Racerrob

I am putting a new cage in my car (SP2) and could use some guidance. My goal is a safer cage than I had with more protection around me. It will be a custom job, 8 point with dash bar. Some issues: nascar bars or an "X" on my side? From what I have read the "X" is safer but I am 6'3 200, hans device and halo seat so I am concerned about exit speed from the car. Also, where is best to mount the rear down tubes in the hatch area. There does not appear to be a very good spot back there? Any opinions, pics appreciated.

Thanks!

J Silverman

Im in about the same position as you, but I already have the rear section of the cage in the car. Ive heard of people saying that if you can get the rear braces right on top of the rear shock mounts, and keep the angle of the bar correct that is a good way to go. My fabricator ran the bars all the way to the back of the car and mounted them near the spare tire well. Here is a pic of the drivers side, I can get one of the passeneger side if youd like.



Im also a big guy, so Im concerned about getting in and out of the car as well. I think that NASCAR bars will give the greatest amount of room which should make getting in and out of the car easier and quicker.

Cris Brady

Hey Rob,

I have an X on the passengers side but a different arrangement on the drivers side. I'm not quite as big as you, but with the cage and winged seat, the only way I can get in and out is with a detachable steering wheel. Here's my drivers side:



My rear goes all the way. I've heard arguments pro and con about it but that's the way my builder did it and I'm not changing it. Here's a pic:



I've got a bunch more pics of my cage under construction on my website,take a look: http://www.crisbrady.net/944na.html

Racerrob

Thanks guys. J, I dont think I am allowed to tie into suspension, I have to check PCA and NASA?

I think that I am going to have to do nascar bars and the removable wheel for another reason that I just thought of: a friend who regularly co drives with me is, wel, not small

Chris, thanks for the pics they are very helpful. I know that your cage got a little test last year at Nationals, how did it do?

I am hopeful that Comat will chime in here as I know his cage is very nice also.

Geo

Here is a small page I put up showing my cage.

http://home.earthlink.net/~geo31/Geo's_944_Cage.html

I built it myself so I can tell you the what and why for everything. My main hoop support tubes are 32 degrees from verticle (a 2 degree cushion). As you can see I routed my dash bar through the dash. I actually cut my dash along the length to accommodate this arrangement.

If I were to do things differently, I would have changed the front down tubes so the bend at the dash was lower, thus changing where the top front of the X attaches (I attached it to the bend to add strength to the bend). This would preclude the dash bar from intersecting at the same place as the X however, but it would improve the ingress/egress. A compromise. I'm not fond of "kneecappers."

As for X vs NASCAR bars, I have always been a proponent of the X for a variety of reasons. However, rudimentary FEA analysis has shown the NASCAR bars to be marginally more effective. I am thinking seriously of adding two horizontal tubes that extend outside the X for additional driver protection (while retaining the X). Probably worth the 5-10 lbs.

Matt Marks

J - looks like a piper cage, correct? I had the same one and loved it - had it done in Chromoly to save a few pounds - though more expense in welding and materials as it had to be TIG'd

Geo

While I am not intimately familiar with their rules, I can't see why it would be illegal with a 8 point cage.

That said, on a 944 you are not really stiffening the suspension mounting points. The main hoop only attaches a few inches above the TT mounting point and tying to the upper shock mount doesn't really do much.

Cris Brady

The body shop guys were amazed at how of lots of the panels that are normally f*ed up in a collision remained true and straight. The damages were confined to areas outside of the cage. I was happy with the result

Racerrob

That is some fine work George, thanks for the pics. Is there a reason that you did not go further back into the hatch area?

I was going to do a "footbox" but in looking at some of these pics, I may not bother. I need to talk to my builder and show him this thread.

Geo

I tied to the top of the shock mount. It probably doesn't do much if anything, but I did it anyway. It's as good a place as any, right? I tied the main hoop over the top of the rear seat bulkhead, approximately the attachment point of the TT mount. I have been meaning to add a tube from the bottom of the front downtubes to the firewall. Space is at a premium on the driver's side however. I don't want ANYTHING to interfere with my feet.

Thnaks for the kind words. It was fun building it. It was my first cage (and so far still my only, although I plan to build one for my business partner).

RedlineMan

Hey;

If you position things correctly, you can get your rear stays in at the shock mount point, and still have 30* to your main hoop, even with the main hoop as far back as this one. This one sits right on 31*. The advantage here is short tubes (= strong) and bracing EXACTLY where the shock mount is in the frame rail.



On my early car, I mounted the stays at the transmission x-member, which is quite close to the shock mount. I also have a x-member tube added at the shock mount, so my rear frame has a bit of a beam structure working.



Running the rear stays any longer than the ones I have pictured has a number of dissadvantages in my estimation. First, it is heavier. Second, the angle to main hoop is pretty shallow, which offers less geometric strength. Third, the longer tube is weaker. Fourth, it is reducing the crush zone of the car, which you do not want to do. It also transfers crash forces into the main cage that it does not need to deal with, but does less to directly brace suspension forces.

Try to get your rear stays somewhere in front of the fuel filler. Anything past that quickly transitions into the realm of diminishing return.

Regarding door bars, build anything that will facilitate ingress/egress. This is much more of an issue on a 944. The key that most people miss (including me, previously) is to get the side hoops UP as high inside the roof as possible (less emphasis on out to the side). If they are visible from the side (remember to factor for padding!), they will reduce the size of the door aperture and make it MUCH harder to get in and out.

M758

My rear tubes also attach close to Geo's tubes. There are a couple benfits.

1) close to shock mount and top of t-bar make the chassis stiffer? maybe
2) more up right rear support provide greater strength to the main hoop to prevent it from laying down during an incident.
3) shorter tubes = less weight.

Re door bars.

Right now I have a single door bar. I wanted to build this into an X, but given my seating postion I would be hitting the upper bar with my elbow. So in turn I will do a modded nascar style by adding in an upper bar that bends out into the door. The lower bar will be straight at the upper bar will have two bends putting into the door. Where the two bends I will attach to the lower bar with two short straight bars. So it will look like a typical 2 bar NASCAR style bar, but with the lower bar not bending out into the door. The pass side will get and X.

Rich Sandor

This is "daigo"'s cage, which I will be copying for my car:











The Driver's side cage actually protudes out Nascar style, although it's hard to see in the pics.

https://rennlist.com/forums/showthre...irth+track+car

chrisp

Also, what's the compromise to the car's inherent crumple zone if you have roll cage tubes out into the crumple zone? Good to have tubes far from driver to increase size of driver compartment but any reduction in the crumple zone will spike g-loading.

J Silverman

Yep. Ive never heard a bad thing about their shop, and Mitch was great to deal with. I did make a mistake when I had the rollbar installed and I did not have the steering wheel disconnect that Im using in the car so when we did the seat mounting everything was great, but now my wheel is 2" closer to me, so I need to have the main hoop cut out and moved rearwards. Should have thought of that the first time around.