The End of Brass?

You describe one of several schemes to allow the individual axles to swivel (align with curved track) while being driven by more-or-less rigid siderods. Other possibilities include variations "cone and cup" drives.

For long 'rigid' (again a misnomer) wheelbase locos often the front and rear, or perhaps the middle, axles were given what is referred to as a "lateral Motion device". A means whereby the wheels were allowed a certain amount of sideplay. This allowed the wheelbase more flexibility to conform to the curved track. This did not, in itself, imply any ANGULAR adjustment of the axles to keep them parallel to the track. That's doable too (as the system you describe proves), but is far more complicated.

Even today with Diesels these same problems arise. On curved track the axles in a rigid truck frame cannot all remain parallel and 'track' properly. For short wheelbases this was not much of a problem, except at high speeds or very high power loadings. Since both are now becoming more important, even modern Diesel trucks have 'steering' to allow the individual axles to pivot in the truck frames, and better follow the track.

With most Diesels at least you don't have to figure out how to couple siderods to the moving axles.

Dan Mitchell ==========

Gregory Procter wrote:

It's one that worked.

The Golsdorf system replaced Klose's designs. (0-10-0 and 2-12-0)

There are examples of uncoupled steam locomotives and coupled Diesel locomotives

- it's scarcely fair to compare designs/technologies 50-100 years apart and conclude the more modern one to be superior.

Regards, Greg.P.

"Gregory Procter" > > On the Triplex there's also an

between the "loco"

Because the last +8-4 engine was under the "tender".

-- Cheers Roger T.

of the Great Eastern Railway

Talking standard gauge, only one small batch of locos had inside cylinders and valve gear, the majority outside. None of them had Stutz tenders. Inside cylinders have the advantage of less side imbalances for a loco intended to run at higher speeds (entirely relative of course - 65Km/hr vs 45Km/hr) That advantage has to be balanced against higher maintainance costs. Most of the Klose "additional mechanisim" only moved on curves, otherwise it just sat there. It was simpler than the extra mechanisim of a Mallet, Meyer, Hagan etc which were the alternatives at the time.

Regards, Greg.P.

If the tender already carrys sufficient weight to act as an engine, why steal weight from the locomotive just when undulating track is reached?

(I only passed "Model Locomotive equalization 101 - theory and practical")

Regards, Greg.P.

"Gregory Procter"

As I understand it, all steam locos tranfer weight when they start. The weight (Centre of gravity) moves to the rear as the loco starts forward and "digs into" its train. This is why, for example, 4-6-0s are generally less "slippery" that 4-6-2s as the weight transfer bares down on the rear pair of drivers on a 4-6-0 but bares donw onto the trailing (non-driving) wheels of the trailing truck on a 4-6-2.

So, I'm guessing that with an articulated, and I'm way out of my technical depth here, there has to be some provision for weight transfer between each of the engines. Engine defined as the coupled wheels driven by a set of pistons.

A 4-6-2 has one engine.

A 2-6+6-2 has two engines.

A 4-8+8+8-4 has three.

Not much better than me. :-)

-- Cheers Roger T.

of the Great Eastern Railway

There's very little point in transfering weight from one engine to another, so why make the mechanical provision. Re the 4-6-2; the trailing axle generally gets included in the equalization on undulating lines, otherwise that little axle-set starts stealing weight from the drivers just when it's needed.

Sure, that's a good generalization., but there are exceptions. The German BR19.1001 2-8-2 had four engines. The British Railways "Leader" 0-8-0 had two engines. The NZR Kb had two engines. The NZR H had two engines. etc.

equalization on

Actually, it's a given that 4-6-2s are more slippery that 4-6-0, equalisation/compensation or not.

Engines should not be confused with number of cylinders. An "engine" is all the coupled wheels driven by one set of pistons, be there, one, two, three, four or more. I'm not sure where a Shay would fit into this description as all the wheels were driven by gears. perhaps the Shay, and all it's driving wheels, are one engine?

The ill fated Leader class was an 0-6-0+0-6-0T Yes, this locomotive had two engines. Each 4 cylinder engine drove each of the six coupled pair of drivers and baked the fireman in the process.

BTW, the much vaunted 4-8+8+8-4 was really a 4-8+8+8-4T. Yes, it was a tank engine as it didn't tow a tender. :-)

No, it's one engine. They were two cylinder 4-8-4s

See

They were also two cylinder "Fell" 0-4-2T locomotives. One engine, two cylinders.

See

BTW, good listing of all Kiwi steam engines at: -

-- Cheers Roger T.

of the Great Eastern Railway

Like Roger, I am out of my depth here, never having had any experience with Mallet articulateds. However, going by what various publications have to say on the subject, I'm fairly certain that the equalisation/compensation arrangements on such engines are independent of each other, that is to say there is no connection between the equalising beams or rigging of each engine unit.

Cheers,

Mark .

Well, there you go - I didn't even realise that there were standard gauge locos with Klose mechanisms. I was only familiar of the Sachsen IIIks and the JZ 189s.

And the joys of digging out the smokebox lining to get at the valve chests!

Simple being a relative term in this context, eh? :-)

Cheers,

Mark

Yep! Been there, done that, had my fire pulled to bits!

Each cylinder engine, you mean. :-)

I often wonder what posessed Ollie Bulleid to persist with sleeve valves for these engines, after the disappointing performance of 'Hartland Point'.

I reckon he's referring to the trailing truck booster engine :-))

Greg's right about the Fell engines - I've had a poke around underneath the one in the little museum at Featherstone(?), and it's definitely got four cylinders. Two drive the coupled wheels as in a conventional adhesion loco, and the other two drive the horizontally mounted wheels that grasp the centre rail.

