[4]

Need help wiring a motor/drum switch

[3]
[10] Like what you see?
Click here to donate to this forum and upgrade your account!

tjb031750

Registered
Registered
Joined
May 2, 2018
Messages
1
I have a 1/2 horsepower motor for an old Atlas lathe I am restoring. It is connected to a drum switch to allow me to reverse the motor direction. I partially disassembled the wiring thinking I knew how it went back together but I was wrong. I can't figure out how to reconnect the wiring. Almost all of the wires are connected just like they were when the motor was working; I only remember disconnecting a few wires; I believe it may have only been the 120VAC power cord. The main problem is the six wires coming out of the motor are not colored; they are the old fabric covered wires and I suppose over the last 50-60 years the color has all faded out of them. They are all just a dingy gray now. You can see what I’m talking about in one of the photos. In some of the photos you’ll see a bunch of numbered white pigtails attached with wire nuts; those are what I added just to make my testing process a little easier. Any suggestions you can provide would be appreciated. Thanks. Tom
 

Attachments

wa5cab

Downloads Moderator
Staff member
H-M Platinum Supporter ($50)
Joined
Dec 25, 2011
Messages
4,493
OK. Do you know whether the motor is a capacitor start or some other kind of single phase AC motor? The wiring is actually the same but how you ID the Start winding varies.
 

wa5cab

Downloads Moderator
Staff member
H-M Platinum Supporter ($50)
Joined
Dec 25, 2011
Messages
4,493
Further, do you have an ohmmeter and do you know how to use it?

Your motor is simpler than most in that it has six obvious wires. Two wires (one pair) are for the start circuit. And two pairs are for the run windings. It can be connected for either 120 or 240 VAC. One good thing about a motor that can be connected to run off of either 120 or 240 VAC is that it will safely start and run off of the start winding and either one of the run windings by itself.

The following assumes that you are connecting the motor to run on 120 VAC. And that your line cord has 120 VAC on it. If it doesn't, make it so temporarily.

So first step is to ID the wires that each go to the same circuit. The two run windings should each show the same resistance reading on your ohm meter. If the motor is a capacitor start type, the ohmmeter will show a momentary resistance and then drop back to infinity. If it is a split phase or other type, it should show a higher resistance. Once you know which winding is the start winding, connect the ground wire (normally green) to the frame of the motor. Connect the two wires from the start winding to the two wires from one of the run windings, and to the two remaining wires from the line cord. That is, connect one wire from the start winding to one wire from the run winding and to one wire from the line cord. Connect the other two winding wires to the other wire from the line cord.

Turn off the circuit breaker and plug in the line cord plug. Turn on the breaker and note which direction the motor turns. Turn off the breaker. ID or tag one group of three wires as 1 and the other group as 2. And ID the two wires from that run winding as A. Disconnect the two wires from the number A run winding and connect #B run windings to the start winding and line cord as before. Turn on the breaker and note which direction the motor turns. If it is turning in the same direction as before, ID its two wires as 1 and 2. If not, swap just the two wires from the second run winding, turn on the breaker and confirm it is now turning the same direction as with the other run winding. Mark the two wires from the second run winding as 1 and 2 to match the numbers assigned to the line cord and start winding. Tie the three 1's together and the three 2's together. Turn on the breaker and confirm that the motor starts and runs.

Now that you have ID'd the six wires, use the schematic of the switch and connect the six motor wires and the two line wires to the switch and test it.

If you actually want to run the motor on 240 VAC, come back for chapter 2.
 

tjb031750

Registered
Registered
Joined
May 2, 2018
Messages
1
I'm not very savvy about electric motors, or electricity in general for that matter, but if you look at the photos you'll see a tubular shaped device attached to the top of the motor, I think that might be a capacitor, so if I had to say, I'd guess it's a capacitor start motor. I'll read your instructions over this evening when I get home and am in front of the motor with and ohmmeter and see if I can begin to identify the circuits you describe. I intend to run the motor at 120 VAC which is what it was wired for when I took things apart so that should (hopefully) not be an issue. Thanks for you reply. Tom
 

wa5cab

Downloads Moderator
Staff member
H-M Platinum Supporter ($50)
Joined
Dec 25, 2011
Messages
4,493
OK. I see the start capacitor housing now. Missed it early this morning. So it is a capacitor start motor, which today is probably the most common type of single phase motor from about 1/4 horsepower to 2 HP. what I would suggest that you do is to remove all of the wire nuts and any other splices and get rid of all of the short pieces of wire. I can see in one or two of the photos some damage to the insulation on a couple of the wires coming out of the motor. Locate an electronics store that sells to hobbyists and small businesses. NOT one with a bunch of computers and computer accessories for sale. Measure the OD of the insulation on the motor wires with the damaged insulation. Tell the counter person that you need a stalk (on most commonly comes in reels of 50 to 250 feet (which you do not need) and 3 foot lengths. One length is all that you need. Tell the counter person what the OD of the good insulation on the motor wires. And you will need one of their cheapest heat guns (which will not most likely be shaped like a pistol).

