# DC Series Wound Motor - Brush Advance Issue



## major (Apr 4, 2008)

Start from the original factory position for the brushes relative to the motor frame. This is typically lining brush to comm contact patch to the bolts in the frame holding the pole shoes in place. From there rotate the brush holder assembly only 4-7° mechanically. That's four (4) to seven (7) degrees. Not far at all.

Sounds like you're going way too far like 45°. Have you run the motor in your application yet? Why do you think you need to advance the timing?

major


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## Squidlings (Aug 1, 2019)

From the left of each brush there is a bolt, that is where the brush originally was. I've moved each brush around 11mm to the right. (should I have gone left?)

brush advance so I can push higher volts and amps to the motor and avoid arching on the commutator.


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## Squidlings (Aug 1, 2019)

I think you think the brushed were originally where the big arms are on the comm end. But if you look inside the blue disc, they were on the smaller arms.


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## Squidlings (Aug 1, 2019)

No ive not connected the motor to the transmission. I dont have a controller yet. But i have a 48v curtis on order to play with...which obviously wont require the brush advance. However im planning to buy a 144v 500amp controller.


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## Eddie49 (Dec 6, 2018)

Apologies for these rather basic questions/suggestions:

- are all of the brush holders insulated from the "7 inch tile cutter disc" ?
- the bare thick copper wire that joins diagonally across the motor power connectors could be shorting to the allen bolt in the centre
- the angle of the armature wires to the commutator bars, known as skew, is to prevent cogging
- advance, whether left or right, would mean towards the original direction of rotation of the motor

Without load, I would not expect the motor to draw more that a few tens of amps, not enough to set your batteries on fire. Perhaps a clamp-on meter that can measure DC current would be useful for your project. E.g.:
https://www.ebay.co.uk/itm/MASTECH-...C-Digital-Clamp-Meter-Multimeter/283492976019


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## Squidlings (Aug 1, 2019)

Good question maybe you are onto something. The brushes are on a brown leather type substance so yes they are insulated on normal use. However they held onto the brown material with 4 rivots which now im thinking about it are touching the metal disc i made which would be causing a short... hmmmm its to late for me to try now but youve given me a great idea there! Thank you so much.


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## Squidlings (Aug 1, 2019)

Very strange...the ebay listing you sent is from Stockport....i live 4 miles from stockport.


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## Squidlings (Aug 1, 2019)

Regarding the copper wire touching the allan bolt/screw. You could be right, however ive had it working with that in place before i did the brush advance. Ill keep it in mind. Keen eye you have!

Ill slide some plastic under the rivets tomorrow to prevent the short and test it.


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## major (Apr 4, 2008)

I took another look at the photos. 










See the 4 slots on the outside flange. These should provide enough adjustment for position of brushes. 

major


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## Squidlings (Aug 1, 2019)

Eddie49 said:


> Apologies for these rather basic questions/suggestions:
> 
> [*] 1 - are all of the brush holders insulated from the "7 inch tile cutter disc" ?
> [*]
> ...






Eddie49 said:


> https://www.ebay.co.uk/itm/MASTECH-...C-Digital-Clamp-Meter-Multimeter/283492976019


Eddie!! You nailed it, it was the rivets which were causing a short on the tile cutter disc I'd added. Man...to see her spin was sooooo good. I made a video but I can't upload it here due to the size!!!

So chuffed!!! I also bought the ebay link amp multimeter. 

Funnily enough, now the brush advancement is complete, when I put the connection on the battery, there is much less sparking when contact is first made. 

Thx Major for your input too!!! I think on this occasion Eddie understood what I'd done but I can see from your point that it isn't easy to see the original place where the brushes were.


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## Squidlings (Aug 1, 2019)

I'm going to try the amp reader to see how many amps it uses on 12v with and without the brush advance. Hmmm I suppose I need a way to find the max RPM of both as well?

I'd like to know if the motor is more efficient with the brushes in their normal position otherwise why wouldn't all manufacturers just make them with the brush advance? It'd make sense right?


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## major (Apr 4, 2008)

Squidlings said:


> I'm going to try the amp reader to see how many amps it uses on 12v with and without the brush advance. Hmmm I suppose I need a way to find the max RPM of both as well?
> ...


