RS Motorsport :: Classic Speed Restored

Survived this:
(Cage photos were taken in the replacement shell - cut the roof off to transfer the cage in 1 piece)

Talk to Keith at KCF Rallysport he survived hitting a tree head on and when from 100km/h + to 0km/h in 0 seconds and they lived and theres no way they would have with out the cage and he says he would not change his design!

Booked in to Walker Chassis. 5 week wait.

The FIA are currently paying a lot of attention to WRC car cage design and much of it is focused on side impact protection.
New rules apparently are mandating 2" or 50 mm side intrusion members in a pattern more reminiscent of Nascar than what we are used to seeing. They are also mandating 60 litres or so of impact absorbing foam per door.

I'd make the cage out of the 'next size up tubing'. Use 2.0" or 50 mm for the hoop and 1.75" for everything else. Definitely pick up the front towers and run 2 members under the dash, one horizontal and the other angled down to the passenger side floor and strongly footed to the tunnel. This obviously strenghthens across the car and also helps to direct the engine and box down in a big one. With the strut tower bracing this may save the shell from compressing behind the towers, making a repair easier, and also reducing the chance of a wheel coming back and trapping the feet.

The door opening should not have a welded cross. Two continuous lengths here, horizontal and parallel in the mid section and bent up and down to meet the hoops at the footings and mid bends.
These should be closed-webbed on at least the horizontal section and bowed out. If you get a chance have a look at a GT3 Porker factory cage.
A tunnel-tagged lower horizontal on the hoop as well as the now mandatory gusseted double cross is a good idea.
Consider the seat mounts and integrate them so in a side on they move with the cage. And support the back at shoulder height. This is often overlooked. I have a PDF of a SAE? paper on race seat sled testing somewhere that I will try and post; it is illuminating on double acceleration caused by seat springing.

Cheers

interesting thanks.

some good food for thought in that previous post !
when you say side impact absorbing foam ,
i like the theory of multi layers of polyurethane foam ,
starting with low density thru medium density to high density
foam ,
its very similar to a maxi yacht i built , the front was multi layers
of various densitys foam with kevlar in between to absorb & slow down the impact ,
same principle for side impact on a car ,
ive seen some race cars with alloy honeycomb in the
side panels but problem is they are not realy attatched
to the car but just sitting there
its gotta be encapsulated some how

I had a mate with foamed filled sills - was really interesting when we tried to weld a repair onto them

Thick blocks, laminated, of aluminium honey comb panel make sense. I kow of acouple of Sports Sedans and Sports Cars looking at doing this as a by product use of leftovers from under tray manufacture.

you say , retained by the inner panel ,, how ? is the
inner panel retained ? pop rivets ??????

ps
have a look at the sports sedan / transam rules
it says to run a rear difuser you must have side impact
either extra bars or honeycomb , it shows how to do
the intrusion bars but no mention
of ("AFFIXING the ally honeycomb )

The idea of potting the door cavity with appropriate foam appeals to me, and then closing it with a panel and pop rivets if convenient; they are an engineering fastener when correctly selected.
Loose al. honeycomb could be a bit harder; I would install so that the impact material will quickly bear up against the side intrusion. This looks like what WRC and I think DTM tourers are doing.

Tarmac Rally regs currently state that the windows must retain the ability to open (if originally fitted) so this severely limits the room inside the door cavity. Dare say a few honetcombe/foam panels could still be fitted but what a pain when the window binds up on them

quote .. The door opening should not have a welded cross. Two continuous lengths here, horizontal and parallel in the mid section and bent up and down to meet the hoops at the footings and mid bends.
These should be closed-webbed on at least the horizontal section and bowed out.
BUT
i have to say this design may "arguably be stronger than a welded cross brace " with gussets "
but far heavier for a marginal strength gain

Now here is a theory , use larger diam tube with a lesser wall thickness
for substantial increase in stiffness with a relatively small increase in weight

quote ;; pop rivets an engineering fastener ?

a PK self tapping wood screw is an "engineering fastener " too
you would be safer being wrapped in bubble wrap plastic
than relying on a pop rivet

You don't know what you are talking about.

If you use a garden variety Emhart, or Huck or Avdel etc, 3/16 diameter stainless steel pop rivet, properly set it will have a shear strength of around 900 lbs and a tensile strength of around 1375 lbs.

So, just two rivets would be strong enough to lift an Escort. It is not hard to arrange a dozen or 20 of these to hold a door panel in place.

If you know what to ask for you can get 3/16" stainless steel rivets that your garden variety setting tool can handle that will take 4300 pounds in shear and 4400 in tension.

Have a look at Bay Fastening Systems web site if you want to be properly informed.