Derek Round renovates a Shay

This unusual Shay came from the estate of John Orson, and I’ve just finished rebuilding it.

I’ll just put as short a comment as I can to explain the pictures.

Fairly obviously the first two pictures are as it is now, ready to run.

The cab roof has been redone, which took an age as the only corrugated sheets I could get hold of were aluminium, and finding a glue that worked to glue them in place took an age! A log load was needed (straightforward), and the motor (an early osmotor?) main bearings were completely worn out. The bogies, drive shafts and sliding joints needed some maintenance. As acquired, the safety valve vented inside the cab, filling everything with steam, so a short extension has been added to vent above the cab roof.

This loco was manually controlled, which doesn’t suit me, so firstly, three servos were fitted to control the usual functions of forward/reverse, regulator and gas valve control. Twas a tad tight but the only real difficulty was where to put the servo to operate the forward/reverse valve. The only place it would fit was behind and close to the valve, and this necessitated making an extra grey toolbox to cover it up, which I think looks OK.

The gas tank controls took a little sorting. The servo is mounted onto the tank on a brass plate which is (exterior) sticky padded to the gas tank, the sticky pads don’t like too much heat (as they lose their stickiness(!) but gas tanks run cool . And the servo arm needed an extension to increase the gas valve movement. (Just found out there is unit available that electrically increases servo angular movement) You can also see the linkage to the regulator from the servo, that the driver is sitting on!

The engine appears to be a variation on the Osmotor (your suggestions and thoughts on this would be appreciated), and the main bearings were very worn. This was easily fixed, and the engine then ran nicely on air.

Next the drive shafts, universal joints and slidey bits were all replaced, and the complete loco was tested on a 3ft radius curve to prove it would go around without anything locking up or binding.

Then the trucks were attended to. There were wear and tear issues with excessive or too tight clearances, but what took some brain cells was how to fix the wheels to the axles, as they were now quite loose on the axles (originally assembled on the axles as a tight fit). The really thin Loctite didn’t work, and you can see how I did that in the next few pictures.

There, you can see the solid aluminium spacer in the middle of the wheels. This is grub screwed to the axles in the centre (just out if sight), and brass pegs are inserted in each flat end, so that they engage with the wheel spokes at both ends, hence driving the wheels.

On test, everything worked (eventually), except raising steam took an inordinate amount of time, which was odd. Heat output from the burner was poor, as in raising steam took ages, and steam output also was poor as the motor would not run continuously. Together with the fact that the burner howled like a banshee indicated something was very wrong! But what?

The burner was a circular ceramic one and running outside the boiler into a flue (same size as the boiler) showed combustion was poor, not enough air was being sucked in for good combustion. Some research found that Clevedon Steam had a replacement burner that they said produced more heat than the original, so this was tried...result no change...the burn was still lacking air!

So I tried a different jet, just to see the effect. I realised that the burner originally had a very large jet, so changed it (reduced it) to a normal sized jet. Result, EUREKA! A really hot flame, no howling, loads of heat, lots of air being sucked in with the gas, and less gas being used; result happiness!

This result is most odd, and counter-intuitive? Apparently, in this case, reducing the jet orifice size gives more heat and reduces gas consumption as well. Perhaps what is happening is that reducing the jet size, increases the gas velocity as it comes out the jet, and this high speed jet sucks more air into the air/gas mix, which burns hotter. And of course gas consumption is lower. Any more thoughts out there?

Anyway, I look forward to running my Shay, when we are allowed to!!!


























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