Another productive Saturday afternoon. We managed to get the heater core out, as shown in the Disassembly gallery starting on page 4. Unfortunately, as it turned out there was indeed a leak in the core as I’d suspected when running the heater. The reddish GM Dexcool had congealed into a nasty syrupy glop in the bottom of the vent unit, which I’ll have to clean. Fortunately it looks like the heat/vent module disassembles further, so with some luck I can get it all out.

Following that, the cheap heaters I bought for their ceramic elements came apart; see the story unfolding here over the next couple weeks. I’ll need to create some kind of heater core replacement out of these elements, which will fit in the space previously occupied by the old core.

Also, I wired up the motor with 6-gauge wire to test it at 12 volts. I was quite surprised by how fast the motor spins at this low voltage, though there was very little torque and I could easily slow the shaft with my hand. Typical of a series-wound DC motor, there’s very little torque at the upper end of the speed range; you have to slow the motor way down before it starts drawing enough amps to maintain speed. Other motor types (shunt wound, permanent magnet) are much more speed sensitive, such that they immediately draw more current and provide more torque as load increases — they “want” to stay at the same RPM no matter what. Interestingly, most folks concur that this makes them less suited to be EV motors, since smooth application of torque and a large RPM range are more desireable than this speed-sensitive characteristic.

After spinning the motor up, we removed the rock shield from around the commutator-end vent windows, and I pulled one of the brushes to check its state of wear. I was pleased to see that it appears to be fully broken-in, so I won’t have to leave it spinning on low power for days waiting for that to happen. Getting the brush back in without chipping or damaging it turned out to be a bit of a challenge for my inexperienced hands; the brush springs are much stiffer than on smaller motors like the 9″ ADC.

There are some videos at the end of the First Test section showing the motor spinning up. They’re in MJPEG formatted AVIs from my Canon G1, which Quicktime player can view. I’ll convert them soon to MPEGs to make them more easily accessible to those who don’t have Quicktime or an MJPEG codec.

Lending a hand for the afternoon were Aaron Choate, Vivek Gani, RD Childers, and Alamo City EAA’s Nick Viera. Thanks guys!