90 Mph Mainline Running In The UK

Tom Parkins · **Posted:** Wed Aug 14, 2013 9:31 pm

WOW! The first video sure looks like it could have been on the NEC. Good stuff. Thanks for sharing.

solar1953 · **Joined:** Mon Oct 03, 2011 9:30 pm **Posts:** 56

OUTSTANDING!! Never thought I'd live to see such speeds out of steam power again!!

Bobharbison · **Joined:** Fri Dec 03, 2004 9:42 pm **Posts:** 2949

Great videos, but I'm curious about the first two scenes on the first video.

In those two scenes, especially the first one, you can hear distinct chuffing sounds. Given the speed, and the blur of the rods, it seems like it should be a constant roar. How is it that chugs are distinguishable? Dubbed sound? But the coach sounds seem reasonable?

NW Class J · **Posted:** Tue Aug 20, 2013 4:12 am

She sounds like who ever set her valves knew what they were doing, and the driver has her hooked up. Great videos.

Dave Stephenson · **Posted:** Tue Aug 20, 2013 7:45 am

I believe the "chuff" that we an hear in the first two videos is evidence of the legendary "Gresley beat". The A4's use a conjugated valve gear, and regardless how well the valves are set, there's always some leeway in the levers to the center cylinder. This produces a distinct "beat" at higher speeds and short cutoff. Great sound, though. This is the highest documented steam speed I've ever seen/heard.

Alexander D. Mitchell IV · **Posted:** Tue Aug 20, 2013 7:59 am

Bobharbison wrote:

Great videos, but I'm curious about the first two scenes on the first video.

In those two scenes, especially the first one, you can hear distinct chuffing sounds. Given the speed, and the blur of the rods, it seems like it should be a constant roar. How is it that chugs are distinguishable? Dubbed sound? But the coach sounds seem reasonable?

From http://en.wikipedia.org/wiki/Gresley_co ... valve_gear :

Quote:

Locomotives with Gresley valve gear must have the three pistons operating at precisely 120 degree intervals. (Different spacings could be accommodated by different lever proportions, if there were any advantage to a spacing other than 120-120-120.) In order for the inside crank to clear the leading coupled axle, the inside cylinder of a locomotive with Gresley valve gear is typically positioned higher than the outside cylinders and angled downward.[2] To maintain a smooth flow of torque, the crank angles are offset from equal 120 degree spacing to compensate for the angle of the inside cylinder (e.g. 120/113/127 degrees).

Although the Wikipedia article then claims that:

Quote:

The resultant timing of the blast from steam exiting the cylinders still gives these three-cylinder locomotives a regular exhaust beat

... those of us who know Gresley three-cylinder locos intimately know better. That ever-so-slight change in spacing results in a perceptible syncopation or "off-beat" sound, most perceptible at slow, hard departure. This even has its own name in British rail jargon: "the Gresley beat." The name was used for a Transacord recording of LNER three-cylinder locos, and later still for a well-known modular layout of the approach to Kings Cross still making the rounds of shows today.

The result of that "offbeat" syncopation is that even at high speeds one can manage to distinguish the beat of a Gresley conjugated-valve steamer as it "roars" down the track. That clip with Bittern is sort of an extreme example, but.....

Richard Glueck · **Posted:** Tue Aug 20, 2013 9:28 am

Doing what she was built to do, where she was built to do it.

Bobharbison · **Joined:** Fri Dec 03, 2004 9:42 pm **Posts:** 2949

Alexander D. Mitchell IV wrote:

... those of us who know Gresley three-cylinder locos intimately know better. That ever-so-slight change in spacing results in a perceptible syncopation or "off-beat" sound, most perceptible at slow, hard departure. This even has its own name in British rail jargon: "the Gresley beat." The name was used for a Transacord recording of LNER three-cylinder locos, and later still for a well-known modular layout of the approach to Kings Cross still making the rounds of shows today.

The result of that "offbeat" syncopation is that even at high speeds one can manage to distinguish the beat of a Gresley conjugated-valve steamer as it "roars" down the track. That clip with Bittern is sort of an extreme example, but.....

Ah, thank you for the explanation. The only 3 cylinder locomotives I've spent any time with were built by Lima and Willamette. While they sometimes _sound_ like thy're doing 90, it's actually more like 9 most of the time, with 15 being scary fast.

90 Mph Mainline Running In The UK

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