On Fri, Jan 9, 2015 at 1:51 PM, David C Brown wrote: > Thanks for that. The size of the motor did rather surprise me. > But I think there is a mistake in this sum > >> t =3D m*r^2*a =3D 5kg * 1m^2 * 5/3*pi rad/sec^2 =3D 25/3 * kg*m^2 / sec= ^2 =3D >> 25/3 N * m =3D 8.33 N*m >> > > You are a factor of pi short Indeed, silly mistake. It only just occurred to that 4 meters is just over 12 feet long. 100ms might be rather quick to get a long arm like that moving at full speed. On the other hand, a motor capable of that would be less likely to stall. Would you care to share more about your project? Perhaps a picture or two? --=20 Jason White --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .