# DC Motor education



## Woodsmith (Jun 5, 2008)

Hiya and welcome.

that motor looks interesting, and old. It doesn't appear to have a male shaft at the drive end.

I posted some links in another thread that may be of use to you at this stage.
http://www.diyelectriccar.com/forums/showthread.php/probably-stupid-question-39609.html
Look at the links I posted in post 35 and then maybe download the book I posted in post 27. 

Some basics.
The big round tubular part is the case or frame of the motor.
Inside it you will find a laminated steel construction with copper wire coils. these are the field coils or windings and they generate the magnetic field around the motor. Show us a photo of the copper wire in the windings so we can see how big they are.

The long part with the bearing on each end is the armature.
The chunky part in the middle of it is made of steel laminations with copper wire coils, these are the armature coils or windings. These generate a magnetic field on the armature.

The end of the armature has some copper strips. These are the commutator bars. They are connected to the windings on the armature, one winding to a pair of comm bars. This is where the electricity is connected to the spinning armature. Show us a photo of the commutator bars with a rule for scale and also tell us how long and wide they are and how many there are.

The carbon blocks are the brushes. The electricity passes through the brushes and into the commutator. As the armature spins the brushes make contact with a pair of comm bars in turn energising a winding in turn.
You motor shows four brush boxes, the brass boxes that the brushes are fitted into.

I hope this helps for now.


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## TheConverted (Jun 20, 2009)

Mate, thanks for the quick reply, and that link, I did do a limited search on this forum. And thanks for explaining all the parts too, starting to make sense. Is it a Series wound DC and 4 or 2 pole, not that I know what these terms mean. Could you(or others) explain? It has 2 terminals, labelled A and AA.

Yeah, the motor looks old, Im guessing from the 70s but who knows. I had no luck finding any info about it online. Any one recognise it? It was fairly easy to pull apart and reconstruct again, ideal for a home mechanic like me.

It is a female splined shaft, however, reasonably large in diameter. I will take more pics and post the relative size of the commutator bars. Will this indicate some proportion to its maximum power handling capabilities? Or does the size and number of the brushes indicate this too?

Keep smiling,
Moe


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## Georgia Tech (Dec 5, 2008)

This is an Ole Pump motor...
What was said in the previous post was the basics...have you have any further questions for more details ask and we will be glad to answer...


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## TheConverted (Jun 20, 2009)

I counted the commutator bars at 45 and they measure 7cm long by 7mm wide. What does this mean??


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## Woodsmith (Jun 5, 2008)

It should be a reasonable motor to use with the exception of the female shaft. That could cause you problems with coupling it. It would help if you had a male shaft to connect to it. Reshafting it may make it non viable economically but it depends on what you want to do with it and what you need it to be able to do.

Hopefully some motor experts may come along and offer some more useful information.

I am still learning my way around DC motors.


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## TheConverted (Jun 20, 2009)

I dont think the coupling is going to be an issue with me, the GTV has a transaxle, meaning the gearbox is part of the differential, so the electric motor will directly couple to the prop shaft(tailshaft). The prop shaft bolts up to the flywheel (which will not be used) with 3 bolts. 

I really need some good advice on this DC motor to determine if I should go ahead and start making the adaptor plate and the coupler.

Any Dc motor gurus, please help.


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## major (Apr 4, 2008)

TheConverted said:


> Is it a Series wound DC and 4 or 2 pole, not that I know what these terms mean. Could you(or others) explain? It has 2 terminals, labelled A and AA.


Hi Moe,

Not sure how you determined it is series wound. Mind giving me you rationale? From the pictures, which are not real good, it appears to have some field jumpers which make me wonder if it ain't compound. Seeing as how it has an internal spline, likely it is a pump motor, and a lot of those were compound.



> Im guessing from the 70s but who knows.


Old motors are cool  Just dirty and in need of TLC.



> Any one recognise it?


Well not in particular. But it looks like a thousand of other forklift pump motors I've seen. Nothing wrong with that. EDC made some good ones.



> It is a female spline shaft, however, reasonably large in diameter. I will take more pics and post the relative size of the commutator bars. Will this indicate some proportion to its maximum power handling capabilities? Or does the size and number of the brushes indicate this too?


Yes, no, well maybe  It appears to have 8 total brushes of decent size. Just not all intact  Get a new brush set and springs if needed. Can't tell from here, but comm may need turned and undercut. The whole thing needs some professional care. It may not be shorted or otherwise inoperative, but pretty damn ugly. 

