From Bolt-in to Tube Frame... and Everything in Between!
Building any cage requires expertise and some expensive, specialized tools. Building a truly effective cage takes a lot more. Many people can do it. The differences between good and truly effective can be small, but are ultimately quite important.
The prime considerations are space efficiency, protection, weight, and adding structural stiffness, and I would offer these to you in that prioritized order, depending on ones intent. These parameters seem mutually exclusive, but they are inextricably linked and must be combined in the right manner to achieve the desired result: a stiff, light, safe cage that one can get into and out of!
Some builders are tempted to go minimal, only just meeting the letter of the rules. They are usually trying to save weight, but this obviously gives short shrift to one of the main goals... SAFETY.
Inexperienced fabricators are prone to adding tubes everywhere in order to make things stiff and safe. This adds too
much weight, and can be infringing or actually injurious if the tubes are not well placed. Somewhere out there is an illusive middle ground. But how to find it?
Patience, thought, and insight! There are any number of places you can put a tube. Many of them are even fairly effective. But there is one place to put that tube that works better... if you have the skill to know where it goes. The trick is in studying the various parameters involved, and making sure that one tube does not overloook or counter-act any of those parameters to an unacceptable degree. Compromise is indeed necessary, but should not be called upon to excuse a lack of skill!
This cage was built for a PCA F-stock 944 Turbo. The parameters were reasonable weight, good protection,
chassis bracing, and ease of ingress/egress. As always, I strive to take up as little useable cockpit volume as possible, running the tubes out to the interior walls in most cases. The side hoops go through the side air ducts in the dash.
This cage was built for a PCA F-stock 944 Turbo. The parameters were reasonable weight, good protection, chassis bracing, and ease of ingress/egress. As always, I strive to take up as little useable cockpit volume as possible, running the tubes out to the interior walls in most cases. The side hoops go through the side air vents (like in the Turbo Cup cars of old) and the door bar ties in low to maximise footwell access. The main hoops weld to the inner roof frame, tying the upper unibody to the cage for added stiffness. The triangulation and cross bracing keep intrusion to a minimum and lend much stiffness to the chassis at critical points.
Will your elbow clear the door bars? Will your head hit the side or front hoops? Can you get your self into the cockpit without need of chiropractics? Will you be able to adjust your seat so your helmet clears the roof?
Will the shoulder belts address your body at the proper angle?
This cage was designed and hand fabricated to meet the specific needs of the owner and eliminate the endless frustrating compromises found in off-the-shelf, store-bought designs.
Considering the purchase price of a prefab cage, plus the not inconsiderable cost to have it installed,
getting what you really want and need is no more expensive in the end!
All in all, a Safe, Stiff, Tidy Environment to do your Business!
Don't go Broke, Don't go Nuts . . . GO
This is a cage I built in a
VW Rabbit for Ice Racing
The cage I built in
Project 930S
Fully integrated
INTO the existing chassis for maximum stiffness and minimal intrusion.
Here is a recent project in a 79 Porsche 928 destined for more serious Driver's Education use. The owner wanted to start with the rear portion of a full cage. The rest can easily be added later.
The first salvo in the battle is something I developed in my own car -
The Endo-Skeletal cage system.
I start out with a sill tube on either side. This gives a complete unbroken connection between main tubes that normally would only be attached to isolated steel plates. I feel this gives a much more harmonious sense
of integrity to the cage, and adds stiffness through increased triangulation.
As you might imagine, these are tricky tubes to
bend, and on the 928 they are particularly challenging, with 4 separate bends in different plains.
The main cage components are then built on top of this sill tube foundation. As always, I tuck them in as close to the existing unibody as possible to maximize space utilization and to compliment the stiffness of the existing chassis.
The main cage is a design that mimics my 944 bolt-in roll bars. Since the car is not intended for racing, I use a different pattern than would be dictated by racing rules. Instead of a diagonal x-brace that only protects the driver, and only in one direction, I use this design which I feel gives much more vertical support. It also has other
advantages such as not fouling the rearward view, offering potential seat support, stiffens the belt mount area and minimizes belt slide.
Another example of offering maximum protection with minimal use of space and minimal encumbrence to vision or ingress/egress.
Building any cage requires expertise and some expensive, specialized tools. Building a truly effective cage takes a lot more. Many people can do it. The differences between good and truly effective can be small, but are ultimately quite important.
