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Switching electric motor rotation direction

DanielHowden

Plastic
Joined
Oct 30, 2019
I have recently bought an old Brimsdown bench top pillar drill. I'm gonna guess that it is around 1960's for the year of manufacture. When I got it the motor pulley was running clockwise and not anti-clockwise as I was expecting. I had a check on the wiring and found that it had be recently wired up - more to the point the wires had been stripped back and refitted as they were clean and shiny. I figured whoever did this wiring job didn't really pay attention to what they were doing and got the wires reversed hence the running in a clockwise fashion.

It did get me thinking though that there is a possibility that I would like to run the motor in reverse when I am dealing with threaded parts and I wondered if anyone could confirm if it is possible to run a switching unit that would indeed allow me to select the direction of travel if I needed to choose.

Thanks for reading, Daniel.

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"...if it is possible to run a switching unit that would indeed allow me to select the direction of travel if I needed to choose."

Maybe. Depends on the motor, but you did not describe the motor.

Tapmatic tapping heads let you tap a hole with a pillar drill without reversing the motor. It is all done with reversing gears inside the head. That is why drill presses usually do not have reversing switches; there is practically no use for one unless the drill was specifically designed with tapping capability.

Larry
 
Daniel,

Welcome to the forum. That's a nice looking setup, and to make it super versatile for most jobs including tapping I certainly would entertain putting a VFD and a small 3 phase motor on it. They really make a drill press shine, variable speed, instant reverse and braking too.

It's just food for thought.

Stuart
 
Daniel,

Welcome to the forum. That's a nice looking setup, and to make it super versatile for most jobs including tapping I certainly would entertain putting a VFD and a small 3 phase motor on it. They really make a drill press shine, variable speed, instant reverse and braking too.

It's just food for thought.

Stuart

Thanks for the comment, I only have single phase so a little stuck with the upgrade.

Daniel.
 
Daniel,

Most manufacturers of frequency drives have many that accept single phase power, and of course output 3 phase, although I'm not familiar with what you have for power on your side of the 'pond'.

Do a little research on VFD's and take a look at some used, 3 phase motors that would fit your machine and you may find the upgrade to be very affordable.

Stuart
 
Just show us the wiring diagram plate, and the pix of the connection box and get on with using it as is....

Some people would put a VFD on the throne if they could.....They find it very easy to spend other peoples money.
 
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Since it is running backwards now, it obviously can be reversed. This does not mean that it will develop full power in reverse as there are some details of motor construction that can have an effect on that. But your motor CAN be reversed.

You do not show or say what kind of motor it is. But there are two general possibilities: it probably has brushes and they will ride on either commutator segments or on solid rings on the rotor. In either case, you can use a low resistance scale on a multimeter to sort out those wires. Just disconnect the wires and check out the resistance between all the combinations. You should find two pairs that have a low resistance reading between them (A to B is low and C to D is low) and when you measure between those two pairs, you should see a very high resistance (A to C, A to D, B to D, and B to D are all high resistance). Then A-B is one winding and C-D is the other. If you rotate the shaft while measuring the coils, one of them will jump around a bit: that one will be through the brushes and it is the one you want to reverse.

Motors with brushes can usually be reversed by reversing the wires to those brushes. That can be done at the connection terminals on the motor or you can extend the brush wires and the terminal wires to a DPDT (double pole, double throw) switch and reverse it there. If you extend them to an external switch I would use a wire gauge that is either equal to the supply cord's conductors or that is at least one size larger than the internal wires in the motor. You would need a four wire cable to run to this switch: such cordage can be purchased from many sources including better local hardware stores, Grainger, McMaster, and electrical supply houses.

And don't be surprised if the motor has less power when running in reverse.
 
Since it is running backwards now, it obviously can be reversed. This does not mean that it will develop full power in reverse as there are some details of motor construction that can have an effect on that. But your motor CAN be reversed.

You do not show or say what kind of motor it is. But there are two general possibilities: it probably has brushes and they will ride on either commutator segments or on solid rings on the rotor. In either case, you can use a low resistance scale on a multimeter to sort out those wires. Just disconnect the wires and check out the resistance between all the combinations. You should find two pairs that have a low resistance reading between them (A to B is low and C to D is low) and when you measure between those two pairs, you should see a very high resistance (A to C, A to D, B to D, and B to D are all high resistance). Then A-B is one winding and C-D is the other. If you rotate the shaft while measuring the coils, one of them will jump around a bit: that one will be through the brushes and it is the one you want to reverse.

