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Steaming right off track again.....metaphorically that is....

Non can beat the mighty LMS................

Watching a Scots express drifting down the hill through Lancaster or thundering through Carnforth is a sight I'll never forget.

image.jpeg.0367a30901a57480053d5a20608448c0.jpeg

Edited by Graham_Robinson

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On ‎11‎/‎05‎/‎2019 at 14:57, Athy said:

Did the Leader fiasco prompt Bulleid's move from Southern region to his new post in Ireland?

No, it was the thought of Nationalisation and Standardisation,  not his scene at all.

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8 hours ago, Graham_Robinson said:

Steaming right off track again.....metaphorically that is....

Non can beat the mighty LMS................

Watching a Scots express drifting down the hill through Lancaster or thundering through Carnforth is a sight I'll never forget.

image.jpeg.0367a30901a57480053d5a20608448c0.jpeg

Err - it appears to be in reverse gear.  Weren't some given an upside-down bathtub with 'Go Faster' stripes?

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38 minutes ago, Chris Williams said:

Err - it appears to be in reverse gear.  Weren't some given an upside-down bathtub with 'Go Faster' stripes?

 

Do steam engines have gears then? 

 

 

That is a particularly pleasing steam engine to my eye.

 

 

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12 minutes ago, Mike the Boilerman said:

Do steam engines have gears then?

 

That is a particularly pleasing steam engine to my eye.


So you can appreciate some really fine things then, even if you don't get it with big air-cooled Listers! ?

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10 minutes ago, Mike the Boilerman said:

Do steam engines have gears then? 

They sometimes need to go astern.  The one shown has Walschearts gear,  others have Stevenson gear.  It alters the point where the steam is 'cut off' and expansion is used.  You start off in full gear, and 'notch up' as you go faster.

Yes, it is a good looking engine, unlike the inverted bathtubs.

scot[1].jpg

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My God how horrid!

 

What's the reason for the bogey with four small wheels at the front? Is it actually supporting any of the engine weight or does it do something else?

 

 

15 minutes ago, alan_fincher said:


So you can appreciate some really fine things then

 

Indeed! This is why I prefer Kelvins and Gleniffers to coarse, noisy and fast-revving Listers.

 

 

 

Edited by Mike the Boilerman

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3 minutes ago, Mike the Boilerman said:

My God how horrid!

 

What's the reason for the bogey with four small wheels at the front? Is it actually supporting any of the engine weight or does it do something else?

 

 

Both, and it’s a bogie. A bogey is something else ?.

 

It assists with the steering of the locomotive and the weight distribution. Otherwise there would be huge mass overhanging the driving wheels and excessive axle loads.

 

JP

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1 minute ago, Mike the Boilerman said:

 

In what way? 

 

The right way, otherwise it comes off the tracks.

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Just now, matty40s said:

The right way, otherwise it comes off the tracks.

 

Well we know that trains stay on the tracks due to the slight inward slope of the top of the rails. Not the flanges on the wheels. Look at the inside edges of any railway line. It is always untouched and unpolished. 

  • Greenie 1

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16 minutes ago, Mike the Boilerman said:

 

In what way? 

 

Probably in a couple of ways. The main driving wheels are held in the frames of the locomotive so all three have to point in the same direction and coupled with being very big means they don’t fit well between the rails on curves. The leading driving wheels will not be square to the rails so high forces will be applied to the outer rail. Through the front truck (which I think was the terminology used rather than bogie) a turning force can be applied to the locomotive to lessen the angle of attack of the leading driving wheels. The front truck wasn’t rigidly held laterally because again that would just make the whole thing too long and rigid.

 

The other advantage is that the leading truck wheels being undriven will steer more naturally than the driving wheels which due to the way drive forces are asymmetrically applied to each side in turn (notwithstanding this is a four cylinder loco) would have a tendency to shuffle which would be detrimental to curving at speed.

