Jake Latham's Brake Design Page Question

[optiluca]

Hi all. I am working on a new brake system for my university's fsae team, and have come across this rather handy website http://www.jakelatham.com/radi...ke_calculators.shtml (http://www.jakelatham.com/radical/info/brake_calculators.shtml) .

It is little more than a glorified spreadsheet I suppose, but quite good for some initial calculations. Anyway, I am a bit confused by the fields "Rear rotor Torque", vs. "Rear Tire Torque" for example (bottom left of the page). Why are these torques different? Surely a torque on the rear axle is just a torque on the rear axle? http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[optiluca]

Hi all. I am working on a new brake system for my university's fsae team, and have come across this rather handy website http://www.jakelatham.com/radi...ke_calculators.shtml (http://www.jakelatham.com/radical/info/brake_calculators.shtml) .

It is little more than a glorified spreadsheet I suppose, but quite good for some initial calculations. Anyway, I am a bit confused by the fields "Rear rotor Torque", vs. "Rear Tire Torque" for example (bottom left of the page). Why are these torques different? Surely a torque on the rear axle is just a torque on the rear axle? http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[Pete Marsh]

Looks like that might be the force the pads are applying to the rotor, instead of the torque.

Pete

[optiluca]

Hey. I though of that as well, but If I make the rotor size equal to the tire size, I get the same values for rotor and tire torques. Could it be that Mr. Latham has erroneously decided that torque somehow scales with radius?? Or am I missing something fundamental... :S

[Adambomb]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by optiluca:
Hey. I though of that as well, but If I make the rotor size equal to the tire size, I get the same values for rotor and tire torques. Could it be that Mr. Latham has erroneously decided that torque somehow scales with radius?? Or am I missing something fundamental... :S </div></BLOCKQUOTE>

My guess would be that it's not you who is missing something fundamental...

Just another reason to not believe everything you find on the internet!

[John_Burford]

Yes, there is an error in the calculations not just the labeling which has a mistake as well.

[John_Burford]

I contacted Jake and the corrections have been made. There may be enhancements yet to come as well.

[swong46]

Does anyone get the pedal movement number to be anything other than 0? It never seemes to change.

[optiluca]

Hey. I contacted him about the error as well, so he fixed it. I also asked about the pedal movement number, apparently he never got round to programming that... http://fsae.com/groupee_common/emoticons/icon_razz.gif