< Driving Wheel Assembly 1 >
Full scale driving wheel is secured on axle
with rectangle "key". After that,
quartering is done with "Quartering
machine" that can bore crankpin hole
or turn crankpin O.D. at desired radius and
angle from the axle center. I employ similar
procedure. Crankpin holes will be opened
before assembly. And then, the wheels will
be put on an axle with keys. Finally, I measure
quartering error and prepare 'eccentric'
crankpins that can compensate the error.
Anyway, the crankpin hole should be opened
in correct position as much as possible.
Key way in a wheel is cut by "Slotter". I had already made a hand slotter on Feb.2007. So I prepare a cutter for the tool.
I utilized 5 mm square tool bit of high speed steel for the cutter. It was broken in a desired length and silver soldered into groove of a steel round bar. Note a hard stainless steel wire secures the bit in the groove.
The cutter was finished with grinder and oil stone.
After clamping the wheel on the extended face plate, the center spigot is driven out. Then, the face plate is locked in suitable angle with a wood block between the saddle and the faceplate. After that the key way is cut by the tool. It was cut to 1.5 mm depth with 0.05 mm step inching.
The crankpin hole should be opened in true radius from the axle center and in truly opposite from the key position. To do this, I prepared a drilling jig like the photo. The hole's diameter is 12.9 mm. The brass C-shape ring is for adjusting diameter of the axle, because the 2nd driving axle is larger than the 1st and 3rd axles.
Due to diameter error of the wheel center hole, the jig sometimes has minute play in angle. In such cases, I measured the play with DTI, found midpoint of the play and fixed the jig at the point. After that, I drilled 12.9 mm through the jig and reamed to 13.0 mm without the jig.
Here I make axleboxes. They are made from gunmetal castings. In the lathe, I finished the bottom face, turned over, finished top face and center hole.
The top face was finished first. Note a round bar determine height from the hole. After that, the bottom face was finished.
The photo shows how to cut the side grooves of the axlebox symmetrically. A dummy axle is passed through the axlebox and is supported by a pair of blocks at both ends. Then the axlebox is chuck in a vise. After finishing one side, the job is turned over and chucked again. Thus the both grooves can be cut in the same distance from the axle center.
So as to allow the axlebox to roll in the frame, the groove was extended to X-shape. To do this, the vise was leaned +/- 3 degrees from square. Incidentally, full size axlebox cannot roll in the frame. The axle itself rolls in the axlebox.
Channel for lubrication was cut. It consists of longitudinal groove and center hole with CSK. When practice, I drop oil on the axlebox through spokes of the wheel. And then axle and side grooves are lubricated at the same time.
In order to ease maintenance, I split the axlebox. First, horizontal hole for secure pin was drilled and reamed just under the axle hole. Next, two vertical slits were cut from the bottom with 0.5 mm slitting saw.
Finally horizontal slits from the axle hole were cut with a fret saw. Then the axlebox is separated.
The photo shows completed axleboxes with secure pins. 0.5 mm gap is left after assembly. But it is no problem because the lower part is exactly located by the pin and the axle itself. Moreover the axle weight always loads on upper semicircle of the hole.