Posted: Thu Mar 15, 2007 4:39 pm
Yes Dave I do have a Mallard in her original LNER Duck Blue, most Engines are not rated in HP but in tracktive force, in this case the A4's had around 36,000lbs.
The Valve motion was a specific design that Gresley developed earlier (1921) for the A1-2-3 Pacific Class Engines and had three cylinders, two on the outside, running a modified Walchaert system,and another in the center of the Engine running a proprietary design of Gresley's.
The thing that makes the motion appear more elegant is the fact that the driving wheels on the A 3&4's were 80" in diameter, compare that to those on a Berkshire 2-8-4 at 60" Also the linkage connections on UK engines tend to be a lot slimmer compared to those in the US.
Although the engine horsepower was never officially published, I've uncovered several references to the estimated horsepower that was developed, in in this case you're not far off, Gresley estimated that his streamlining was saving approximately 800Hp, or 30% when the engine was traveling at 100 Mph, so that would place the overall power at 3000 Hp
The Flying Scotsman was a modified A3 Pacific designed by Gresley and was built in 1923. It had a tender very similar to that of the A4's. It's tractive effort was close that of the A4 at 36,400lbs
This is her on the day she rolled out of the Doncaster Engine works in 1923, she remained in regualr service until 1963.
The Valve motion was a specific design that Gresley developed earlier (1921) for the A1-2-3 Pacific Class Engines and had three cylinders, two on the outside, running a modified Walchaert system,and another in the center of the Engine running a proprietary design of Gresley's.
The thing that makes the motion appear more elegant is the fact that the driving wheels on the A 3&4's were 80" in diameter, compare that to those on a Berkshire 2-8-4 at 60" Also the linkage connections on UK engines tend to be a lot slimmer compared to those in the US.
Although the engine horsepower was never officially published, I've uncovered several references to the estimated horsepower that was developed, in in this case you're not far off, Gresley estimated that his streamlining was saving approximately 800Hp, or 30% when the engine was traveling at 100 Mph, so that would place the overall power at 3000 Hp
The Flying Scotsman was a modified A3 Pacific designed by Gresley and was built in 1923. It had a tender very similar to that of the A4's. It's tractive effort was close that of the A4 at 36,400lbs
This is her on the day she rolled out of the Doncaster Engine works in 1923, she remained in regualr service until 1963.