Knee room rule?

[Brian]

I was reading the rules for one of the UK Formula Ford series and their chassis build rules seem pretty different to ours in a lot of ways. they have a rule about the driver being able to lift his knees up to a plane level with the steering wheel. Seems like a really very good idea to me! I looked at some fairly recent cars and they seemed to have the cockpit constructed in a way that would facilitate this. When did this rule come into play in the UK, and any ideas on why the SCCA rules haven't adopted this?

I'm thinking of modifying my RF86 to allow this. I would need to remove the lower dash support tube and create another way of supporting the steering column. The ARB and the springs may get in the way anyway, haven't really measured yet. Also haven't thought through what that would do for chassis stiffness. Or where I would put the instruments...

Cheers, Brian

[Jon Jeffords]

Brian,

I don't understand the value of this rule. What are the benefits for the driver to be able to lift his knees to the aforementioned plane?

Makes it easier to pull an unconscious driver out of the cockpit, perhaps?

[Brian]

The thing that leapt to my mind was pulling your feet back from the pedals when you hit the concrete wall head on at 90 mph...maybe that's just my imagination, but that is probably what the rule crafters had in mind.

Brian

[Jon Jeffords]

I don't think that's it. Whether it be legs, arms, or head/neck, your muscles are no match for the G-force loads that are incurred during a significant crash.

[R. Pare]

The ability to draw your knees back thru the dash will allow them to be driven back by the front bulkhead in a hard crash. Most top level series demand this in their chassis - it prevents a lot of leg injuries in severe crashes - if the knees get trapped by the dash, it usually means instant massive trauma, if not total leg loss.

[John LaRue]

ala DB1......

Richard/Steve you should elaborate on the dash board and how you mount it in the Citation to break free in event of a crash.

[Dave Harmison]

I heard Gordon Cuppock talk at SAE a few years ago and the history as I remember him relating it was this:

After the year of all the crashes when it was so cold at the Indy 500 and drivers where getting feet smashed, they implimented a design where the pivot on the bottom of the brake and clutch pedals was connected to the master cylinder but not totally secured to the tub. The problem they fixed was in a head-on with the wall the master cylinders caused the pedals to fold back on the driver's feet. With the new design, the whole pedal, top and bottom, moved rearward pushing the driver's legs back and up.

Then they discovered that some driver's couldn't withdraw their legs through the dash opening and lower leg injuries were going to be a problem. So they wrote a rule that the driver had to be able to withdraw his legs through the dash all the way up to his chest.

It's a great design philosophy but totally impossible for me to implement on my old Club Ford car and unlikely for me to comply even if I bought a new car. I'm too big. I'd have to go race something with fenders. :-( It's a risk I am aware of and just have to accept.

It's a good point to check when buying a car as it depends a great deal on the relative lengths of the driver's upper and lower legs and seating position.

Please don't add another rule.

[R. Pare]

The construction is nothing special, and could be copied in just about any chassis.

The dash is made either from aircraft plywood ( some guys laminate it with carbon for looks), or from lexan. It is held to the dash hoop with 4 'well nuts' - rubber grommets with a threaded insert molded into them. The steering column mount is nothing more than a hole through the dash - you can get fancy an add in a wear bushing or some sort of vertical adjustment devise if you wish, but we've found that a decently smooth steel column tube running right in the lexan will last for many years before the lexan opens up enough to be annoying.

In the event of a crash severe enough to push your legs back that far, the dash is easily popped out of the dash hoop by pulling out the well nuts from their holes. Thankfully, none of our drivers have ever has to test that action!

The worst car out there for its ability to trap legs is the DB-1. Unfortunately, there isn't much you can do to fix that.

[R. Pare]

Dave:

I think that the rule is meant as a design feature, not a mandatory driver action test. There are very few, if any, drivers small enough to draw their legs back under the dash to the steering wheel, but just about anyone can draw their legs back through an empty dash hoop if it is designed right. It's a ton better to have your knees absorb only the force of popping out 4 well nuts than bending some sort of steel cross tube!

[rickb99]

Just looked closely at our 90 Reynard cockpit. Even with a break away dash, our 6' 2" driver couldn't fold his knees to his chest. the steering wheel would stop the dash after a rearward movement of only 2.5".

We'd have to mount the steering wheel so the bottom of the wheel was on an even plane with the TOP of the front hoop! That would look pretty silly. Only other option would be a break away steering wheel. Or, use a plastic steering wheel from a Tonka truck so it would disinegrate on impact Does anybody make a frangable steering wheel?

[EYERACE]

don't even think of this thread leading to another SCCA rule..........puleeeezzz

[R. Pare]

Just looked closely at our 90 Reynard cockpit. Even with a break away dash, our 6' 2" driver couldn't fold his knees to his chest. the steering wheel would stop the dash after a rearward movement of only 2.5".

I think you'd find that in an actual crash where his legs were being driven backwards, his knees would break the steering wheel, if they were driven that far. Breaking the steering wheel would be a lot easier on the knees than breaking a steel cross tube! In reducing injury potential, it many times comes down to a choice of potential over absolute.

I don't know of anyone who is proposing this as a new rule over here, so don't get all excited!

[Brian]

Thanks for all the info. Looked up "wellnuts" in my catalog, excellent idea as since the torch is out anyway, easy to implement (have to change the dash mounts to make the wellnuts work). The UK idea is bring the knees back as far as the steering wheel, I think, and having bent a few steering wheels with various bits of my anatomy I agree with Richard that the steering wheel won't pose much of a barrier if worst comes to worst. A 1" diameter chassis tube poses a far more realistic challenge to the old kneecaps...

Brian

[S Lathrop]

In the event of a crash severe enough to push your legs back that far, the dash is easily popped out of the dash hoop by pulling out the well nuts from their holes. Thankfully, none of our drivers have ever has to test that action

Actually there has been at test of this feature in an '87 Citation. The car did 5 end to end flips. The foot box held up but the belly pan failed at the dash and the lower frame rails forward of the dash collapsed. The driver sustained a minor shin fracture from the impact with a component above his legs. His knees did knock the dash out of its mounts.

The belly pan failed because the original one piece pan had been replaced with a 2 piece pan that was split at the dash and rivited to one half of a 1 inch square tube.

To make this story even more scary, the driver lost his helmet on the first flip. He spent Sunday night in the Hospital but went home Monday morning. He had to be driven home because his shoulders impacted the frame rails at the top of the cockpit and he could not lift his arms heigh enough to drive a car. His shoulders were dislocated and severly brused but nothing was broken. This is a lession in designing the side head restraints/pads.