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Posted by David Sherman [24.32.202.83] on Thursday, February 04, 2010 at 19:59:39 :
In Reply to: Electric/hybrid Power Wagon? posted by Tom in Oregon [128.193.15.53] on Thursday, February 04, 2010 at 19:26:06 :
I'd be interested if I was near enough to take a look first and not have to pay for freight. I like synchros and servos. Along with magams (magnetic amplifirs), they're really a very elegant solution to electromechanical control systems. If somebody had been designing a "drive by wire" Toyota throttle control system 40 years ago, they would have used synchros and it wouldn't have gone berzerk on them.
If you get serious about a wind generator driving a battery bank, I have some good 200 amp 28 volt alternators and I would trade one for some of your navy stuff. Best bet nowadays with alternative energy schemes is to generate DC (from solar, wind, or hydro) and charge batteries, then use an inverter to make AC out of it as needed. Inverters have come way down in price, and by generating DC you eliminate all the complexity of trying to control both voltage and frequency at the same time.
I have thought about electrifying an old truck, especially since I expect gasoline to become unavailable or insanely expensive in 10 or 20 years. The biggest catch for doing a homebrew hybrid conversion is finding a large-horsepower DC motor. Since VFDs have become standard in factories, DC motors have disappeared. I have one 100 year old 10 HP DC motor, about the size of a modern 40 HP AC motor, that came out of an elevator. To drive a truck, you'd probably want at least 50 HP, which is going to be tough to find. The good thing is that with a shunt-wound DC motor you could do away with the transmission and clutch, since you can adjust the field current to get maximum torque at minimum speed (also called a "constant-HP" design) The downside is you waste power in field current, which is why the hybrid cars use permanent magnet fields, and fancy electronics. I would still think it would be fun to give it a try. I have seen some huge DC motors around here in mine hoists -- probably the last application in the world that really benefits from a DC motor. They need very smooth control of speed over a wide range, and lots of starting torque when they're pulling muck. The motors are hundreds to a thousand HP and each motor needs a comparably-sized MG set to drive it. The main hoist at the Sunshine is a wonderful old (1930s) machine with a beautiful control panel the of maybe 10' x 20' covered with switches, gauges, and indicators mounted on thick black bakelite and very neatly wired up with all the wiring harnesses wrapped up in black friction tape. The small ("chippy") hoist is a modern (1970s) design with solid-state controls. When I was in there, the controller kept blowing fuses for no obvious reason. When the fuses are $50 apiece and you blow 6 of them every time you fire the thing up, troubleshooting gets expensive fast.
Anyway, say you put a 40 hp motor in a PW, and in normal driving you only needed 20 HP out of that, average. That's roughly 20 kW, allowing for losses. Many industrial DC motors are rated at 250 volts on the armature for full power, so that means you'd be drawing 80 amps average out of your stack of 20 golf cart batteries, or surplus telco batteries. A typical golf cart battery is rated at 240 amp-hours, so you could go 3 hours on a charge. You could implement simple non-electronic regenerative braking like electric trolleys did years ago, and extend that a bit. Obviously these are just rough numbers, but they should be reasonably close (+/- 50%) to what you could put together from readily available part without a lot of fancy electronics. If they were 6 volt batteries, you'd need 40 of them. Total battery weight should be close to 1 ton, so you wouldn't have any payload capacity left, but that's the problem with even the fancy hybrid vehicles today.
The alternative I'd really like to see is something I've read hints of in quite a few old WWII stories, but have never seen written up in technical terms: a wood-fired truck. During the big war, especially in Nazi Germany, lots of trucks were converted to run on wood. They didn't run well, but they ran, and they allowed farmers to haul their produce to market. Quite often I've run across a passing reference, as in "we hitched a ride on a wood-fired truck", but never a description of how they worked. I know they used a gas generator in which wood was "cooked" to release combustible gasses that were fed into the engine, but I'd like to know about the particulars of the gas generator design, and whether they kept the stock carburetor, substituted an entirely different carburetor, or merely stuck a hose from the gas generator down into the top of the carb and figured the throttle would be wide open most of the time anyway.
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