Thread: Mars Lathe DC motor conversion.

Hi Rob,

Glad to hear all is great! I'm not sure that AC induction motors draw their full current unless they are asked to, ie they get loaded up. I had recently been playing with my VFD and 2.2Kw motor and noticed that running it at 50Hz @ 1490 rpm under no load it only uses 400 watts. The reading was in agreement with an inline power meter which I connected the VFD through. So I could be wrong but I think that AC and DC motors may have that in common. Perhaps Chris can verify or otherwise this.

Cheers,

Simon

Hi Simon,

I'm interested to hear comments on this aspect of the conversion.

It's a point that would be interesting to ponder over.

We need an expert on this sort of stuff

Seeing as Ewan put up a video of his conversion, I thought I would do a quick pan around my poor old lathe for your interest.

CQ9325 Chinese 10 x 18 lathe with DC treadmill motor and KBIC-240 controller - YouTube

Rob

Hi Rob,

I enjoyed watching your video. My lathe conversion (DC or VFD) may come around sooner than I imagined, I was turning down the shaft on my new motor for the mill and the lathe motor nearly died. I'll have another look tomorrow but at last check, the motor needed encouraging before each start up and seems to lack HP. That's just great! I need the lathe to finish the mill and I'll need the mill to work on the lathe! It never rains, it pours!

The motor has been doing some weird stuff from time to time over the last year. Bearing noise every now and again, sometimes it won't start - just humms , sometimes it trips the CB. I just put it down to a cheap Chinese motor. I'm not too worried, I think it will last the distance but will need attention sooner rather than later. It easily justifies the variable speed. I'd never buy a new single phase replacement motor.

Simon

Hi Simon,

My AC lathe motor never ever gave any trouble, and it did a lot of work and got fairly warm over the years.

BUT I have two other Asian motors, one on the pillar drill (Frejoth - maybe Taiwanese) which very occasionally flashes and trips the CB on start up. Not enough to worry about.

And one on my linisher (no name brand - definitely Chinese) which used to regularly flash on start up and trip the CB.

I investigated the linisher and it was the inertia switch was shorting against the cast iron case. A bit of work with the die grinder fixed that.

So maybe it's the same for you in that the inertia switch is sticky or the contacts are burnt, worn.

I get the impression this area is a bit sub par with asian motors.

Never had a cap blow though, on any of my equipment.

Rob

Hi Rob, i did not realize your machine was so small, no wonder you get flex in the post with the 1 1/2 HP you now have.

As far as i know Simon is correct, an ac motor only uses as much as needed to turn over, and will use about 1 1/2 to 2 times the actual rated amount when under full load.

I have done some cold coging tests and even with the IR turned right down i still get it for a few seconds.......it may be that the hard braking is effecting the brushes/commutator???

Hi Ewan,

Yes my lathe is just a baby.

But I flog it mercilessly

Slightly OT did you see the Mars lathe currently for sale on Ebay - called a "Jupiter". Bigger than yours.

I noticed Lathes UK has no info on this model so I contacted Tony Griffiths (web owner) and pointed him to it and some other info on one in New Zealand.

He got back to me and apparently he was pretty pleased and has nabbed the Ebay photos for future use. I've been in touch with him once before about a Russian lathe.

He's always looking to add to his great site.

I've no idea what else would cause the cogging.

Cheers

Rob

OK guys,

Here's a video of my little lathe struttin it's stuff

CQ9325 metal bench lathe with DC variable drive conversion - power demonstration - YouTube

Cheers all

Rob

Hi Rob,
To go a little OT, have you tried running the lathe in rev when you are grinding?

Back OT, I'm going to put together a taco like yours but would like it to run on a 12VAC supply. With the head thats easy as they come in a 12-24VDC version. With the hall sensor I found these
5 Pcs 3144 Hall Effect Sensor Magnetic Detector 4.5-24V | eBay
Do you think they would work or would I be better off using one like yours with a resistor?

Thank you

Stuart

Hi Stuart,

Normally I run the spindle in reverse when grinding, but when I did the video, the lathe DC reverse switch was cactus (I overtightened and broke it doh !) and I've only just fitted the replacement. So I just ground in the forward position as I had the video camera handy.

Reverse is better, but it's not an enormous difference as the spindle speed is not fast in comparison to the 20 K rpm of the grindstone. I sometimes grind both directions at the end of the job very lightly to help remove any hatching marks from the stone.

The quality of the grindstone (grit rating) and correct dressing have the biggest effect.

Idealy I should have gone on and used the wide fine grit stone, but the medium disc was good enough for a drill bit - I just ran it over the wire buff to polish it up.

Ewan is the Hall sensor expert, and those ones look a lot like what he bought. He sent me across a sample but I already had the Ebay one with the LEDs installed so I have yet to try it.

I will use one on my linisher when I can get another treadmill motor. I still have to play around some more with the dud 2 HP one to see what's going on - it's very strange as I spun it over in the drill press and it puts out a steady current, and the commutator seems fine

Maybe there's a high voltage arc or something. Also the armature in that motor is not epoxy coated, so it's not SCR rated. The 1.5 HP is.

All interesting stuff.

Cheers

Rob

Hi

I managed to watch the videos at the library . Looking very good . With the amount of cheap electronics around these days , and some imagination , it's amazing what is possible to make up nowadays .

We bitch about cheap Asian manufacturing standards, but without their cheaper prices, the hobby would not be so much fun these days

Mike

Originally Posted by morrisman

Hi


We bitch about cheap Asian manufacturing standards, but without their cheaper prices, the hobby would not be so much fun these days

Mike

For sure Mike.

I remember when my Dad got a Black and Decker drill in a metal case back in the early sixties and he thought he was made. Everyone one else had the turn the handle jobs that broke more drills than made holes in those days.

Now you can buy quite capable lathes for peanuts. I could have gone a lot larger, but as I mostly do small/ medium jobs the 10 inch CQ is plenty good enough.

We have a monster lathe up the farm (big old 1 tonne flat belt McPherson) but it rarely gets used. Just too much lathe.

We don't know how lucky we are tool wise these days.

Cheers

Rob

For sure Mike.

I remember when my Dad got a Black and Decker drill in a metal case back in the early sixties and he thought he was made. Everyone one else had the turn the handle jobs that broke more drills than made holes in those days.

Now you can buy quite capable lathes for peanuts. I could have gone a lot larger, but as I mostly do small/ medium jobs the 10 inch CQ is plenty good enough.

We have a monster lathe up the farm (big old 1 tonne flat belt McPherson) but it rarely gets used. Just too much lathe.

We don't know how lucky we are tool wise these days.



This might be a brag

My old Hendey lathe can do that magic thread cutting as in Ewans video , and repeat the stopping at a pre determined point , all done with mechanically operated devices e.g., when cutting internal threads , no running into the end of the bored hole and messing up the job .

Yes, even owning a petrol mower was the bees knees , the HG Palmer special

Mike

I have been following this thread with interest and have picked up some ideas for a possible upgrade of the underpowered motor on my Hercus Compulathe, great work by you guys. I have also got the tacho bug and set about fitting one to my milling machine using an inductive sensor, it works perfectly but the flashing digit behind the decimal point is annoying.
I noticed that some have 2 decimal places on theirs so this function must be adjustable somehow but the instructions don't show how, any ideas guys?

Hi Eric,

Your private message inbox is full. I have sent you a link to the scanned KBIC-240 user manual for the controller.

If it has failed to go through, please message me again.

Cheers

Rob