Construction of Stohr/West Tubs/Chassis

[Jerry Poole]

Is the tub/chassis/ cockpit surround used on the Stohr/West P1/2 cars constructed on a tubular space frame or a composite material? Appreciate any information and insight. Thanks, Jerry

[Fred Michael]

Steel space frame with carbon composite panels riveted to the sides

[lowside67]

I have attached a great photo of the Stohr chassis that I managed to dig up. (Note: behind the main roll hoop is the original/old style engine bay and spar attachment points but this is generally still a good representation of the construction of a new car).

What you can see is that the chassis itself is a traditional steel frame design, but where you would typically see triangulating bars on each side of the driver compartment, these are instead very significant carbon panels which provide both stiffening and anti-intrusion characteristics.

These panels are "bowed" outwards so provide a good bit more elbow room than most formula car chassis. I also know that for my own purposes where in a hillclimb one might encounter a tree once in awhile, I feel that the anti-intrusion characteristics of these VERY significant panels make me feel a lot safer for what it's worth.

-Mark

[Stan Clayton]

Mark's description is correct, and I can add some details. As the frames are welded in the jig the bottom rails from the firewall to the steering wheel bulkhead are simply tacked in place. When the cockpit anti-intrusion panels are ready to install the frame is inverted, the lower frame rails knocked out, and after test fitting and drilling the rivet holes, adhesive epoxy is applied and the panels slid into place and riveted before the epoxy cures. The bottom rails are then epoxied and riveted in place, and final-welded.

The anti-intrusion panels are an inch apart with honeycomb core in the middle with parallel inner and outer walls. Additional outer walls constructed from carbon and 15 layers of kevlar are available for extra anti-intrusion protection. They fit to the outside of the panels and can be bonded and/or riveted in place.

[BeerBudgetRacing]

This type of construction is interesting to me, but I have a likely ignorant question.

We talk about CF pieces on track causing punctures and potential harm to drivers.

So how is the driver protected from chards of carbon?
Is kevlar the outer layer on BOTH sides of a carbon panel?
So the kevlar contains any cf fractures?

In the image I see the panels in the cockpit, but why are panels not extended forward to protect the drivers legs?

[lowside67]

There is no Kevlar on the stock panels. Stan described an optional extra layer that can go outside of the stock panels to provide additional anti-intrusion capability over and above the regular.

The point about sharp carbon is well made, but to get to that point, that also means that another car or hard object has to have hit so hard as to break through these incredibly stiff panels... which likely means I am in fairly big trouble each way.

From a theoretical standpoint, you might be right that an extra layer of Kevlar inside might "contain" the carbon, but generally I believe most carbon tub cars do not have this construction. And in any event, Kevlar might be better than the basic carbon construction, but in my opinion, these carbon panels are a "compromise" to the complexity and cost of a true carbon tub.

Ie to me, they are far better than the "traditional" steel frame that has been used for many years and basically no longer exists on new, professionally designed and built racecars.

-Mark