Yes! Thank you.
> On Jul 22, 2020, at 11:07 PM, John Dammeyer <jo...@autoartisans.com> wrote: > > >> -----Original Message----- >> From: Thaddeus Waldner [mailto:thadw...@gmail.com] >> Sent: July-22-20 8:43 PM >> To: Enhanced Machine Controller (EMC) >> Subject: Re: [Emc-users] Calculating table acceleration. Was: Need help with >> Bostomatic BD18-2 to linuxcnc >> >> 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? >> > > 1 G is 32 ft/sec^2 or 384 in/sec^2 and that's where it falls apart. Based on > real life the acceleration value is out by a factor of about 100. > > And I don't understand why > " since our unit is in lb in, we need to go from a pulley with diameter of > Pi, to diameter of .2" > > It could well be that Jon Elson's explanation of linear force is incorrect. > > John > > >> >> >>> 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 > > > > _______________________________________________ > 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
