From: muratlanne@gmail.com   
      
   "Richard Smith"  wrote in message news:m1ldsc42kf.fsf@void.com...   
      
   Going single-phase,   
   thinking that one motor should be able to serve various projects...   
      
   4-pole single-phase motor?   
      
   If 2-pole 3000RPM motor were cheaper, maybe can get one with eg. a   
   10:1 gearbox giving 300RPM output giving maybe only a single-stage   
   speed reduction with flat-belts for quite a range of projects?   
      
   I am not overly hopeful of coming-by single-phase motors   
   second-hand...   
      
   Advice on brands and sources of motors - what is best value-for-money   
   if price alone is not what dictates that?   
      
   Category of motor?   
   There are various "capacitor-start" / "capacitor-run" specs.   
      
   What size of motor, given 1/2HP looks like about the minimum for this   
   particular project but not necessarily future projects?   
      
   This is very wide-open as a question, for sure...   
      
   I think of mounting the motor on a plate of some simple rectangular   
   dimension, which can be moved between projects and bolted into place.   
   Being free to drill new holes in the plate for unique features to that   
   project.   
      
   Thanks in advance,   
   Rich S   
      
   ---------------------------------------   
   Capacitor-start motors are for loads like air compressors that require high   
   starting torque, unless they have an unloader. You could probably use any   
   available motor and adjust the required power to match it by changing the   
   reduction ratio or drum loading.   
      
   My 1/2 HP air compressor won't start on a 3KW generator unless I manually   
   unload it by opening the pressure relief, for which I made a cam lever to   
   raise and hold the plunger. My sawmill needs the heavy wheels declutched for   
   starting, then gradually engaged over several seconds. There are many   
   work-arounds.   
      
   A simple multi-use motor mount is a plywood square with loose pin hinges on   
   the edge and a tension adjusting screw or wedge, push or pull depending on   
   which way the belt goes, or maybe both.   
      
   The hinge pin is gas welding rod. A loose pin fit is OK because the belt   
   tension removes slack. The hinges need to straddle the pulley position to   
   hold belt alignment. Tight pin hinges can be converted by grinding off one   
   pin end and punching it out. I learned this trick in theatre scenery   
   construction where they are a standard way to join flats (panels), with   
   nails dropped in as pins.   
      
   If the motor can run but not start the load add an over-center cam or toggle   
   detensioner to either the hinged motor plate or a belt idler pulley. The   
   clutch on my sawmill is a long rod from the operator position bent into a   
   crank that pulls or releases a spring-loaded idler pulley, with an   
   over-center stop for the crank. The spring was a longer one with the right   
   stretch rate, shortened and rebent to hook over the rod. I can do either   
   expensive first or cheap third world engineering as needed for the salvaged   
   gear I've found.   
      
   The best type of motor for a dusty job is Totally Enclosed Fan Cooled, TEFC.   
   WEG (Brazil) is a decent lower priced brand, but I take what's available as   
   long as the bearings aren't loose, which may indicate erosion from   
   electrical leakage. My small lathe has an ex washing machine motor with its   
   large cooling slots protected from flying metal chips by a beercan metal   
   shield. My father's bench grinder was even worse, the motor had burned out   
   its start winding and needed to be pull-started by hand.   
      
   I suspect that one driven and one free support roller won't drive the drum   
   as well as two driven rollers widely spaced to increase the wedging force   
   between them. The pulleys or bicycle chain sprockets between them can be any   
   size as long as identical. If their bearings are nylon sleeves that drop   
   into frame slots the chain or belt will be easy to install.   
      
   You could drive both roller shafts separately with belts that support the   
   weight of the motor, and then be able to adjust the roller spacing as needed   
   for sufficient drum friction. A drive tensioned by motor weight or springs   
   may jump and relieve the load's torque when started. A clamp-on ammeter on   
   one motor lead may help tuning for efficiency or avoiding overload but power   
   factor is more useful.   
   jsw   
      
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