How to estimate forces on rotor bobbins

[Matt Gignac]

For the radial direction, I'm not having any troubles figuring out the forces that our bobbins will see, but can't really figure out how to quantify the forces in the axial direction, which i think would be the most critical (seperating both halves of the bobbin).

I'd assume the major contributor would be disc un-flatness, but that's about as far as I got. How do others who have used floating rotors estimated the axial force on the bobbins? Or did you use the logic that if it's good enough for a motorcycle, it's good enough for FSAE (and a little "ummm, yea, that looks like it'll hold").

If you went custom, what size c-clips did you use.

Matt Gignac
McGill Racing Team

[Matt Gignac]

For the radial direction, I'm not having any troubles figuring out the forces that our bobbins will see, but can't really figure out how to quantify the forces in the axial direction, which i think would be the most critical (seperating both halves of the bobbin).

I'd assume the major contributor would be disc un-flatness, but that's about as far as I got. How do others who have used floating rotors estimated the axial force on the bobbins? Or did you use the logic that if it's good enough for a motorcycle, it's good enough for FSAE (and a little "ummm, yea, that looks like it'll hold").

If you went custom, what size c-clips did you use.

Matt Gignac
McGill Racing Team

[rjwoods77]

As far as I can tell:

Radially: Find max. brake torque from tire Cf and reduce the radius down to your bobbins for find force.

Axially: Assume that the bobbins arent working correctly (rotor sticking for some reason, runout, thermal expansion, etc.) and take the clamping force of the caliper and the distance from effective clamping radius to the bobbin center to get a moment arm from that force.

Take the two forces and create a force vector. Also you have multiple "bobbins" so I dont know if the radial forces gets split equally and the axial forces I assume are just for the couple "bobbins" that would be in the "quadrant" of sticking rotor. I might be wrong but that seems like what the forces would be. I am trying to do the same calculation and that is as far as I have gotten.