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Barry · Post by **Barry** » Wed Mar 08, 2006 8:32 pm

Mike,Ive done a few cages in 105 cars before..Ive not done any 116 cars..
The reason?I dont know what Im doing..Up to 3 years ago when we did the Gta cup cars,my experience with cages was pretty zero.

Along come the cup cars from Alfa Corse and we look at these..Hell,we can improve on these,no problems..
We Fly out a very knowledgeable cage guy all the way from Prodrive in the U.K. he looks at these,and says dont touch them,they cannot be improved upon..mmmmmmmmmm..

If I were to build a cage,Id be stealing with my eye`s.Looking at top race cars and teams efforts is the way Id go..
The trick though is,do I add 200kg in the cage,or only 40 kg ??Im a firm believer in walking away from a 200kg cage than kowing the 40kg cage was not good enough..Its the same with seats..I need to mention these here as S.A. is in this terrible grip of Chinese rip off `s.The ricer crowd here are fitting all these inferior stuff that looks a million dollars and dont regard the safety aspect of there desicion..Its all based on price here..

Anyhow,I picked up some reasonable experience in cages and will be able to do my own ..with some degree of knowing its the correct way and design for safety and strength..

But I also believe in every dung beetle on his dungball..Stay with what you know and get help when you dont..

Barry · Post by **Barry** » Wed Mar 08, 2006 8:45 pm

This is the 156 Gta which we built 3 years ago.Dawie and I sat looking at European race Alfa`s and came up with this cage.The rear suspension part of the cage is very eloborate,copied from the 156 touring cars..

Barry · Post by **Barry** » Wed Mar 08, 2006 8:47 pm

The 3rd Gta cup car we recieved.I have a better pic somewhere,need to find it though..This is Lfa Corse `s cage..

Maurizio · Post by **Maurizio** » Thu Mar 09, 2006 12:04 am

Why not get a hold of the rules that apply for the type of event you want to be involved in your locality and using the approved design, make one yourself?

I don't like the standard bolt in cages that can be bought.
I do some of rigid and lightweight design for my work, so I see the challenge, but time......... To do it right you start on a clean shell, I'm way past that and not even thinking about removing suspension again. So it will not be the ultimate design

MD · Post by MD » Thu Mar 09, 2006 1:11 am

Yeah Barry, we can all look back a few years and say we know more now than we did then. The first photo you provided is of my car's half cage. It is a road car and never used on the track. The design idea was to cater not only for roll over but side impacts from other road users and keep the cabin shell from compressing the passengers by pushing out the opposite side if necessary. It is also a fully removable cage and I can add and remove components as I choose.

If I was to built it again, I would take a slightly different approach but then that is my point here. If you don't have a go how are you going to develop skills? There are too many keyboard jokeys out there already that never get their hands dirty. What a waste of talent.

There is nothing like working on your machine and then enjoying the fruits of your labour. Unbeatable. By all means get help and advice but don't be a "spectator"only. I am only trying to inspire here, that's all.

Mats · Post by **Mats** » Thu Mar 09, 2006 1:44 am

For good design-pointers look at the FIA regulations. There are lots of drawings and alternatives and they are designs driven from decades of motorsport accidents and lessons learned.
No need to re-invent the wheel here.

ar4me · Post by **ar4me** » Tue Mar 14, 2006 8:20 am

Find below some pics of the cage in my 3.7 track car. In those pics door X'es still remain to be welded in.
Jes

ar4me · Post by **ar4me** » Tue Mar 14, 2006 8:21 am

A few more...
Jes

ar4me · Post by **ar4me** » Tue Mar 14, 2006 8:30 am

Does anyone have a good idea whether the above with seam welding and a cross brace would strengthen the front sufficiently to run coil-over ONLY at the front? (i.e. ditch the torsion bars).

Jes

Barry · Post by **Barry** » Tue Mar 14, 2006 9:27 am

Jes,I have not tried it ,but I reckon its way good enough..Ive run coilovers without any strengthening and its lasted..
Nice cage....lots of work....

ar4me · Post by **ar4me** » Tue Mar 14, 2006 10:35 am

Ok, I think I'll get in contact with Ron for a suitable front spring rate (matching the RS kit without the torsion bars).
Credit for the cage goes to our outstanding Icelandic fabricator, Jonni. It is his work of art with input from me, JJ, and the guys at group2.
Jes

MD · Post by MD » Tue Mar 14, 2006 2:06 pm

Jes,

There is good and there is better. Depends on what the car is going to be used for . Track or Rally.
What is the engine 4 or 6 ?
If it is a 4, then my suggested illustration will work for engine clearance. However if it is a 6, you would need to get creative to get around it but keep the traingulation principle. The returns to the firewall could be taken through to meet the crossbar infront of the dashboard that you already have.
The second thing is minimal. I would seam weld and preferably add at least a 2mm plate inside the shock tower mount that will be carrying the suspension/spring loads. I am doing this in the next couple of weeks. Can PM you a pic when its done if you like.

Nice welds..

ar4me · Post by **ar4me** » Tue Mar 14, 2006 2:10 pm

MD,
Thanks for the pointers! Yes, I would certainly appreciate some photos of your setup. It is a 3.7 V6 - currently out to allow construction of roll cage, extension forward of firewall.

The car is a pure track car (for road coarse - no ovals for me

).
Jes

la_strega_nera · Post by **la_strega_nera** » Tue Mar 14, 2006 3:27 pm

Nice fab work, but I would have done the rear half of that cage differently, and run a diagonal in the main hoop. You've got alot of tubing there that's not really doing much in terms of stiffness.
One of the early M3 websites has an excellent collection of assorted cage designs as used in Supertourers and Trans-Am, these are a good starting point for seeing how cages are done properly (ie designed and analysed using FEA packages).
http://e30m3performance.com/tech_articl ... posium.htm (Found it!)

Main issues I have are:
The tubes that run forward to the suspension pickups don't really triangulate much. I'd run an extra pair of tubes back to the firewall/under dash brace (tied into the firewall, not just passing through). These might have to be bolt in for engine removal. The braces don't need to run all the way to the CCA mounts, just to the shock mount, because if you hit something front-on, those things will distort the cage more than they help.

The Main hoop needs a diagonal to help keep it from moving sideways. The bends in the main hoop uprights should have the seatbelt bar running across them (raise bar or lower bends)

The rear tubes shouldn't pickup off the top of the arches, they should run down to the base of the rear "firewall", and share pickup points with the cross brace. (The horizontal tube between them does bugger all for stiffness, its tubing that would be better used elsewhere) I'd also run a pair of tubes from the base of the main hoop to the base of the rear diagonals.

Needs a diagonal in the "Halo". THis will pick up a bunch of stiffness in torsion, and help prevent cage distorsion in a big hit.

Gussets in the corners of the windscreen - both at the under dash bar and where they connect to the Halo.

Just my 2c, not trying to get anyone off side....

Ben

Daniel · Post by **Daniel** » Tue Mar 14, 2006 6:32 pm

Ben
I agree with most of what you're saying in theory but some of that is practically impossible to do. I've had to make some compromises with my cage to keep it street legal (door cross is not street legal in Qld).

The rear tubes shouldn't pickup off the top of the arches, they should run down to the base of the rear "firewall",

The angle that this produces from the main hoop means it will not meet CAMS schedule J, hence you need to run to the arches.

I'll post some pics of how I did mine - not that I'm saying it is in any way the right way to build a cage.