 

JP

Edited by Captain Pegg

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13 minutes ago, Mike the Boilerman said:

 

Well we know that trains stay on the tracks due to the slight inward slope of the top of the rails. Not the flanges on the wheels. Look at the inside edges of any railway line. It is always untouched and unpolished. 

A popular myth busted ?

 

The wheel profile and rail head are curved in a complementary way and the wheel steers itself along the rail by the natural correction of out of balance forces. The flange should indeed never touch the side of the rail and in theory it’s redundant.

 

JP

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Except it isn't redundant at all. Without the flange, rolling stock and locomotives would not stay on the rails, nor negotiate points successfully. Sharp bends often have 'check rails' fitted, and the squealing and screeching that can be heard when negotiating such bends is made by the flanges grinding on the rails. Were they not there, de-railments would be commonplace. The systems is a reverse of the plate ways with upstanding angles against which the iron shod wooden wheels of carts would be kept 'in check' and running true to the plateways. Any schoolboy from the fifties would tell you that - it's no myth.

 

It has been said that Stephenson chose 8' 4" as the original gauge, but found the rolling stock jammed against the wheel flanges (also 8' 4" apart). When opened out to 8' 4½" they ran freely. Without a flange stock would run off rail.

 

proxy.duckduckgo_com.png.867324fe901198a2a9998fcae4959f91.png

 

Steam locos (and most stationary engines including pit-head winding engines) have two gears - forward and reverse. The cut-off is a degree of movement of the gear which (as previously mentioned) cuts off the amount of steam entering the cylinders to maximise on the available steam dependent upon load and speed.

Edited by Derek R.

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There's an experiment done with coned wheels and non-coned wheels in these two You tube videos.

Watch the coned wheels stay on track - but - observer the way in which they veer off and back before the end of the track. Flanges stop that.

 

 

 

 

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29 minutes ago, Derek R. said:

.

 

It has been said that Stephenson chose 8' 4" as the original gauge, but found the rolling stock jammed against the wheel flanges (also 8' 4" apart). When opened out to 8' 4½" they ran freely. 

 

 

Er, not as broad as that, I don't think. That would have been a widebeam.

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1 hour ago, Derek R. said:

There's an experiment done with coned wheels and non-coned wheels in these two You tube videos.

Watch the coned wheels stay on track - but - observer the way in which they veer off and back before the end of the track. Flanges stop that.

 

 

 

 

There’s a difference in what we are describing as the flange. That model demonstrates that the steering comes from the equilibrium of forces between the head of rail and the profile of the wheel tread and not by the side of the rail exerting a lateral force on the flange - by which I mean a predominately vertical down stand of the wheel tread which is present on real wheels but entirely absent on those models.

 

Note also I did say the flange is redundant in theory; the reality of vehicle steering doesn’t quite work as per the theory. No real vehicle consists of a single wheelset with freedom of movement and in reality no wheel in a bogie or fixed wheelbase vehicle is truly square to the rails in a curve. This is why sharp curves may exhibit wear to the gauge face.

 

Most of the squealing noise you hear on sharp curves is wheel squeal rather than flange squeal. At extremes the principle of the conicity of the wheels allowing the two wheelsets to travel different distances around the curve despite being on a fixed axle doesn’t work - particularly with worn wheel and rail profiles - and the outside wheelset exhibits a combination of rotation and slippage as it’s dragged along the head of the rail by the inside wheel and axle. Flange squeal is often heard from the back (inside) edge of the wheelset in check rails in pointwork - or on very sharp curves - which are designed to give positive control of the wheel position. This is one scenario where the extended flange of the wheel is advantageous.

 

JP

 

 

Edited by Captain Pegg

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7 hours ago, Captain Pegg said:

Probably in a couple of ways. The main driving wheels are held in the frames of the locomotive so all three have to point in the same direction and coupled with being very big means they don’t fit well between the rails on curves. The leading driving wheels will not be square to the rails so high forces will be applied to the outer rail. Through the front truck (which I think was the terminology used rather than bogie) a turning force can be applied to the locomotive to lessen the angle of attack of the leading driving wheels. The front truck wasn’t rigidly held laterally because again that would just make the whole thing too long and rigid.