Don't get me wrong. Could be a real sweet EV motor. From what I see, every bit as good as a Warp9. 

Regards,

major


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## major (Apr 4, 2008)

TheConverted said:


> and 4 or 2 pole, not that I know what these terms mean. Could you(or others) explain? It has 2 terminals, labelled A and AA.


Sorry Moe,

Forgot  It is a 4 pole motor, 2 south and 2 north. That would be those steel "shoes" inside the field coils attached to the outer frame. Two terminals means that it is a unidirectional motor. It rotates CW or CCW, regardless of the electrical polarity connected to the 2 terminals. Pumps only worked in one direction of rotation, so pump motors were made unidirectional. Hopefully it is the rotation direction you need. Otherwise some internal motor wiring mods are needed.

Regards,

major


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## Big-Foot (Jun 8, 2008)

What determines the Voltage Rating of a Motor? IE 36v, 48v, 72v 


What happens if you run a 36v motor on 72v?


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## major (Apr 4, 2008)

Big-Foot said:


> What determines the Voltage Rating of a Motor? IE 36v, 48v, 72v


Hi foot,

The nameplate, I guess. DC motors are designed for particular applications, meaning particular supply voltage. That does not mean you can not run that motor at different voltage than the name plate. But it will perform differently. And may or may not survive. You basically have to know what you're doing 



> What happens if you run a 36v motor on 72v?


It depends on what type of motor it is. If it is a series or PM motor, double the voltage, you double the RPM and power at a given load.

Boy, there has been a lot of talk about this on the forum here. Did you run thru any searches or nose around?

Regards,

major


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## TheConverted (Jun 20, 2009)

Thanks for the info Major and others, lot to think about and some tested needed before I go further with my conversion with this motor. Having said that, it does feel like a nice heavy duty motor that is capable. 

The broken brushes, I have located a local manufacturer to replace them for me. The springs are a simple design and have plenty pressure.



> Not sure how you determined it is series wound. Mind giving me you rationale?


Sorry about the bad punctuation, should have added a '?' at the end of my question. I wasnt indicating that it IS a series wound motor, rather asking if it was a series wound motor.

So this motor if connect to a voltage supply will only spin one way, regardless of the polarity connection? Because I dont have any spare batteries laying around, could I use a 12 volt car battery charger to test the motor, to see which direction it will turn???



> Can't tell from here, but comm may need turned and undercut


Can you please explain what this means and its effects on functionality and/or performance??

Keep smiling,
Moe


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## major (Apr 4, 2008)

TheConverted said:


> So this motor if connect to a voltage supply will only spin one way, regardless of the polarity connection? Because I dont have any spare batteries laying around, could I use a 12 volt car battery charger to test the motor, to see which direction it will turn???


Hi Moe,

If it does in fact have only 2 electrical terminals, it is unidirectional. And yes, you can use a 12 volt battery to test it, if still has at least one good brush per box. Actually you should not use a higher voltage to test an unknown motor at no load. You'll draw an arc when you close (or open) the circuit from the battery to the motor. And the motor, if it turns, will tend to roll as it speeds up. So use some blocks to secure it.



> Can you please explain what this means and its effects on functionality and/or performance??


This is a reconditioning of the commutator surface. Done on a lathe. The copper comm surface has to be smooth and true. If not, it may work but can spark a lot and wear out your new brushes real fast. Comm reconditioning is recommended when replacing brushes as a rule. An expert could look at it and decide differently.

Regards,

major


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## TheConverted (Jun 20, 2009)

Thanks again Major, starting to make some sense....

Regarding testing the motor to see which way it spins, will it be ok with a 12v car battery CHARGER? I understand about the sparking/arching issue with high current draw. I will getting new brushes for it before I do the test.

Interesting to know that about the commutators needing finishing off. Im guessing any compotent machinist can handle this job?


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## electrabishi (Mar 11, 2008)

major said:


> This is a reconditioning of the commutator surface. Done on a lathe. The copper comm surface has to be smooth and true. If not, it may work but can spark a lot and wear out your new brushes real fast. Comm reconditioning is recommended when replacing brushes as a rule. An expert could look at it and decide differently.


If the commutator is not in too bad a shape you could also apply a comm stone to it. Comm stones are also used to seat in new brushes. That means that when you get new brushes they are either square or only partially rounded. If you apply a semi abrasive material to the commutator while its spinning it 1.) smoothes the commutator out some and 2.) wears the brushes so they are rounded and follow the contour of the commutator. This increases the surface area the brush makes contact with the commutator bars. If the brush is designed to span multiple comm bars (to increase the current the motor can handle) it may not span them fully if not seated. a fully seated brush will be rounded from leading edge to trailing edge.

