There are many driveline components involved that transfer the power from the Shay steam engine to the wheels. Geared Shay locomotives are unique in that driveshafts connect the engine’s crankshaft to the front and rear trucks via slip joints and universal joints. This allows the locomotive to traverse steep inclines, sharp turns, and uneven track work usually found in mountainous mining and lumber railroads. A geared locomotive’s distinct advantage over a side rod locomotive is that all the power is distributed evenly to each weight-bearing wheel, making geared locomotives some of the most powerful steam engines in the world. They are not fast, but they are mighty.

Each universal joint has two yokes, one on each side. One type of yoke is designed to fit a round shaft while the other is permanently attached to a square slip joint tube. Both begin life on the lathe, and this one will fit a round drive shaft.
 

Drilling the cross hole for the yoke posts that will connect to the u-joint housing.
 

Milling flat sides on the yoke.
 

I used a digital level to turn the yoke 90° in order to mill out the center of the yoke. The trick to using a digital level is to “zero” it on the vise or mill table and then placing it on the part.
 

Milling the center of the yoke.
 

It was important to leave the end of the yoke flat for the key way broaching operation on the hydraulic press.
 

Once the key ways were broached, then the final shape was milled using a corner rounding endmill.
 

Short sections of drill rod were then inserted though the cross holes and silver soldered in place. The center part of the rod was then milled away and the inside contact points of the yoke posts were further strengthened with TIG welds.
 

The hubs that were cut off earlier from the backs of the ring gears were turned into u-joint housings.
 

I cut four sections from a chunk of 2-3/8″ pipe I had laying around and turned them down for u-joint retaining rings.
 

Drilling and counter boring the u-joint retaining rings. Each ring was matched to its own housing so I scribed lines to help with re-positioning later on.
 

One of four sets of u-joint housings and retaining rings ready to be cross-drilled.
 

I assembled a u-joint housing and ring with all the correct length bolts except for two longer protruding bolts which rested on top of the rear vise jaw. I also set up an adjustable work stop locator against the housing. When it came time to rotate the housing for the next operation, I simply moved the longer bolts to the next set of holes and re-positioned it against the work stop locator rod.
 

Drilling and reaming the holes for the u-joint yokes.
 

Here, the housing has been rotated 90° to begin the next set of operations.
 

Turning and parting off bronze bearings for the u-joint yokes.
 

Four assembled universal joint housings ready for their yokes.
 

Milling one of the yokes that will be attached to a slip joint square tube.
 

Slip joint square tubes ready to be joined to their respective yokes. These were eventually brazed together.
 

Steel slip joint shaft that telescopes inside of the square tube was turned from square stock.
 

One of the assembled drive shaft slip joints with universal joints on the Shay. The engine’s crankshaft is now connected to the trucks!