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Discussion Starter · #1 · (Edited)
It seems that early in the history of steam locomotives, inside cylinders was the favoured design. I'm wondering why? The only thing I can come up with, is that it ought to decrease the tendency that the whole locomotive behaves like the tail of a happy dog, as the cylinders work.

I have read about a design, that was scrapped, because the first series of locomotives rocked heavy back and forth sideways. Those had outside cylinders, with Walchaerts / Heusinger valve gear.

But many inside cylinder locomotives in the 19th century ran so slow, that this rocking motion seems an unlikely problem. Sideway inertia ought to be enough?

I would like to find a 0-6-0 prototype, with outside cylinders, but inside valvegear. In model, ocillating cylinders would look acceptable. Also an open cab, like I've seen on on English tender locomotives, would make coal firing simpler, having no roof getting in you way.

Of course, one can always just do a freelance design. 馃槃 As long as it captures the general idea and impression of some prototypes, that's pretty okey with me.
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Pauli;

Inside cylinders did help to reduce dynamic augment (US term for the side-to-side rocking). Labor was cheap at that time, so using a pit to perform maintenance on the cylinders was cost effective. I am guessing that the problems with maintaining crank axles eventually led to a favoring of outside cylinders. At the same time improvements in counter balancing the drive wheels plus better suspension/equalization systems allowed placing the machinery outside the frames.

Best, David Meashey
 

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It seems that early in the history of steam locomotives, inside cylinders was the favoured design.
Rocket has outside cylinders. ;) [I say 'has' as the original, and 2 or 3 replicas, are still around.)

I can't recall an 0-6-0, but the Midland Compounds had outside cylinders and inside valve gear (and an inside cylinder too.)

 

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Discussion Starter · #4 · (Edited)
There is a point to having a short wheelbase, that accomondates sharp radius track. I can't run my German outline 1:32 scale 4-6-0's or 4-6-2 on friend's tracks, because their LGB tracks incorporate the occasional very sharp curves. Even though the leading pony trycks have exeptionel sideway movement.

Even the Aster P8 (BR38), which is stated as having 2,5m minimum operating radius, is actually designed to negotiate close to 1m! One just has to remove the piston rod covers, for it to work! (And they are made removable,) All Maerklin engines and rolling stock, negotiate 1m radius. Without exception. Though it sometimes looks pretty strange. 馃槃

The vast majority run narrow gauge prototypes. Even Garrat and Mallet types, without problems.:rolleyes:

Luckily, I have an 0-6-0 BR89 (Preussian T3) engine, that I use to pull a local traffic two axle coach trainconsist with, that negotiates the horrible curves. The main problem beeing switches, as they are considerably much cheaper and more frequent to come by used, than any larger radius ones.

So, this explaines my interest in plain short wheelbase, without any leading or trailing trucks. It's rather difficult to get the right pressure against the tracks, to avoid derailing, besides sideway movement.

Of course compound engines need to have inside cylinders as well. Unless they are articulated frame types.

As I'm aiming at a rock-bottom cheap and simple to build design, I want to avoid outside valve gear. Also, the engine will only run in forward, as my experience is, nobody runs backwards anyway. Or, it will run either way, because ocillating cylinders can actually serve and replace a safetyvalve. Haven't decided yet.

Personally, I'm not to fond of saddle tank engines, but this serves as an idea of what my idea of the appearance of outside ocillating cylinders might look like. The guide gland rods (name / term?) and crosshead, would rock with the cylinders. There would be no actual moving connection in between the pistonrod, and the driving rod. (Funnily, there have been ship ocillating cylinders, with a moving crosshead joint, as it allowed better fit in a ship hull! They also had Stephenson's valve gear, as I recall it.)

I suspect the actual length of this engine comes pretty close to the previous picture of an 0-6-0. This design is very tempting, because of ease to make a dropping grate and ashpan. Also. I would make an oval, or even keyhole cross-section boiler, just using the saddle water tank as disguise.

Actually, this would make an exceptionally good outline for 5" or even an easy to handle 7 1/4" engine. (7 1/4" also beeing the more popular of the two gauges in Sweden. But not so on continental Europe.)
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That's similar to the Roundhouse Davenport (which they picked as an outside frame loco so it could run on 32mm or 45mm track.

 

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Pauli,

A simple 0-6-0 design for Gauge 1 is the G1 Model Railway Assocation (G1MRA) "Project". It has a single inside cylinder with slip-eccentric valve gear. Many, many variations on the basic loco have been built over the years, including side- and saddle-tank versions. Wheel castings are available from Walsall Model Industries (no personal connection), but those are the only castings needed for the basic loco.

Inside cylinders, despite their apparent drawbacks (access for servicing, vulnerability of crank axle, limit on cylinder diameter, etc) were popular in the UK all the way up to the end of steam locomotive production. British railways were/are constrained by a very tight loading gauge, and inside cylinders avoided the issue of fouling tunnels, station platforms and other objects.
 
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