Need help wiring up a lathe motor

This topic has 6 replies, 6 voices, and was last updated 28 January 2017 at 11:00 by JohnF.

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28 August 2016 at 16:44 #252743
Taris Jewell
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@tarisjewell61133
So I bought a lathe yesterday and the guy disconnected the motor wiring from the Dewhurst drum switch.

So i have no idea how it gose bake. The wires are all the same colour but i did trace them with a malt-meater the lathe is a Drummond but no idea on the motor make i can tell you that it has a1 a2 and z1 z2 and i did find a thread on wiring this up and i did that but it seems to only go clockwise in the reverse position on the switch even if i flib the z1 and z2 and the same with the a1 and a2 but the motor dose make a noise when i put it in forward but doesn't move it also seams to spark a lot. So I stopped so not to damage anything. The wiring coming from the plug is right but im now confused.

Edited By JasonB on 28/08/2016 17:12:28
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28 August 2016 at 16:44 #32769
Taris Jewell
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@tarisjewell61133
28 August 2016 at 19:16 #252765
Les Jones 1
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@lesjones1
Hi Taris,
I suspect a1 and a2 are one winding and z1 and z2 the other. Without the wires connected to the switch measure the resistance between a1 and a2 and between z1 and z2. Also check that you get a very high resistance reading between the a connections and the z connections. If the motor does not have a start capacitor the windings with the lowest resistance will be the run winding. If the motor does have a start capacitor the start winding resistance (Via the capacitor) will briefly show a lowish reading that will increase to a higher reading over a period of a few seconds. If the links are in the normal configuration on the dewhurst switch then the mains should be connected to terminals 1 and 3. The run winding should be connected to terminals 5 and 7. The start winding (Via the start capacitor if fitted.) should be connected to terminals 2 and 6. How did you have it connected in your tests ? To test if the Dewhurst switch is linked in the normal way with the switch not connected to the mains or the motor confirm that for the forward position you get continuity between terminals 1,5,6 and between terminals 2,3,7 (But no continuity between the two groups.) Confirm that in the reverse position you get continuity between terminals 1,2,5 and terminals 3,6,7 (But no continuity between the two groups.)

Les,
23 January 2017 at 21:28 #279775
peak4
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@peak4
A picture speaks a thousand words. I believe this link might assist. **LINK**

I'd expect A1/2 to be the run windings and Z1/2 the start windings.

Not ideal to use a Dewhurst as a start stop device though, better to add a no-volt release switch for that function and use the Dewhurst purely for reversing the motor.

Just bear in mind that the chuck screws on, so you don't want it barreling off down the workshop when you reverse the spindle rotation.

Head up to the top of his page to see how this chap smartened his switch up a bit.

https://misterlinnsworkshop.wordpress.com/category/myford-ml7b/page/19/

Edited By peak4 on 23/01/2017 21:36:13
24 January 2017 at 21:48 #279987
Phil Whitley
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@philwhitley94135
Just to confim the Above, and add a bit, A1 and A2 are the run winding, Z1 and Z2 are the start winding, and to reverse the motor, you reverse the polarity of the start winding, or reverse Z! and Z2. This is what the Dewhirst switch does, but allow the lathe to come to a complete stop before changing direction, I also recomend fitting a NVR type starter, and again, beware of the chuck unscrewing, or fit a set screw so it can't!
25 January 2017 at 00:26 #280010
Ady1
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@ady1
There's a bit on old motors here
28 January 2017 at 11:00 #280775
JohnF
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@johnf59703
Taris look at your messages
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