Engines > From Plans
Another Pennsylvania A3 Switcher
JCvdW:
Thanks for the comments Kim! I still remember following along as you fabricated your drivers. What a feat, and they came out great! At the time I could not even spell "silver solder" yet.
I closely followed Kozo's instructions to machine the drivers.
After the second chucking:
And after completing all the lathe work:
The drilling jig that was used to accurately drill the crank pin holes came in handy later to hold the pump and lubricator eccentrics to locate and drill the holes for the set screws.
And finally the drivers, axles, eccentrics, crank pins and side rod pins are complete. Could not resist putting them all together for a family shot:
The 11mm axles were turned from 12 mm silver steel. It took a few attempts to hit the correct diameter for a snug fit in the drivers and axle boxes. Using wet and dry sanding paper to remove the last 30 micron turned out to be the answer. This was also the technique used for the crank pins, which were turned from the scrapped axles.
Next up are painting and quartering the drivers. But I first need to test the 2 component automative paint that was used on the tender, to see if it can handle to heat of the engine.
Kim:
The drivers came out really nicely! You must be pleased with those! :ThumbsUp: :popcorn: :popcorn:
Kim
Roger B:
Your vibration reduction system worked well :ThumbsUp: :ThumbsUp:
The frames and wheels are looking good :praise2:
JCvdW:
Kim & Roger, thanks very much for the kind comments!
Before painting and quartering the drivers, I thought it a good idea to visit the Western Province Live Steamers and verify that the engine and tender actually fit on their 3.5 inch track. They graciously allowed me to push it through a switch or two, and it rolled through without a hitch!
The red 2K automative paint used on the tender was heat tested in the kitchen oven. It lost a bit of colour at 250 deg C, but there was no sign of it coming off at all. It should be more than suitable for the drivers.
After painting, the front and rear drivers were quartered in a wooden jig that was cut with my CNC router. The drivers were glued to the axles with Loctile 638 retaining compound.
Before proceeding any further, the accuracy of the quartering had to be checked. The holes in the side rods were located and drilled using Kozo's ingenious jig. With the bronze bushes inserted in the side rods, quartering could then be checked ... and with the side rods installed on both sides, the drivers would not move at all!
Putting the driver assemblies back onto the quartering jig revealed the problem. Neither of the assemblies accurately fit the jig! There was a bit of play between the jig and the crank pins of the rear drivers, while the axle of the front drivers did not touch the 90 deg notch of the jig on one side at all.
To redo the quartering, one of the drivers had to be removed from each axle. Fearing possible paint damage or warping, I did not want to use heat to weaken the Loctite. The assemblies were taken to a local engineering workshop, where the drivers were easily removed undamaged using an arbour press.
To ensure accurate alignment during quartering, the axles and crank pins must be constrained in the jig as far as possible. Holes were drilled in the base of the jig for cable ties that can hold the axle and crank pins securely in place while the Loctile cures. The quartering jig was also held in the bench vice for more control during assembly.
To my relief, this solved the problem! The connected drivers now smoothly turn as one!
http://www.youtube.com/watch?v=kfwEToaDSdE
Time to shape the side rods!
Kim:
They seem to run beautifully now! :ThumbsUp: :popcorn: :popcorn:
That's a pretty exciting thing, to get to see your tender and engine chassis on some real track! They look good!
Kim
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