That won't indicate what you're looking for. The only way is direct observation of commutation under load at voltage, which means going fast uphill or acceleration near top speed. Anymore this doesn't mean climbing under the hood while your buddy drives. You can do it with a cell phone camera or such.



Squidlings said:


> ...
> I'd like to know if the motor is more efficient with the brushes in their normal position otherwise why wouldn't all manufacturers just make them with the brush advance? It'd make sense right?


Typically brush advance makes some difference in efficiency but not always the same in magnitude or direction. And it is usually just a percent or two. This depends on the particular motor design, degree of advance, load, speed, comm and brush seating and phase of the moon. So in a nutshell, advance vs efficiency, within reason, is negligible. 

As far as OEM advance on DC motors: Reversible series wound, or SepEx, are most likely intended for traction applications where forward/reverse is a 50/50 proposition. Since advance depends on rotation direction, they set it to neutral. Some, on some unidirectional motors, like pump drives, will in fact advance. 

Advance will lower the torque per amp. At a particular current value, on a 4-pole motor, you can roughly estimate a 2% torque loss for every 1° shift mechanically. A 45° shift yields zero torque (100% reduction) and a 90° shift results in full torque in opposite direction of rotation.

It didn't appear you did this, but before disassembly, one should stamp the radial alignment of the end bell to frame location with a steel chisel. Figure the linear length per degree for the bolt circle of the fasteners of the bell to frame. Rotate the entire bell wrt frame and reattach using the slots or drilling new threaded holes in the frame. 

Remaking the brush holder attachment plate is a ton extra work and plagued with problems.

major


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## Squidlings (Aug 1, 2019)

Wow Major, that's taught me a ton. So I'll be losing torque but ill be gaining a motor able to take more power, if I understood correctly.

I'm not trained and made markings which I understood, it'd be nice to know how the experts do it. Did you learn via experience or university?

I didn't want to make a brush holder disc, but there wasn't any other way I could do the advance...I'll see if I can find a pic of the comm end without the disc. You'll understand why I did the disc.

There we go, I've found a pic which shows my first attempt. Originally, there is no disc, the brushes are bolted directly into the legs. It was a pain and all the other examples I've seen, they all had a simple disc.

I've bought a cheap curtis, 48v 500amp sepex motor controller. Just to mess around with  Ill be posting some questions about that tomorrow


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## Duncan (Dec 8, 2008)

Squidlings said:


> Wow Major, that's taught me a ton. So I'll be losing torque but ill be gaining a motor able to take more power, if I understood correctly.
> 
> I'm not trained and made markings which I understood, it'd be nice to know how the experts do it. Did you learn via experience or university?
> 
> ...


Hi 
Throw away your modifications - put it all back together as standard

AND THEN just use the slots to advance the whole end cap - which will advance the brushes


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## Squidlings (Aug 1, 2019)

Duncan duncan duncan, if i wasnt so angry with myself right now id show more appreciation to your post... ill reply once ive calmed down.


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## Duncan (Dec 8, 2008)

Just a thought

I went through all this about 8 years ago - I've just remembered something

The armature is bloody heavy - when I was doing all of this faffing about with the brushes I think I damaged one of the "wires" on the armature

At least that is what I blamed when I blew my motor last year!

So when I did my "new motor" I used a hoist and cut a hole in my workbench for the drive end so that I could work by lifting everything along the axis of the motor 

Major (the expert) reckons 2% initial torque loss per degree - I used 8 degrees so 16% drop in torque

And that is just about what it feels like as that torque comes back as the motor revs rise 

I am being cruel to my motor
1200 amps and 340 volts


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## Squidlings (Aug 1, 2019)

Yes, I'd like that controller very much!!!  But it's a P and S isn't it? They don't make them anymore and I don't think I'm the man to build one just yet.


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## Squidlings (Aug 1, 2019)

wouldn't mind seeing some pic's of your setup if you'd be kind enough


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## Duncan (Dec 8, 2008)

Squidlings said:


> wouldn't mind seeing some pic's of your setup if you'd be kind enough


https://www.diyelectriccar.com/foru...dubious-device-44370p15.html?highlight=duncan

This is my "device"


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