Sunday, November 13, 2005
The Gamera 9 is Born!
Who is Gamera, you ask? Why only a fire-breating turtle, hero of Godzilla knockoff movies and Guardian of the Universe. Okay dorko, so why'd you name your electric car motor after a Japanese movie monster? Well, it's green and short for one, it means business at both ends, it breaks stereotypes about the slowness of it's species, and since I matched the color of Zilla controllers, why not continue the naming convention? Long live the Gamera Nine!
Gamera 9 artwork courtesy of Andy Chung
So, the legendary motor finally came to life this week, unveiled before the gawking hordes at November's Oregon Electric Vehicle Association meeting. Well, the horde only consisted of @ 20 fellow EV geeks, but it was a great treat for Jim Husted of Hi Torque Motors to come on up and demonstrate the motor's innovative features to the club. Besides shortening the body to a compact 14.25 inches, (leaving less than 1/4 of airspace between the motor body and the ghia's rearpost portions) Jim threw in another first-of-it's-kind feature, series/parallel shifting within the same motor. That's right, The four field coils can be run as matched pairs, or one right after the other. At 12 volts, the effect was immediately apparent, as the motor drew 30 amps idling in parallel mode, but cut back to 18 amps in series. Series windings allow greater influence from the field coils, resulting in increased torque and lower amp draws, but at reduced speed. I still don't have a full understanding of the theory behind this, but I've sure seen the results in Wayland's drag racing, and now my motor will have a bit of the magic as well. The Adjustable Brush Ring assembly was run through it's paces as well, demonstrating the amazing tunability of a DC motor with 15 degrees of variable brush timing. At 12 volts and full advance, the motor started complaining and spitting carbon sparks, but at 170 motor volts and high rpm, it'll be very thankful for a little advanced treatment....
Here's a little wisdom from the Maker:
(Jim Husted writes)
"Wire size and turns are not the only things that effect coil / armature
relationships. How the fields are plumbed play a key role also. Jay Donnaways
motor is plumbed to be operated in either series or parallel."
In series the motor runs 1200 RPM @ 18 amps 12 volts, 0 load.
In parallel the motor runs 1850 RPM @ 30 amps @ 12 volts, 0 load.
"Every EV motor I’ve seen so far has been plumbed parallel, which gives you
higher speed, but less torque. Jay’s motor should put to rest whether going to
series will be beneficial or not. I believe that being able to switch the
fields to series would benefit those that face long or steep uphill drives.
Even if one could only get a 10 % improvement would that not be the same as what
some are getting out of regen? What I do know is that Prestolite used a two
speed motors (motors wired for both series and parallel) for years. If you were
going up a ramp the unit stayed in series as switching it over to parallel would
bog down the motor as torque dropped and the amps would skyrocket. I believe
this applies the same for anyone facing the same issues."
After the excitement of Gamera Nine's unveiling, this weekend's task was to 'dry-fit' the motor into Karmann Eclectric, seeing how well it slid into place, and how much trimming of the body would be required to do so.. Well, the good news is that practically none at all was required. The bad news, as you can see, is that I got a bit carried away and cut a big'ol slot for the motor shaft to slide through, which turned out to be rather unecessary. Of course, when I wind up installing some sort of accessory on that tailshaft, that slot will need to become much larger. Till then, the motor shaft will be visible, but reside below the stock decklid latch.
Installing the motor was fairly straightforward, but simplified since I left off the flywheel and clutch for this first test-fit. The extra clearance required by this hardware will indeed require me to lift the body whenever removing the motor, or go ahead with my earlier plans to make the rear valance removeable. Any new car, or motor for that matter, is treated with kid gloves until that first scratch, which I promptly inflicted with a little slide over my floor jack, removing @ 1/4" of powder coating from the motor's underbelly. Time to mix up a can of touch-up paint. Fortunately, I've already got the code for Zilla Green...
Thank you Jim Husted, burning rubber can't be far off now!
Posted by Jay Donnaway