Valve Gear Varieties

To answer your original question, several of these were tried before Walschaerts was widely adopted, so the comparison might be better made with Stephenson's gear.
Joy's valve gear, for example, was found to give not just more room for decent bearings but actually improved performance on the L&Y, including better steaming and reduced coal consumption (compared to Stephenson's). But how much of this was the gear being better set up, for example, rather than intrinsic to the design?
I don't think you can say that Smith's compound gear didn't take off. It was highly successful in its own way, and most of the successful compound locos in the British isles used it (not classes but individual locos). It was surely compounding rather than the gear which didn't "take off". There's a Smith compound on the mainline still today!

 

For anyone that is interested there is a photo of 1850 with Marshall Valve Gear at http://www.semgonline.com/steam/nclass_01.html


Caption: This photograph of Nº1850 in Eastleigh paint shop was taken in February 1934 and shows the locomotive fitted with Marshall valve gear and indicator shelters. The experiment with the Marshall valve gear was quite short-lived as although successful at slow speeds it "knocked" when near 50-55 m.p.h and, ideed, disintegrated when at speed near Woking.
The Walschaerts valve gear was replaced at Brighton and the loco returned to traffic in "normal" guise on 11th April 1934.

 

I'm just wondering what varieties of conjugated valvegear were tried.

It's not impossible devise a scheme that would give the correct motion (in the mathematical sense) with an arrangement of hydraulic cylinders, or, for that matter, a length of bike chain and a few pulleys, but would these have stood up to railway usage?

 

An interesting 'horizontal' version of inside Walschaerts Motion - STEPHENSON-MOLYNEUX shown here ...

https://railwaywondersoftheworld.com/valvegears2.html

 

It is surprising - or maybe significant - that Holcroft did not say anything in his autobiography about the Marshall gear on the N class, as he was working for Maunsell at the time and must have been aware of the experiment.

 

Holcroft does write about it in Locomotive Adventure Volume 2.
He says it was removed following damage to the gear

 

Jon, thanks for that, I have not managed to find an affordable copy of Volume 2.

I wonder which part of the gear it was that broke? It suggests overloading, which seems possible since one set of standard valve gear was adapted to drive two sets of valves. The sort of thing which happens with prototypes. It was an interesting idea and as with so many other innovations in steam locos it was dismissed what it did not work properly first time.

 

The thing is both Stephensons and Walschaerts valve gears are difficult to beat if designed correctly. Often these other variations are to avoid patents or deal with other constraints such as space. There are many attempts to fix percived issues with these gears that usually makes them worse.

Walschaerts is interesting because you need a nice long oblong space to fit it in. Ideal for outside cylinder express engines. It can be tricky to design for middle cylinders where space is a premium, without compromising the valve events though. This gives rise to things like conjugated valve gear and Bullieds miniature Walschaerts.

Poppet valve gears bring with them their own complications often to do with materials. Something these days we can solve however these days the whole concept of a steam loco is well out of date.

Tim

 

There is little known, but already as a 4-year old the undersigned developed his first valve gear design!



Knut

 

On the Europe picture puzzle thread, there has just been an appearance from some Czechoslovakian engines.

The linked You-Tube of CSD Class 498 illustatrates one of the solutions for driving the inside valve gear of a 3-cylinder engine. The drive is taken from an additional outside crank on the 3rd coupled axle. The valve gears for the outside cylinders are driven from cranks on the 2nd coupled axle in the normal manner.



Similar arrangements found on other Czechoslovak and some German and Danish 3-cylinder engines, but I don't think it was ever tried in Britain.

 

I take it that that is a water carrier for the steam locomotive at the rear of the train, ahead of the Diesel.

 

Tennessee Valley Railroad, Soul Shops 21/10/2017. Southern R/R 2-8-0 630 ,fitted with Southern R/R valve gear.Not in use on my day of visit but fully opperational.

 

You can also add Andre Chapelon`s world known french SNCF 242A1, not to mention his six-cylindered 160A1




Knut

 

The outside 3rd crank is new to me. I know that the German 3-cylinder locos had a short throw crank on the axle behind the driving axle to act as an eccentric. Both arrangements, by driving the motion off a driven (as opposed to driving) axle remind me of Fletcher Jennings and the 'very peculiar' motion of the Talyllyn's Dolgoch (and some others).
Pat

 

Valvegear makes my head hurt...

This quote from the page did make me chuckle though "JOY’S VALVE GEAR, invented by the late David Joy in 1879,"
If he was inventing valve gears in 1879 , I think it's some while since you'd need to clarify he'd passed on...

 

The 'scissors link' modified Walschaerts gear fitted to GWR 40 'North Star' (later 4000...) was interesting in that it derived its motion from the adjacent crosshead.

 

This french Bonnefond valve gear is quite interesting. Though complex and difficult to understand

https://www.cparama.com/forum/cartes2014a/1400506674-3.jpg

Knut

 

A few to be going on with.

 

Yes, but I think that article is a transcript of a much earlier book, probably 1920s or 1930s.

Tom

 

The advantage of Fletcher-Jennings motion is it is very compact. The eccentrics are on the leading axle and the eccentric rods run backwards to the expansion link; the drive then turns back on itself to the valve rods. So the whole takes up only about half the space you would need for a conventional layout.

On “Baxter”, because it has outside cylinders, the driving axle is plain and fits below the firebox.m; that layout would be impossible on a conventional 0-4-0 layout, where the firebox would typically be behind the rear axle to allow space for the eccentrics.

Tom