Ah yes In lb is radius, so the ballscrew factor is 2pi*threads per inch
Which would double the acceleration from my earlier numbers. > On Jul 22, 2020, at 10:43 PM, Thaddeus Waldner <thadw...@gmail.com> wrote: > > > > > Start with a 226 oz in > > / 16 = 14.125 lb in > > 5 threads per inch is the same as a belt pulley with a circumference of 0.2 > inches > > since our unit is in lb in, we need to go from a pulley with diameter of Pi, > to diameter of .2 > > thus our final force is 14.125 * (pi/0.2) = 221.875 pounds (poundal?) force > > divide that by your mass of 200lb and you get > > 1.109 g > > 1g = roughly 32in/s^2 so > > 35.69 in/s^2 > > This is close to your ballpark guess of 40 > > Did I make a mistake anywhere? > > > > >> On Wed, Jul 22, 2020 at 5:24 PM Nicklas SB Karlsson >> <nicklas.karlsso...@gmail.com> wrote: >> On Wed, 22 Jul 2020 11:29:36 -0700 >> Chris Albertson <albertson.ch...@gmail.com> wrote: >> >> > I don't see any relation between max acceleration and max speed. >> > Acceleration is determined by (1) the mass of the table and (2) the >> > torque the motor can produce while speed is determined by the max RPM >> > of the motor. >> >> Mostly agree though as torque usually depend mostly on current there will be >> a resistive voltage drop at higher torque which will reduce speed at higher >> torque, speed reduction is usually small. For example series connected DC >> motors and induction motors made for direct will reduce speed so there are >> exceptions but do not expect these are used as servo motors anyway. >> >> Change gear ratio and use motor with same power different speed may change >> acceleration due to rotor inertia. >> >> > It is very easy to buy a tiny motor with low torque that spins very >> > fast. Or you can find powerful but slow motors. Multiplying the >> > speed by three to find acceleration, if it works is just a >> > coincidence. The factor could be 0.5 or 10. >> >> High torque motors usually need a gear box or will become heavy. This is >> because flux and current is multiplied to get force while there is choice >> between current or flux in electric motor air gap, there is an optimal >> choice then either air gap area or diameter need to be increased. Magnetic >> materials will saturate then flux get high enough while conductor losses >> increase with current. >> >> > There are two whys to go. A mechanical engineer would start with a >> > requirement for a certain speed and a certain acceleration. His boss >> > would give him those goals and then he would select a motor and drive. >> > The other way used by most amateurs is to just buy a motor that >> > "seems right" and then test it to see what speed and a certain >> > acceleration you can get from it. >> >> Not sure the boss will ask mechanical engineer about speed and a certain >> acceleration and then give these as a goal to the engineer. It is common >> boss read economics and contract but then it come to technical details odd >> things may happen. >> >> >> Nicklas SB Karlsson >> >> >> _______________________________________________ >> Emc-users mailing list >> Emc-users@lists.sourceforge.net >> https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