Pull the wires with the damaged insulation back into the small original box on the motor and straighten it out. Cut the shrink tubing in 1" lengths I think (only as many pieces as there are wires with damaged insulation, so 6 or less). Mash the damaged insulation back down onto the wire. You may find that you need to trim a little of the frayed insulation off but be careful not to cut any wire strands. Slide one piece of shrink tubing over the wire and center it on the damaged spot. Shrink the tubing. Do the next one, etc.

Examine the six wires and see whether or not two are smaller than the other four. If so, those are probably the start circuit. In any case, ID the wires as I wrote this morning. The start circuit, which consists of the start winding, the start capacitor and a centrifugal normally closed switch, The start circuit wires will show a fairly low resistance when you first connect the ohmmeter leads to them. But as the capacitor charges up, this resistance should increase to at least several megohms.

At the electronics place, also buy some extension cord, #12-3 or #14-3 ,aybe 25 feet for the line cord, which after you have ID'd the wires should run to the switch, not to the motor. And a piece of #14-4 long enough to easily reach from the motor to the switch when they are mounted on the lathe. If the switch is not to be mounted to the lathe but to be on the wall or under the bench, you should buy #14-5 instead of #14-4. The green wire should eventually be connected to the motor frame or to the junction box at one end and to the switch frame at the other. You may need to get this at a place like Ace Hardware of Home Depot. Do the wire identification steps and mark the six wires. Once they are ID'd and marked, pull the wires back into the second box and splice them to the #14-4 or #14-5 cordage, taking note as to what color is tied to what. I would use black and white for the two run windings. At the other end, wire the line cord and the motor cord per the switch instructions for single phase capacitor start or split phase motors and for 120, 115 or 110 V. You may need to install one or two jumpers in the switch.

Be careful and don't get electrocuted.
 

markba633csi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Apr 30, 2015
Messages
3,180
Tom: here is a step by step version of Robert's instructions above: (ignore drum switch until you reach step 7)
  1. Using an ohmmeter identify the start pair of wires: meter should dip and rise each time you reverse test leads. Label start pair 1 and 2 (doesn't matter which is which) note: this is easier with an analog needle type meter
  2. Using ohmmeter identify run windings A and B: should see steady low ohms reading for each pair. Label them A1, A2 and B1, B2
  3. Connect start pair to winding A (1 to A1, 2 to A2) then apply power and note direction of motor
  4. Do step 3 again but substitute winding B for A, note direction of motor
  5. Connect winding A and B in parallel: A1 to B1, A2 to B2 if motor direction same for steps 3 and 4. If different, connect A1 to B2 and A2 to B1.
  6. Connect start pair 1 and 2 in parallel with A and B pairs from step 5 and apply power to verify motor runs properly (direction not important)
  7. Connect drum switch as shown: (swap start pair if motor direction is backwards from desired)
286619
Mark
 
Last edited:

wa5cab

Downloads Moderator
Staff member
H-M Platinum Supporter ($50)
Joined
Dec 25, 2011
Messages
4,493
OK except that I would do three things differently. Label the start circuit leads S1 and S2. Do not label the B winding leads until step 4, which would read something like "Connect the B winding leads to the S leads. If the motor turns in the same direction as in Step 3, label the leads B1 and B2 to match S1 and S2. If it doesn't, label the lead on S1 as B2 and the one on S2 as B1". Ten or twenty years from now, you or the next guy will be glad that you did.

Also, note that not all barrel switches are the same as the one you have. So if down the road you have to replace the switch, either make sure they give you another one that connects the same way or wire it according to the wiring diagram supplied. Note also that some switches that are listed as being for 3-phase motors can't be connected properly for single phase motors.

And finally, if your lathe has a motor ON/OFF switch mounted on the headstock, and if you have either rug rats or knob twiddlers sometimes wandering through your shop, I would keep that switch and mount the reversing switch on the wall or bulkhead behind the lathe. And when you aren't using the lathe, leave the barrel switch in the OFF position. If someone flips the motor switch on, nothing will happen.
 

markba633csi

H-M Supporter - Gold Member
H-M Supporter - Gold Member ($25)
Joined
Apr 30, 2015
Messages
3,180
All good points. And one more VERY important one: Be careful your chuck doesn't spin off when you use reverse
mark
ps Tom your motor pulley looks rather large- you might want to use a smaller diameter one
 
Last edited:

mmcmdl

H-M Supporter - Gold Member
Staff member
H-M Supporter - Gold Member ($25)
Joined
Jan 31, 2016
Messages
1,153
I thought this post seemed familiar , I read it on Craigslist today . Where in Bmore ?
 
[6]
[5] [7]
Top