true tube frame, it is tricky. The relative lack of cockpit height to spare in a 944 makes it all the more difficult. I think the best you can reasonably do is to send the forces into panels that have some amount of beam strength; the center tunnel and inner rocker panel. Running tranverse members of some sort between the tunnel and rocker, and then bolting through them, will render the loads into these unibody beams - in shear, no less - instead of tension like the floor sees now. This certainly stands to be far stronger and more reliable, and is also not that hard to accomplish. That is what I end up to doing to all my dedicated track cars, be they mine or a customer's.
The main goal of building the cage is cockpit preservation. Next is stiffening, and getting the same structure to do both is certainly attainable. In the case of a 944, I don't see protecting the tank as something that easily coincides with the above. If you feel you need something there, that is fine, but I would not compromise the first two (particualrly the first) to get it. I feel that giving up a rear stay that SUBSTANTIALLY braces the main hoop, and counters suspension forces at the same time, is not a good compromise.
If you were relying on that very long tube - from the main hoop all the way back to under the tail lamps - to brace much of anything, I think you'd be kidding yourself. Not only would it provide very little bracing for the main hoop (it's main purpose), but it would only counter suspension forces very indirectly. Even if it did not have the bend at the end (like the DAS kit), I think you would be amazed at how little force it would take to cause a tube that long and unsupported to fail completely.
As for seat mounting, that is pretty tough. The setup you have now still relies on the floor pan with its factory holes, and arguably renders them less effective than if they were directly utilized as they were originally. Having points where the seat bolts to the plate that are remote from the points where the plate bolts to the floor likely enters funky offset loads into the fasteners and mounts. The closer these two sets of points are, the better - obviously - but I'm not sure that it is ideal in any event.
As you say, without a true tube frame, it is tricky. The relative lack of cockpit height to spare in a 944 makes it all the more difficult. I think the best you can reasonably do is to send the forces into panels that have some amount of beam strength; the center tunnel and inner rocker panel. Running tranverse members of some sort between the tunnel and rocker, and then bolting through them, will render the loads into these unibody beams - in shear, no less - instead of tension like the floor sees now. This certainly stands to be far stronger and more reliable, and is also not that hard to accomplish. That is what I end up to doing to all my dedicated track cars, be they mine or a customer's.
Last edited by RedlineMan; 01-22-2008 at 09:26 AM. Reason: Schpelling
01-22-2008, 01:04 AM
#42
Herr Unmöglich
Rennlist Member
Rennlist Member
I was speaking with a cage builder today regarding my car. Brant, I really like your cage design. Looks to deal with a lot of the issues well. The shop I spoke with likes pyramid bars for the doors. They build a lot of cages for SCCA rules, and they seem to have a pretty good knowledge. I definitely need the header bar far forward as possible as I am 6 foot tall and have little clearance with a helmet on.
I also need to do something for seat mounting... thanks for all the pics guys.
I also need to do something for seat mounting... thanks for all the pics guys.
01-22-2008, 11:06 AM
#43
Rennlist Member
Schwank, I wish I could take credit for the design but all I did was drop it off and say " make me a great cage for this car!" Mark (rollcageguy.com) took care of the rest!!
