Love of lathes.

[Retired]

Hi,

Thanks for asking Alan; it will be a four pole motor because the speed is 1,450 rpm. I doubt very much the brushes movement will reverse it thinking as stated previously it might be associated with speed/torque? The easiest way to check is to get the motor running again and test it. Nameplate picture below for you to study.

Kind regards, Col.

   

[Joe]

The speed of an an AC motor is set by the frequency of the supply and the number of pairs of poles.

With DC motors, which is what this basically is, the input voltage effects the speed but it's also determined by the relative strengths of the Armature and Yoke magnetic fields: the stronger the armature field the quicker it goes.

Where a variable control is required it's more practical to strengthen or weaken the field as this has less of an effect on the torque. A rheostat is fitted in parallel with it to divert the some of the current.

Interesting to note that the plate says "Rotor A" though.

Motors with brushes that operate on AC mains are strictly speaking Universal ones which will run on AC or DC. The difference between these and DC only ones is that the armatures and pole pieces are made from laminations to prevent eddy currents - for DC only use they could be solid.

The fact that the supply polarity is changing fifty times a second doesn't matter to the direction of rotation as to change that the connections to EITHER the Yoke or Armature have to be reversed, not both.

I'm surprised just how much of this guff I can remember.

- Joe

[Refugee]

I many years ago found a motor that was a prize find for a teenager. The shaft was the same size as a Meccano axle. The only other was the non reversible BSR record deck motor.
This little DC motor proved to be even better when I took it apart and checked it out as there were two sets of fixings for the brushes and the 15 degrees also comes to mind. By fitting it in the alternate positions gave half speed and double torque but always the same power.
You now have a vintage variable speed power tool there in your workshop.
It is a nice low mileage motor going by the low wear on the commutator. Perhaps those modern sealed bearings will keep the swarf out.
Looking at the quality of the castings and just how little of the old paint is still there I would consider waxing the natural iron so that the quality will remain on display when the restoration is complete.
I can't in any of the photos see what colour the old paint was anyway.

[Alan Douglas]

If the brushes are grounded to the frame, or cross-connected, with no mains connections, it's a repulsion motor. Those were popular here in the 1930s for household refrigeration compressors since they have high starting torque but low starting current (say 1.5 times full-load current). But they were expensive to make. Modern homes can handle the extra starting current of a split-phase or capacitor-start motor.

[Radio Fixer]

What age is it Colin?

Gary

[Retired]

Hi,

Many thanks everyone for your interesting information. I'm not into lots of motor theory and have extremely little knowledge of DC motors so as I've said previously this is a very strange motor for me to come across in my home workshop and most unexpected. Although I worked at Brook Motors for 24 years my knowledge of the electrical side of motors has been learnt on a need to know basis; I actually worked in packing/distribution and the timber departments during my time at Brooks. When I used to ask the motor testers about technical details they always seemed vague on the subject; possibly not wanting me to electrocute myself or more likely because their knowledge of the subject equaled mine after all they spent their full day doing nothing more than hooking motors up to their test panel; this must have been a soul destroying job. Occasionally there would be an explosion as a motor was hooked up incorrectly which used to bring a cheer from the surrounding workers.

When I saw the crude steel strip linkage disappearing into the motor I hadn't a clue what it's function was and as such I had no intention of pushing or pulling the linkage whilst the motor was powered up; it's so easy to cause a lot of damage through ignorance so I played safe and waited until I removed the motor to investigate?

The motor paint colour was black Refugee and I would like to show the quality of the castings off as you suggest but the motor is out of sight to the rear of the lathe so I'll paint it to match the lathe.

Very good question Gary as to it's age. All I can say at this moment is that it is old; there is nothing visible on the motor to date it accurately and even worse I can't find any Lorch lathe of this model so far on the web. Whilst at Brooks I could easily identify any Brook motor from the motor serial number on the name plate giving full details of date and who purchased the motor.

