Slowing down belt/disc sander


It's a Transpower w/2hp motor, turns at 3400+. Is it possible to slow this down to a reasonable rate of rpm? It's wired for 220 and pulls 14 amps.
Tom TIA
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Plug it into 110V? Not sure how many amps you'd be pulling,probably less than 14.
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Please don't do that.... We want you and your equipment around tomorrow too...
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Regards,
Joe Agro, Jr.
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we do?
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We want the equipment around, anyway, and in good condition, so we can gloat about the good deal we got at the estate sale.

-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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Tom Cavanagh wrote:

slow this

amps.
The cheapest option is to replace the pulleys. Put as small as possible on the motor and as large as possible on the machine. Linkbelt can tolerate operating on smaller pulleys than regular rubber V-belt.
Speed changes according to ratio of pulley sizes: RPMout/RPMin = DIAMETERin/DIAMETERout
If space doesn't allow a larger machine pulley, you could add an intermediate shaft with bearings and pulleys. Then you'd have a belt from the motor to this shaft, and a second belt from the shaft to the machine. This would give you more flexibility for speed changes.
Swapping the motor for a 1750 rpm motor would be the more expensive fix.
The next step up is an industrial variable frequency drive and three phase motor, but that'll cost much more than your sander.
Connecting a 240V induction motor to 120V power will simply burn it out.
Good luck,
Tim
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why would it burn out?
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snipped-for-privacy@yahoo.com wrote:

Without going into issues such as back EMF and impedance, let's just say induction motors are more or less constant power devices.
Electrical power is voltage times current. If voltage drops, an induction motor will draw proportionately more current. Halve the voltage and it'll draw twice the amps (roughly speaking).
Resistance heating varies with the square of the current. Double the amps gives four times the heating inside the motor.
The motor is designed to dissipate only the heat generated at its rated current. It can't get rid of this extra heat, so it cooks itself.
If you're interested, there's more details at places like http://www.ecmweb.com/mag/electric_highs_lows_motor /
Tim
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An elegantly simple explanation - I like it!
On 11 May 2005 11:51:10 -0700, snipped-for-privacy@yahoo.com wrote:

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wrote:

assuming that it has 2 pulleys, (no idea what a transpower is), and that they're different sizes, see if the pulleys both have the same shaft size.. if so, try switching them to change the "gear ratio".. YMMV
mac
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Indeed an elegant explanation! I like it too.
What about using a dmmer? There is a 2000W dimmer available online (I have one), and I have run several fans off various dimmers and they run perfectly and for ever. Of course they may be a different kind of motor, so I will stand corrected once again if this is a stupid post!
Dean
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Same problem.
-- Regards, Doug Miller (alphageek at milmac dot com)
Nobody ever left footprints in the sands of time by sitting on his butt. And who wants to leave buttprints in the sands of time?
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Does it not depend on the type of motor?
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snipped-for-privacy@yahoo.com wrote:

Yes, very much.
Universal motors (the motors in many power tools that have brushes on the commutator) can be slowed with a dimmer switch, although you're better off with an official "router speed control" since it's designed to tolerate the heavy inductive load of the motor.
Induction motors (the kind in stationary equipment) rely on the frequency of the AC line power and their internal construction to determine how fast they turn. There are some fancy two and three speed induction motors used on furnace fans, but these are expensive and uncommon. They change speeds by connecting different internal windings, but those speeds are still fixed, like 1750/1150 rpm. So, to change the speed of a standard induction motor the only thing you can do is change the frequency of the AC. Variable frequency drives do this electronically, but they cost several hundred dollars.
There's probably a couple of dozen other types of motors, but they don't show up in woodworking shops very much.
Tim
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On 12 May 2005 07:32:41 -0700, snipped-for-privacy@yahoo.com wrote:

Not in the UK, for the dimmer switches we have these days. Since they started being made so they can be used for two-way switching circuits, the damn things are so fragile that the switches die when a light bulb fails and gives an over-current spike. I can't imagine these things lasting _seconds_ with a real motor connected to them.
If you want a simple phase control module, go to an industrial supplier (like http://rswww.com ) and buy a real module sold for loads up to a few kW. They're cheaper too.
--
Cats have nine lives, which is why they rarely post to Usenet.

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There's probably room on the motor shaft to mount a large pulley. Then use another motor, with small pulley, to drive everything. In other words, use the motor for a jackshaft. If you need to go fast again, just take off the new belt. Wilson

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