Friday, May 16, 2008

Plowing with a John Deere A

This is an unstyled A, made from 1935-38 when the "styled" version with the familiar slotted grille took over. If you look at the hood, you see a red fuel cap at the very back, then a green one further along the hood. That denotes a distillate/kerosene fueled tractor. The red cap is for a small tank holding gasoline for starting; once the engine is warm, one switches over to "tractor fuel" as it was called then, in the main tank. The distillate tractor had the same engine as the gasoline tractor, except lower compression ratio and a preheated (by the engine coolant) intake manifold. This is what has to say about the subject:

"Tractor fuel (or distillate) was similar to kerosene, but derived from petroleum (kerosene is often derived from coal). Think of paint thinner - it says on the label "Contains petroleum distillates". The engine needed to be really hot in order to vaporize that stuff. You couldn't start up the tractor with it. That is why there is a small gasoline tank on an "All Fuel" tractor. Once you got the engine started and warmed up, you switched a valve to the distillate tank. It wouldn't develop as much power as gasoline; but at the time, during the thirties and early forties, it was much, much cheaper than gasoline. THAT was the advantage! When gasoline became as cheap as tractor fuel, the all-fuel engines were discontinued. When that happened, the engine compression was increased in order to get more horsepower (the full potential of the gasoline).
Now, we ALL run them on gasoline! The engine needs to be really HOT to work well with the "heavier" fuels. It needs to be "WORKING" to get that hot. When we use the tractors for putt-putting around, it is difficult to keep the engine temperature up high enough. Don't worry, your two cylinder tractor, no matter how OLD it is, does NOT require special fuel. As is, the engine will run beautifully on gasoline. You just won't get any horsepower advantage over the tractor fuel, because of the low compression engine. Just buy "regular" gas. You don't need any "octane" because the engine compression is low. Your tractor will never "ping"."

I've often wondered if these tractors will run on straight biodiesel. I'll bet they would. Or maybe even plain filtered WVO, mixed with some proportion of gasoline.

I love these old tractors for their simplicity. Hand start, no battery necessary. No water pump or thermostat; they relied on thermosiphon coolant flow, and a lever controlled air shutters in the grille to regulate temperature. Antifreeze wasn't generally used either, the water was simply drained into a waiting pail at the end of the day's work if a freeze was expected.

Here's another video of a 2-cylinder John Deere, this one a styled G. This is a good demonstration of just how well these old tractors can pull. Notice that even when he throttled it back to probably about 300 rpm, it was still pulling; it just didn't have enough weight to hold the frontend down. It's a balancing act between frontend weight to keep the front down and weight on the rear wheels for traction, without going over the allowed weight for the pulling class.
For those who don't know, that sled the tractor is pulling has a large weight which slides forward over a skid on the ground as the tractor progresses down the track, adding more and more resistance to forward motion. I like watching it, because it gives those old tractors a real workout and demonstrates what they can do.

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