2.5" Gauge Green Arrow Build

Hi Kim, just an FYI - Union Pacific Railroad had some 4-12-2 locomotives, class 9000, with 3 cylinders. Two outside ones as usual but also a big honkin 27 x 31" one between the frames under the smokebox. These were big locomotives. The third cylinder required a huge crank axle on one set of drivers of course, and rods, valve gear etc between the frames, which complicated maintenance and repairs. UP gave up on three cyl engines after a few years I believe.

Some years later UP tried a much simpler approach to big power , the 4-6-6-4 Challengers and 4-8-8-4 Big Boys .... 

In the UK another engine which had three cylinders was Southern Railway's 4-4-0 "Schools" class. One, #926, still operates on the North Yorkshire Moors Railway, there are YT videos of it running in Sept this year.

Careful about watching YT train videos - it's easy to fall down the rabbit hole and every other project comes to a halt! 

Did some preliminary machining on the steam chest casting I made with the cylinder and I believe it's going to work ok.

Another interesting feature on these engines, the offset of the valve rod from the center of the chest, don't think I've ever seen that before either. I love how they did the rocker linkages for the third cylinder chest too.

It's going to be a bit of extra work, but I hope I can get everything right.

Did another pour yesterday and I believe I got a good cylinder!!

Second cylinder looks good so far. Got a clean bore.

Got the steam ports machined in and drilled. Only mistake I made was not compensating for the depth of the flanges when I first started machining the cylinder. One is thicker than the other. I'll have to do something on one side for the drain cocks.

Also made another pour and got another good cylinder and steam chest. You can see how much material has to be removed. This time I vented the core better and baked the core some before using it.

Got some initial machinging done on the second outside cylinder. Also got the faceplate ballanced better this go-around. Still have some inclusion on the port face I hope will clean up.

This is impressive work done on the skilful casting of the cylinder blocks and the crisp machining of the nice castings, coming on very well.  Dave

nice start on this magnificent loco...
and very instructive thread too !

Quote from: ChipswitheverythingThis is impressive work done on the skilful casting of the cylinder blocks and the crisp machining of the nice castings, coming on very well.  Dave

Thanks Dave. I've been trying to do my own castings for a little over a year now. It's definately been a learning curve.

Quote from: Zephyrinnice start on this magnificent loco...
and very instructive thread too !

Thanks Zephyrin.

After doing some more detailed measurements with the placement on the frames, I found that I had miss calculated one of the side depths on the mold. So, These will go back into the melting pot and I'll start over on the cylinders  I've adjusted the measurements so the new ones should be good. The side that bolts to the frame is supposed to be 1" in hight. And the frames are already drilled.
I've aslo increased the cylinder flange size slightly, for better fitment of the drain cocks.

Bummer!  We've  all been there. Take it as more playtime in the shop, and good practice.

Sorry about that setback...  That's always frustrating. 

I'd like to say I've never had to redo a part before.  But we all know I'd be lying! 

You'll get it next time! 

Kim

Thanks Kim and Crueby,
I've found another issue I think I can work around. The holes in the frame should be at 1.4* from parallel, and they were drilled at 5.5*. I don't think I'll have to fill and re-drill them yet. and the reversing rod hole is in the wrong place as well. It's tucked behind the driving wheels and should be infront of them.