Blackstaffe Beginner's Locomotive Part 1

Beginner's Locomotive

An 0-4-0 Switcher of Simple Design

by Cliff Blackstaffe

Victoria Society of Model Engineers

The Miniature Locomotive, September-October 1952

When the Victoria Society of Model Engineers was formed I was given the job of designing a standard locomotive for members to build, which would be simple, inexpensive, and suited to our local material sources.

In introducing this little engine to the Model Engineering fraternity, I want to explain from the start, that it is primarily designed for the beginner in the hobby. The builder that doesn't have much spare time, for the man with a small income or the man who wants something for his boy to run. Unlike most designs this engine is designed to use all or as much locally obtainable material possible; which reduces the cost enormously.

Here it is. The main dimensions are; length over buffers eighteen and three-fourth inches, width ditto seven inches, frame thickness one-fourth inch, depth one and three-fourths inches, cylinders one by one and one-help inches and slide valves with loose eccentric reversing. Drivers are three inches in diameter. The boiler is four inch diameter. Fuel, coal or atomized oil burner. Feed water by axle pump and injector.

There may be some who object to this unorthodox method of building a locomotive; well there are lots of harder ways for them, but I don't know of any quicker. One builder, with the aid of a metal bandsaw and shaper, had a frame all assembled and brazed six hours after he started to lay out the frames on steel.

For the frames we'll need two pieces of 1/4 inch by 1-3/4 inch mild steel. Cold rolled is to be discouraged because of the strain release on the cutting causing it to warp. We also need two seven inch lengths of five-eights inch square steel for pilot and drag beams. The beams and exhaust cross connections can be of one-help or five-eighth inch square steel and should be three and one-eighth inches long to start with.



The plan and elevation drawings of the complete engine were gotten out as the numberplate suggests in 1949 and were the basis of design, so to speak. To lay out the frames give a coat of white paint or marking fluid and when dry proceed. Scribe the cylinder center line, dotted on the drawing, one-half inch up from the bottom of the stock. Then at two and seven-eights inches from the front edge scribe the vertical center line of the cylinders. Another three and one-eighth inches and we have the center line of the leading axle. Five inches more is the center of the main driving axle which would leave seven and one-fourth inches of trailing frame. Now mark out the axle box slots three-fourths inch wide by one inch deep on the center lines. If you have had to use two-inch wide steel, run a line along one and three-fourths inches from the bottom over the two axle box centers for seven-eighths of an inch each side of same. At one and one-half inches up from the bottom scribe a line which is the main level of the frame where the firebox sets and valve chest level. There is a little bump up on this to give enough metal over the rocker shaft bearing holes. Note the frame top line curves up to the extra height over the axle box openings. By this full three-fourths inch frame depth over the axle box openings the hornstays or keeps have to do nothing but keep the wheels in when the engine is lifted and simply two 1/8 inch by 3/8 inch strips of steel held on with 6/32 screws. Round head will do here if you aren't too fussy as they're out of sight. The reason the keeper strips are wider than the frame is because the three-sixteenths inch hole for the spring suspension stud cuts out the center of the strip.

Lay out the rocker shaft bearing holes at eleven-sixteenths inch above the cylinder center line and two and one-fourth inches ahead from driving axle center line. Three-fourths inch ahead of the rocker shaft center scribe another vertical line, on which, in the center of each top and bottom frame bar is a none-sixty-fourths inch hole to clear the number six cap screws holding the guide bracket to the frames. Mark out two more holes in the top frame member under the firebox which will be used later to hold the boiler. At the front end mark out the centers for the steam and exhaust cross connections and the three cylinder hold-on bolts. Clamp the two frames together and drill the four nine-sixty-fourths inch holes to one-eighth inch only and river the two frames together. Now drill steam and exhaust cross connection holes five-sixteenth inch and cylinder bolting holes one-fourth inch, finally the rocker shaft, three-eights inch. A three-fourths inch hole is drilled in each end of the center lightening hole and a five-eights inch and a one-fourth inch hole at front and back of rear lightening hole. Now saw out the frame by any means at your disposal. If the hand hacksaw is the only tool, fear not, but using about a fourteen or eighteen tooth blade and a dash of cutting oil proceed with slow steady strokes and lots of pressure on the cutting stroke and you'll be surprised how fast you can go through steel and the blade will last.

Leave enough to dress up the axle box slots. This can be done in many ways--milled in the lathe or milling machine, shaped on a shaper or, take heart, filed by hand. To do the last method, file, say the front edge of each opening to the scribed line, trying with a square as you go to get the edge vertical, and straight across the frames. Now, having gotten one edge right, file the other side until a bit of three-fourths inch square steel or brass will just slide all the way up. IN case you beginners think you can't do it, well, I'm not preaching what I've not done myself. With the outline of the frame filed to suit one's desired degree of finish, be sure to get the top of the frame at the cylinder level and parallel to the cylinder center line. The fitting of cylinders is done later by placing the valve face level with the top of the frame. The frames can now be separated and the four rivet holes drilled to nine-sixty-fourths inch ready for screws. Now we want the pilot and drag beams. These are five-eights inch square steel, seven inches long and have notches milled, shaped or sawn in them to take the frame with two and one-half inches between. The outer ends are tapered off to half width.

The steam and exhaust cross connection pipes are made from square steel and have their ends turned to about one-help inch. leaving a square boss in the middle for the exhaust and a square boss off to one side for the steam pipe. The reason for this is to make smokebox piping easier. The ends are turned down to five-sixteenths inch diameter for five-sixteenth inch length to go thru the frames and are drilled through one-fourth inch. Do not drill holes for steam or exhaust taping till after brazing up.

Now we can set up for brazing and we need two spaces of three-fourths or one inch iron pipe with each end faced square and to a length of two and one-help inches, a couple of odd bolts that will pass through the axle box and we can start assembling.

Lay the frames on their backs on the bench and fit the cross connections. Drop in the pipe distance pieces between the frames with washers outside and bolts resting in axle box slots. Tighten gently.

Mix some wet brazing flux and anoint the frame ends and apply the beams. A wire tourniquet will hold them onto the frame if the fit is not tight enough to hold. Now set the frame right way up on a level surface. See that it doesn't teeter and that the beams are level with the frame top. Turn over and try with square across the axle box slots to be sure they are square across the frames so the engine won't run crab fashion.

When you're satisfied all is right tighten the tie bolts. Stand on end, drag beam down, and get your torch going. Bring up the whole beam around the frame and frame ends to a bright red. Add a little more flux and apply the brazing rod, which will run like water down into the joint. Apply rod to each side of each joint. Now let her nose dive onto your brazing hearth and ditto the pilot beam. Lay on one side, flux the inside around the cross connections. Bring up the heat and run a brass fillet around each. Ditto the other side. If the brass doesn't flow like water, but remains lumpy or plastic, it's not hot enough. Don't try any super stunts and start welding this up or warping will set in.

Clean up and file the projecting ends of the cross connections flush with the frame, which must be dressed flat for a joint surface. Use care here. You now have a one-piece frame that will stand taking to the ditch or even a cornfield meet within reason and still be an engine frame.