On Saturday 11 May 2013 22:24:58 John Kasunich did opine: > > --- On Sat, 5/11/13, Gene Heskett <[email protected]> wrote: > > > When I did the PMDX-106 for the mill, I used 2 relays, one > > > to switch > > > between the output of the controller with its DPDT poles, > > > the back side of > > > which dropped a 10 ohm 20 watt resistor across the motor to > > > make use of its > > > generating ability as a means of stopping it fairly rapidly. > > > As in 2500 > > > revs to zero in just a hair over 1 second. The 2nd > > > relay was used in the > > > usual DPDT reversing circuit. > > > > > > There isn't that much inertia in that setup, but this will > > > have a cast iron > > > fan cum flywheel that weighs a good 2 pounds to stop. > > > So a 10 ohm 20 > > > watter, taking the dump from 7000 rpm, is likely to be > > > considerably hotter > > > than bright red internally by the time its down to 100 rpms > > > as that will > > > translate to about a kilowatt of stored energy. > > > > > > 20 ohms won't have to take quite as much of a rapid thermal > > > shock, but the > > > wattage will be similar, so I don't see any way to make it > > > work that > > > doesn't involve a panel of at least 8 similar resistors. > > > > > > > > > Basically anything I can make off the local walmart shelves > > > (for under 50 > > > bucks that is). > > http://www.walmart.com/ip/Reliance-4-500-Watt-240-Volt-Universal-Flange- > Water-Heater-Element/15815368?findingMethod=rr > > 12.8 ohms, 4500 watts peak (or continuous, if you put it in water). > I suspect that you don't need the water given the short time needed to > decel.
That sounds like awfully close to what the Dr. ordered, but I wasn't aware they drew that much, thats about 19 amps from a 240 volt line. There are several styles available, and there may be lower wattage versions too. Definitely worth checking out as they will have a decent, dependable connection too, unlike using the halogen lamp sticks, which burn up the contact at about half the rates as the lamps fail. Then conjuring up a delay in the hal file to make it wait for a full stop going into reverse, with an identical delay on stopping to turn fwd. Thanks John and all. I just stumbled over an identical timing belt pulley to replace the somewhat worn one, with one diff, where mine has an 8mm bore, the one from the HiTorque model that LSM is selling has a 9mm bore, both with keys. I was not able to find a 17 or 18 tooth pulley on the net with a bore more than 1/4"/6.35mm. As I haven't yet finished the end of the shaft, its still chucked up at about 9.25mm ATM, I'll wait for this new pulley and turn the shaft to fit. Since that will be the torque delivery of that 1HP motor geared down about 3/1, I'll need ALL the help I can get, and will probably clean everything up and superglue it in place hoping the keyway won't get reamed out. They are Acetel or some such black, looks faintly like carbonate plastic. I also found my 4 jaw chuck isn't grabbing things correctly, I put a dial indicator on the end of the shaft and can pull it 2 thou or more sideways, but move my hand back to the chuck proper and its only .0002" or so I can bend that. I had to write a .07mm taper into the cut to make it cut true. Its about time for a new chuck anyway. This 4" one was only around $70 new, and its been too small too many times. Does anyone make a decent 4 jaw, about 5" in diameter that will fit the spindle flange of a mini-lathe for < $250? Most of the chuck peddlers on the net don't brag about what machines their product might fit. Thanks all. Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! My views <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> I surely do hope that's a syntax error. -- Larry Wall in <[email protected]> A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. ------------------------------------------------------------------------------ Learn Graph Databases - Download FREE O'Reilly Book "Graph Databases" is the definitive new guide to graph databases and their applications. This 200-page book is written by three acclaimed leaders in the field. The early access version is available now. Download your free book today! http://p.sf.net/sfu/neotech_d2d_may _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
