I have an old Emerson dynamotor B supply. The motor brushes are tiny squares similar to a square carpenter's pencil, set in small clamped cups on four spring-loaded arms. These cups are worn out and loose. Any ideas on what electrical applinances might contain something similar for replacement of these cups? Is there an adhesive that might bond the graphite brushes to the tin cups?

Old appliances with universal motors (work on either AC or DC) would have brushes. Kitchen mixers, electric drills, etc. Most adhesives are electrical insulators and so would not be good choices for your job. The only one I know of that is electrically conductive is the adhesive sold in auto parts stores for repairing heated windshield connections. It's pretty expensive, but the only easily available one.

Be aware that carbon brushes are specifically designed for particular jobs. Their hardness and conductivity is chosen for the speed and current required. Brushes from a household motor may work, but may not last long.
Good luck........rich

:I have an old Emerson dynamotor B supply. The motor brushes are tiny squares similar to a square carpenter's pencil, set in small clamped cups on four spring-loaded arms. These cups are worn out and loose. Any ideas on what electrical applinances might contain something similar for replacement of these cups? Is there an adhesive that might bond the graphite brushes to the tin cups?

In most rural towns there are still shops that rebuild starter motors and generators for older cars. They are quite resourcefull due to the scarce nature of the parts they use. Check the yellow pages or go by an older auto parts house and ask if there is a starter motor rebuilder in the area, if so they can set you up with the correct brushes

Bob,
Easy solution. Brass/aluminum, square or rectangular tubing is available at larger hobby shops (not toy stores) in small lengths appropriate for your job. Conductive epoxy is readily available also at some, and larger hardware stores, or on line at some of the links at this site. Although its been a long time since I was intimate with a Dynamotor, I seem to recall the metal sleeve/brush housing being rigidly attached to the electrical connection and housing, allowing the spring loaded, self lubricating graphite brushes to slide within the tube as they wear down in length. Much like any DC motor of today. I suggest that you closely inspect the assembly to verify my suspicions. Vaccuum cleaner repair, sewing machine repair stores, and many hardware/appliance establishments may have graphite brushes of the appropriate size for your application. Don't change the brush size, because its' relationship to the copper slabs on the commutator are somewhat critical. All brushes are not created equal, so be cognizant of the the amperage demand, and copper/silver vs graphite mixture.
marv

:I have an old Emerson dynamotor B supply. The motor brushes are tiny squares similar to a square carpenter's pencil, set in small clamped cups on four spring-loaded arms. These cups are worn out and loose. Any ideas on what electrical applinances might contain something similar for replacement of these cups? Is there an adhesive that might bond the graphite brushes to the tin cups?

I've seen graphite brushes at hardware stores and Sears Hardware. I've used them to repair mixers, etc. Depending on the size, you can also get them at a train-repair shop. Lionel used graphite brushes for years in its Pullmor train-engine motor.

Joe Connor

If the set-up is of the type where a square brush fits inside of a square tube, DO NOT BOND IT TO THE TUBE WITH GLUE. There is supposed to be a spring behind the brush to maintain tension on the brush. Due to any slack or eccentricity of the shaft and bearings, and eccentricity of the commutator, the brushes must be able to move about. Most brushes of the hard type will work for you. Do not worry about current carrying capacity. A B current generator will not likely produce more current than a large fan motor. Equipment that demands a lot of power--saw motor (repulsion-induction or simply repulsion), lawn mower (repulsion universal), vacuum cleaner (repulsion universal), will usually hava braded wire fastened to the brush for a positive electrical connection. The spring itself cannot supply the full current without being manufactured with excessive stiffness. For your work, however, this wire is not necessary. If the end of the spring can be fastened to the metal tube with the plastic cap that fits over the end, or if the end of the spring can be expanded so that it firmly rubs against the metal tube, this will likely provide enough of a connection.

As others have mentioned, hardware stores carry brushes of many types. True Value in my area carries an assortment of brushes. Both carbon and bronze powder will be well suited for the purpose.

THomas

The setup looks like a pair of calipers with the two ends fittd with the brushes touching each opposite side of the commutator. Two springs about an inch long give these caliper-like arms the tension. If I could find some kind of compound to give these little brushes some extra support it would be great. So far, I've used very fine wire to wrap them in place.

:If the set-up is of the type where a square brush fits inside of a square tube, DO NOT BOND IT TO THE TUBE WITH GLUE. There is supposed to be a spring behind the brush to maintain tension on the brush. Due to any slack or eccentricity of the shaft and bearings, and eccentricity of the commutator, the brushes must be able to move about. Most brushes of the hard type will work for you. Do not worry about current carrying capacity. A B current generator will not likely produce more current than a large fan motor. Equipment that demands a lot of power--saw motor (repulsion-induction or simply repulsion), lawn mower (repulsion universal), vacuum cleaner (repulsion universal), will usually hava braded wire fastened to the brush for a positive electrical connection. The spring itself cannot supply the full current without being manufactured with excessive stiffness. For your work, however, this wire is not necessary. If the end of the spring can be fastened to the metal tube with the plastic cap that fits over the end, or if the end of the spring can be expanded so that it firmly rubs against the metal tube, this will likely provide enough of a connection.
:
:As others have mentioned, hardware stores carry brushes of many types. True Value in my area carries an assortment of brushes. Both carbon and bronze powder will be well suited for the purpose.
:
:THomas

Sounds like the brushes are glued to these caliper arms? Interesting. In that case you may need glue. Whatever you do, the brushes must be able to move towards and away from the commutator. Probably would be best if you e-mailed a picture of the brush assembly to someone on here--whoever you want to answer your question.

Thomas