35018 British India Line

I think you've taken a tongue-in-cheek comment rather more seriously than it deserved. I'm sorry if I caused offence. None intended.

 

This little squabble would never have arisen if Bulleid had built the design he wanted to produce. He wasn't perfect but he understood the value of an eight coupled design. He benefited handsomely from having a good teacher.

 

Don't worry they just upset cause they can't handle that they might actually be a troll.

 

How about this one?

 

I go back to the days of real steam and the Bulleids were complete masters of the job on the SW Mainline. Can't be too bad for a clapped out MN to do 106mph even if it was on a relatively light train, one of the highlights that I will never forget

 

Pacifics are generally powerful locomotives and designed to haul heavy loads at relatively high speed. To haul a heavy load needs a tractive effort to match so the loco has to produce this TE at speed. It is a fundamental of a steam loco that TE falls off as speed increases. It happens with diesels, too. Thus, to have the TE at the required speed means that the TE at low speed is much higher than is needed for the train. With a diesel the control system limits the TE to a figure that is unlikely to cause problems. However, with a steam loco, the control system is nothing else but the driver. If you designed it so that it wouldn't slip at low speeds, it would be unnecessarily heavy. That's why large locos slip easily.

 

If it was only that simple. Add in piston stroke to wheel diameter, Number of cylinders, cutoff, steam chest side relative to cylinder volume, quality of streamlining of steam passages and so. They all have an effect not only the torque at low speed but also the drop off in TE at high speed. Read the later pages of the the Red Devil book.

 

All of which is irrelevant to my basic comment that TE will drop off as speed increases and, unlike a diesel, the torque control is solely down to the driver. I am also talking about existing steam locos built 50 or more years ago.
The later pages of the Red Devil are unread by me because, to be honest, I started to find it boring. The bookmark is at page 376 and is unlikely to move.

 

Add a smiley next time and we'll know you're just pulling our legs. Apologies accepted and I'll withdraw my caustic remarks.

 

All joking aside, what do you consider low speed? 34067 storming Hemerdon at 29mph or lower still?

 

I do like your idea of taking a pub in tow but I think you'll find it would be out of gauge.

 

Have already had a trip behind 5043. It was alright, but didn't exactly set the world alight.

 

Keighley and Worth Valley Buffet car would do, and it's in gauge. Is it still in the Good Beer Guide?

 

Hard to know an exact figure, but I'd suggest lower than 20MPH.

 

The largest locos were presumably designed to have the maximum permitted axle loads, or not much lower, so the adhesion weights of the 4-6-0s and 4-6-2s must be similar. On an upward gradient the pull on the drawbar causes a slight transfer of weight to the trailing axle of a 4-6-2, and the movement of water to the back of boiler must do likewise, so the loco with trailing wheels is likely to have a slightly greater tendency to slip in any given conditions, other things being equal. There are other variables too. For the same actual average TE the larger loco might be working at shorter cut-off, causing more variation of TE over each revolution. Except at starting, a 3-cylinder loco has a more even TE then a 2- or 4-cylinder loco (other than a LN). All these variables are outweighed by the skill of the driver in avoiding slips or recovering quickly when they do occur.

 

Meanwhile...back at Carnforth...any news?

 

Any every time you trot out the same photo... Just saying...