Book 3

Figure 25: M o d d in g the b ru sh holder. File
d o w n (sh a d e d area) until only 1/64 in.
rem ains below bru sh hole.
Check that the brush will easily slide through the brush holder,
otherwise deburr the edges with a square file. With the complete
bullet plates on, check for alignment by sticking in a piece of 3/32 in
square tubing through the whole assembly.
Variations on a theme: if you wish, skip filing down the brush holder
and instead cut a slot in the plate so that the unmodified brush
holder can protrude down into the Vee. Solder as before.
To have even more efficient heat dissipation, your bullet proofing
plates can be done 'elephant ear' size, sticking out a good bit from
the endbell. This is dependent on how much space you have in the
chassis. It won't look pretty, but it's efficient.
A rather primitive form we invented about a year before 'real'
bullet proofing became the vogue, was to solder a piece of braid to
clip and brush holder. This piece is allowed to stick out a good bit
and will dissipate heat surprisingly efficiently.
Concerning the bearing, use either a Mura or a Champion bearing,
according to the endbell make. A Mabuchi bearing will quickly develop
an oval hole, so I cannot recommend it.
Bullet proofing the bearing is frequently done. Either remove the
outside edges around the bearing hole screw on the plate and apply a
few quick dabs of solder, or reverse the bearing and solder it to the
plate from the outside. See photos. As with the case bearing, polishing
the inner surface to a high gloss is advisable. Bullet proofing the
bearing is usually only done on can drive' motors.
★ ★ ★ ★
21 brushes & springs
With that, we have completed the requirements for the first two
items, bearing and heat proofing. Remains securing the current
conduction.
On a stock endbell. the current will go via the spring and via
contact between brush and brush holder. The latter is rather erratic
when the brush is vibrating during running, and the increased current
through the spring will heat it up and make it lose pressure.
What to use here is shunted brushes, meaning that the current will
go directly from lead wire joint via the shunt to the brush. Shunted
22