Rule B6.1 Question (flex axle legality)

[Charles Kaneb]

I've got a question about B6.1.

If I were to mount a kart axle with two bearings only a few inches apart, I might be able to get 1 inch bump and 1 inch droop travel before reaching the yield strain of the axle. Would this be considered a "fully operational suspension system"? My first guess at a kinematically-equivalent system for modeling purposes would be to consider it a low-pivot swing axle with a transverse leaf spring.

Kart axles have built-in damping (in the metal) and varying axle damping characteristics is a major tuning area in karting. Would this be considered a "shock absorber"? If not, would mounting the axle bearings in an elastomeric block with high damping be adequate?

[Michael Royce]

Charles,
If I am the Chief Scrutineer, I would not approve it at Tech Inspection. But I am no longer on the Rules Committee and you will only get an official answer by asking the Rules Committee.

[TMichaels]

I would probably decide in the same way referring to B6.1.1:
"The judges reserve the right to disqualify cars which do not represent a serious attempt at an operational suspension system"

[Drew Price]

Since the rules still explicitly say that the front & rear suspensions must be fitted with dampers, I don't think you could make the argument that the inherent damping characteristics of solid material satisfied the intent of that rule.

[mech5496]

Uhmmmm, a "damper" is essentially a device that provides damping, so yes, you could make that argument if stubborn enough!

[Zac]

I know at least one car has run rubber springs instead of dampers.

[Richard Pare]

No engineer worth his salt would consider a solid piece of steel bar "damped" without an external damping source.

You would not consider a bare coil spring - which is nothing more than a steel bar wound into a spiral - "damped", so why would you consider a straight bare steel bar damped?

Yes, all materials have some degree of self-dampening, but there is a big difference between a piece of material that is free to resonate at its natural frequency, and one that is forced to stop vibrating within one or two cycles.

[mech5496]

One could argue about that too... As long as it will stop vibrating at some point and not vibrating to eternity it IS dampened, although with a very small damping coefficient. I do not consider it as "dampened", but-by definition-it is. (I would not do it on my car either...) There is also the possibility of using polymer pucks at the bearing mounting points as pointed out by Zac.

[TMichaels]

Guys,
honestly, don't start to fiddle with that. I am really sure that it will be rejected by any event that I know of.

[mech5496]

Tobias, i would reject it either if I were a scrutineer, but "by definition" it is NOT illegal, or at least one could claim so!