Stones look like this http://www.graybar.com/webapp/wcs/s...10001&langId=-1&searchCrumbs=++brush++seater;


Mike


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## TheConverted (Jun 20, 2009)

Surely over time the new brushes will bed in to the commutator?


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## Vanquizor (Nov 17, 2009)

Thats the slow way to break them in... just be extra nice to the motor, or run them in on the bench with low voltage for several hours.


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## Guest (Dec 24, 2009)

Not sure if the 12 charger has enough amps to run the motor with out damaging the charger. Try putting the charge on the highest amp output before hooking it up to the motor. Be sure the motor spins real smooth too. You will be putting lots of stress on that charger so be careful. If you blow your charger you have no way to recharge your car battery. I'd suggest you hook it up to your car battery for a short test rather than your charger. Then use your charger to recharge your battery. That way you test the motor and still have a car battery and charger for future use. 

Pete 

PS Get some real good photos of the comm and just everything and post them. Good and close up photos are nice. We all love photos and it really helps us trouble shoot.


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## TheConverted (Jun 20, 2009)

Ok, here are some better pics of the commutator. Having a good inspection, they are nice and smooth and no real ridges as such.

What do you blokes think?

Oh! Why are the other bars angle? The ones above the commutator bars.


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## major (Apr 4, 2008)

TheConverted said:


> Ok, here are some better pics of the commutator. Having a good inspection, they are nice and smooth and real ridges as such.
> 
> What do you blokes think?
> 
> Oh! Why are the other bars angle? The ones above the commutator bars.


I don't see any problems there. The angle? That is called skew. It is done on the core or the steel part of the armature to lessen cogging and noise.

major


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## electrabishi (Mar 11, 2008)

TheConverted said:


> Thanks again Major, starting to make some sense....
> 
> Regarding testing the motor to see which way it spins, will it be ok with a 12v car battery CHARGER? I understand about the sparking/arching issue with high current draw. I will getting new brushes for it before I do the test...


Send us a pic of the brushes. With a commutator that looks that good you may be able to just use the old brushes. It would save you lots of time re-seating new brushes if the old brushes are still good 

Mike


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## electrabishi (Mar 11, 2008)

TheConverted said:


> Thanks again Major, starting to make some sense....
> 
> Regarding testing the motor to see which way it spins, will it be ok with a 12v car battery CHARGER? I understand about the sparking/arching issue with high current draw. I will getting new brushes for it before I do the test...





electrabishi said:


> Send us a pic of the brushes. With a commutator that looks that good you may be able to just use the old brushes. It would save you lots of time re-seating new brushes if the old brushes are still good
> 
> Mike



Sorry, I just read back and saw where you mentioned the brushes were broken :-(


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## TheConverted (Jun 20, 2009)

Thank you again gentleman. 

Before I start building an adaptor plate and a coupler, I will re-assemble it with the good brushes and test it to see which way it turns with a run down car battery with some charge in it.

It would be very interesting to compare to other motors others have pulled apart. Anyone have pictures of motors they have pulled apart? If so, please feel free to post on this thread.


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## Big-Foot (Jun 8, 2008)

major said:


> Hi foot,
> 
> The nameplate, I guess. DC motors are designed for particular applications, meaning particular supply voltage. That does not mean you can not run that motor at different voltage than the name plate. But it will perform differently. And may or may not survive. You basically have to know what you're doing
> 
> ...


Hi Major,

Thanks for your response.. Yes - I did do some searches here but I did not find the answer.

So to put it another way -

What would I do different to engineer a 72v motor vs. 36v motor? 

Is the copper in the field / armature windings larger on one vs. the other?
Would there be a "rule" to use something like 1mm wire for 36v and 2mm wire for 72v? Or would it be in the number of turns?
Or ??

-------

BTW - That commutator looked very nice. I've rebuilt a lot of generators and we used a small lathe and then crocus cloth to polish. Then wrap 400# sand paper around the commutator to ARC IN the brushes (these are carbon brushes on a generator and quite soft).. We would use the same lathe to do 12v starter motors. 
One other thing we did was to use a small circular saw (maybe 1/2" in diameter to my aging memory) to cut a small relief between the commutator strips about 1/16" (1.5mm) deep. I was never too sure why we were told to perform that operation but it was the step between lathe and polish of the commutator. 

