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What is a 'Radial Tank'?


Ruston
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Indeed .... 'cos if you try to fit a pony truck at the rear of a loco you'll find someone's put a firebox where you want the pivot to go !

 

Not for most 0-6-2s and 2-4-2s, where the trailing driving axle is behind the firebox. Nevertheless, as noted, most had radial axles. 

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And even if they haven't, it will be uncomfortably close and hot; your grease will burn off and the pivot will seize up with ash and other firebox debris.

 

To get back to South Wales 0-6-2 tanks, it has been stated, I think originally by Ahrons, that one of the reasons for their popularity in the area was that they ran slowly up the valley gradient with empty wagons and the radial axles assisted steadiness on the faster loaded run downhill.  South Wales did not work like this, most downhill running with coal trains was extremely cautious and much of it involved pulling heavily against the drag of pinned down handbrakes in order to attempt (sometimes with a spectacular lack of success) to retain control, because of the ever present threat of runaways, while the empties, always in demand at the pits which needed them to put coal into as they did not usually carry stockpiles, often put a surprising wiggle on.

 

Most South Wales railways started out with sensible but not particularly imaginative Victorian 0-6-0s, tender ones in the case of the earlier ones and then saddle tanks, but increasing loads brought about the need to mount the cab and bunker further back to get a bigger boiler in, so the obvious development was to add a trailing radial axle to support the cab and bunker and keep axle loads acceptable.  Fast downhill running had little to do with it; indeed, very few sections of the Valley lines are allowed speeds of more than 50mph.  Hence the usefulness of the type for mixed traffic or passenger work in the area, passenger work requiring driving wheels of the sort of size that would be regarded as more suitable for mixed traffic elsewhere.  The constant need to run up steep gradients tended to lead to high pitched boilers in order to ensure that fusible plugs were submerged in boiler water at all times; priming was a risk if you ran downhill with smokebox leading, so the normal situation was to have the smokebox leading going up the valley and bunker leading coming down.

Edited by The Johnster
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Where Beyer Garretts had a trailing truck they always seemed to be of the radial type; or at least, I've never seen a photo of a Garrett with a trailing pony truck. They seemed to have been 'designed in' to provide a lead for the coupled axles rather than having a primary load carrying function

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Further to what The Johnster says, few collieries in the South Wales valleys had room for stockpiles, or the added complexity of plant required to stockpile and retrieve the coal - much easier to use railway wagons as the stockpile and transfer the problem elsewhere!

Regarding pony trucks at the rear, there were a few examples, such as the 39xx series of 2-6-2T's rebuilt from Dean Goods as did the 44xx and 45xx small prairies according to the diagrams in Russell's books.

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I was searching the interwebs for locomotives built by James Cross & Co. when I found this curious radial tank. Now that I know what makes a radial tank a radial tank I have another question about another of Mr. Adams' inventions arising from this:

 

https://www.gracesguide.co.uk/James_Cross_and_Co:_White_Raven

 

 

In addition to the radial axle-boxes, the engine was fitted with the Adams patented spring tires. Between the rim of the wheel and the tire, which was of Krupp steel, a steel hoop spring was placed round the wheel, with the object of making the tire fit the wheel elastically, being neither too loose, or too tight. Mr Adams considered this the safest form of tire, as it had no tendency to burst; it had sufficient yield to minimise the effect of blows, and was pliant enough to case better adhesion between tire and rail.

 

 

 

What exactly is a spring tire [tyre]? Although the above description is given I can't imagine what it looks like and how it worked. Tyres are usually heated to allow them to fit on the wheel and they cool and shrink to hold fast to the wheel, so I can't imagine how any kind of spring can be fitted between the wheel and tyre. :scratchhead:

 

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Mr Adams' patent spring tyre would appear to be an early form of what we now know as a resilient wheel, well known in tramway engineering and, to a lesser extent, in railway applications. There are three common types, the Bochum, which uses rubber blocks compressed between the tyre and wheel centre, the SAB , which uses inclined rubber rings, and the PCC type, which uses rubber blocks in shear and which is virtually confined to trams.

 

What I suspect Mr Adams was trying to solve was the problems of tyres either cracking due to fatigue or working loose, both a consequence of the flexure of the wheel rim between the spokes. The LMS under Stanier developed wheel centres with much stiffer triangular section rims, whilst others, notably Bulleid in this country, developed wheel centres that provided continuous support to the rim. The Scullin wheel, used by some American railways, was another example.

 

The other factor behind the development of resilient wheels is the reduction in impact forces on the track by effectively reducing the unsprung mass, but the understanding the scale of the problem did not really happen until the days of the BR Research department.

