My Steam Tractor Fantasy


| March/April 1993



Tractor

Paul Brien with his tractor under steam at the 1992 Boonville, In. show.

4312 Lone Oak Road Nashville, Tennessee 37215.

This project began some 20 years ago when I acquired an old derelict 3 HP Ottawa drag saw engine that was all apart and in boxes with several broken and missing parts. At the time, it was plainly beyond my ability to restore the engine to its original running condition as a gasoline engine, so the boxes sat around in the way until about four years ago when I felt it was time to do something with them. As this engine used an igniter, there was this neat passage from the outside of the cylinder block where the device mounted, down into the combustion chamber. Now, I have been building 1' scale live steam locomotives and boilers for years, so I know a little something about steam engines and that igniter hole looked like a steam passage to me. Thus the idea of converting the gasoline engine into a single acting steam engine was born. It wasn't difficult to design a simple piston valve to mount over the igniter opening to admit steam to the cylinder for the full length of the power stroke and to exhaust it on the outgoing stroke. I figured that taking steam for the full stroke it would still be using less steam than if it were double acting working with anything more than a 50% cutoff. The valve body is welded up from mild steel with a cast iron sleeve pressed into the bore. The piston valve itself is turned from cast iron. I have found that a cast iron valve running on a cast iron seat with lubrication will last indefinitely.

The timing gear on the crankshaft was replaced with an eccentric also turned from cast iron, and has a strap made from mild steel.

Happily, the engine ran beautifully as a stationary exhibit on around ten pounds steam pressure. It first ran as a stationary exhibit hooked up to a large squirrel cage blower at the Tennessee-Kentucky Thresherman's Association show at Adams, Tennessee in 1989, taking steam from their stationary boiler on the grounds. Later that year I took the engine to a large show in the northeast hoping to get hooked onto their steam line and running there, but was disappointed at not getting encouragement or help at all in doing this. As a result of this experience I was determined that I would never take the engine to another show without being able to supply my own steam.

Thus began the saga of the boiler. Early the following year I began collecting proper materials for the project. A length of 12' schedule 40 (?' wall) SA 53 pipe for the shell; a piece of 10' schedule 20 ( wall) SA-53 pipe for the firebox; some ?' SA-285 plate for the tube sheets and enough OD type K copper tubing to make 43 flues, which were expanded with a tapered punch into the tube sheets. Every treatise on boiler design will tell you that a boiler needs a vigorous water circulation to be a good steam generator. Well, looking at my drawing layout of the boiler, I saw that there would be only a ? wide water leg space between the OD of the firebox and the ID of the outer shell, and as the firebox stands 12' tall, I just couldn't visualize much circulation going on in this restricted area. So I hit on the idea of arranging six external circulating tubes around the OD of the boiler shell as you can see in the photographs. These are pieces of 2' schedule 80 pipe that I split longwise and welded to the shell. There are 2' square holes burned through the shell under these pipes, one at the top about 4' below the water line and one at the bottom just above the mud ring. I call these circulating tubes, and although I can't prove scientifically that these tubes have made this boiler the success it is, I can say I have never been at a loss for steam. Water is supplied to the boiler by a ' Penberthy injector. In late 1990, I operated the engine and boiler mounted on a small flat bed trailer at the Pioneer Power Association tractor show in Eagleville, Tennessee.

But something was still missing. Heck, if I had the engine and the boiler, why not mount them on wheels so I can drive around? Thus began the collection of items needed for this phase of the tractor project: a transaxle from an old Springfield garden tractor, some 2' square steel tubing for the frame, some farm implement wheels found at roadside junk yards, a hand wheel with a 1' Acme thread screw and nut attached from some piece of industrial woodworking machinery to use for the steering gear, etc. A couple of days on the drawing board arranging all these parts together came up with what you see in the pictures. The 11 gallon water tank on the back was formed up and welded from 3/16' black iron sheet stock protected from rusting by coating the inside with a popular gas tank sealer that is sold at most antique gas engine shows. Why did I make the tank out of such heavy metal? Because that's what I had some of, and that's the best reason there is! I made the steam and exhaust connections from the boiler to the engine using high pressure steam hose for both ease of fitting up and to eliminate stresses that would be imposed on fixed piping due to slight flexing between the boiler and engine. When I first got the engine running I found out pretty quickly that there would have to be some kind of canopy overhead as the water/soot/cylinder oil emissions from the stack, until everything got good and hot, was making driving the tractor a mite uncomfortable. Besides that, the wife was beginning to get quite ill at me for ruining so many shirts! The canopy is made from 1/8 pressed board mounted on wooden formers and liberally coated with porch and deck enamel. Driving the tractor is now a pleasure!