------


Thanks one and all - and Happy Holidays!


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## major (Apr 4, 2008)

Big-Foot said:


> What would I do different to engineer a 72v motor vs. 36v motor?


Hi Foot,

O.K. So you have the same output requirements for a motor and use the same core (steel parts) and want to know the difference between what a 36V and 72V design would be. The 72V motor would require half the current as the 36V design for equivalent output. So the 72V design would have twice the number of turns using wire which is half the cross sectional area as the 36V design. The total copper mass of the 2 designs would be equal as would the efficiency. 

The above does take in to account the commutator and brushes, which may need to be altered in changing voltage. And for a change of a low to moderate power motor from 36 to 72V, the same comm gear could probably be used. But with higher power and higher voltage machines, this may not be the case. They may require addition of interpoles and/or an increase in the number of commutator segments.



> One other thing we did was to use a small circular saw (maybe 1/2" in diameter to my aging memory) to cut a small relief between the commutator strips about 1/16" (1.5mm) deep. I was never too sure why we were told to perform that operation but it was the step between lathe and polish of the commutator.


This is called undercutting. Done to insure the turning operation has not exposed any mica and to clean any drag or chips from the slots.

Regards,

major


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## Guest (Dec 28, 2009)

SamsonReen,

Check out the PDF Motor Book for your information. It will keep you busy for some time. Enjoy.

Pete 

http://greenev.zapto.org/electricvw/Electric_VW/PDF_Books.html


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## Amberwolf (May 29, 2009)

SamsonReen is a spammer. Originally all his posts had "happy new year" for the signature, and now is a link to car insurance.


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## Guest (Dec 29, 2009)

Oooop's my bad. Forgot to even look at that. 

Thanks

Pete


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## Amberwolf (May 29, 2009)

It probably still said happy new year when you replied, and only got changed later....


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## Guest (Dec 29, 2009)

Yeah, but life goes on and my conversion keeps getting better. Installing a new cooling fan for my Ghia and it is an original VW part. It is the fan from a newer VW Bay Window bus. Has two out sections but only one needs to be used for now until I can get me a heater core setup for winter heating. I am going to go forward with my install of my NiCad batteries too. Just found that my Quick Charger charges them well and without tons of gassing either. I am well pleased with that. I am going to also install my quickcharger as well. I have just had it sitting in a fair location. Now I want to perm install the charger. I am also building some aluminum side panels for the inside and engine compartment. I want it to look good. New adjustable beam is on the list too. I have lots to do and since I am off from work for a couple more weeks and I am able to now do some work around the place I am going to get as much done as possible. My foot is healing quite well. 

Pete


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## TheConverted (Jun 20, 2009)

OK gents, after a few trial and error sessions, it all went back together ok. Even with a couple of brushes missing, it spun without any issues, and spun the correct way, anti-clock wise looking at the female shaft. Which is clock wise if it was mounted on the the bellhousing and in the engine bay looking at it from the front of the car. 

My understanding is that it will need to be ADVANCED to handle higher voltages than it was designed for. And I have no idea what voltage this motor is designed for, I can only assume 48V, but it is a big motor, so maybe 72V. 

I am going to make the assumption that by turning the end plate of the motor is how one advances the motor, see pic below. Is my assumption correct? And how many degrees will it need advancing?


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## Guest (Jan 8, 2010)

If the brush plate is attached to that end plate then yes. If not then it's the brush ring you want to move. 

You need to go to Jim Husted's site to have a look about advancing. It is just a quickie but says it all. 


Pete


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## TheConverted (Jun 20, 2009)

Yes, the brush assembly is attached to the end plate with those 4 bolts you can see on the end plate.


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## TheConverted (Jun 20, 2009)

I priced some replacement brushes from a local manufacturer today, and got abit of a shock, AU$44 each. 

The size of each brush is; 

25mm wide, 30.3mm used length, 12.4mm thick 

Is this reasonable? Does anyone have a cheap supplier of brushes?


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## Guest (Jan 15, 2010)

I'd have them recheck that quote. Maybe that amount for the set but not each. Not sure where. Never actually priced a set of brushes but I would not think they'd be more than that quoted price for a set. If it's for a set the price is fine. 

Pete


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## TheConverted (Jun 20, 2009)

Unfortunately it is AU$44 EACH, or AU$350 for the set of 8....:-(


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## Amberwolf (May 29, 2009)

Sounds like you could go motor hunting and find a scrapped motor with good brushes but some screwed up bearings or windings or something for that price.


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