Reversible motor

[Jackrae]

That seems rather a small capacitor to be in the order of 190uF Could you please show a photograph of the information that's printed on it.
It could be that the belts running in one direction tend to slacken away from the drive pulley and decrease the wrap so increasing the belt slip and allowing the motor to get up to speed. In the opposite direction the belts could 'wind up' increasing the wrap on the drive pulley, dereasing belt slip, and hence increasing the start load and preventing the motor getting up to speed.

 

[Jackrae]

If the switch is a Dewhurst type with a centre OFF position as well as Forward and Reverse , it'll have mains in and mains out to run windings plus a pair of starter winding wires, ie a total of 6 wires plus earths.

 

[Munroast]

That seems rather a small capacitor to be in the order of 190uF Could you please show a photograph of the information that's printed on it.
It could be that the belts running in one direction tend to slacken away from the drive pulley and decrease the wrap so increasing the belt slip and allowing the motor to get up to speed. In the opposite direction the belts could 'wind up' increasing the wrap on the drive pulley, dereasing belt slip, and hence increasing the start load and preventing the motor getting up to speed.

as I say, it is rated as a 150µF but my multi meter calculates it as 192. I have little experiance f measuring capacitors so don't know how accurate it is. (I have a spare one rated at 30 which measures at 23!)

It is certainly the belts that's causing a load too great for the motor, but that clearly is a fault somewher, when the motor gets to speed, it is amply powerful. Interesting ly if I configue the belts for the slowest milling speed, it will run, but configured to the fastest speed (which will be more work for the motor) and it fails.

This image shows the switch (i don't know what make it is) and the For/Rev switch is what I would describe as a double-throw. .6 connections. The outer pairs are double wired, so 8 black wires presumably heading to the motor but curiously only 4 arriving (2 blk blu & Brwn) arriving at motor ! where they change over I have no idea.

it's certainly more interestig than a book of suduko puzzles. And I would love to figure it out.
would also like to get it working, its a decent size machine and feels very solid, should be able to remove more metal in each pass than the other mini thing we have.

 

[Jackrae]

There doesn't appear to be a self-tensioning idler pulley so forget the varied slip argument. Your photo doesn't show the reversing switch (or it's jumble of wires) Can you photograph the switch and it's wired connections. Do you have the manual for that particular machine complete with wiring diagram - if so a photo of the wiring diagram woud be useful. That machine presumably uses two drive motors, one for the drill/mill quill and one for the lathe spindle. Do both drive at the same time or is there a motor selector switch system.
I've attached a drawing from a similar type of machine that shows how the reversing switch system is configured for each motor. Whilst yours might not be identical, the drawing may help clarify things for you. You may note that no capacitor is shown on the drawing - it may be considered as being included as part of the V1 or V2 lead within the motor.

 

[Munroast]

the reverse switch is behind that yellow flap.
I haven't ran both motors at the same time, but knowing the wiring I don't see anything to stop that happening. (can't imagine anyone would ever need too) Both motors do share an emergency stop though.

I may not be back down in the workshop till tuesday, wife has other plans for tomorrow. But I will do as you ask and get some detailed images of the wiring behind the switch, and we may have some sort of wiring diagram, its not very good though!

One final thought that makes me wonder if the wiring is a mess. The cover for the belts has a micro switch that prevents the machine being run with the cover off. However if you press the start button with the cover off, the motor just Hums. as if only the starter windings are being disabled. Why does it not dissable the entire motor ? does that seem odd to you?

 

[Jackrae]

Are you sure it's the motor that's 'humming' That safety switch will be part of the system inhibit loop and will drive a master contactor which interupts all the system electrics - typically shown as "K" in the circuit I provided. Some contactors can be prone to humming when energised. However, if the system wiring has been 'played with' anything is possible

 

[conny]

Swap the blue motor lead at U1 with the brown motor lead at U2.
If you haven't damaged the windings then it should run in the reverse direction that it does now.
HOWEVER! If there is some form of mechanical device inside the milling machine, which prevents running the miller in reverse, then the motor will trip out again, (or worse).
Do NOT swap any other wires round at the same time. For clarity, can you tell us which terminals you have your mains incoming leads connected to please?

 

[Munroast]

Are you sure it's the motor that's 'humming' That safety switch will be part of the system inhibit loop and will drive a master contactor which interupts all the system electrics - typically shown as "K" in the circuit I provided. Some contactors can be prone to humming when energised. However, if the system wiring has been 'played with' anything is possible

I will take a more close listen

 

[SimonH2]

If the centrifugal switch (which I haven't got to yet) is so dirty/pitted that it is not making contact.

