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wiper motor brush length


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I'm rebuilding a couple of wiper motors, the original and a spare. I bought some brushes from the hardware store that are the correct size to fit into the brush holders but they are too long. I wonder if anyone knows what the approx length should be for this motor ?. Looking at images online they could be anywhere from 3/8 to 1/2 inch. The new brushes are contoured at the end to match the commutator.

 

Stan

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1/2in is too long. 3/8in is about right.

About as much sticks out as the "cup" is deep.

https://flic.kr/p/nfejv8

 

The arms will be about parallel to each other.

https://www.flickr.com/gp/90670218@N04/a4D1cT

 

Reduce with a coarse file. Don't try too hard it goes away quickly.

 

Check for corrosion on the spring.

Edited by AlanT
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Be Aware

 

The carbon of carbon brushes is a different 'Hardness & Grade' for whatever voltage/speed motor/commutator diameter it is intended to be used with - or so I was told by Morgan Crucible the carbon brush makers 25 years ago when resourcing the TR wiper motor brushes.

 

I have no idea where the repro ones come from these days. - China, Turkey or India certainly sound like reasonable guesses.

 

http://www.morganadvancedmaterials.com/products/carbon-brushes

 

Cheers

Peter W

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Here we go again.

 

I have original carbons in 1950's packaging.

They are loaded with copper dust and have a lower-resistance than the modern ones.

They are also harder.

 

The soft repros run fine. There is not enough resistance to really matter. But they won't run as long I think.

But the originals run for years and at least 50K miles I guess.

 

So its a mtter of checking the brushes more often. Fortunately this is easy to do without removing the motors.

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The brushes were easy to trim to length with a file and I will test the motor later today. One more question.. one of the motors had a strip of insulating material that is shaped to straddle the brushes, the other did not. Did some motors get them and others not (these are both DR2's but they are not identical) ?. Also where should this insulator be placed, it just fell out when I took the motor apart and I didnt see where it came from.

 

Stan

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The insulator strip as far as I could work out is there to be sure the metal wiper brush holders do not drop loose in the motor casing, causing a dead short, if the squeezer spring or its fibre tabs break. I have come across broken fibre tabs over the years.

Cheers

Peter W

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The insulator strip as far as I could work out is there to be sure the metal wiper brush holders do not drop loose in the motor casing, causing a dead short, if the squeezer spring or its fibre tabs break. I have come across broken fibre tabs over the years.

Cheers

Peter W

 

cool, thanks. That makes sense. I see that one of my little fiber tabs is looking a bit worn now that you mention it. No wonder the brush kits for this motor include the whole shebang as by the time the brushes have worn out the spring and it attachment tabs are probably getting tired too.

 

Stan

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Goes under the nylon plate. Is not "wonderful" at retaining the arms. They get lost and the motors seem to carry on OK.

 

The early DR2 have screw terminals. later ones push on spades.

 

There are two kinds on parker cap and the gear-wheel must be chosen to suit.

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The main difference between my two motors is that one has the spade terminals integrated into the unit with the ground terminal under one of the body bolts while the other one has the spade terminals screwed to posts and a dedicated mounting location for the ground terminal. Perhaps this latter design allowed for screw or spade terminals to be used depending on the application.

 

Stan

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Thats typical. The screws in the terminals often break off.

 

https://www.flickr.com/gp/90670218@N04/56631f/

 

If the wiper arms jam with a DR2 the gear arrangements make it more likely to burn out the armature.

These are hard to find.

 

The last photo is a thermal trip for the DR2 which protects against this.

 

A DR3A also benefits from one of these but the often survive after a fashion by "skipping" the gear teeth.

Edited by AlanT
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