Motors with brushes can usually be reversed by reversing the wires to those brushes. That can be done at the connection terminals on the motor or you can extend the brush wires and the terminal wires to a DPDT (double pole, double throw) switch and reverse it there. If you extend them to an external switch I would use a wire gauge that is either equal to the supply cord's conductors or that is at least one size larger than the internal wires in the motor. You would need a four wire cable to run to this switch: such cordage can be purchased from many sources including better local hardware stores, Grainger, McMaster, and electrical supply houses.

And don't be surprised if the motor has less power when running in reverse.

I didn't read anywhere in the OP about "brushes"....He said "1960's"
and the outward appearance of said motor doesn't scream "repulsion induction"
Let's see what the Op comes back with.
 
A single phase motor will probably be reversible, but it won't be the instant reversible you need for tapping. For that you need a three phase motor. Or do as L Vanice suggested and use a tapping head.
 
A single phase motor will probably be reversible, but it won't be the instant reversible you need for tapping. For that you need a three phase motor. Or do as L Vanice suggested and use a tapping head.

I have brought out the starting windings on a few single phase DP's, and added a dpdt switch along with a footpedal.

Tapping is easy, just get off the foot pedal before you bottom out, coast to a stop, and re-engage the foot pedal (switched the dpdt soon after starting, so it's pre set to back up)
 
If reversing a single phase just make sure that that it stops completely or it will just keep running the same direction.
I have used the typical drum switch on single phase to rev direction.

There are instant reversing single phase motors available but are pretty rare on the used market.
 
ok so today I got the drill out of the back of the car and got it upright. I took some pictures of the wiring. I would point out that there is an earth from the switch that runs to the motor chassis but if it is advised that I rewire from the switch to the motor giving a new earth from where this has been cut I will do that.

I would still be very happy about comments regarding tapping with this drill and being able to run the motor backwards to remove the tap from the work piece. I have used a tapmatic tool before - fascinating how they work but they are out of my price range for this project.

The problem that is far higher than running backwards it of course running forwards and even though it did run when it was laying in my car it is not happy to get going on the start cycle as you can see from the video I have attached.

Any advice is always welcome, Daniel.

Link to video - Shared album - Daniel Howden - Google Photos

IMG_20191102_164904.jpg

IMG_20191102_164820.jpg

IMG_20191102_164812.jpg


Edit: following some research on this it seems like it could just be that there is a need to clean the contacts on the centrifugal clutch mechanism in the motor. Does that sound reasonable to anyone?
 
That's a common problem with centrifugal switch contacts so inspect and clean or replace.Actually if never overloaded the start switch is usually the first thing to go in that type of motor.
 
Just show us the wiring diagram plate, and the pix of the connection box and get on with using it as is....

Some people would put a VFD on the throne if they could.....They find it very easy to spend other peoples money.

Well Doug..the OP posted what you requested and I haven't seen you pop in with any sage advice..talk is cheap.

Stuart
 
Well Doug..the OP posted what you requested and I haven't seen you pop in with any sage advice..talk is cheap.

Stuart

V-A-C-A-T-I-o-N....Jeesh.

Look like OP forgot nameplate as requested.

Barring that, look like "lower leads" on the pix are incoming power or "line"
top screws each have qty (2) wires each, note one is smaller on each terminal.

Thinking the thinner (smaller gage) wires are the starting circuit, simple exchange those on the terminals, leaving the thicker (main run winding) wires
connected as they are.

any else ?
 
Barring that, look like "lower leads" on the pix are incoming power or "line"
top screws each have qty (2) wires each, note one is smaller on each terminal.

Thinking the thinner (smaller gage) wires are the starting circuit, simple exchange those on the terminals, leaving the thicker (main run winding) wires
connected as they are.

This is what I was about to post as well. A drum switch can be wired up to reverse the start winding connections to provide forward and reverse. However as previously noted motor needs to be completely stopped before reversing or it will continue on in the same direction until stopped and restarted.
 








 
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