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Len Rahilly
04-26-2007 14:49:56
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Re: The Danger of Hand Cranking in reply to El Toro, 04-23-2007 17:13:53
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I had YEARS of hand-cranking F-12, F-20, "Regular" Farmall, 10-20, Oliver Hart-Parr RC, and H. Never got kicked. All the advice given here about ALWAYS pulling up is certainly correct. If you are away from the crank, and pull up only, you should be safe. As some of the fellows say here, the mag has to be timed right to begin with. It doesn't hurt also to retard the spark on those tractors that have the spark lever (H does not). What really prevents a kickback is the impulse coupling. Many of the early IH tractors had a manually-operated impulse coupling, and you HAD TO REMEMBER to set it. One good thing about this was that you could see if it was latching. If the mag is set and the coupling latches, there shouldn't be any kickback, because the latch holds back the magneto until the piston goes over TDC. The later tractors had automatic couplings, which you can't see unless you take the cover off (not convenient to do every time you start the tractor!). BUT, I remember vividly that on the IHC F-4 magneto (F-12, F-20), you could hear the impulse coupling jingle a bit as you pulled slowly on the crank toward compression. When it stopped jingling, it was latched, and you could then safely pull up.
I will say that I was never terribly comfortable cranking, and finding a way to avoid this is a great idea.
Some tractors were hard to start if they had been stalled or shut off after working hard. Possibly vapor lock occurred. We didn't know what that was back in those years. Some people would spin the crank hoping to make the engine start better (I think they assumed that a hotter spark would result; I believe that the hot spark was provided mostly by the spin put on the mag when the impulse coupling released). Very risky to spin because if the impulse were to miss getting latched as the engine was spun, the cranker could really get hurt.
My dad broke his arm spinning a Ford T. Like the Fordson, this had a retard lever for the ignition, and some people probably forgot to retard. Neither the Fordson nor the T had any kind of impulse coupling, so people wanted to spin them to get a hotter spark. When the crankshaft endplay increased with wear, the magnets would get farther from the coils, and the spark would be weaker. Some people resorted to running the car or tractor up on blocks before stopping it, so the magnets and coils would be closer! Can't remember if it was the front or the back wheels.
By the way, most cars and trucks up until sometime in the thirties had a spark lever, and in some cases, if you didn't retard the spark, you could break the Bendix coupling in the starter. I think this danger was reduced when distributors had automatic advance/retard. Still, I always retarded the spark on our '32 Chevvy truck, just to be sure. The fact that later cars didn't have spark levers or retard buttons suggests that automatic advance/retard were enough to keep the engine from kicking back and breaking the starter.
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