The End of Brass?

"Gregory Procter"

Now there's an interesting point.

I'd ASSume so, but my education never really got that far as I was only on the shovel from 16 years to 19/20 years old and steam was already on the way out. It ended on the Southern in 1967, about 18 months after I came to Canada and about a year before steam finally ended on BR in August, 1968. I only took the job, dirty and filthy as it was, just to fire steam, not as a career in the railway. Besides, I don't like working outdoors in wet weather, especially if it's cold, wet and miserable, like most UK winters.

I know, for example, that Bulleid Pacifics in the WC/BB and MN classes were very prone to slipping when starting away. Usually not a violent slip, because the drivers (engineers) were skilled, but the wheels rotating slightly faster than the engine was travelling. I gather other regions Pacifics, while prone to slipping, were not has bad.

-- Cheers Roger T.

of the Great Eastern Railway

Granted - but I have someone else to delegate the diesel repairs to!

Cheers,

Mark.

The rear frame is mounted rigidly on a Mallet. In theory, there should be no weight transfered through the articulation joint between the frames, but as that joint took care of the tractive forces, I'm sure there was some.

When did you change your name from O.Bullied?

Regards, Greg.P.

A steam locomotive "today" could easily be built as a B'B' or any other bogie configuration. The engine could be modernised to a high speed multi-cylinder unit driving cardan shafts to gear boxes on each axle, just as utilized on European Diesel Hydraulics and Electrics.

Such a modern steam locomotive wouldn't look too much different to a "car-body" style Diesel, other than exhaust and a tender. Why would anyone want to? To burn fuels other than imported oil.

Regards, Greg.P.

On Sat, 23 Aug 2003 08:45:50 UTC, Mark Newton wrote: 2000

Yes, but a diesel is modular. When a steamer has a breakdown the whole loco is tied up in the shop. For many breakdowns on a diseasel a module (i.e engine, truck, etc.) can be replaced and it is on its way.

Frankly I would much rather try to maintain a diseasel than a steam boiler, especially in bad water country.

Sure, go compare the complexity of a Diseasel!

Regards, Greg.P.

Be careful guys! You're comparing apples to oranges when you state that a wheel arrangement is slipperyer than another class! The Pacific arrangement usually had larger cylinders and higher boiler pressure so that they could maintain higher speeds with a larger train with better efficiency. Change those factors and you have a higher HP loco with a higher starting force and thus the drivers will slip easier. I'll also notee that axle loadings also affect the slipperyness of a loco. Some locos were notorious for slipping while others were hard to slip. The differences weren't in the wheel arrangement but rather the excess power available at the starting speeds.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!

The front support on some of the mallet type locos actually had a centering mechanism in there that pushed up the boiler when off of center - specifically the UP Challenger and Big Boy locos in particular. The rear joint was intended to hold the two loco chassis in alignment and thus the front loco frame was kept parallel to the rear frame at the minimum. I'll note also that European locos often had some strange suspension systems where they weren't fully equalized and thus often had problems from that aspect.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!

At least in the UK, discuss this with ex steam railwaymen and they'll almost all agree that a 4-6-2 was slipperier than a 4-6-0 or a 2-8-0 or 2-10-0 for that matter.

Tank locos were a different matter.

-- Cheers Roger T.

of the Great Eastern Railway

On Sat, 23 Aug 2003 22:08:45 UTC, "Roger T." wrote: 2000

No UK experience, just US. While appliances could/would be changed out this was not true of major parts. AFAIK there were no spare major parts sitting around. OTOH Espee was noted for swapping tenders.

When the LMS railway was formed amalgamating the Midland and the LNW the bosses came from the Midland and imposed the Midland policy of putting the engine number on the smokebox door and on the tender sides. Pretty soon ex LNW engines were running around with two different numbers confusing everybody, the policy was then changed to number on the cam side sheets and just the LMS emblem on the tender. The LNW was very big on workshop organisation and since overhaul of a tender was much quicker than a loco they never built as many tenders as locos. The opposite went for boilers, overhauling a boiler took longer than the chassis so there were always spare boilers built for each class. So a loco in for overhaul almost always came out with a different boiler and tender. After the merger the accountants made sure this practice became universal and it continued to the end of steam on BR. Keith

Make friends in the hobby. Visit Garratt photos for the big steam lovers.

