Shay Line Shafts,
Universals & Drive Shafts
The new lathe drive belt finally arrived so I was able to finish and document this part before I have to shelve the project for a few weeks.
Line Shafts: A line shaft subsystem consisting of bearings, line shaft, bevel gears, collars and spacers is located on the right side of each truck. The subsystem for the middle truck is shown below. The truck is setting on the test fixture. (I see I left one of the screws off the rear bearing cover plate.)
This shows the second attempt at assembling the line shafts. The first time I used 3/16" diameter expansion pins to hold the pinion gears and collars to the line shaft. The pieces must have slipped when I drilled the holes and the result was unsatisfactory. Before redoing the shaft I checked everything very carefully to make sure I wouldn't have to do it the third time. It was at that point I discovered that I had mounted the pinion gears behind the axel. Dumb! The pinion gears go in front of the axels as shown in the photo. That made the redo less painful since I had to fix two problems.
I decided to use set screws in the redo. Since I had already drilled 3/16": holes through the gears and collars, the minimum size set screw I could use was 1/4" diameter. I chose 1/4"-28 dog point set screws for the bevel gears and 1/4"-28 hollow set screws for the collars. The dog point is ~ 3/16" diameter so it should have the same holding force as the expansion pin. With the two set screws, I can tighten one to hold the gear and drill the 1/8" deep hole for the dog point of the other set screw --- then inset that set screw, remove the first set screw and drill the hole for that dog point. The forces on the collars are less so I'm hoping the hollow point set screws will hold them in place.
Drive Shafts: The drive shafts are made up a male and a female slip joint as shown below. All the female parts are the same length whereas the male parts of have different lengths as required. The longest male part for between the middle and rear truck is shown below. Kenneth used brass for the male part. I used steel like the prototype.
The combined line shaft - universal - drive shaft is shown in photo below. That's the middle truck with the engine on the right.
The installation of the line and drive shafts made it possible to run the locomotive on compressed air. It ran slick --- can't wait to get it on a track.
Some of the techniques used to fabricate the line shafts, universals and drive shafts are described in the accompanying notes.