Longevity of Carbon Motor Brushes

[Chris F.]

Don't know if this is the right NG for this or not, but here goes. I've
got a pair of old Kalart-Victor movie projectors (16mm) that I've been
restoring over the past few weeks. Both are from the model 70 series, made
in the late 40's or early 50's. They mostly just needed basic mechanical
repairs - belts, lubricants, etc. Other adjustments, such as shutter timing
and sprocket protrusion depth (how far the two spikes penetrate into the
sprocket holes) were somewhat harder. The motors in particular are an area
of concern. The motors spin at a very high RPM, necessary for the fan to
cool the 1000-watt projection bulb. The motors have brushes which are easily
removed by unscrewing two plastic clasps. The original brushes aren't in too
bad shape, both are about 1/2" long, though one set is just slightly shorter
than the other (more wear on the machine, I assume). I wanted to replace
them with new ones just as a precaution, as I intend to eventually sell one
if not both of the machines. But I could only find company, in California,
that could custom-make these brushes. And at a hefty fee - the setup charge
alone would be up to $60. Not worth it considering I can only get about $100
apiece for these projectors. My question is this; how long could the
original brushes be expected to last, under normal conditions? Are they
reliable enough to sell the machines as working?
Thanks.

 

[Sam Goldwasser]

Don't know if this is the right NG for this or not, but here goes. I've
got a pair of old Kalart-Victor movie projectors (16mm) that I've been
restoring over the past few weeks. Both are from the model 70 series, made
in the late 40's or early 50's. They mostly just needed basic mechanical
repairs - belts, lubricants, etc. Other adjustments, such as shutter timing
and sprocket protrusion depth (how far the two spikes penetrate into the
sprocket holes) were somewhat harder. The motors in particular are an area
of concern. The motors spin at a very high RPM, necessary for the fan to
cool the 1000-watt projection bulb. The motors have brushes which are easily
removed by unscrewing two plastic clasps. The original brushes aren't in too
bad shape, both are about 1/2" long, though one set is just slightly shorter
than the other (more wear on the machine, I assume). I wanted to replace
them with new ones just as a precaution, as I intend to eventually sell one
if not both of the machines. But I could only find company, in California,
that could custom-make these brushes. And at a hefty fee - the setup charge
alone would be up to $60. Not worth it considering I can only get about $100
apiece for these projectors. My question is this; how long could the
original brushes be expected to last, under normal conditions? Are they
reliable enough to sell the machines as working?

Carbon motor brushes do not wear much as long as the commutator isn't
damaged and the motor is running normally. Don't worry about it.
1/2" is a lot of brush, probably almost like new.

And, you can take stock brushes and file them down if need be.

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[gothika]

Don't know if this is the right NG for this or not, but here goes. I've
got a pair of old Kalart-Victor movie projectors (16mm) that I've been
restoring over the past few weeks. Both are from the model 70 series, made
in the late 40's or early 50's. They mostly just needed basic mechanical
repairs - belts, lubricants, etc. Other adjustments, such as shutter timing
and sprocket protrusion depth (how far the two spikes penetrate into the
sprocket holes) were somewhat harder. The motors in particular are an area
of concern. The motors spin at a very high RPM, necessary for the fan to
cool the 1000-watt projection bulb. The motors have brushes which are easily
removed by unscrewing two plastic clasps. The original brushes aren't in too
bad shape, both are about 1/2" long, though one set is just slightly shorter
than the other (more wear on the machine, I assume). I wanted to replace
them with new ones just as a precaution, as I intend to eventually sell one
if not both of the machines. But I could only find company, in California,
that could custom-make these brushes. And at a hefty fee - the setup charge
alone would be up to $60. Not worth it considering I can only get about $100
apiece for these projectors. My question is this; how long could the
original brushes be expected to last, under normal conditions? Are they
reliable enough to sell the machines as working?
Thanks.

the original brushes should be ok.
However you should be able to get replacement brushes fairly easy,
most electrical hardware made that far back used off the shelf
standardized components.
I do remember those model projectors tho' it's been more than 35 years
since I've seen any in use.(I did camera repair during my service
days.)
You didn't mention the actual diminsions of the brushes. They could be
crossed to newer ones using better materials.(straight carbon is
almost never used these days.)
If you can't get the same size at your local electrical/electronics
supply shop you can try industrial motor shops and auto-electric
repair shops.(I have a local automotive electrics shop that supplies
many of the brushes I need for various restore jobs I do. They supply
me with ones made of high performance composites. Silver in color with
fine gold colored granules in them. Haven't worn any of them out yet
and they seem to work better than the originals.)
If you can post the diminsions I'll cross them and post back a part #
and manufacturer. Give me the spring measurements as well, length,
diameter and if they are soft/med/heavy tension.

Just had another thought. Have you tried anyone at Graflex.org?
They are pros at restoring antique gear and might be interested in
buying as well.
www.graflex.org

 

[Jim Adney]

My question is this; how long could the
original brushes be expected to last, under normal conditions? Are they
reliable enough to sell the machines as working?

The brushes you have will probably be fine for a very long time. If
you, or someone else, should ever need brushes in the future, try
checking out your local hardware store or a local shop that repairs
electric motors. There are dozens of rather standard sizes and one of
them can almost always be filed to fit. The carbon files VERY easily.

-

 

[H. R. Bob Hofmann]

The brushes you have will probably be fine for a very long time. If
you, or someone else, should ever need brushes in the future, try
checking out your local hardware store or a local shop that repairs
electric motors. There are dozens of rather standard sizes and one of
them can almost always be filed to fit. The carbon files VERY easily.

-

I always go to my local ACE Hardware store and look through their box
of various sized brushes until I find one that matches, or is slightly
larger than what I need to replace. Then, using regular sandpaper,
maybe 200 grit, I rub the side of the brush that needs to be reduced
back and forth on the sandpaper until the brush is reduced to the
right size. Works every time. I make sure to clean any sandpaper
grit off the brush before using the brush. The sandpaper is usually
still usable if you are sanding something very black.

H. R. (Bob) Hofmann