THE MITCHELL FLOAT-PUMP

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Charles Bertram—in his letter on page 156 of MOTHER NO. 38asked if anyone knows of a way he can lift water from a small spring to a trickle irrigation tank for apple trees situated 65 feet higher up a slope.

Perhaps the float-pumpwhich fills a niche between the familiar hydraulic ram (that MOTHER has featured several times in the past and that requires a swift stream for its operation) and the waterwheel (which MOTHER has also featured and which must have several feet of fall)is just what Mr. Bertram needs. This handy-dandy little device combines pump and prime mover into one assembly . . . and can operate on as little as six inches of head!

I'm not really sure of the float-pump's origin, although I think it was developed around the turn of the century. I first ran across the idea when I was told about one of the units that had been installed near Walton (north of Lexington), Kentucky. As a result, I sat down and designed the pump you see here "from scratch" with the typical semiskilled back-to-the-lander in mind.

No, this probably is not the way I'll build one of these little rigs for my own farm (since I own a fairly elaborate machine shop and research lab). But the one shown here should work, and should be fairly easy to build.

The largest component (the casing) of this pump is a 55-gallon drum with a removable head. Such a barrel—which is easy to obtain at low cost almost any place in the worldestablishes the maximum usable head of the finished float-pump at approximately 2.5 feet of water. The largest float that we can reasonably expect to use in such a casing will have a diameter of 20 inches, and I've chosen to make that float ten inches in height (see drawing).

(The pump's float, as I'm sure you realize, should come as close to completely filling the inside of its casing as possible . . . without actually contacting the barrel's wall. Too much clearance simply wastes water without improving either output pressure or flow. Too little can cause the float to "hang up" and slow or completely stop the pump's action.)

Since the float doesn't actually wear against its casing, it canfor the most partbe made of fairly fragile materials. Consider a block of styrofoam (which can be worked with a saw, knife, or even a hot wire!) sandwiched between top and bottom plates of aluminum or steel. The entire assembly can then be painted with melted paraffin to decrease its absorption of water and, thereby, improve its buoyancy.

I've specified a pump of the so-called "ram" design for installation on this float because of its low cost and simplicity. The only parts of the assembly that you should have to take to a machine shop for precision finishing are the seal plate and the ram pipe. (The outside diameter of the ram pipe should be turned and polished and the hole in the seal plate through which the ram pipe slides should be bored with some precision. Perhaps most critical of all, however, is the machining of the groove for the O-ring seal.) And while you're at the machine shop, you might as well have the check valve seat made up and welded into the bottom of the ram pipe. All the other parts of this float-pump can be fabricated by a handyman in any good home shop.

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