Hi IHNF - I have just downloaded Sigmaselect as its called. I have had a play with it and by the time I have waded through the menus I would have calculated the torque required manually. Using sigmaselect I still have to calculate the rotational inertia of the ballscrew and I have to select a motor vs use the known motor inertia. It does do some things that are more difficult like inclines and cranks and flywheels. So IHNF I'm not trying to give you a hard time. I'm just presenting easy stuff for people to use to design their machines.... I tried to match it up to my earlier calc but its difficult I will continue to look at it. It also includes jerk which is quite interesting (to me anyway) cheers Peter