Anyone got a clue?

Hi all

Does anyone know what this is all about, the greenhouse!! on the side of this loco, andanyone speculate a date?
http://www.steamlocomotives.photos.gb.net/p62520607.html

Neil

 

I think it's called an indicator shelter.

Something similar, but full width appears in some pictures I saw yonks ago, of a loco undergoing testing.

Presumably sensitive instrumentation, with a brave apprentice sitting up front writing up notes of the readings.

Before the days of remote electrical measuring and recording.

 

A V2 was fitted with a similar contraption when tested by Swindon after nationalisation.

Regards,

Dan

 

That's exactly what it is. An 'indicator' was an instrument for measuring the variation of the pressure of steam in the cylinders along its stroke. It enabled the engineers to work out what was happening in the cylinders. Indicators generally had a rotating drum, to which a 'card' was attached.There was a physical connection to the crosshead, which rotated the drum and thus created the 'X' axis of a graph, steam pressure providing the 'Y' axis. A pencil was pressed against the card and produced the indicator diagram. Indicator diagrams could be used to establish valve events and a host of other information relative to a steam engine's performance. Indicating stationary engines was once quite common but it isn't easy with a mobile engine. The engineers would be couped up in the shelter for a considerable length of time if the loco was on a long run.
I've got an indicator, if anybody fancies indicating a locomotive in the traditional way, today. 71000 would be an interesting choice but I doubt that Network Rail would allow it! I guess that modern instrumentation might enable you to do it from the comfort of the cab or coach. Measurement of the piston position throughout its stroke would be an interesting exercise, though.

 

71000 had one fitted in April 1955 whilst undergoing trials based at Swindon.
Photo on page 144 of the RCTS book BR Standard Steam Locos Vol1.

 

We take 'cards' often on big marine diesel engines. Myself, I prefer to take them the 'old-fashioned way', by hand, but modern engines allow it to be done electronically, indeed on a continuous basis if necessary. Pickup for the crank position (X-Axis) and a piezo-electric cell attached to the Indicator Cock connection for the Y-Axis, all monitored by a microprocessor.

The thought of being at the front of a locomotive at speed on the main line, taking 'cards' by hand, is, frankly, scary.

 

You tell the youth of today that you spent hours in a cramped space, vibrating like hell, taking indicator diagrams, changing cards and keeping records and they just won't believe you.

Thesedays it is all done with sensors and remotely as well. Sometimes it's done with just a data logger and the data is down loaded at the end of the run.

 

I agree that it is an indicator shelter, but the presence of a Pullman vehicle in the train indicates an early date. The loco is the first of all the Johnson 4-2-2 engines No25. It was the first of a batch of engines 25-29 which entered service in June to August 1887 which is consistant with the Pullman.

I suspect that this is a very early run to test the design. The engine appears to be in early condition before a second, trailing, sand pipe was added to the rear of the driving wheel.

There is what appears to be a pipe on the outside of the tender and a circular extension to the external axle box on the driving wheel which is interesting. Not seen them before, perhaps they too are part of the test equipment.

The shelter has a roof and windows; many of the later shelters, although larger, lacked both amenities!

Regards

 

Mind you, it can't have been too draughty in the shelter at speed, as I swear I've read somewhere that there's a 'bow-wave' effect where the air is pushed just in front of the moving locomotive, one of the reasons why smoke deflection was a problem due to the difficulties in getting adequate air flow. I may be wrong, though and that it's just my imagination...