 

Jim

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Seeing as attention has been brought to this topic today, I'll add that in addition to radial axles, T.W. Worsdell made use of a radial truck for at least his Class F 4-4-0s for the North Eastern; I'm not sure about the Class I and J 4-2-2s. The centre of curvature of the radial guides was the centre of the driving axle [J.M. Flemming, North Eastern Record Vol. 3 (HMRS, 2000)]. Any other instances of this arrangement?

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18 minutes ago, Talltim said:

A very long time ago there was an article in MRJ. By someone who had made a radius axle by turning a large ring from acrylic and cutting a section out and boring it lengthways for the axle. Can anyone pinpoint the article?

 

Hmm surely the term radial axle is an oxymoron - can an axle ever be anything other than dead straight?

 

 For those like myself daft enough to want to understand these things this might help...

 

http://www.tonysimons.me.uk/bestt/Downloads/BESTT LM6 springs.pdf

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2 hours ago, Phil Bullock said:

 

Hmm surely the term radial axle is an oxymoron - can an axle ever be anything other than dead straight?

 

 For those like myself daft enough to want to understand these things this might help...

 

http://www.tonysimons.me.uk/bestt/Downloads/BESTT LM6 springs.pdf

Sorry, he made a radial internal axlebox. The axle itself was straight

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8 hours ago, Phil Bullock said:

 

Hmm surely the term radial axle is an oxymoron

 

But it is nevertheless the standard term. The axle can move along an arc defined by the curvature of the guides - i.e. along a line of constant radius, hence "radial".

 

Here "radial" and "axle" are not opposed or contradictory terms (as required for an oxymoron); "radial" is an adjective describing the motion of the axle.

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On ‎12‎/‎12‎/‎2019 at 07:27, Compound2632 said:

Seeing as attention has been brought to this topic today, I'll add that in addition to radial axles, T.W. Worsdell made use of a radial truck for at least his Class F 4-4-0s for the North Eastern; I'm not sure about the Class I and J 4-2-2s. The centre of curvature of the radial guides was the centre of the driving axle [J.M. Flemming, North Eastern Record Vol. 3 (HMRS, 2000)]. Any other instances of this arrangement?

Frank Webb always used either a radial axle (two wheels) or a radial truck (four wheels. What you see under LNWR engines are neither pony trucks or bogies.

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T.W. Worsdell was evidently drawing on his Crewe experience in his use of radial axles. His NER Class F predate Webb's use of a radial truck, which can only first have appeared with the Jubilees in 1897. The LNWR Metropolitan 4-4-0Ts, later converted to 4-4-2Ts, have the Beyer Peacock leading truck which I believe was a true Bissell truck?

 

I'm now trying to track down the first instance of a true leading bogie, with rotation about a centre pivot and lateral side-play controlled by springs - I suspect it is the type introduced William Adams on his North London 4-4-0Ts from 1863? To add to the confusion, the radial axle was invented at about the same time by William Bridges Adams, who was no relation, though of course William Adams made use of it in his celebrated LSWR 4-4-2Ts, the Adams Radials...

 

 

Edited by Compound2632
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As an aside, F.W. Webb took out patents on his radial axles and trucks, although it must be said that he was very adept at taking other people's ideas and modifying them just sufficiently to avoid their patents, and then patenting his version. On the other hand, he was a brilliant engineer and inventor.

 

One of his premium apprentices was (later Sir) John A.F. Aspinall. When the latter took up the role of CME at the L&YR, he produced a 2-4-2T using Webb's radial axles, and the L&YR built several hundred of these over different permutations. Later, Webb found out about this and reminded his old friend of the still extant patent and he could he have his money, please?

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On 13/12/2019 at 20:46, Compound2632 said:

 

I'm now trying to track down the first instance of a true leading bogie, with rotation about a centre pivot and lateral side-play controlled by springs - I suspect it is the type introduced William Adams on his North London 4-4-0Ts from 1863? To add to the confusion, the radial axle was invented at about the same time by William Bridges Adams, who was no relation, though of course William Adams made use of it in his celebrated LSWR 4-4-2Ts, the Adams Radials...

 

 

Was it not the Norris 4-2-0 locomotive type, and its evolution into the “American” 4-4-0?  (The variation in technical terms between Great Britain and the USA muddy the waters).

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On 12/12/2019 at 08:15, Talltim said:

A very long time ago there was an article in MRJ. By someone who had made a radius axle by turning a large ring from acrylic and cutting a section out and boring it lengthways for the axle. Can anyone pinpoint the article?

No, they weren't pinpoint, they used inside bearings. :) :) :)

 

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