GALLOWAY 5HP HIT & MISS BUILD IN 1:3 SCALE
By Jason Ballamy 
Part seven -  Bearings and piston
M4. C4n

The bronze governor weight was cleaned up and the pivot bolt machined.

And finally bolted in place
Looking back at the balance weight we can see it pivots on the central hole, on the left is the actual weight and the curved arm to the right has an angled face. As the revs increase the weight will pivot outwards causing the angled face on the other side to move inwards which in turn acts against a matching angled edge on the spool and, in effect, wedges the spool away from the flywheel.

On the Galloway the spool carries one end of a forked lever, part way down the lever is a pad which acts against a shaft that passes through the timing gear stud. In turn this shaft acts against the latch arm which is attached to the latch and pushes the latch into the latch block on the exhaust push rod until the movement is sufficient to latch the rod in the open position.
























With the crankshaft and flywheels done the bearings were next on the list. A length of 27mm bronze was cut with the hacksaw to get the basic split bearings.

The faces were milled flat and then soft soldered together before transferring to the lathe to machine to shape.
The finished bearings sitting in place.
Looking for a quick job one evening I decided to make the supplied timing gear a bit more like the ones on the full size engine as the supplied one is just a plain gear.
I dished out the face and then used the rotary table to cut the window in the central web.
The piston is supplied as an aluminium casting with a large chucking spigot on one end, this was trued up first to get a decent surface to hold onto.
I clocked the inner cast surfaces true and then took a cut off the end and took the OD down to 0.050" oversize.
And then used a boring bar to hollow out the skirt to size before leaving the casting to cool.
I then went back and machined the OD to size at which point the casting started to look a bit porous but it should be OK in use.
So I carried on and cut the ring and oil grooves


Over to the mill to take the gap for the con rod to width.
Then without rotating the table mounted it vertically so the pin hole is at right angles to the previously machined faces
Then drill and thread the holes for the pin retaining screws.
It was then machined to length to complete.


PART ONE HERE   PART TWO HERE   PART THREE HERE  PART FOUR HERE

PART FIVE HERE   PART SIX HERE     PART SEVEN