Smokebox Throttle Valves

[Bill Shields]

Started in 1997 and that's way too long?

Seems like I am running in reverse in comparison...

Either that, or I have waaaaay too many other things to do.

Looks exquisite (if that is a permissible description for a loco).

[Harold_V]

Harold - Waaaaay too long! I started in 1997.

Thanks!

I disagree that it's "way too long". The amount of work in building an engine (properly) is huge. Frankly, I'm surprised you accomplished the task in such short order. If your workmanship is as good as it appears, you have an excellent engine. Love to see it in person!

Two years ago Susan and I were in town to see the Daylight and UP 844 at the same time. Very impressive engines.

Thanks for the web site link. Now to find some spare time to explore!

Harold

[PRR 5741]

Hi all,
That throttle looks very similar to the front-end throttle that LBSC designed for his 3.5" gauge Brittannia in the Model Engineer. I like the throttle design, and I'm thinking of building my own version for my own engines someday.

Safe and Happy Steaming,
Matt T.

[Dan Willey]

Dan... beautiful locomotive!

Question: Where did you get your compound compressor castings?

Thanks,
Dan

[Dan_M]

I got the Westinghouse duplex compressor castings from "SuperPower Detail" which is no longer in business.

Dan

[SF2900]

Dan... beautiful locomotive!

Question: Where did you get your compound compressor castings?

Ed Yungling of cab forward fame makes some great looking dummy compressor castings. You might want to check with him. He goes by LSGOD here on chaski.

[Mark in Modesto]

Back in the later 70's I had the pleasure of working on an ATSF 2900 series Northern, which continues to lanquish in a local park. In order to hydro the boiler, the throttle had to be rebuilt. Removing the cover revealed a line of poppets, about six, plus a smaller 'pilot' valve for the initial crack of the throttle.

The brass box gcarson posted looks like someone's attempt to create the same sort of thing...a progressive pair of poppets.

As previously noted, steam doesn't need a big hole to get where it's going, and it seems logical to me that a neat throttle valve could be built using three or four tiny passages, with SS balls instead of poppets, with lifting rods successively pushed by a carefully made cam.

It could certainly be a fun challenge to design and build, and it might result in a very neat package to throttle higher powered live steamers.

As also suggested earlier in this thread, the original poster's problem will probably be resolved by considerably reducing the size of the delivery pipe's innards.

My 3 cents worth...


Mark in Modesto

ps. Our giant 4-8-4 passed the squeeze test...COLD...yet still rots in a park, over thirty years later. Sigh...

[Dick_Morris]

It could certainly be a fun challenge to design and build, and it might result in a very neat package to throttle higher powered live steamers.

My recollection is that the "4 aces" series in Modeltec included a multi-poppet valve throttle.

[PRR 5741]

Hi all,
Indeed, Roy Johnston's Timken "4 Aces" did possess a multiple-valve front-end poppet-valve throttle, however, it was upstream of the superheater, rather than downstream, as it would be on the prototype. Also, Roy's throttle had four different sizes of poppet valves, whereas the prototype had only two sizes of valves, at least that is my understanding, the pilot valve, and the main valves.
The same holds true for LBSC's poppet-valve throttle for his 3 1/2 inch gauge Britannia, at least the fact that it is upstream of the superheaters. I have, however, learned a great deal from both Roy's design and LBSC's design, but if I were to take design cues from them, their designs would require substantial modification to work in my locomotive, as Roys throttle is for a 4-8-4, and LBSC's design is for a 4-6-2, and neither design would fit in the smokebox of the G5s 4-6-0 I'm building: Roy's throttle of course is way too long and wide, and LBSC's is too small as it has only two valves, the pilot and main valve, where I would use no fewer than four main valves for a G5s, but that's just me.

Happy Easter,
Matt T.

P.S.: What, if any, benefits are there in having more main valves in the throttle?

[Mark in Modesto]

>P.S.: What, if any, benefits are there in having more main valves in the throttle?


I think it would be to effect finer control, but the sizes of the valves, or more accurately, the opening exposed with each valve, would have to be carefully calculated so you wouldn't hit the maximum size with the first valve's opening.

If I were building an experimental throttle, I'd use replaceable jets in each valve passage, so I could fool around with different hole sizes to get the smoothest transition from closed to fully open, but it's from the closed to partly open I'd be most concerned about getting right for fine control in between.

I feel certain it could all be packaged to fit your available space, and I think it would be a fun project, if one had the time and need.


Mark in Modesto