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A puzzling design in Nurnberg museum

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Tim Stevens28/06/2019 15:36:48
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I recently spent an hour or so in Nurnberg Railway Museum. [It is an ideal place for a family visit as right next door is a wonderful shop full of dirndles]

Just as I was leaving I noticed a loco of some sort under a tarpaulin. It was short, with two axles, and may have relied on steam supplied from elsewhere (as used in some explosion-prone mines). The cylinders were outside the frame, and in the centre, between the axles, and each end had a conventional but short connecting rod to the wheel nearby, one forward, one to the rear. Outside all this, the two axles were also connected by long rods in the standard loco manner.

This seems to me to be a geometry which cannot work. As the axles rotate, the outer rod maintains the axle-separation distance between the crank pins on the wheels, so that the wheels rotate together. But the shorter rods to the pistons must pull the crank pins together at the top and bottom positions, relative to their positions when both the short rods are central and in line.

I did wonder if the cylinders each contained two independent pistons, as this would avoid this problem - but surely it would add other problems including what happens between the two pistons, and the cylinder did not look (to my amateur eyes) long enough for this.

Do I need to go back and have a proper look, with photographs,or can anyone explain, please?

Regards, Tim

PS the museum also included a wide range of railway models, many of which were of superb quality.

Edited By Tim Stevens on 28/06/2019 15:39:24

Brian G28/06/2019 16:50:59
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Closest I can think of is the ML 2/2, but I didn't think any were preserved. Bayerische_ML_2-2.jpg In order for the wheels of an opposed piston engine to rotate in the same direction, the cranks must be opposite on the front and rear axles as in this photo, but that would mean that any coupling rod would have to be on a return crank at one end, or else, as on the ML 2/2, inside the frames.

Brian

Unless of course it was a railcar bogie, not a locomotive?  The MCCi bogie fits your description exactly Bayerischer_MCCi.jpg

Edited By Brian G on 28/06/2019 16:52:38

Edited By Brian G on 28/06/2019 16:57:51

Tim Stevens28/06/2019 18:08:19
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Brian: what I saw was certainly very like the front (left) end of your Bavarian carriage, but only as far as the front bogie. In other words, it might have been a shunting device or similar adaptation of the front end of the carriage, but no longer that the 5th window from the left. The tarpaulin was tied down and prevented any examination of the bodywork as distinct from the undercarriage, and I admit I spent the few moments I had gazing at the power unit.

And if I used the term loco wrongly, sorry, I just meant a self-propelled engine - and is the term I would apply to other four-wheeled devices like the Rocket and Catch-me-who-can. It was more than a bogie - the tarpaulin covered a shed-shape extending up well over 2 metres from the track. Unless, of course, my 'bogie' is not the same as your 'bogie'.

If the horizontal bar between the wheels on your picture is not an outside connecting rod, what is it?

Still puzzled, Tim

Brian G28/06/2019 19:28:33
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To be honest Tim, although I was aware of the ML 2/2, Maffei's rival to Krauss' Glaskasten (which could be pretty odd themselves with the first batch having inside cylinders and jackshaft drive), which gave me a start in searching, the MCCi was unknown to me. I had a quick search on Google, and Micro Metalkit produced a model a few years back.

They say that it had the same running gear as the locomotive except that it ran at a higher pressure (four had water tube boilers), had smaller cylinders, and the coupling rods were moved from between the frames to outside the rest of the motion, which sounds very much as you describe. There is a slightly clearer photo in this document, PDF which seems to show that, unlike the ML 2/2, the Heusinger valve gear was operated by an eccentric.

I wonder if the shape under the tarpaulin was the boiler, which, as they were one-man operated and gravity fired would originally have been topped with a coal hopper?

Brian

Journeyman28/06/2019 19:33:26
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Sound similar to a loco I spotted in the Budapest Railway Museum some time ago. This is a fireless 0-4-0 tank loco 91,001 (UIC B-f2t). Technically it probably isn’t a tank engine as it has no tank or firebox, just a large steam receiver. Designed for working in hazardous environments, the receiver was just filled from the factory steam main as required. Built by Lokomotivfabrik Krauss & Co. of Linz am Donau, Austria in 1915.

90001loco.jpg

The manufacturer might be a place to start.

John

Tim Stevens28/06/2019 20:06:36
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Journeyman - the loco you offer is not the same in the relevant bits - your cylinders are at the end (front or back) whereas my problem device has cylinders in the middle, driving axles front and back. Sorry.

I did come across one of these Linz engines at work in the 1970s, somewhere in (probably) Austria. My interest was arroused because I had never read about such things in the tecnical steam history stuff.

Cheers, Tim

Edited By Tim Stevens on 28/06/2019 20:07:17

MichaelR28/06/2019 20:11:11
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Tim, Is this what you were looking at LINK I have given myself a head ache trying to visualise how that motion operates it is certainly interesting. Scroll down a little to see picture.

Mike.

Edited By MichaelR on 28/06/2019 20:12:39

duncan webster28/06/2019 20:36:48
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I suspect there are 2 pistons in the one cylinder which move in opposite directions, both going out at the same time and coming in at the same time. I think then that one piston valve with 3 heads can supply the steam /exhaust events, There is only one set of valve gear. Similar to the Dendy Marshal set up tried by the LNWR on Prospero, a 4 cylinder Prince of Wales.

Balance would be pretty good, not perfect as the short conrod angularity would impose some deviation from sinusoidal motion. Pretty complicated tho!

