Imaginary Locomotives

[PhilJ W]

The lighter wheels were all about unsprung weight. Whether this has an effect on slippage I don't know. It seems that OVB tried to cut down the unsprung weight with his chain driven valve gear and other features.

[The Johnster]

Assuming that the axle loads are adhered to, I can’t see that the weight of the wheels makes any difference in terms of ‘kindness to the track’, since the rotational masses of the loco’s wheels are balanced out.  It is reciprocating mass, from the backward and forwardy bits, the piston and whatever is connected to it, that causes ‘unkindness to the track’ in the form of hammer-blow, a problem that became serious as engines became bigger and this mass increased at the same time as driving wheels started to become smaller, aided by improvements in bearing and lubrication, which drove piston speeds up.  
 

This is a fundamental weakness of the Stepensonian locomotive, and has never been overcome on that type of loco.  It’s not just unkind to the track, it helps the loco to batter itself into pieces as well!

[Jeremy Cumberland]

Unsprung mass is important in relation to track damage. Just imagine how a wheel hits a joint or a crossing nose. The wheel and all the other unsprung mass drops slightly, and then needs to be raised up again by the next bit of rail.

 

This is just as important for more modern forms of traction, which may have part of the mass of the motor or transmission supported by the axle.

[Flying Pig]

1 hour ago, Jeremy C said:

Unsprung mass is important in relation to track damage. Just imagine how a wheel hits a joint or a crossing nose. The wheel and all the other unsprung mass drops slightly, and then needs to be raised up again by the next bit of rail.

 

This is just as important for more modern forms of traction, which may have part of the mass of the motor or transmission supported by the axle.

 

As demonstrated by the sad case of the AL6 on which the traction motors were axle-hung, in contrast to the AL1-5 which had bogie mounted motors requiring flexible drives.  The intention was to simplify and add cheapness, but the result was that the AL6 as built was very hard on the track.  The AC Loco Group article on the class suggests that research on track forces previously carried out using diesels with axle-hung motors was misinterpreted.

[rodent279]

3 hours ago, Jeremy C said:

Unsprung mass is important in relation to track damage. Just imagine how a wheel hits a joint or a crossing nose. The wheel and all the other unsprung mass drops slightly, and then needs to be raised up again by the next bit of rail.

 

This is just as important for more modern forms of traction, which may have part of the mass of the motor or transmission supported by the axle.

Agree, the most well known example being the class 86's. All the prototype  AC electric classes had fully springborne traction motors, whereas most diesels, including the Deltics, had axle-hung motors. The motors on an AC electric loco, capable of developing 2-3 times the power at rail of even a Deltic, are necessarily significantly larger and heavier than on a diesel.

The 86's had axle-hung traction motors, which simplified the final drive, as it does not have to be flexible to accommodate movement of the wheels etc within the suspension. Once in service, prolonged and regular 100mph running with class 86's rapidly started to knock 7 bells out of the track. The southern  WCML became  notorious for wet spots, no doubt in part due to the hammering it was getting.

There were also problems with brushgear on 86's deteriorating and disintegrating prematurely. There was a proposal to mount a small camera inside a traction motor and observe what was happening to the brushgear. Some calculations of the acceleration forces on the traction motors were made, and it came out in excess of 100G. No camera was available that was capable of withstanding such forces.

Edited April 26, 2022 by rodent279

[billbedford]

12 hours ago, DenysW said:

I'd assumed that the Bulleid-Firth wheels (apologies to Firth for omitting his part) were to be (a bit) kinder to the track than spoked wheels, have less wind resistance, and possibly be cheaper.

 

Actually it was Beaumont-Firth-Brown accoring to the patent. Mr Beaumont being a manager the Firth-Brown's works in Sheffield. 

 

 

 

[Northmoor]

21 minutes ago, R. Knowles said:

Class 41 question - not related to the HST prototype or the NBL D600 "Warship".

