RedlineMan

Hey;

Someone was asking for pics of these the other day. Don?

Since cages are always a popular topic for discussion, here we go.

The replacement for the "Deathcage" (as the owner refered to it)(see "What do you think of this Cage" thread) has begun. Where does it start? Base plates. There is more to baseplating a cage than just welding in a plate... like the original one in the CaliforniaCar.



Not enough weight bearing surface area to suit me. The idea is to give a good place for the tube to attach, bear the forces it might see, and increase the surface area in which those forces are carried. This one is probably designed solely to not have to remove the interior panel!



If the main hoop saw a large vertical force, it could depress the surface of any plate fairly substantially. To some extent, this represents absorbtion of energy, but I would rather the tube do that than the frame. I was moving the hoop a bit rearward for one thing. So too am I looking to transmit some of the force from the horizontal top surface of the frame rail (where it is weak to a piercing force) to the vertical side portion, where the load is in shear and the panel is exceptionally strong. Creating that corner between horiz. and vertical also creates strength of its own. A little mini beam effect. Above are the pieces made and tacked in place to effect that change.



Here is the finished product. More along the lines of what I would make from the start. The main hoop will land somewhere in the middle. Also note that the plating extends to the vertical inner quarter panel structure. I like to tie in here as it gives more shear loading, which is usually always advantageous.

chancecasey

WOW - all I can say is thank you for sharing this very valuable knowlege and tecnique. Please - keep it coming! The pics and descriptions so far are very illuminating.

trackjunky

Slick work John.

I was reading the original post on this the other day. This just proves that installing a proper roll cage is more invovled than being able to butt weld.

(that didn't come out the way I planned - sorry)

RedlineMan

Hey;

The latest progress. The main hoop tacked in place, and the left rear stay. The hoop is a nice snug fit (this car will have full interior). Not more than 1/2" of clearance to any interior panel, and mostly less than that. I did the right mount plate just before I left tonight, and am now ready to do the other stay.

Cory M

I'm curious why you built the new pad around the existing pads, rather than grinding them off and starting fresh?

A930Rocket

Looks a heck of lot better!

Is there a reason not to bring the foot of the stay back further? Seems like it would give the main hoop more stability.

But, then I'm just guessing here....

Sean F

Slow down, John. I wanted to come see you in action.

Geo

Nice work John.

Just a quick question before you get too far....

Do you have a minimum 30* included angle for the main hoop supports? It is very similar to mine and I think I have a bit more spacing between the bace of the main hoop and the base of the supports and I only have 32*.

Wouldn't want you to run into a problem down the road.

RedlineMan

Yeh;

I stewed over that. Some thoughts;

- I didn't want to do further damage to the steel. Sounds dumb, but you can only grind and weld so much. Those plates were quite welded in place.

- I was not sure it represented a good use of the labor time relative to what I did. This will be a very expensive project, and little economies add up.

- The plate is there mostly to keep the tube from piercing the rail, so in that regard I don't see any real difference. It may, however, see some pulling force if something tries to yank the tube up and away. If it were one big plate, it might pull off the frame rail some because the welds would only be around the perimeter. As it is, it has a lot of extra attachment area to work from.

I guess in the end I didn't see it as much of an issue.

RedlineMan

Yes;

Good point. The 944 has the gas filler hose to deal with. On the passenger side, it is right aft of where you see this driver's side stay attached. Also, this is EXACTLY where the shock mount is on the frame rail, i.e. the perfect place to counter suspension forces as well as stay the main hoop. More than one job per tube = smart!

RedlineMan

Yep;

This is a question I knew I would get. Of course I imagine both of us would have liked a little more angle, but then we know the architecture does not make that easy either. I uz a thinkin, G. No worries. 33*

In some respects this is smart. The short tube is stronger & stiffer. It may do more to keep the roof up as well, being more in plain with the main hoop. It is certainly space efficient, and that short tube is lighter. I think it works just fine.

Russ Murphy

How do you keep the seam filler from catching on fire and messing with the weld quality?

Geo

I agree with you John. A relatively narrow angle like that is idea for supporting the main hoop.

chrisp

This is why sometimes a pre-fabricated cage is a good idea. There are plusses and minuses to everything and ALWAYS room for improvement. However, something that should be heavily engineered like a piece of safety equipment is often better suited to large scale producers who have the resources to produce multiple iterations and make improvements before it hits the end consumer. This is one of the shortcomings of custom cages. They are all one-off designs and if not watched closely are subject to a single person's idea for what is right. I had mine built by an engineer who heavily referenced what Porsche has done in factory race cars (leveraging already proven designs), other mass produced designs (like Safety Devices) and then made some tweeks to take full advantage of the fact that it was being made by hand to accomodate my seat position, my head clearance needs, and anything else that needed to be unique because of me.

Cory M

I don't really agree with this and I have yet to see a prefabricated cage that is better than any decent custom cage. The cage kits I have seen, weld in and bolt in, have a lot of compromises and rarely fit tight to the body. Cage kits have to be desgned to have a more universal fit so they can bolt or weld into a variety of cars whether or not the have interiors, sunroofs, etc. Most of these "large scale producers" are simply welding shops that have a few jigs on hand and no degreed engineers on the payroll, the guy welding your cage is probably making $12 per hour so it isn't like these kits are coming out of Porsche or BMW motorsport. As an example Autopower is down the street from where I work, their cage and rollbar kits attach to the floor rather than the sills and don't fit very tight to the body, but the custom cages they build are actually very nice and are supeior to their kits in every way - which is why they cost 2-3X as much as their kits.

Of course there are plenty of examples or poorly designed and built custom cages and that is why it pays to educate yourself on the characteristics of a good cage and find a cage builder with a solid understanding of these principles as well as excellent fabrication skills.