Re: gear speeds on an F-20

Posted by Len Rahilly on September 06, 2007 at 14:47:09 from (75.69.99.42):

In Reply to: gear speeds on an F-20 posted by F-20 guy on September 03, 2007 at 16:26:09:

Looks like Bob Kerr has the right speeds for the steel-wheeled F-20 from the factory. As far as I know, IHC never quoted speeds on rubber, although they did sell tractors with factory rubber from about 1936, I believe. I had a lot of experience with F-20s, "Regulars" and F-12s back in the 40s and 50s, so I think I can add something useful here.
There were two kinds of rubber put on the F-20. In some cases, a tire of about the same diameter as the original steel wheel was used (the standard steel wheel was 40" in diameter, bare, as I remember). I do not recall the size designation for this tire. The problem with this solution was that the tire RIM would not clear the brake drums, and the wheel had to be turned out. This made for a VERY wide tractor, but I assume that the ground speeds would have been similar to the steel-wheeled tractor. In order not to have such a wide tractor, many F-20s were equipped with a 36" rim (9.00-36 tires were very common on these tractors in the late 30s). This resulted in a TIRE DIAMETER that was much greater than 40"--about 48", I would estimate. The ground speeds were much faster. I once "raced" an F-20 in second gear against an F-12 in third gear, and the speeds were about the same. The F-12 was supposed to do about 4 mph in third gear. Steel wheels rob a lot of power (I'd estimate 30 to 40 percent), and rubber robs a lot less. This fact accounts for the ratings of the early tractors--the drawbar horsepower was rated at about 1/2 of the belt power, to account for the enormous waste through the lugs (10-20, for example). Converting a tractor to rubber gives it a lot more horsepower at the wheels than it had originally on steel. The F-20 on rubber "moved up a gear," in a way, because in second gear at 4 mph it would pull the same load that it would have had to pull at just over 3 mph on steel (and I can tell you from a lot of experience with several steel-wheeled tractors that none of them would pull any kind of heavy load at much above 3 mph--often called "plowing speed" in the sales literature of the day).
I can only estimate the speeds of the F-20 on 9.00-36 rubber, but I'd say close to 3 mph in first, nearly 4 in second, about 4.5 in third, and close to 6 in fourth.
IHC supplied a "road gear" for both the F-20 and F-12. I seem to recall that this was called a "7 mph road gear." You can find these gears listed in an F-20 parts book.
My memory of this is getting a little fuzzy, but I am pretty sure that when the tractors came from the factory with this high-speed transmission, the third and fourth gear positions were reversed (third now between first and second, and fourth low and forward, where third was originally). The new gear-position numbers were cast into the housing, just as they had been on the conventional model.
On another note: If you need to replace a 9.00-36 with a tire made today, 9-36 will NOT give you the same carcass width--it will look narrow and skinny. Did this with an F-20 I owned a few years ago, and was disappointed with the appearance. A tire dealer should be able to give an equivalent size in the new numbering system (possibly something like 11-36 would look similar to a 9.00-36). Everybody always called the earlier tires "nine-hundred thirty-six"). I hope this isn't more than you ever wanted to know. My wife thinks I'm a little squirrelly for keeping this kind of stuff in memory, but I tell her a guy has to have SOMETHING to be nutty about, it doesn't cost any money, it shows that I still have some memory left, and besides, it takes me back to a time when I was young and thought it was great fun to bounce around all day on one of these old beasts.

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