Indicator shelters on steam locos

[pete_mcfarlane]

I've seen a few photos of locos with these indicator shelters in front of the smokebox, of varying degrees of sophistications from plain planks to fully lined out.

 

There's a photo in the Locomotives Illustrated on larger Brighton locos of a H1 Atlantic fitted with a shelter and two bowler hatted engineers standing up in it, so I'm assuming they were to shelter engineers on test runs, but what were they doing in there? Monitoring instruments of some kind?

[APOLLO]

The shelter was to house indicator diagram apparatus, and I presume their operators. A diagram is essentially a pressure / volume graph, produced on an apparatus which moved a sheet of graph paper wrapped round a drum in conjunction with the piston / crosshead, whilst a moving pen was operated by the cylinder pressure.

 

These sites describe them far better than I could.

 

http://opensourceeco...icator_Diagrams

 

http://www.archiving...contentback.htm

 

http://en.wikipedia...._volume_diagram

 

http://straction.fil...atordiagram.jpg

 

When I did my ONC mechanical engineering at Riversdale Tech Liverpool back in the early 70's we took indicator diagrams from a live steam stationary engine in the Heat engines lab. Frightening stuff back then. We had to hook the indicator up to the moving crosshead whilst the engine was running !!- Elf' n' safety = Zero. Still have the diagram somewhere, though the scald marks healed years ago !!.

 

Brit15

[JeremyC]

The shelter was to house indicator diagram apparatus, and I presume their operators. A diagram is essentially a pressure / volume graph, produced on an apparatus which moved a sheet of graph paper wrapped round a drum in conjunction with the piston / crosshead, whilst a moving pen was operated by the cylinder pressure.

 

These sites describe them far better than I could.

 

http://opensourceeco...icator_Diagrams

 

http://www.archiving...contentback.htm

 

http://en.wikipedia...._volume_diagram

 

http://straction.fil...atordiagram.jpg

 

When I did my ONC mechanical engineering at Riversdale Tech Liverpool back in the early 70's we took indicator diagrams from a live steam stationary engine in the Heat engines lab. Frightening stuff back then. We had to hook the indicator up to the moving crosshead whilst the engine was running !!- Elf' n' safety = Zero. Still have the diagram somewhere, though the scald marks healed years ago !!.

 

Brit15

Oh dear, I'm getting old! I can remember using these instruments [including the planimeter] to take indicator diagrams and work out [long hand; no calculators] the power of large slow speed marine diesel engines. The difficult one was the draw card where you had to pull the indicator drum by hand [synchronised with the engine speed],

Nowadays we have nice little computerised instruments which take the diagrams, do all the calculations and display it all on a computer screen and they can cope with engines running at high speeds.

 

Jeremy

[APOLLO]

Yes, I remember the "working out" bit, with my trusty Faber Castell slide rule (couldn't afford a British Thornton) !!

 

If I remember correctly, the basic formula for the Brake Horse Power of an engine (any engine) was BHP = PxAxLxN

P = Max pressure in cylynder

A = Area of cylinder

L = Length of stroke (piston)

N = No of cylynders (2 cylinder would be N/2 etc)

 

With steam locos it got a bit more complicated, especially Steam Tables - god how I hated those. Still have mine, "Thermodynamic Properties of Wet, Dry & Superheated Steam" (or something like it).

 

For a supposedly simple machine, a steam engine got awfully complicated mathematically the more you studied it.

 

Brit15

[Invicta]

I've often seen these in photos, so it's useful to have more of an idea of what they were used for, and what was inside. Looking at a few pics, as Pete said, they seemed to vary from something that looked like a garden shed had been lashed to the front of the loco, to more elaborate affairs.

 

A handful of examples:

 

Southern 'N' 2-6-0 found on SEMGOnline, with individual shelters either side of the boiler

http://www.semgonline.com/steam/pics/sr_1850.jpg

 

The experimental Kitson-Still loco, looking like it's had some fence panels nailed to the front....

http://www.aqpl43.dsl.pipex.com/MUSEUM/LOCOLOCO/kitson/kitson3a.jpg

 

...and a GWR garden shed, complete with porthole windows and a tarpaulin roof across the top, on a 'Hall', found on http://www.traintesting.com/steam.htm

http://www.traintesting.com/images/7916%20Wantage%20Road.jpg

 

Similar structure on an LNER V2

http://www.traintesting.com/images/60845%20near%20Swindon.jpg

 

...and an LMS Ivatt 4 2-6-0

http://www.traintesting.com/images/43094%20on%20road%20nr%20Swindon.jpg

 

The LNER equivalent, on a Gresley Pacific

http://www.engrailhistory.info/imfile/r02000.jpg

 

Looking at this from a modelling point of view, excluding the Southern and Kitson examples, there's clearly some commonality in the way they're designed, but did railway companies keep a supply of them ready-made at a works, or were they built as required?- Theres an obvious similarity in the three WR examples, despite being fitted to locos from three different regions- a simple standard fitting, or something that had to be built/modified to fit the class of loco under test?

[pete_mcfarlane]

Thanks for all the information. It must have been an interesting experience travelling in one, especially on some of the more rough riding steam locos.

[62613]

Yes, I remember the "working out" bit, with my trusty Faber Castell slide rule (couldn't afford a British Thornton) !!

 

If I remember correctly, the basic formula for the Brake Horse Power of an engine (any engine) was BHP = PxAxLxN

P = Max pressure in cylynder

A = Area of cylinder

L = Length of stroke (piston)

N = No of cylynders (2 cylinder would be N/2 etc)

 

P=mean effective pressure in the cylinder, found by working out the area enclosed by the diagram, multiplied by the spring constant

L = length of piston stroke

A= cross-sectional area of piston; on a double-acting engine, this would be less on the side of the piston with the piston rod.

N=number of power strokes per minute =rpmx2 for a d.a. engine; rpmx1 for a 2-stroke ic engine; rpm/2 for a 4-stroke ic engine

 

The formula as I understood it was P.L.A.N./33,000 to give ihp per cylinder. each cylinder would be separately indicated.

 

With steam locos it got a bit more complicated, especially Steam Tables - god how I hated those. Still have mine, "Thermodynamic Properties of Wet, Dry & Superheated Steam" (or something like it).

 

For a supposedly simple machine, a steam engine got awfully complicated mathematically the more you studied it.

 

Brit15

[Titan]

Yes, I remember the "working out" bit, with my trusty Faber Castell slide rule (couldn't afford a British Thornton) !!

 

If I remember correctly, the basic formula for the Brake Horse Power of an engine (any engine) was BHP = PxAxLxN

P = Max pressure in cylynder

A = Area of cylinder

L = Length of stroke (piston)

N = No of cylynders (2 cylinder would be N/2 etc)

 

With steam locos it got a bit more complicated, especially Steam Tables - god how I hated those. Still have mine, "Thermodynamic Properties of Wet, Dry & Superheated Steam" (or something like it).

 

For a supposedly simple machine, a steam engine got awfully complicated mathematically the more you studied it.

 

Brit15

 

I think you mean IHP - Indicated Horse Power. Brake Horse Power is the actual power available at the flywheel/wheel obtained by putting a Brake (hence Brake Horse Power) or other resistance against it and measuring torque and RPM, and takes in to acount all frictional, heat losses etc. and is therefore is often much lower than IHP.

 

BHP = torque x rpm x a factor dependent on the units of measurement.