I appreciate the points you're making Bob, and yes, we are comparing apples and oranges. But that's valid in this context. I'm specifically comparing a 1920s ten-wheeler with a 1940s Pacific. And I've found that all other things being more or less equal, the 4-6-2 will slip at certain locations where the 4-6-0, with the same trailing load, and under the same conditions, won't. Whatever the ultimate cause - wheel arrangement, factor of adhesion, greater starting torque - it all makes for an interesting discussion.

All the best,

Mark.

Tractive forces are not the issue.

Assume a Mallet style loco sitting on level track. The articulated joint (probably) has minimal VERTICAL load applied. The front engine is loaded by the front portion of the boiler weight, carried on the pedestal and cross-slide. The rear engine is loaded by the weight of the rear of the boiler applied directly to the rear frame. Within each frame, equalization will share the applied weight.

Now, move the entire front engine UPWARDS (bump in track). The articulated joint is now loaded so as to pull DOWN on the back of the front engine, and UP on the front of the rear engine. As little play is involved, actual motion will result. The front engine will carry MORE weight, and the rear engine LESS. This will be somewhat compensated for by the boiler motion that results. As the front of the rear engine frame is lifted, so will be the front of the boiler. This will REMOVE some of the front pedestal loading on the front engine. It gets complicated, basically an interconnected set of levers, but weight TRANSFER sure does occur. In effect, there *IS* an form of equalization between the front and rear engines, with the boiler as one lever. Within each frame, equalization will again share the applied weight, but the total weight on each frame changes, both in magnitude and points of application.

Total weight on drivers does not change, as what's gained by one engine is lost by the other.

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

Gregory Procter wrote:

One thing to note here in addition to my other post today is that the Pacific is designed to handle that train at a higher speed. The higher BP, smaller cylinders both maximize the useage of the steam at a higher speed. Unfortunately, that BP increase hurts the low speed performance - the wise engineer would probably tell the fireman to hold BP to 210 around the station so that the engine won't develop the necessary torque to make it slippery. He'll still get about the same power as the 36 class but when he got out on the road and rolling along, the increase of BP to the working max. will provide the additional HP to run the train along at a much higher clip.

-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!

The problem is Mark the expert has not truly represented the engines performance and has found out nothing. He has simply misinterpreted what he or probably what others have seen . The reality is the 4-6-0 locomotive Mark talked about (NSW 36) is less powerful than the 4-6-2 locomotive (NSW 38). The 4-6-2 locomotive Mark mentioned also has a slightly heavier axle load, which means it is actually 'less slippery'. The 4-6-2 Mark mentioned out performed the 4-6-0 all round, including maximum load it could move. Mark's example shows Bob is correct.

The real problem is that Terry's only source of knowledge is what he has read. His "expertise", such as it is, is purely theoretical. Experience shows that a 38 will outperform a 36, no argument there. And experience also shows that in certain circumstances, which were clearly stated, a

38 will slip where a 36 won't. There is nothing to misinterpret.

Bob makes a valid case for the 38 being more slippery than the 36, which has been my experience. That contradicts your assertion that they are less slippery.

You then wrote :"Mark's example shows Bob is correct."

Surely that can't be right? You're actually acknowledging that someone else is right, and that you're wrong????

Unbelievable.

And the theory matches the performance. The 38 wheel 'slips' because it has more power, and this wheel slip is usually a function of poor driving. The wheel arrangement has only a small effect, which is negated by the heavier axle load in the NSW 38 V NSW 36 comparison. Those who designed the NSW 38 new their theory, and built a locomotive that would be less slippery than a NSW 36, to avoid double heading on passenger trains at the time. They were successful. As for experience, Mark the expert's experience shovelling coal on the foot plate clearly is not enough to understand the mechanics and dynamics of a steam locomotive.

It's not what Bob said. Only you directly compared the NSW 38 with the NSW

36, and as I have shown in a previous post the NSW 38 is less 'slippery compared to the NSW 36, as proven by the maximum load it can pull. The practical outcome of allot of theory you are not familiar with..

Yes your twisting of facts is. Mark the expert has been caught out again.

Agreed.

A theorist and practical engineer once argued with me that it is impossible to get a three cylinder engine stuck on "dead centre" as a three cylinder loco doesn't have a "dead centre".

Obviously never been on the footplate of a WC/BB class 4-6-2. :-)

-- Cheers Roger T.

of the Great Eastern Railway