Recent content by Allen3

Found one error I found one error. The first reference above contains a misprint. Eqn 6.26 should not contain a factor of pi. Instead, it should be: From Eqn 6.26: Friction Torque T = 0.5*Cf*rho*w^2*(R^5-r^5) = 0.5*0.00433*1.2*1257^2*(0.190^5-0.110^5) = 0.95 N-m Windage power P = T*w...

Hi, I'm attempting to estimate the windage losses in an axial motor design, and I'm having trouble with the formulas. It might be a math error, or a misunderstanding of the formulas, but I seem to be stuck. An axial motor can be modeled as an annular disk spinning in an enclosure. The disk...

Ah, thanks. For some reason I have no specific memory of learning that, but apparently the lesson soaked in somehow and helped me figure it out. Thanks.

Yes, C is a constant. Looking back at my notes, it looks like what I did was to set q(t) = B+C*t, then di/dt = i*A/q, and since dq/dt = C, (di/dt)*(dt/dq) = di/dq = i*A/(C*q) and I then integrated (1/i)*di = (A/C)*(1/q)*dq to find i(q) and made some substitutions to find i(t). But back to...

Forget it--I figured it out OK, my apologies. I was able to solve the problem using variable substitution--basically, finding di/dC and then finding i(C). Sorry for the false alarm.

I'm working on a problem where the current i is described by the equation: di/dt = i*A/(B+C*t) The rate of change in i therefore depends on both i and t. I'm looking for a closed-form solution for i(t) given i(0)=I. I have to admit my calculus is pretty rusty and I'm having trouble...