 

Wasn't sure where else to post this but my understanding that this was for a proposed class of Class 60-esque locomotives with 2,500bhp engines in the early 1990s. There was also a mention of it in the 1991-edition of Ian Railway Book (which I have a copy of), in a Roger Ford written-piece with the following paragraphs: "Also proposed is a 'mini-Class 60' for the coal business. This was designated Class 41 and recognises the fact that not all collieries can produce Class 60-sized loads. At 2,200-2,800bhp, it might be considered to be the modern equivalent of the Class 37. On its own could handle maximum loads from a number of collieries. Multiple operation would allow heavier loads to be hauled".

Is there possible further info on this proposal?

One of the reasons I ask is because I've also picked up a superficially demic model of a Hornby Class 60, which I also intend to model it as!

Cheers!

Very interesting, I don't remember reading about that before.  Perhaps fortunate that they weren't built, otherwise they could very quickly have become largely redundant (although it would have hastened the withdrawal of other classes, e.g. 31, 33, 47) after the 1992 pit closure programme which roughly halved the remaining coal industry.

 

The economics of freight operation completely changed with privatisation.  EWS demonstrated what had really been obvious for years; the value of an almost standard loco fleet and that it was cheaper to run a large loco on part load than to maintain a separate fleet of smaller locos for lighter traffics.  The creation of Railtrack also threw the cost of paths into the mix; I remember reading how BR Railfreight were happy to run the Margam - Llanwern Iron Ore up Stormy Bank behind a single Class 60 running at the "most economical speed" of about 12mph.  That became unacceptable in the New Railway where such operation took up three potential passenger paths, so it would always be preferable to have too much power rather than just enough.

 

Good luck with your fictional Class 41 though; what are you going to name it?

[Johnson044]

Not sure which thread to post this. Imaginary Locomotives possibly not quite right because it actually existed - but it's pretty wild - this is a new one on me. I've seen an image of an American friction drive loco before but never come across one tried in the UK. Is it just me or is this completely bonkers? I completely see the logic and the difficulty of using gears but rather thought that friction was something to be avoided.

[JimC]

10 minutes ago, Johnson044 said:

...rather thought that friction was something to be avoided.

There's friction and friction. As a general rule friction is purely parasitic and best avoided. But what's going on here is effectively a clutch using friction in much the same principle as a clutch on an internal combustion engine. So provided the clutch is working fully effectively with no slippage there isn't any more loss than on a motor car clutch. That's the good news. The bad news? I don't suppose the tiny little contact area of that friction drive has any more chance of working efficiently without slipping than I have of winning a tug of war with a GWR 2-8-0 tank engine...

Edited May 2, 2022 by JimC

[Johnson044]

You're probably right - but this is Francis Webb and no-one dared tell him he might be wrong.

[John Besley]

Actual fact isn't that going to have the opposite effect ... Be acting more like a brake

[Johnson044]

Well - I rather think so too TBH -  as the idler wheel (or whatever it should be called) is pulled upwards, presumably by some sort of screw system, like a tender hand brake, the forces applied to both driving and trailing wheels would have to be quite considerable in order to achieve the friction needed to pull the trailing wheels around. Would these forces not act on the axles / bearings and try to push the two axles apart?  Duuno. Part of me rather thinks it might be made to work - but presumably it didn't. I do wonder why the trailing wheels have balance weights. Maybe the wheels were from scrapped Bloomers?

[JimC]

Quite agree. But then even Webb just tried it as an experiment and never built another. It started life as a 2-4-0, so presumably the [grief, cant think of the word, not crank]  place where the rod was connected is under the valance. 

[MikeOxon]

24 minutes ago, JimC said:

Webb just tried it as an experiment and never built another.

In fact, Webb was copying a much older idea.

 

According to Ahrons in 'The British Steam Locomotive 1825-1925 " : 'Arrow', which was put to work in May, 1837, had this arrangement when new, for the patent was that of John Melling, locomotive superintendent of the Liverpool and Manchester Railway, to whom it was granted in July, 1837. It is of interest to note that F. W. Webb applied a similar friction wheel coupling to a London and North-Western passenger engine about sixty years later."

 

Brunel, who seems to have been a bit of a 'sucker' for such things, also took an interest in this device and wrote to Gooch on 7th September 1837 : "If the addition of Melling's wheels is to cause much delay, I must do without them, although for command of stopping and starting, I would have liked them"  - it seems that Brunel didn't get them!

