Blackstaffe Beginner's Locomotive Part 2
An 0-4-0 Switcher of Simple Design
Victoria Society of Model Engineers
The Miniature Locomotive, November-December 1952
This time we'll tackle the guide bracket pump stay, etc. This is cut out of one-eighth inch steel plate. You'll need a piece two and one-half by six inches. Mark out the outline, the three-eights inch holes at the top, each side, are for the valve stems to pass through and one-half inch hole is for pump body. It should fit snugly between the frames. Now rivet a couple of strips of one-fourth by one-fourth inch steel one and one-half inches long on each side of the extension going down between the frames. The little lugs that take the guide bar bolts are three-sixteenths by one-fourth inch, same material as the guides. If this is unobtainable, one-fourth by one-fourth inch guides can be used but are not so neat looking. If so, these little lugs will only be one-eighth inch thick by one-fourth inch wide.
It will be as well not to braze these on until the guides are in place. Lay this aside as we need the rocker shaft bearings in order to locate the guide bracket in the frame. So, we'll turn to a little lighter work for a change.
The rocker shaft outer bearings are turned from five-eighths inch round brass rod. Chuck, turn down the three-eighths inch for seven-sixteenths inch length and screw three-eighths inch S.A.E. for half-way. Center, drill fifteen-sixty-fourths inch and ream one-fourth inch. Leaving one-eighth inch thick flange, run a round nose tool in and turn a gentle taper (by eye) climaxing at about three-eighths inch diameter. One-half inch away from frame face. Part off to length.
For the center bearing make another bush of one-half inch diameter by three-fourths inch long. It is brazed to a bracket made from a scrap of one-eighth inch thick angle iron or alternatively it could be brazed to a bit of one-fourth thick steel. The main thing is to get a bearing parallel to this base and whose center is one-half inch from its base. Drill two nine-sixty-fourths holes in the foot just above the base.
Now thin down two three-eights inch S.A.E. nuts to one-eighth inch thick and hold in the outer bearings with these nuts. Slip a bit of straight one-fourth inch rod through these with the center bearing on it. Now put the guide bracket into place ie; when the foot of the center bearings is flat against the bracket and the bracket is vertical to the frame and square across it. Two bits of three-eights inch steel slipped between the rocker shaft and bracket should ensure the latter. A cross bolt through the frames on each side of the bracket will hold it in place while you spot the holes through the frame into the one-fourth inch square uprights. Follow up with seven-sixty-fourths inch holes and tap number 6-32. Use hex head.
Heat up your soldering iron and solder the center bearing to the guide bracket. Remove and drill through nine-sixty-fourths inch and bolt on with nuts on rear side. The solder is done with and can be melted off.
You may feel like a little fancy work so drill oil holes in the bearings and prepare to make the rocker arms. The outside ones are brazed onto the shafts and are made from the three-eighths inch square steel. Mark out the holes and drill them first. Double drill the one-fourth inch holes; i.e--drill first fifteen-sixty-fourths inch, then one-fourth inch to get a good fit on the shaft. The top hole is half clearing and half tapped. Saw down and in, cutting away most of the metal, leave a boss at the small end. Round this boss up by filing before you taper the arm and can still hold it in a vise. Now round off the big end and taper to small end. Slightly countersink on the back the one-fourth inch hole. They can now be driven onto two lengths of one-fourth inch cold rolled steel. Set them square, flux, heat up and give a touch of silver solder as we do want a penetrated strong joint. File off the projecting shaft on the outside and plush up. Cut off shafts to two inches from inside. This should just about let them butt in the center bearing. The inside rocker arms are made from three-eighths by one-fourth inch or three-eighths inch square thinned down. The one-fourth inch hole should be reamed for the shaft so the clamp screw don't have to do more than clamp. The lower side is drilled nine-sixty-fourths inch for number of six pin.
The pins for the attachment of eccentric rods to these arms are turned from one-fourth inch steel to three-sixteenths diameter for one-eighth inch full length for th eone-eighth inch thick eccentric rod to work on and the end turned down to nine-sixty-fourths inch and threaded enough to take a number six nut.
The pins for the attachment of the valve rods are also from one-fourth inch steel and are turned nine-sixty-fourths inch up to the head and threaded halfway, being three-fourths inch long under the head. They will be screwed in to leave a working end clearance on the valve rod and locked by a number six nut. These nuts will need to be made as a standard number six is five-sixteenths inch across the flats and would look awful against a one-fourth inch diameter boss. Make six of three-sixteenths inch hex while you are at it. You'll need four more for piston rod glands.
The stem and exhaust cross connections can now be drilled right through twenty-one-sixty-fourths and tapped one-eighth inch pipe thread both top and bottom. Get these holes tapped as vertically as possible so your pipes won't look "Morning after the night before." The reason why these are tapped from bottom up as well is that the oil pipe enters opposite the steam pipe and the blower nozzle is housed inside the main exhaust nozzle where it won't get knocked out of place during tube punching.
Now for some general information on the job.
The wheels used on the local engines are Juliet's wheels from Kenions of England but as there are quite a few low-wheeled switchers in the eastern United States I think possibly Mr. Friend of the Yankee Model Shop may be able to supply an American casting.
The cylinders are of cast iron and I will start the next installment on this little locomotive with the making of the cylinder pattern not a hard job at all. For fast workers who gets this done and are waiting. I might say that the tender under frame is made just the same as the engine frame and there is enough information on the drawing to let you make it up as a spare project.
The boiler is made of one-sixteenth copper which at these times may take a little while to scrounge so start looking.