 

The other advantage is that the leading truck wheels being undriven will steer more naturally than the driving wheels which due to the way drive forces are asymmetrically applied to each side in turn (notwithstanding this is a four cylinder loco) would have a tendency to shuffle which would be detrimental to curving at speed.

 

JP

The Gresley P2's, 2-8-2 passenger loco's were accused of spreading the track on the Aberdeen Road because of the fixed length of the driving wheels.

 

Thompson used this reason to convert them into, IMHO, rather ugly A2/2 4-6-2's.

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4 cylinders but technically if you like 8 cylinders as they are double acting.    ''City of Bristol''.

463111 City of Bristol. 4-6-2.jpg

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3 hours ago, Derek R. said:

Steam locos (and most stationary engines including pit-head winding engines) have two gears - forward and reverse.

 

I thought forward and reverse running on a steam engine was achieved by altering valve timings, making gears unnecessary for going backwards.

 

Are you saying on steam locos the valve timing method is not used and reversing gears are installed for this? Or is my basic understanding incorrect?

 

 

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Steam engines are external combustion engines as opposed to ICEngines.  Reciprocating steam engines can start from rest without any gearing by altering the valve events from forward to reverse is called ''fore or reverse gear'', and the control for this in the cab is called ''The Reverser''. As steam engine cylinders are double acting,'' Steam is admitted to both sides of the pistons ''front and from behind in turn'' at the end of each back and forth stroke, hence a 4 cyl loco is technically an 8cyl and a 3cyl a 6, and a 2cyl a 4.  Railway steam loco's go exactly the same in reverse as they do in forwards.

 There are single acting steam engines ''occillating'' but mainly for toys.

Edited by bizzard

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52 minutes ago, Mike the Boilerman said:

 

I thought forward and reverse running on a steam engine was achieved by altering valve timings, making gears unnecessary for going backwards.

 

Are you saying on steam locos the valve timing method is not used and reversing gears are installed for this? Or is my basic understanding incorrect?

 

 

I think your basic understanding is correct. Direction is changed by moving the valve gear through half a cycle relative to the piston and thereby reversing the high pressure/low pressure sequence around the piston.

 

JP

 

ETA - removed bit about Bizzard’s post because I now understand what he meant by 8 cylinders.

Edited by Captain Pegg

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12 minutes ago, bizzard said:

 There are single acting steam engines ''occillating'' but mainly for toys.

Paddle steamers (full size) seemed to have used oscillating engines. But I think many incorporated mechanical  valve gear rather than Mamod type timing - so were these double-acting too?

 

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2 minutes ago, Captain Pegg said:

I think your basic understanding is correct. Direction is changed by moving the valve gear through half a cycle relative to the piston and thereby reversing the high pressure/low pressure sequence around the piston.

 

I don’t follow Bizz’s statement about 8 cylinders. The upper chamber on the outside cylinder in his photo contains the valve timing gear which is driven via the link motion.

 

JP

Ok. An ICE engine is single acting ignition shoving the piston down only and comes back up unpowered.  A steam engine ''double acting'' you get two power strokes on the same piston as steam is admitted first to one side of the it and then the other side on its return.  Hence compared with an ICE you can call sinle steam double acting cylinder a 2 cylinder even though the piston is working in that same cylinder. 

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2 minutes ago, bizzard said:

Ok. An ICE engine is single acting ignition shoving the piston down only and comes back up unpowered.  A steam engine ''double acting'' you get two power strokes on the same piston as steam is admitted first to one side of the it and then the other side on its return.  Hence compared with an ICE you can call sinle steam double acting cylinder a 2 cylinder even though the piston is working in that same cylinder. 

I got that from your response to Mike hence my edit. Sorry if you’ve been forming a response all this time.

 

JP

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