 

Mike

[tythatguy1312]

7 minutes ago, MikeOxon said:

it seems that Brunel didn't get them!

Considering Brunel's many... intriguing ideas about locomotive development, I'm honestly surprised. In theory, these might save a little bit of weight on the axles, which Brunel was so fanatical about that it resulted in Hurricane and Thunderer, the only locomotives I'd actually describe as incapable of working.

[MikeOxon]

3 minutes ago, tythatguy1312 said:

Hurricane and Thunderer, the only locomotives I'd actually describe as incapable of working.

According to Gibbs, an early GWR Director, Thunderer gave a very smooth ride at 60 mph.  In 1839,  Gooch wrote that Thunderer had been at work for some time but then needed extensive repairs and was laid up.  Hurricane made a good first impression but, on an early run, a water tank fell off and got entangled in the driving-wheel spokes.  That seems to have been the end, although the boiler was apparently re-used in the 0-6-0 Bacchus.

 

Mike

[rockershovel]

1 hour ago, JimC said:

Quite agree. But then even Webb just tried it as an experiment and never built another. It started life as a 2-4-0, so presumably the [grief, cant think of the word, not crank]  place where the rod was connected is under the valance. 

As ever, Mr Self appears to have something to offer on the subject 

 

http://www.douglas-self.com/MUSEUM/LOCOLOCO/friction/friction.htm

 

I've also seen another loco using the "friction wheel to provide occasional extra drive" but I'm unable to find any details. 

[tythatguy1312]

56 minutes ago, rockershovel said:

I've also seen another loco using the "friction wheel to provide occasional extra drive" but I'm unable to find any details. 

That might've been the Fontaine or Holman locomotive, which both represent an intriguing yet incredibly flawed attempt at this sort of technology.

Well that and the Holman was an investment scam.

Edited May 2, 2022 by tythatguy1312

[rockershovel]

4 minutes ago, tythatguy1312 said:

That might've been the Fontaine or Holman locomotive, which both represent an intriguing yet incredibly flawed attempt at this sort of technology.

Well that and the Holman was an investment scam.

No, it's an experimental locomotive akin to the Webb one; I think from France? 

 

The main point appears to be that it wasn't thought to be worth pursuing. 

[rockershovel]

Thanks as ever, to the ubiquitous Mr Self; these seem to be self-contained booster axles, raised and lowered as required 

 

http://www.douglas-self.com/MUSEUM/LOCOLOCO/booster/booster.htm

Edited May 2, 2022 by rockershovel

[PhilJ W]

4 hours ago, Johnson044 said:

Not sure which thread to post this. Imaginary Locomotives possibly not quite right because it actually existed - but it's pretty wild - this is a new one on me. I've seen an image of an American friction drive loco before but never come across one tried in the UK. Is it just me or is this completely bonkers? I completely see the logic and the difficulty of using gears but rather thought that friction was something to be avoided.

 

4 hours ago, JimC said:

There's friction and friction. As a general rule friction is purely parasitic and best avoided. But what's going on here is effectively a clutch using friction in much the same principle as a clutch on an internal combustion engine. So provided the clutch is working fully effectively with no slippage there isn't any more loss than on a motor car clutch. That's the good news. The bad news? I don't suppose the tiny little contact area of that friction drive has any more chance of working efficiently without slipping than I have of winning a tug of war with a GWR 2-8-0 tank engine...

The system could be found on UK railways until quite recently. Some of the Wickham trollies were fitted with  friction drive. It consisted of a flywheel connected to the engine with a wheel at right angles and in contact with it. The wheel could be slid from side to side across the flywheel giving infinite gear ratios and in either direction. The moveable wheel was connected to the driving axle(s) by chain. The flywheel sometimes had a clutch plate to ease the operation and the wheel often had a solid rubber tyre. Some early (Edwardian) cars were fitted with a similar system.

[The Johnster]

3 hours ago, tythatguy1312 said:

Hurricane and Thunderer, the only locomotives I'd actually describe as incapable of working.

