Motor Reverse

[VicParticipant @vic]

I have a Record Power BDS250 belt and disc sander that gets used among other things for tool sharpening. There are times that I feel it would be useful if I could reverse the direction of rotation. I’m aware, or rather have been told that some motors cannot be reversed? Can you tell fairly easily by looking at the motor? I’d like to fit a reversing switch if I can.

Its either this or buy a new reversible belt grinder but it’s best part of £500.

Edited By Vic on 06/05/2020 13:14:40

[VicParticipant @vic]

[Michael GilliganParticipant @michaelgilligan61133]

It looks a decent machine with a properly specified motor: **LINK**

https://www.recordpower.co.uk/product/10-x-6-belt–disc-sander#.XrKqMS_TWhA

[ ndiy should be pleased to see that ]

Can you get a photo of the motor and its rating plate, Vic ?

MichaelG.

[not done it yetParticipant @notdoneityet]

Vic,

Just to use the disc sander? Do remember that belts will need to be reversed if running them in t’other direction, or they may not last long if used the wrong way round.🙂

[VicParticipant @vic]

I’ll see how much of a job it is to expose the motor as I don’t want to have to do it twice. NDIY, I sometimes make my own belts and even with the bought ones it seems to make little difference which way they are run. Having said that I don’t use the old scarfed jointed belts which can only be run in one direction.

[Ian ParkinParticipant @ianparkin39383]

On all my belts for my grinder (2 x 72) i run them both ways cant say I’ve ever had a problem

what difference does a scarfed joint make? What other types of joints are there?

[VicParticipant @vic]

Scarfed joints are the old way of joining belts where they overlap. The modern butt jointed belts are much better and you don’t get the “thump, thump, as the belt goes round. If you’ve ever used both types the difference is obvious.

[VicParticipant @vic]

Sadly there’s no motor plate. The black cable on the left goes to the plug and the NVR switch, the blue cable with the N and L leads connects to two Red wires on the motor and the Capacitor. The other black wire goes between the NVR and the motor. There is no connection box on the motor that you often get.

[VicParticipant @vic]

This is the motor end.

[Les Jones 1Participant @lesjones1]

Assuming that the black cable is the only other cable going to the motor as well as the blue cable to the capacitor then if the black cable is two conductors plus earth then the motor can't be reversed externally. If it is four conductors plus earth then it probably can be reversed externally. If you are prepared to take the motor apart then it may be possible to reverse it. This may involve digging into the end of the winding to get at the point where one end of the start winding is connected to one end of the run winding and to an external wire. the connection between these winding ends would have to be separated and brought out as two separate wires.

Les.

[Pete RimmerParticipant @peterimmer30576]

How is the sanding disc fitted? If it's screwed on it could come undone if sanding on it in reverse.

[VicParticipant @vic]

As seen in the picture there are Five wires going into the motor, the two Red wires, one Earth and I assume a Live and Neutral (black wire) going to the NVR. I’m not keen on taking the motor apart. To be clear I want to be able to run it in either direction at the flick of a switch. The disc is held on with four screws so can’t unscrew.

Edited By Vic on 06/05/2020 22:16:36

[Anthony KnightsParticipant @anthonyknights16741]

Hi Vic. I don't know how you are with electrics, so I've tried to keep it simple. It all depends on whether the motor has an internal centrifugal switch. If it has, it's a capacitor start machine, if not it's a capacitor run motor. The sketch below shows a capacitor run motor. A capacitor start motor would have a switch where I have marked X.

If it is a capacitor run motor it is dead easy to reverse them. Make sure the power is OFF. Dis-connect the live feed from the NVR to the motor and make sure the loose end is well insulated. Run a new live feed from the NVR to the common terminal of a suitably rated 2way switch and wire the switched outputs to either side of the capacitor (one to A the other to B). Operating the switch should reverse the motor but DON'T DO IT WHEN THE MOTOR'S RUNNING. You wouldn't select reverse while you were driving down the motorway.

If there is a centrifugal switch fitted, then I'm afraid you have problems. To reverse the motor you need to reverse the live and neutral connection to ONE of the field coils. This means you would need to open the motor and find the neutral ends of the field coils, separate them and bring them out on individual wires. You would also need a double pole change over switch.

Hope this helps.Anthony

[duncan webster 1Participant @duncanwebster1]

This book explains it all and much more in easily understood language, and it only costs a few quid

**LINK**

[VicParticipant @vic]

Yes that does help Anthony, thank you. I’ve never heard a centrifugal switch clicking in or out but the running abrasive belt is quite noisy. When I get a minute I will remove the drive belt and listen out for the click.

I’ve actually got that book Duncan. The last time I looked at it though it seemed heavy going but I’ll have another look if I can identify what type of motor I have. It’s a real shame it doesn’t have a motor plate or a proper terminal box like the other motors I’ve dealt with.

Thinking back I’ve already replaced the capacitor and the NVR on this machine.

I’ve also in the past swapped a few leads and added a capacitor and switch on a three phase motor on an old mill I had to run it on single phase. I made a diagram for reference, it’s in my V1 album.

[Anthony KnightsParticipant @anthonyknights16741]

Hi Vic. If you have access to a test meter with a low ohms range, you could check the resistance of the field windings. A capacitor run motor would have windings of the same value. The windings on a capacitor start motor could well be significantly different, as the start winding is switched out of circuit when the motor is up to speed.

Using the drawing in my last post, measure live to neutral (first field coil) and point B to neutral (second field coil)

[Author]

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