Thursday, January 15, 2009

Recent items of interest (to me, not you)

Some of Conor's work is published in (ny tyrant). I hate NY and people from it, but that has nothing to do with this magazine.
So whaddo we got. I can swallow 1/4 of a chicken in 10 seconds. Humans shouldn't swallow chicken bones. Otherwise I could do it faster.
Some machines in the shop died. Maybe it was the cold, maybe it was just time for them to go, or maybe they're Chinese made cast shit. I'll take China for $100, Alex.
Here's one of the problems: fractional horsepower single phase capacitor start/run AC inverter motors. Capacitors die. Cheap ones last between 1 hour and 3 years. Cheap ones tell you they're dead by exploding in a cloud of green smoke. Exploding is also their way of telling you they're too hot. They have a limited safe operating temperature range. Expensive, military spec capacitors are expected to last 30 or so years under a wide range of conditions without exploding.
You won't find anything like that on a typical inductionm motor. AC induction motors also depend on the freqency of the AC, unlike DC motors, which just spin faster as the current increases. You can't increase/decrease the current on an AC motor and expect anything good to happen.
1/3 hp @ 3450 rpms is too weak and too fast for steel work. Most ~$100 machines use a cheap motor like this to save money. The motor isn't rated for continuous duty. It's also not rated to handle the load typical operations generate.
High torque, lower RPM motors are ideal. Speed control is really nice, but that gets into more expensive electronics. Belt drives with stepped pulleys can provide a few different speeds using one motor. This can be done with much less expensive motors. Motors made for 115v/15 amp operation should be at least 3/4 HP and under 1700 RPM. A 1.5 hp 1700 RPM induction motor is good for most shop machines whether it be a saw, grinder, polisher etc.

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