I think they worked well enough in one respect, the use of a large enough driving wheel to enable the loco to run at high speeds with low piston rates, essential in the early days when lubrication and bearing technology were not as advanced as they were even 20 years after this.  Once they were under way and had built up momentum, they were probably fine, but the obvious problem is that they have very little adhesive weight, so while you might get them to pop along at a good enough rate to be impressive, and 60mph was impressive in those days, you'd have all sorts of problems getting them there.  Clearly, they wern't going to be able to handle much of a load on the drawhook, even by the standards of the lightweight wooden vehicles of the day, and are likely to be defeated by relatively minor gradients, dragging brakes, wet rails, even headwinds...

 

The game in those days was big driving wheels to keep piston speeds low and provide a better ride on the indifferent track, and it led to all sorts of wierdness, like the Cramptons, or Cornwall.  The broad gauge had an advantage in that they could get a fair size boiler beween the drivers, see Pearson 4-2-4T for the Bristol and Exeter.

[Flying Pig]

I photoshopped a drawing of Hurricane into a Garratt arrangement years ago.  The weight distribution was far from ideal of course.  I sent the result to Mr Self but from his terse reply I have a horrible feeling he thought I was being serious...

[DCB]

7 hours ago, Johnson044 said:

Well - I rather think so too TBH -  as the idler wheel (or whatever it should be called) is pulled upwards, presumably by some sort of screw system, like a tender hand brake, the forces applied to both driving and trailing wheels would have to be quite considerable in order to achieve the friction needed to pull the trailing wheels around. Would these forces not act on the axles / bearings and try to push the two axles apart?  Duuno. Part of me rather thinks it might be made to work - but presumably it didn't. I do wonder why the trailing wheels have balance weights. Maybe the wheels were from scrapped Bloomers?

It could be the fact they left the balance weights on the rear wheels led to terrible riding and caused Webb to abandon this revolutionary feature which could have transformed his compounds, coupling the wheels without using rods.   I read of a GWR Grange being towed with the rods off at over 30MPH  damaging many hundreds of yards of track due to out of balance forces.

[Compound2632]

16 hours ago, Johnson044 said:

Well - I rather think so too TBH -  as the idler wheel (or whatever it should be called) is pulled upwards, presumably by some sort of screw system, like a tender hand brake, the forces applied to both driving and trailing wheels would have to be quite considerable in order to achieve the friction needed to pull the trailing wheels around. Would these forces not act on the axles / bearings and try to push the two axles apart?  Duuno. Part of me rather thinks it might be made to work - but presumably it didn't. I do wonder why the trailing wheels have balance weights. Maybe the wheels were from scrapped Bloomers?

 

The trailing wheels have balance weights to balance the coupling rods, the experimental locomotive being a withdrawn 2-4-0.

 

9 hours ago, DCB said:

It could be the fact they left the balance weights on the rear wheels led to terrible riding and caused Webb to abandon this revolutionary feature which could have transformed his compounds, coupling the wheels without using rods.   I read of a GWR Grange being towed with the rods off at over 30MPH  damaging many hundreds of yards of track due to out of balance forces.

 

I would imagine that the experiment had as its object improving the starting of the compounds. Setting aside all the nonsense about driving wheels rotating in opposite directions, it is true that for the first half-cycle, before steam reached the low pressure cylinder, the starting tractive effort was limited to that of two relatively small high pressure cylinders - 13" dia x 24" stroke on the Experiments, vs 17" dia x 24" stroke on the Precedents - only 60% of the volume, though the compounds worked at higher pressure. Although coupling the drivers wouldn't change the power available, it would increase the adhesion, giving a better chance of getting underway without slipping. 

 

If this was the case, then the intermediate wheel would only be engaged on starting, at low speed, so the now-unbalanced driving wheels of the test locomotive wouldn't be an issue. One underway, the intermediate wheel would be disengaged so that the locomotive would benefit from the free-running obtained without the constraint of coupling rods.

 

The device was clearly an unnecessary complication and expense since for the 15 years or so in which the various classes of three-cylinder compounds were on the front-rank expresses, they routinely got heavy trains away without too much difficulty. That they were exceptionally free-running machines is amply demonstrated by their performances in the '95. 

Edited May 3, 2022 by Compound2632