Is it bi-electrical?
Background- I have my father in laws ’60 era floor mounted 9 inch disc and 6×48 inch belt sander. It has a Dunlap 1/3 HP split phase (ball bearing!) motor. I got a drive belt and hooked it up today.
When you turn it on, each time it runs the opposite direction from before. No i have not been drinking (not today).
Anyone ever heard of this? two wire 110 volt. no visible capacitor.
I am not a motor expert but have never heard of this?
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Replies
Squirrel cage motor run windings will work either direction. It's the start windings that determine which way it goes. Years ago I had one with bad start windings, and I was able to start it either direction by spinning it with a pull cord before hitting the switch.
If you want to use this machine, probably best to take the motor to a rebuilder to see what it needs rather than taking a chance on frying something.
-- J.S.
Sometimes there is a start winding and a centrifugal switch on the small motors. If the switch is bad, the motor doesn't get the starting kick and can go either direction. You might be able to take off the end bell and clean the switch. For all that work, I'd just buy a new motor. Its quick and safe, unlike a 40 year old motor. Sears sells them. So do most any tool or electrical supplier.
whats odd about it is that it is repeatable, always goes the other way.
thats no good with directional sanding belts tho
there is nothing wrong with the motor. A motor is just magnet and winding. If the magnet is just off one side when energy applie it will turn to the closes magnet, that is the direction the motor runs. I alway just spin the disc before turning on the power. They really nothing wrong it just life,. But using this trick I also made a motorcyle run backwards.
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I suspect that this motor was taken from some other application and has auto reverse built into it.
Off the top of my head the only thing that I can think of that uses this kind of motor are garbage displosals. But those are built in and don't have standard frames.
What does the label on the motor say?
Dunlap 1/3 HP ball bearing split phase 6.2 amps 110 v 1963 0r 1968 can not read it
really odd i tried it several more times and it does not always reverse itself. that is some times it runs twice when starting in the same direction
it also has low starting torque
really strange
no this is not a test
The centrifugal switch or the start winding itself is bad. It could also be a loose connection in the junction box. If instructions for reversing the direction of rotation are on the motor, or under the j-box cover, the two leads that you reverse (or swap) to reverse the rotation are the start winding leads. Check for tight connections. You can also use an ohmmeter to check the continuity of the start winding (remove at least one of the leads). A small motor like that will typically have a couple of ohms DC resistance across the start winding, if there is continuity through it and the start switch.
You can also blow out the centrifugal switch through the openings in the end bell with compressed air, assuming it's an open frame motor. With such motors on wood equipment, most of the time when the start winding isn't working it's because there's wood dust in the switch. Some of them are pretty crude items (old Westinghouse fractional hp motors have particularly crude switches, IMO).
FYI, a split-phase motor is essentially the same as a capacitor-start motor (technically, a cap-start motor IS a split-phase motor), but without the capacitor. They have lower locked-rotor and pull-up torque, and are used in applications requiring low hp and light starting loads. Compared to a capacitor-start motor, a split-phase motor will have wimpy starting torque, but if the start circuit isn't working, if it moves at all it will have very very slow starting until it gets a bit of speed.Be seeing you...
Sounds like a "Democrate" motor, always changing diretion!!
Oh Ship, here it comes!! I see Bob Walker storming this way!!
Edited 11/19/2003 7:37:00 AM ET by CarpenterPJE
no it's not bi electrical
it's Bi Polar ( sorry....couldn't resist )
regards
mark
Quittintime