I doesn't necessarily have a switch. Particularly for small motors, and for application where the poor starting torque isn't a problem, they may have the cap and second winding permanently in-circuit - see Permanent Split Capacitor Induction Motor

One final thought that makes me wonder if the wiring is a mess. The cover for the belts has a micro switch that prevents the machine being run with the cover off. However if you press the start button with the cover off, the motor just Hums. as if only the starter windings are being disabled. Why does it not dissable the entire motor ? does that seem odd to you?

Does seem odd (I would expect a safety interlock to fully disable the system), but there are many explanations.
I had a quick look for a wiring diagram online but didn't find one. Do you have the manual for the machine ? If not, and I have no idea whether it includes the wiring diagram, but I see they are for sale on eBay for not a lot of money.

 

[Munroast]

We did download this

And an image on this page

https://www.aliexpress.com/i/1005003922530643.html

is making me think it does have a centrifugal switch, I am also sure I can hear it engage and disengaging when the motor passes a certain RPM a distinctive click, very notable when slowing down with power off

I do think from the symptoms the contacts on this switch are probably in very poor condition, hence either not getting a reading from this winding or something daft lie 80 meg. Im thinking the voltage manages to jump through this dirt/pitting hence it still starting but poorly?
However, I do think the wiring has been interfered with, possibly to try and get the motor to run clockwise instead of anticlockwise, and obviously this is a concern. (nearly all cutting is done clockwise).

 

[flameport]

Switch K2 changes direction by swapping the connections to the second winding, either LN or NL depending on position.
The cutoff switch JWL2-11 as shown would remove power to both windings (as expected) but leaves the contactor in circuit which could be what the humming noise is.
If the motor makes any noise with the cutoff switch open, then the wiring is wrong.

Suggestions:
Trace out the wiring and confirm it's actually wired correctly
Check the switch to make sure it's actually working as intended (no high resistance or busted contacts)
Rotate the mechanical parts manually in each direction, the effort required in each direction should be similar. If not, it suggests a mechanical problem rather than an electrical one.

 

[SUNRAY]

Switch K2 changes direction by swapping the connections to the second winding, either LN or NL depending on position.
The cutoff switch JWL2-11 as shown would remove power to both windings (as expected) but leaves the contactor in circuit which could be what the humming noise is.
If the motor makes any noise with the cutoff switch open, then the wiring is wrong.

Suggestions:
Trace out the wiring and confirm it's actually wired correctly
Check the switch to make sure it's actually working as intended (no high resistance or busted contacts)
Rotate the mechanical parts manually in each direction, the effort required in each direction should be similar. If not, it suggests a mechanical problem rather than an electrical one.

No, the cut off switch removes all power to both windings and the contactor coil.

 

[Munroast]

by the contactor coil, do you mean the on off switch (KJD11-10D ), When the cut-off switch for the cover is open, on pressing the start button, the motor hums until the button is released. it is not the button that hums
The set up for the lathe motor is siillar, and the motor for that does not hum under similar circumstances.

Clearly there is something amiss! the cutoff switch must only be isolating the start up windings!

Luckily, from the wiring diagram, the lathe motor wiring is the same as the Mill. This should help a lot in sorting this out.

 

[Munroast]

OK, had a bit of spare time today and I am may be a little further forward.

Printed out the wiring diagram and very carefully went through it all, re arranging one or two wires to how it should be. I believe it is all working correctly now. And the cover cut-off switch does now actually isolate the motor. However non of this improved the motors ability to start correctly

So next step was to dismantle the motor and take a look at the centrifugal switch. And I think I have found the problem, although it still doesnt seem to answer all the symptoms

these are the contacts on the centrifugal switch! even pressing them together with my hand I can barely get an electrical contact. It looks like it has been sparking for quite some time

i have now been able to measure the starting winding and it is showing 15 ohms, this compares to 5.8 for the main winding - does that sound about right ?

and here is a shot from further back to show the location of the points

one thing that does puzzle me is; I don't understand why the contacts are open as it is, may be it is an assembly thing, may be they come together when assembled?

I will clean the contacts up (unless otherwise advised) and see if it all works. If it does I will try and buy some new ones, I take the contacts should have a plated finish, that presumably has long been burned off.

 

[Jackrae]

Is the contact on the moving arm missing or is it an optical illusion?