Each bearing is shown with two standards.  The doubling increases rigidity, and enables an oil cup to be fixed centrally.

The shape of the standards will be gathered from Fig. 53, their outline being dotted in behind the crank.

Cut out and bend the standards—­after drilling the holes for the foot screws—­before measuring off for the centres of the holes; in fact, follow the course laid down with regard to the cylinder standards.

Make a bold scratch across the bedplate to show where the centre line of the shaft should be, and another along the bed for the piston-rod centre line. (Position given on p. 138.)

Bore holes in the bearings for the oil cups, which may be merely forced in after the engine is complete.

The crank boss may be made out of a brass disc 2-3/4 inches diameter and 3/16 inch thick, from which two curved pieces are cut to reduce the crank to the shape shown in Fig. 53.  The heavier portion, on the side of the shaft away from the crank pin, helps to counterbalance the weight of the connecting and piston rods.  In Fig. 54 (plan of engine) you will see that extra weight in this part has been obtained by fixing a piece of suitably curved metal to the back of the boss.

The mounting of the crank boss on the shaft and the insertion of the crank pin into the boss might well be entrusted to an expert mechanic, as absolute “squareness” is essential for satisfactory working.  Screw-thread attachments should be used, and the crankshaft should project sufficiently to allow room for a flat lock nut.  The crank pin will be rendered immovable by a small lock screw penetrating the boss edgeways and engaging with a nick in the pin.

Fixing the Standards and Bearings.—­Place the two bearings in their standards and slip the crank shaft through them.  Place standards on the bed, with their centre lines on the crank-shaft centre line.  The face of the crank should be about 3/8 inch away from the piston rod centre line.  Bring the nearer bearing up against the back of the disc, and arrange the standards equidistantly from the ends of the bearing.  The other bearing should overlap the edge of the bed by about 1/8 inch.  Get all standards square to the edge of the bed, and mark off the positions of screw holes in bed.  Remove the standards, drill and tap the bed-plate holes, and replace parts as before, taking care that the lubricating holes in the bearings point vertically upwards.  Then solder bearings to standards.

If any difficulty is experienced in getting all four standards to bed properly, make the bearing holes in the two inner ones a rather easy fit.  The presence of the crank-shaft will assure the bearings being in line when the soldering is completed.

The standards and bed should have matching marks made on them.

The Eccentric.—­This can be formed by soldering two thin brass discs 1-15/16-inch diameter concentrically to the sides of a disc of 1-15/16-inch diameter and 5/16 inch thick.  The centre of the shaft hole must be exactly 9/32 inch from the centre of the eccentric to give the proper valve-travel.  Drill and tap the eccentric edgeways for a lock screw.