The deflection measurement wasn't by me, but it was correctly done.
Your 13 stone isn't applied all at the centre of your 50mm axle, but close to the ends. This reduces the bending moment, and therefore the amount of deflection. A "quick and dirty" calculation to figure out the deflection at the end of a 50mm axle is to treat the bearing housing as if it's infinitely stiff, and to consider the load applied by the ground pushing up against the tyre centre (Newton's third law). I've worked this with the assumption of the tyre centre 300mm outboard from the bearing housing. If I was less lazy I'd go down and take a measurement from my kart, but it's a wild guess.
The deflection measured at the tyre centre due to bending of the axle when you get in the kart comes out at a whopping 0.047mm. Obviously it will be more than this due to the oversimplified calculation, but not by a great deal. Even taking into account the weight of the kart itself as well as the driver, the difference in "ride height" caused by axle bending under weight will be less than 0.1mm. This is completely swamped by the springiness of the pneumatic tyres and flex of the 30mm chassis tubes in real terms.
Temperature effects? The elastic stiffness of steel drops off a bit with temperature, but unless your axle is glowing red the above calculation will stay fairly true. It does become easier to permanently deform as it gets warm, but it really does have to get pretty warm before the effects are dramatic.
Bone handled butter knife has to be an optical illusion.
Hope that helps.
Liam
|
|
