Thread: 1/4 HP enough for a disk sander

G'day noodle_snacks,
I've got such a machine and I use it all the time. If it slows down with pressure, I use less pressure, I change grits fairly often depending what's being done.
When you removed the motor did you remove the starter capacitor as well?
Washing machines usually use capacitor start motors, so that component will be necessary to use the motor.
Regards,
Noel

It would depend on the size of your disc it would work reasonably well on a 150mm, if you want something in the area of 300mm, you would need to move up to 1-1.5hp

I agree with Watson about being gentle when it starts to slow down. I have a 1/3 hp standing drill and a 1/3 hp grinder of the dark blue 3 letter variety that do just that - slow down with any sort of work. A good idea to go easy on the sanding but it doesn't help as a drill to get half way through and start doing it tough.

Carry Pine

I have a couple of W/M motors stashed as well, same deal - waiting on figuring out the wiring.

Bit of a side query, if it didn't have the start capacitor, you could start it by spinning it by hand then hitting the switch - correct?

Same thing if you spin it backwards then hit the switch - it would run fine backwards?

Think I read this somewhere. :confused:


Cheers................Sean

Originally Posted by scooter

I have a couple of W/M motors stashed as well, same deal - waiting on figuring out the wiring.

Bit of a side query, if it didn't have the start capacitor, you could start it by spinning it by hand then hitting the switch - correct?

Same thing if you spin it backwards then hit the switch - it would run fine backwards?

Think I read this somewhere. :confused:


Cheers................Sean

Theoretically that would work fine Sean. Also with some W/M motors they have two sets of windings to enable a slow speed for the washing and high speed for spin dry. Might be able to use that to your advantage too!

Spinning by hand is fine in theory, but is a bit impractical, as some machines have a centrifigal switch system that switches out the start winding and capacitor once the run winding has got to speed....and that's at rated speed .
Some motors are also wound such that via the capacitor and the start winding a difference in phase occurs, which actually starts the thing moving.
Its a lot easier to wire in the starting capacitor.....gospel truth!

Regards,
Noel

Hey Noodles,
have you still got the remains of the washing machine??
I can send a photo or reference to what the capacitor would look like.
Regards,
Noel

Originally Posted by Wood Butcher

Theoretically that would work fine Sean. Also with some W/M motors they have two sets of windings to enable a slow speed for the washing and high speed for spin dry. Might be able to use that to your advantage too!

As in number of poles?:confused:

I've been hassled by my shed aircon the last few days, my BIL(industrial sparky)reckons the pole's(windings?) for the high speed are burnt out and on the low speed its only using 1/2 of the poles... thus giving no torque.(must spin fan by hand to start)
Bloody annoying just cut a hole in me shed to fit this thing... seems when the last person removed the unit they for some reason removed the water flow tap after the pump, so I've been running it flat out overflowing the water troughs for the batts and which ended up in the motor!:mad:
Replacement is about $350!(ripoff:eek: )



Ps, highjack over!
My disc sander is a 300mm with 1.5hp... still slows under a medium load at the outer edge of the disc.

Originally Posted by Harry72

As in number of poles?:confused:

Not sure how it works, I mentioned it cause I remember someone posting about using W/M motors in the past.

Edit: Found the link, was Apricotripper and his grinder setup.
Makeshift grinders...

Originally Posted by Harry72

My disc sander is a 300mm with 1.5hp... still slows under a medium load at the outer edge of the disc.

G'day Harry,
That's really relevant for the bush mechanic types. Is your machine a commercial unit or a home-built one??
Noel

If you wanted to buy the facilities that Apricotripper has on his machine..what would that cost??
I've got to research his threads more thoroughly.
Not pretty....but useful!!!!!
Noel

Hi, i did remember to remove the start capactior, only catch is i have four wires to deal with, one being earth, so three to deal with, how do i wire things up?

If i did use this motor whats the consensus for disk size? 6in/9in? Ideally what size do i want for a disk sander anyway? i'd rather find a 1hp/1.5hp motor and do things right, once if a 12in is really the go.

Hi all, I have a home made disc sander! Use a 1/3 HP washer motor with a 7 inch disc & velcro backing. Motor is centrifugal switch type, in other words no cap. The unit works very well with minimal slowing unless I am brutal with it. I made a second one for my son & he is quite happy with it. Cheers, Les.

G'day Noodle_snacks,
attached is a diagram of how the capacitor and windings are connected. You will need to identify the two windings......motor winding has more resistance that the start winding measured with an ohm meter. Typical values are 12 ohms for the motor winding, 8 ohms for the starting winding.
Hope this helps.
Noel