When I saw this motor I knew it would be of interest to forum members hence I added the few details I have of it. As Alan D states these motors must have been expensive to make and for an 1/2hp motor this one is heavy and I bet it will be very sweet running once the new bearings are installed. When I disconnected the motor it was only on two supply leads without an earth but the leads were in conduit so perhaps this is earthed; I'll be looking into this in due course for safety reasons. At the moment I've got my hands full in removing the rust and original paint which is proving very time consuming and a very dirty job.

Both the motor and lathe are worth restoring to full working order; the quality is there for everyone to see and I feel extremely fortunate to have bought this lathe with my sincere thanks to Big Al for tipping me off about it being for sale through eBay. The timing was perfect because I had been saying for a while I wanted a decent sized lathe expecting to pay around £1,200 for a Boxford or similar so when this Lorch suddenly appeared I already had cash on hand and the deal was quickly done. Next time you and Joe visit us Alan you'll be able to have a look at this Lorch in detail and I'm sure you both will be impressed by its high quality.

It's pouring with rain and windy so today is a garage free day whilst I sort out other jobs indoors. Once the new bearings arrive I'll reassemble the motor just to prevent parts becoming damaged and to get it off the bench.

Kind regards, Col.

[Joe]

I was probably one of the last to study DC machines in depth. We were told at the time that it was obsolescent knowledge but we had to do it as it was still on the City and Guilds syllabus. I've certainly never needed to use it. The only time I've undercut a commutator was on a Land Rover starter motor.

- Joe

[Refugee]

The motor would best come up with the most durable easy to clean finish you have to hand.
The machine castings are nice enough to open up the option of a coat of clear wax or lacquer to show them off.
The motor will give the full half horse over the full speed range the brush gear rotation offers and it will be something like two to one.
Then there is another excuse to start the Graduate up again to make spindles with slots turned into them so that once they are built into a rack each gears will fit exactly into its correct slots while they are in storage.

[Alan Douglas]

I did study DC machines in college; there was a full year on large machinery, primarily because the department head taught the course. There were five of us in the class; it was Greek to them but I rather enjoyed it since I had already spent two summers in the repair shop and understood what was going on without having to read books. It was the math part that was Greek to me. Still is, but I didn't have to design them, just repair them.

We had an undercutting lathe in the shop but I never saw it in use the whole time I was there. Far too much trouble to set it up. We used old hacksaw blades, with one end ground into a hook. You pull it back toward you, away from the windings.

[Retired]

Hi,

I'm starting to feel old Joe with all this vintage technology; I can still vividly remember the old magneto/dynamo units on my motorcycles the ones having the fiber gear which would strip its teeth leaving a row of gums; good old days but no money at all then in my pocket.

http://archives.jampot.dk/Technical/Elec...ctions.pdf

The above sure brings back happy memories of my old Norton ES2 500cc bike throwing me gracefully in slow motion over the handlebars if I forgot to retard the ignition before attempting to kick it off; many of these big single cylinder bikes were also fitted with a valve lifter; again I'm showing my age.

Thanks Refugee regarding your suggestions; I'll see what the motor looks like once re-assembled and cleaned before making a decision as to its finish. Good idea to use the Graduate to make spindles with slots but I think the easiest and compact solution to storing these gears is to mount them onto a single upright spindle pyramid fashion as seen in many old pictures.

Strange how I remembered using an hacksaw blade for undercutting the com Alan D; I must have done this years ago because it's coming back to me that an hacksaw blade fitted perfectly into the com slots and as you rightly state the blade was pulled away from the winding's taking care not to let it slip?

I don't want to turn this Lorch into a showpiece because after all I want a working lathe but I do want it to look much better than it did; I don't think an inch thick patina adds to the value when it comes to vintage lathes?

Now where's the sunshine because I want to get stuck into this lathe before another year slips quietly by.

Kind regards, Col.