Large Scale Central

Performance Upgrades for Accucraft 2Cyl Shay

Electronics Live Steam
#1

I recently pulled my 2 Cylinder live steam Shay from moth ball storage, where it has been for 10 years, for a run around the railroad in a recent snow fall. This rekindled my interest in live steam and prompted me to look into improving it’s performance. Jason Kovac at The Train Department offers a number of simple upgrades that don’t require getting into more complicated adjustments like timing. Specifically, Jason offers two control valve upgrades; one for the finicky gas valve that is difficult to adjust and fails to hold it’s adjustment for the duration of a run. The second is a steam valve that offers finer throttle adjustment that promises to improve low-speed performance.

I ordered them up and they arrived on Monday. Last evening I began the task of installing them. First up was the Gas Valve shown here below the stock valve…

Jason’s replacement consists of a thread adapter that screws into the existing valve body using a high temperature thread sealant, then a new needle with a much shallower taper, finer adjustment thread, and two O rings. Installation is a matter of removing the old, inserting the adapter and then screwing in the new valve using the knob. On some locos this is very simple, but the Accucraft Shay gas tank is very close to the rear cab wall preventing the old valve from being removed. The cab superstructure / water tank needs to be detached from the deck to allow access. There are 8 screws. Two at the rear of the tank, two on top of the T-Boiler and 4 under the deck attaching the rear cab wall to the deck which are removed from underneath…

With the screws removed, I was able to shift the superstructure to allow access to the valve stem. Fortunately, the home made Johnson Bar/ Servo link was flexible enough that I did not need to detach it…

Once the valve was in and everything back together, I realized that the replacement shaft was too long and wouldn’t allow the valve to be opened more than a crack before conflicting with the cab wall. So everything came apart again so I could cut 2mm from the shaft with my Dremel. Jason’s site does mention that the length may require trimming.

With the modified gas valve installed and the super structure replaced again, it was time to move on to the steam valve. The photo below shows the stock valve on top and the replacement on the bottom. The replacement has a much finer needle, more adjustment threads, and two O rings…

This valve is a very simple swap. Just unscrew the existing one using the knob, swap the knob to the new valve, then screw it back in. No conflict with the super structure at all. Here is everything put back together awaiting the battery box and RC gear…

Once everything was opened up, it seemed like a good time to swap the RC batteries. The last time they were replaced was 2010. Still plenty of life left, but a royal pain to chnge so I did it anyway! I cobbled this battery box together from two boxes so batteries would fit in the tank with the servo…

The wood load at the right hides the radio gear and power switch…

Gee, look at that. Model airplane parts used for a train. How ridiculous!!!

Battery case closed up and back in place ready for the tank top and load to be installed. Operational testing is scheduled for today.

Two more upgrades I am considering is a servo for throttle control and a pop style safety valve. Need to get a mini servo and experiment with placement.

#2

Jon my only point was the joysticks on the throttle, not servos or necessarily receivers.

Glad you found a way to rekindle your interest.

#3

Very authentic looking rust on that old loco. Nice work!

#4

Thanks Pete. I did that about 12-14 years ago with a brush in my living room. It really looked great before I clear coated it which took away a lot of the dry brush effects, but from the right angle where you don’t see the gloss (it was a matte clear), it looks pretty good. While it was on the bench I wiped it down. On the cranks and rods I lost a bit of the paint from the oil.

#5

I am considering is a servo for throttle control and a pop style safety valve

Well, the pop valves are easy - though personally I have lived with weeping Accucraft valves (very prototypical) on most of my locos and they don’t seem to do any harm.

Your new throttle is going to make things interesting for the servo. Accucraft locos are at full open when about 90-120 degrees turned, which is pretty easy to achieve with a lever and rod setup. If your new throttle valve gives you 180+ degrees to full throttle, you are going to have to try something else. Many of my steamers have/had 1/8" chain drive for the throttle, and (in theory) you can set up the sprocket sizes so that a 90 degree servo can move the throttle 180 degrees. In practice I found that the servo struggled with the torque need that resulted from the 2:1 ratio, especially shifting the throttle from fully closed where it tended to stick. I’d look at something like the Hitec HS85MG with metal gears.

#6

Thanks. That’s an MG model in there now. I was concerned about heat. I haven’t fired it yet so I haven’t played with the new throttle.

#7

I ran it light up the grade as far as Indian Hill Junction and back a few times playing with the throttle. Seems like 90 degrees might be enough, but with careful adjustment prior to starting up the grade, the Johnson bar control seems to be just fine. You can hear through the chuffer when the bar is set just right to match the throttle and it plugs away at a nice prototypical speed up the hill. Trials with some rolling stock soon.

Still runs very choppy in reverse, but I didn’t expect that to change. Probably not smooth enough for switching; but I’ll keep playing - it might be my touch on the bar.