Precious metal brush systems in small DC motors

[Clyde38]

Does anyone have a recommendation for information (literature, websites, whitepapers, etc.) about the design of precious metal brush systems? There is a lot of information about carbon brush systems, but I'm finding it difficult to find anything about precious metal brushes. I'm interested all aspects of precious metal brushes.

 

[mikekilroy]

ScottyUK, that is why I put up a picture of our small Inland 1/2" and up up DC brush motors - we used a silver graphite blob glued to end of the metal since the beginning of making these small dc brush motors in the late 1950's. Model car $ 2.00 motors of course don't bother, but I can't imagine Portescap not using some brush material glued on - but maybe!!

http://www.KilroyWasHere<dot>com

 

[Clyde38]

"but are these 'whisker type brushes' really any different than regular brushed motors? The whisker just has the silver graphite or carbon in a blob on the end of the spring metal arm rather than in a cartridge hole with a spring behind it"

Yes, they are different. These are not whiskers with a blob of graphite or carbon on the end (although this type of brush exists and is usually just one metal finger with the additional graphite contact attached). The fingers or "whiskers" material is the material (precious metal) that makes the sliding contact (take a closer look at the pictures I attached earlier). A lot of these motors operate from 1.5 to 3.0 V DC. They are most often two pole machines, but I have seen four pole configurations.

 

[Clyde38]

I can't imagine Portescap not using some brush material glued on - but maybe!!

See attached excerpt from a MAXON document. MAXON, Portecap, Faulhaber (MicroMo), and several other low voltage, low power motors use this concept (does not have to be ironless coil).

 

[ScottyUK]

Mike - from Portescap via Google:

"The brush holder endcap is made of a plastic material. Depending on the intended use of the motor, the brush could be of two different types; carbon or multi-wire. Carbon types use copper graphite or silver graphite and perfectly suit incremental motion applications where high continuous and peak torque are required. Multi-wire type uses precious metal and will guarantee low starting voltage and improved efficiency, a perfect match for portable battery-powered applications. Portescap's engineer can design endcaps that reduce electromagnetic noise to meet EMC requirements."