On Tuesday 27 July 2021 11:48:29 Earl Weaver wrote: > My 8" chuck has a max 2500 RPM, I would think 1500 RPM would be > sufficient for my use. > The motor has 2 line wires and 2 shunt field wires. plus tachometer > feedback wires. > > On 7/27/2021 10:02 AM, andy pugh wrote: > > On Tue, 27 Jul 2021 at 14:10, Earl Weaver <[email protected]> wrote: > >> Would there be a benefit for me to change the motor pulley to a > >> smaller size? > > > > I think that would depend on your planned use. > > > > My lathe can do 3000rpm but the macros I use with constant surface > > speed top out at 1500rpm and I very, very, rarely find that too > > slow. So, I suspect that, unless you do a lot of very tiny parts, > > gearing for 1500rpm would suit you better if you regularly make 8" > > parts. > > > > My lathe, at 3000rpm, is unusually fast for an 8" lathe. > > > > CNC and carbide has changed the rules a bit, but if you go back to > > the 70s a 10" lathe would tend to top out at 1500 and a 15" at 800 > > rpm. > > > > It seems that your spindle motor is a wound-field motor, I don't > > know very much about those, but I think that they have rather lower > > low-speed torque than a permanent magnet motor. > > (Though this might depend on whether the motor is wired shunt or > > series) But they are typically used where a wider range of operating > > speeds than can be used with an induction motor is required. > Actually, the torque goes up as the speed goes down, because they run at the speed determined by the counter emf generated by varying the current in the field winding, and the higher current actually causes it to slow down, but at the same time, the torque rises because the field magnets get stronger, generating the balancing back emf at a lower armature speed. Unfortunately for those motors, the non-grain oriented steel used in those motors is saturated magnetically, at around 1/4 of the magnetic field we can make with todays magnetic materiel. Not very efficient and it shows in the power bill to run it.
My bet is that since this is a very old tech, the power supply will have both selenium rectifiers and wet electrolyte filter capacitors, and one, or the other or both have reached their retirement age, like me a long time back, and like me, are no longer working very well. Where are your digs located Earl? I am in north central WV. > **Earl Weaver > Email: [email protected] <mailto:[email protected]> > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
