The steam engine described below was designed and built for two reasons: First, it was used as a class project in a school located near the main shops of one of our large railroad systems. Ninety per cent of the graduates will find their way into these shops. Obviously, the more these boys know about steam engines the more rapid will be their advancement. Second, the building of the engine afforded a wide variety of work and an opportunity of proving that 'Necessity is the mother of invention.'

Our shop equipment consisted of an eleven inch lathe and a twenty inch drill press; a power driven emery wheel and a bench with six vises. Other necessary equipments such as drills, reamers, files, chisels, etc., completed our list of tools. We had no shaper, no milling machine, no power hack saw (bandsaw), etc., so that opportunities for demonstrating the uses of the lathe and the necessity of doing lathe work on the drill press were very numerous.

The boys who worked on these engines were all in their second year. Their first year had been spent in carpentry, cabinet making, wood turning and mechanical drawing.

In machining the different parts of the engine no attempt was made to follow any rule for finishing one part after another as necessity required. In turn each boy was assigned a half day at the lathe, about every ten days. To illustrate, each of the ten boys in the class had a number. Thus, when No. 1 had had his half day at the lathe, No. 2 would follow and then No. 3 until each of the ten engine builders had had his half day. Then No. 1 would again have his turn. While the lathe and drill were busy the other boys worked at the bench.

In the following paragraphs I shall not attempt to say which part or parts were finished first, but to explain how each part was finished, naming each operation in its proper sequence.

The cylinder of the engine could have been bored on the lathe or on the drill press. The lathe was so small, however, that we decided to bore it on the drill press. This method was also more advisable, because a much better finish could be obtained, and an opportunity was given for the use of some tools which today are seldom thought of or used in the machine shops.

The next operation is to face the ends to the proper lengths. For this operation the cylinder is pressed on an arbor or mandrel and placed between the centers of the lathe. When pressing the arbor into the cylinder, it is well to spread a small amount of oil over the arbor to prevent any cutting or marring of the cylinder walls.

The various holes in the ends and side were next drilled and tapped. The end holes were drilled by first laying out the cylinder heads, clamping them in place with a parallel clamp and drilling through each head with a 1/4“ drill. The heads were then removed and the holes in the cylinder drilled with a No. 12 or a 13/64” drill.

The next hold drilled was that in the valve slide side for the valve plate stud. This hole drilled with a 17/32“ drill and tapped out with a 5/8” tap. Extreme care must be taken when drilling this hole to avoid drilling through the cylinder wall. When this hole is drilled and tapped, screw the valve plate stud in place and assemble the valve plate and steam plate. Lay out the holes on each corner of the steam plate and drill through with a No. 18 drill. Remove the valve and steam plates and drill the holes in the cylinder 1/2“ deep with a No. 28 drill and tap with an 8/32” tap.

The drilling of the port holes was the very last thing done on the engine. The position of each hole was laid out on the steam plate and the entire engine with all working parts was assembled. The fly wheel was turned until the piston was at the extreme end of the forward stroke and then clamped in place. The inlet and exhaust ports for this stroke were then drilled through the steam plate and valve plate and for a short distance or approximately 1/8“ into the cylinder. After these holes were drilled, the fly wheel was unlocked and rotated in the opposite direction, or to the extreme end of the reverse stroke and the port holes for this drilled as described above.

The cylinder was then removed from the engine and placed on the jig as shown in the drawing, and the port holes drilled through. The inlet ports were drilled at an angle of 30 degrees and the exhaust ports were drilled straight. This was to allow any condensed steam which might enter the cylinder to escape easily. The inlet ports were drilled with a 5/16” drill and the exhaust ports with a 3/8“ drill.

As will be seen in the assembly drawing, two plates were used in the valve mechanism. One was a movable plate, which we called the valve plate, and the other was the inlet and exhaust of the steam. The outer or stationary plate we called the steam plate. The valve plate was finished in the following manner. A 23/32” hole was laid out, drilled through the center of the plate and reamed with a 3/4“ reamer. Care must be taken to have the plate lie flat on the drill press table when reaming the hole.

An arbor was pressed into this hole and placed between the centers of the lathe. The sides were faced off to the proper thickness and the lathe work on this part was finished. The 1/4” hole in the arm was drilled and reamed, but the four valve holes were not drilled until the entire engine was assembled. The valve plate was ground with pulverized emery and oil after all other work had been done. By rocking the plate back and forth in the way that it was to run, a smooth flat face was obtained. If care is taken when facing the plate, time can be saved in grinding it.

The steam plate was finished by grasping it between the jaws of the lathe chuck and facing off the inner side. The holes for the inlet and exhaust pipes were drilled and tapped out. The center hole was worked out to shape by first drilling two 5/16“ holes on 5/16” centers. The remaining metal was chipped out and the hole was filed to fit the valve plate stud. The stream plate was screwed into place on the cylinder and this was also ground to a true bearing surface with the valve plate.

The first operation on the rear cylinder head was to chuck it up true in the lathe chuck and face off the inside. Next cut back 1/32“ to 2-1/4” diameter. This forms a small projection or boss which will help to centralize the head on the cylinder. Layout and drill holes.

The front cylinder head was finished in the same way as the rear with the exception of the hole for the piston rod. When the front head was faced a 7/16“ hole was drilled through the center. A small boring bar was used to true up the hole, after which it was reamed with a 1/2” reamer.

Two of the most simple parts of the engine were the valve rods. These were made from 1/4“ round cold rolled steel. When the length of the valve rods was determined they were cut from a long bar and a hand die was used to thread each end to the required length.

The piston rings for the engines were made up in one lot of twelve rings from a single casting. A hollow casting was made up for this part of the engine and the best mechanic in the class was chosen to do this job.

The outside and inside diameters were first turned and the rings were cut off to the desired thickness. When cutting off each ring, the face of the casting was first trued up smooth before cutting another ring. By doing this it was necessary to face only one side after cutting off.

After the rings had been faced to the proper thickness, they were sawed on an angle of 30 degrees and the proper amount or approximately 3/16” of metal sawed out. The ring was then fitted into a compression jig and a special arbor was used to finish the outside diameter.

The piston was grasped in the chuck and a cut taken off one side. The hole was then drilled, bored and reamed to a 1/2” diameter. The next operation was to counterbore one side 3/4“ diameter 3/16” deep. It was then removed from the chuck, pressed on an arbor and turned to size. The opposite side was faced to the required thickness and a 3/16“ groove was cut in the center for the piston ring.