How Stiff is stiff enough upright hub assembly ?

[Francis Gagné]

Google lead me to this catalog with some numbers, I have no idea how good they are but it is a starting point for at least an order of magnitude.

http://www.nachi-fujikoshi.co....web/pdf/B1031E-5.pdf

There is also a stiffness calculation guide from Schaeffler on there website:

http://medias.ina.com/medias/e.../tg_hr*ST4_102146955

That should get you started!

[Simon Dingle]

It's worth remembering that your bearing stiffness will be highly affected by the operating temperature of the bearings and uprights.

Saw an FSAE car recently where, straight after running while everything was still hot, you could move the wheel by hand and see the play in the wheel bearings with the naked eye.

[Claude Rouelle]

Yep. Preload on bearings should take into account thermal expansion. Want another examples of temperature influence? Chassis torsion stiffness and differential preload. Never have calculated any of the two but have been part of Chassis K&C measurements on test bench at different temperatures in temperature controlled room. Not negligible! As far as diff preload, measure it with a torque wrench with one driven wheel of the ground when the car is at ambient temperature. Make a few laps measure again; you could loose as much as 50 %.

[kkung]

don't neglect the influence of compliance stacking in your analysis, particularly how your bearing configuration will impact installed stiffness. I've seen noticable diffence between a 10" and 13" wheel package.

As measured on a full K&C rig, an installed stiffness for a top level car is .15-.375 deg/kN Lateral Camber Compliance, .2-.3 deg/kN Lateral Steer Compliance (rear toe compliance will be lower than the front).

Hi, I am curious to know where this data came from and if it is available publicly. We're trying to spec stiffness targets for our 2014 car..

[Zac C]

Hi, I am curious to know where this data came from and if it is available publicly. We're trying to spec stiffness targets for our 2014 car..

The full data set is not publicly available. Those numbers also only represent what 'good' teams typically achieve, not an optimal target to shoot for.

[kkung]

The full data set is not publicly available. Those numbers also only represent what 'good' teams typically achieve, not an optimal target to shoot for.

I see. Can you at least tell me which car it was?

[Edward M. Kasprzak]

I see. Can you at least tell me which car it was?

Zac has measured a bunch of Formula SAE/Student cars on a K&C machine, so his comments don't come from just one car.

[kkung]

Zac has measured a bunch of Formula SAE/Student cars on a K&C machine, so his comments don't come from just one car.

Thanks for the clarification!