On Sunday 31 May 2015 14:46:29 andy pugh wrote: > I just bought a new old lathe, as an upgrade to the Cheap Chinese > Lathe. The new lathe actually has a smaller between-centres distance > than the CCL, only 1" more swing, but weighs about 12x as much. > > The drive-train is a 900 rpm motor, then a Kopp Variator, and then a > 2-speed electrically-actuated gearbox. > > I am trying to decide whether to control spindle speed by setting up a > motor to twiddle the speed adjustment of the variator and leave the > VFD (which I need to synthesise 3-phase) at a fixed frequency, or > whether to leave the variator at a fixed setting and control speed > with the VFD. > > The advantage of the variator is that as you reduce the speed there is > more torque available, but that is not the case with a VFD. > > I suppose an alternative would be to swap the motor for a 240V > single-phase item and not have a VFD at all. > > The drive-train can be seen in this photo: > https://picasaweb.google.com/lh/photo/bXi9y-7WGDJSi8r0Rhr6XH69jlxvlrTD >6CexboMrrBE?feat=directlink > > It is fairly substantial.
Even fairly is a bit of an understatement. But the word variator is a strange one to me Andy. Can you get a pix of it from the meat and taters side? I am thinking that if its a big reostat, it might be replaced with one of Jon's pwm servo amplifiers. But the evidence in this message points to its being more of a split pulley setup where the reduction ratio is controlled by adjusting the split distance, with the mating pulley being spring loaded such that squeezing one, spreads the other, ala what we call a salisbury clutch on this side of the pond. That would be a slower reacting device, and the only one I have any great familiarity with was on a tote-goat I had back in the 1960's. It was a bit hard on the v-belt when used for a utility tractor. Actuated by fly-weights that applied the squeeze as the revs went up, I often made the brag that it could do 15 mph on flat ground with the elderly briggs engine about redlined, but it could do 5 mph up any hill you pointed it at, it didn't lose engine revs to bad as it slowed, so even with a 2.5 horse on it, it was unstoppable as long as there was weight enough on the back tire for traction. 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) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