You and I are both having a real run of outs today, Roger.

All the best,

Mark.

I'll be guessing a bit here. I've never read a GOOD dissertation on the Triplex design hopes.

Like all 'tank' type locos, including Garratts, the Triplexes suffered from both decreasing weight and weight transfer as coal and water were consumed. AT low fuel and water levels, the rear engine would have become very 'slippery'. By carrying some loco weight on the rear engine this effect would have been lessened.

Further speculation ...

The Triplexes were unusual in that they were Mallet locos (compound articulateds of mostly conventional design), but had 'all same size' cylinders. The compounding resulted from splitting the exhaust of the center high pressure engine and sending the (once expanded) steam to BOTH the front and real engines. Thus the total cylinder volume of the two low pressure sections was twice that of the high pressure section. IIRC, the rear engine got it's steam from ONE of the high pressure cylinders, while the front engine got it's from the other HP cylinder.

Now, if the rear engine slipped, and rapidly consumed the available low pressure steam, then the sudden loss of back pressure on the one high pressure center cylinder might also initiate a slip on THAT engine as well. It would also create larger than normal asymmetrical forces in the HP engine's frame and axles. None of these effects were good. Thus, I suspect, it was important to keep all three engines working as a team if decent performance was to be achieved. That implied some effort to keep weight distribution under control. I think that was the idea, anyway. It was NOT totally successful, but more-or-less worked. Anyway, that was not their major problem.

Their big limitation was steam production. The boilers of the time, with long narrow fireboxes, simply could not make enough steam to feed six cylinders at any respectable road speed.

The three Erie Triplex locos were semi successful. The VGN loco was not. It's not so much that the locos were very different, but their intended use was different.

Erie used theirs as pushers or helpers on hilly areas. They didn't have to exert full effort for long periods, and could 'recharge' steam pressure between assignments. They lasted in service for a number of years. VGN, on the other hand, wanted their triplex for road service, and it could not produce enough steam to SUSTAIN a road speed of more than 5 mph. That was too slow even for a VGN coal train in the mountains. This loco was a failure due to not meeting it's intended purpose. It was rejected, and later separated and modified into two conventional locos, a 2-8+8-0 and a 2-8-2, both of which were then used by VGN for years.

VGN solved their need for a massive 'coal pusher' loco by acquiring their several AE class 2-10+10-2 Mallets. The AE's were almost as effective starting a train as the Triplex, and could maintain their effort at 15 mph (three times the Triplex's speed) ... which was fast enough. The AE's had the greatest 'TE' of any conventional articulated loco. These engines were used for for years, and moved mountains of coal out of the eastern mountains.

The four Triplexes, while very impressive locos, were NOT large compared to several later Mallet and 'simple' articulated steamers. Even VGN's 'AE's, while having fewer wheels, were considerably larger locos than their Triplex. The Triplexes could produce MASSIVE (unmatched) tractive effort, at very low speeds, or for very short periods of time, but were not 'high horsepower' locos like the later Allegheneys, Challengers, and Big Boys. The Triplexes were great lumbering steam powered 'dinosaurs' whose time quickly passed.

They DO make GREAT models, though!

Dan Mitchell ==========

Gregory Procter wrote:

I think you're right about there being NO coupling of the separate engines' equalization systems between the 'halves' of a Mallet (or conventional simple articulated). The frames ARE connected, semi-rigidly', however. They DON'T just sort of float around like separate Diesel trucks, or Shay trucks. Also, since the rear engine is semi rigid under the boiler, any movement of the boiler initiated by the front engine is transferred to the rear engine through the boiler as well as the articulation joint. Thus weight transfer between frames is inevitable as each move. The frames are each part of a complex coupled system, formally equalized or not.

Dan Mitchell ==========

Mark Newt>

No, it's a given that 4-6-2s without compensation are more slippery than 4-6-0s.

A compensated 4-6-2 with 60 tonnes weight on the drivers will pull exactly what a 4-6-0 with 60 tonnes on the drivers will.

The BR 19.1001 had two cylinders on each driver and no coupling between them.

Ouch! - yeah, I knew it had 6 axles. not 4.

Add the booster. Two engines.

Keep adding - there's the Fell two cylinder engine which was separate and ran at a different rate. The sound of three locos spread through a short train, hammering away, with all six engines making their own speed was magnificent!

Sure, go compare the complexity of a Diseasel!

Regards, Greg.P.

My experience on the pointy end of a shovel, is that, in the UK at least,

4-6-2s were generally more slippery that 4-6-0s. That's why the GWR stuck with 4-6-0s for express passenger working rather that using 4-6-2s. That's not only my experience but will be supported by anyone else who's been a footplateman on steam.

Didn't know that and forgot to check the web.,

Boosters don't count. ;-)

magnificent!

You live and learn. I should have known that. :-)

-- Cheers Roger T.

of the Great Eastern Railway

It's not pull. It's start. When it starts or when it's pulling hard there's weight transfer to the rear axle, especially as the train begins to roll. Simple physics because of the forces in the drawbar. Even with compensation.

Which is why Pacifics slip more on starting than 4-6-0s.

I have to agree with you - from the POV of a trainspotter at the London termini in the late 1950s and early 1960s. My fading memory tells me the ex LNER Pacifics at Kings Cross were the worst. It was nothing to do with the climb through Gasworks Tunnel - this was on starting.

Your experience is almost certainly with non-equalized 4-6-2s. Were _any_ British pacifics equalized in the trailing truck?

It was a one off - got muddled up with WWII. The dud from new boiler was never fixed and the yanks hauled it off to the US around 1948.

They certainly did in the mountains!

I should have got the Leader details right! My dad went to the same school as Bulleid - just 30 odd years later.

Regards, Greg.P.