HO Brass Wars, the
"swan song" for Brass/cans, with detail from the builder Bob Kircher....
(back to riggenho.com)
The last scratchbuilt I made before switching over to A/FX-based cars used a pretty highly customized motor. The can came from a Mini Motorific, which was dimensionally similar to the HT50 except it had curved sides sort of like a mini 16D instead of the flat sides the HT50 had. Incidentally as I'm sure you know the "HT50" designation was made up by Tyco's ad agency; it really was a Mabuchi ST02 and is what we (within Tyco) usually referred to it as. The advantage of the Mini Motorific can was it was considerably narrower at the bottom, which gave me a good bit more "working room" in building the chassis, and also saved having to make another cut on the magnets.
The magnets were indeed cut down Champion Blue Dots, originally intended for
1/24 slot car motors. Pat had
a diamond cutoff wheel which was used to slice the magnets. This was a tricky time-consuming operation,
since you couldn't let the magnets heat up else the heat would kill them. We used water as a cutting fluid/coolant, applied with a small brush. Since the diamond wheel was about four inches in diameter and spinning at a couple thousand RPM it would almost immediately sling the water off again, which was now contaminated with particles from the magnets, so we rigged up shielding from brown wrapping paper to keep from making a mess out of the work area.
After cutting the magnets to size, which took several hours, the inner faces
were re-radiused. The 1/24th
armatures had a diameter of .510 or so while the ST02 arm was about .375. This was done with a 3/8" dia
Dremel grinding stone and took about as long as slicing the things did. I didn't bother reworking the
outside curve of the magnets as it was close enough to begin with.
Pat had developed the techniques for cutting the magnets; he had originally
developed them while
cutting down some magnets from a 36D (Champion 707?) to fit in a T-Jet 500. This was a bit simpler
operation as they just had to be cut to length, no re-radiusing required.
Since the Mini Motorific ran on 3 volts or so, the "whisker" brush
system wasn't up to the job of
handling the 18v the motor would eventually run on, not to mention the much higher amperage. I jury
rigged something to hold the endbell from an ST02 in a lathe so I could trim the square corners down to fit
the can. I usually ruined three or four endbells before getting a good one. I also made a couple
endbells from scratch, fabricating them from G10 epoxy board (printed circuit board material), with brush
holders made from K&S square brass, and cut-down 1/24 motor brushes. The handmade endbell was mostly Pat's
design, very much like the ones he'd made for his anglewinders.
The armature was a rewound ST02 arm; I don't recall the number of turns but
it was 36 gauge wire. I had
bought a Laganke winding machine previously and machined a holder for the ST02 arms for it, patterned
off the 16D and 36D holders that came with the tool. Incidentally, a T-Jet or A/FX armature blank fit
perfectly in the Laganke 36D holder.
After winding, 24-hour epoxy was applied to the windings. The arm was then
set up on end and a
100-watt bulb was set up about an inch or two from it. This did two things: it accelerated the curing time
of the epoxy to just a couple hours, and more importantly, thinned the epoxy so it soaked into the
windings much better. After curing the arm was balanced on a pair of razor blades; we didn't have
access to a dynamic balancer.
The chassis itself was sort of an evolution of the Lead Sled. Instead of a
brass plate under the motor,
a pair of .032 (or was it .047) piano wires were used for chassis rails on each side of the motor. This
lowered the motor by about 1/32". The bat pans were 1/4" by .025 K&S brass with a 1/16" tube soldered on
the inside edge. A piece of 1/32" piano wire was bent into a "U" to serve as the hinge for the bat pans,
very much like the Lead Sled. Strips of lead about .070" thick were soldered to the tops of the batpans,
and the body mount pin tubes were soldered to the top side of the lead.
The drop arm was made of .032 K&S brass, almost identical to the Lead Sled's
except it was wider.
Note that the car in the photos on your site used a slightly different drop arm; mine was bent from a
single piece of brass. The rear bracket/axle carrier was a strip of 1/4" x .032 brass bent into a U shape
with holes for the axle bearings and motor rear bearing. The motor was, of course, soldered into the
The guide flag was an old style TycoPro flag with a quick change wiper setup.
The center post was
threaded with a 1-72 die. A piece of 1/4" dia solid brass rod (not from K&S) was chucked up in a lathe and
a tap drill for a 1-72 thread was drilled in the center then tapped with a 1-72 tap, then 1/8" or 3/16"
was sliced off the end of the rod. This was used as a retaining nut for the guide flag.
This car was raced in the 1972(?) Trenton HOPRA, coming in second place behind
Jocelyn Severin driving
an A/FX-based car. This was pretty much the swan song for can-based cars in HOPRA; by that time everyone
else had switched to A/FXes.