Howard Lewis28/06/2019 21:25:54
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Journeyman's loco is indeed a "fireless cooker".

Probably the last three examples of this type of machine were supplied to ICI by Sentinel in 1958 /early 1959, just as I started my apprenticeship.

If the piston in the Nurnberg loco is double acting and central in the cylinder, the steam driving the piston towards the rear, will be pulling the front crankpin upwards and backwards, while the rear piston rod and con rod will be pushing the rear crankpin backwards and downwards, whilst exhausting. So both piston rod/connecting rod assemblies will be causing rotation in the same direction.

To be efficient, there would need to be very little restriction (back pressure ) of the exhaust steam. But that goes for any double acting steam engine.

Howard

Tim Stevens28/06/2019 22:59:12
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The photo from MichaelR resembles what I saw (but it seems also very close to the Bavarian carriage in the first response to my query. But remember, I could only see the bogie under a sheet in a fairly dark corner of the yard.

And it does seem that my second guess (two separate pistons moving in opposite directions) is the answer which solves the question. Thanks Howard, and duncan, for your helpful comments.

Has anyone every made a model of this type of engine, does it work, and most important, what was the benefit intended compared with a single piston moving twice as far?

Cheers, Tim

Mark Rand28/06/2019 23:51:22
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Posted by Howard Lewis on 28/06/2019 21:25:54:

Journeyman's loco is indeed a "fireless cooker".

Probably the last three examples of this type of machine were supplied to ICI by Sentinel in 1958 /early 1959, just as I started my apprenticeship.

Heysham nuclear power station had one. proudly labeled as the worlds only nuclear fired train (when I was there in 1984). I think its stated purpose was for shunting fuel rod wagons, but I don't think it saw much action.

 

Hah! Just found it:- https://ribblesteam.org.uk/exhibits/steam/andrew-barclay-1950-1928-heysham-no-2/

A Barclay fireless locomotive first delivered in 1928.

Edited By Mark Rand on 28/06/2019 23:56:03

duncan webster29/06/2019 00:33:31
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As about 20% of UK electricity comes from nuclear, 20% of all electric trains in UK are 'nuclear fired'. As I write this, wind is producing 19%, rather better than sail power tho'

Hopper29/06/2019 01:39:32
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Posted by Tim Stevens on 28/06/2019 22:59:12:

... what was the benefit intended compared with a single piston moving twice as far?

Cheers, Tim

Twice as much piston area = twice as much power?

Combined with short wheelbase and necessarily short stroke dictated by small diameter wheels?

Edited By Hopper on 29/06/2019 01:49:41

Tim Stevens29/06/2019 14:46:22
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Sorry Hopper, but your physics is letting you down. To get twice as much power, the two pistons must each move the full stroke. Here we have double the piston area working over half the distance, so no advantage.

I wonder whether the idea was to get the benefit of a reduced crank throw and so higher rpm, which of course matches smaller wheels - and that is a further benefit for tight curves. And at the same time putting the bores head to head reduces any heat loss through the cylinder head (as in effect, there are no such things). Were these engines better at producing power and coping with tight corners, and known to be capable of sustaining high rpm?

Regards, Tim

Edited By Tim Stevens on 29/06/2019 14:47:47

Edited By Tim Stevens on 29/06/2019 14:48:19

Neil Wyatt29/06/2019 19:19:43
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There's also a fireless locomotive at one of the Ironbridge Museums.

Neil

old mart29/06/2019 22:17:36
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That first link in Brian G's post might have a simple explanation, opposed piston cylinder on one side of the engine and coupling rods on the other.

Bazyle29/06/2019 23:00:14
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A bit off topic but i saw a fireless loco shunting at Bowaters paper mill in Kent in the early '70's where their wood processing used vast amounts of superheated water so had plenty to spare for the loco.

duncan webster29/06/2019 23:38:05
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Posted by old mart on 29/06/2019 22:17:36:

That first link in Brian G's post might have a simple explanation, opposed piston cylinder on one side of the engine and coupling rods on the other.

The pistons appear to be 180 degrees out of phase, confirmed by there only being one set of valve gear, so I think there must be a similar setup on the other side or starting would be problematic. Brian tells us the coupling rods were inside the frames, which implies crank-axles. Whoever designed this liked to make things complicated

Brian G30/06/2019 07:58:33
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The German Wikipedia article says that the balanced piston design gave smooth running, but that the locomotives were withdrawn due to the problems of maintaining the mechanism between the frames. I guess German and Hungarian fitters didn't like inside cranks, however the railcars, fitted with outside coupling rods, didn't last much longer before being converted to electric (and in one case diesel) operation, where they formed the prototypes for the ET85s. Perhaps this conversion is why a power bogie survives?

I wonder how many other opposed piston locomotives were built between Bodmer's Brighton, Croydon and Dover locomotives of 1845 and the Maffei locomotives in 1908?

Brian

Nigel Graham 209/07/2019 09:16:23
427 forum posts

A thought regarding Fireless Locomotives...

Anyone here had any experience driving one, so can confirm or correct me here?

Were they charged with steam, or with water at boiler pressure and temperature?

Surely... :

- If steam only, as it is drawn off, the reservoir's pressure and temperature would drop very rapidly.

- Water will retain its heat for a lot longer, refilling the steam space by evaporation as the locomotive moves, and with a far lower pressure and temperature fall.

A parallel is the aerosol spray can, whose propellant is a highly-volatile fluid kept in that state only by its own vapour pressure, but maintaining that pressure to the end.

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