# Fastest steam engine in the shop



## Charles (Jan 2, 2008)

The Aster A4 has arrived to have RC (throttle, blower, Reverser) along with system check for its first ever steam up:


Aster A4 Mallard


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## Pete Thornton (Jan 2, 2008)

Great picture. I'm sure you've noted that the SIX surviving locomotives are gathered at the National Railway Museum for the 75th anniversary of the record run. Including the "Dominion of Canada" from (where else) Canada and the "Dwight D. Eisenhower" from Green Bay's Railroad Museum. The latter two have been cosmetically restored and will be shipped home afterwards. 
(I hear some UK Millionaire tried to buy "Dwight D. Eisenhower" but it is not for sale.) 

Good photos at http://www.flickr.com/photos/[email protected]/8889070333/lightbox/


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## zephyra (Jan 2, 2008)

Posted By Charles on 10 Jul 2013 01:12 PM 
The Aster A4 has arrived to have RC (throttle, blower, Reverser) along with system check for its first ever steam up:


Aster A4 Mallard 

I will be fascinated to hear where/how you position the RC for this machine. Also it will be interesting to see what level of control you are able to achieve - my experience of these machines is they operate in only two modes - stopped and flat out. 

Robert


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## bille1906 (May 2, 2009)

Charles 
I have been interested in building a Streamlined Garratt with drive trains similar to the Mallard. 
I can't tell from any of the photos what type of valving it has. 
The Garratt would only have two cylinders per engine vs three on the Mallard so I am only interested in the outside valving. 
Maybe you can take a photo of the valve gear when you get it dissembled ??? 
I too will be interested to see how you do the reverser. A 9 gram servo works fine on the Uintah with piston valves but I doubt that setup would work on D valves.


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## Charles (Jan 2, 2008)

Bill

We will forward all the information and photos.

Robert
Could be the taper on the throttle as to "all or nothing."


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## zephyra (Jan 2, 2008)

Posted By Charles on 31 Jul 2013 08:42 AM 
Bill



Robert
Could be the taper on the throttle as to "all or nothing."

Maybe - but I have all 3 variants (Mallard, Silver Link and Sir Nigel) and they all behave the same way. Ferocious cylinder lock until you clear the condensate, then takes off like a scalded cat. I'll be interested in your experience - the Aster A4 wouldn't be my first choice for RC. Good luck!

Robert


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## bille1906 (May 2, 2009)

Pete 
I missed your link to the six remaining loco's 
great shots and very good for getting an idea of the construction 
It looks like the speed was generated by an almost 3.5 to 1 crank pin to wheel radius ratio and full Walschaerts along with the center cylinder at 45% cut off and naturally, the streamlining


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## Pete Thornton (Jan 2, 2008)

It looks like the speed was generated by an almost 3.5 to 1 crank pin to wheel radius ratio and full Walschaerts along with the center cylinder at 45% cut off 
Bill, 
Without wishing the divert Charles' thread, I think its a bit more complicated than that. Does the crank-pin-to-wheel-radius have anything to do with speed? I can see the torque issue with a bigger crank, but I would have thought the smaller the better for speed - less reciprocating motion mass. 

These engines had Gresley conjugated valve gear on the center cylinder - the valve motion weas derived from the two outside valve systems. I don't recall them having anything special for speed (apart from the streamlining, which was partly for show on the Silver Link train, like the Dreyfuss Hudsons on the Twentieth Century.) I don't think the Aster A4 has this type of valve gear - the new WuHu model does, apparently.

In fact, the loco had a hot bearing after the run and had to be removed from the special train. The demolition of the motion on "Blue Peter" at Durham [look it up if you want to get horrified,] demonstrated they couldn't handle more than about 150 mph anyway. 

Final note - I read that Gresley was on the train when they made the record attempt [the Dynamometer car is still at the NRM] and the coaches weren't exactly stable at 100mph+ - they rocked around all over the place. Gresley apparently took great delight in complaining about the track to the other bigwigs in the car.


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## Reg Stocking (Sep 29, 2010)

True, Mallard set the official record for steam. In the US the Interstate Commerce Commission and the state regulators had the power to impose speed limits and other restrictions, but the railroad companies were regarded as responsible, so this didn't happen until after WWII. But consider the zillions of unprotected grade crossings. It was common for the 20th Century and other fast ones to hold 80 mph for long distances. When streamlining appeared, some roads let them romp even faster. When the Milwaukee Road began the Hiawatha service in 1935 the employees' operating timetable required an average of 102 mph for a considerable stretch. 

The Hiawatha Atlantics and Baltics had 84" drivers, 300 psi boilers, and Barco speed recorders with the needle pegged at 0 and 128 mph. They were expected to make up time with late trains. On test and with late trains there are several accounts of the needle being pegged at 128 for long distances. The Milwaukee Road didn't want to risk having Big Brother clamp down, so it was don't-ask-don't tell. Also the Mallard run was descending Stoke Bank; the Milwaukee Road was pretty much flat. 

Much the same applies to the question of NYC&HRR 999 and GWR City of Truro. I'm convinced that both did as claimed, again noting that 999 was running on level track while C of T was descending a better than 1% grade when it was timed for a single quarter-mile above 100 mph. I have great respect for British steam, but they weren't the only ones to run fast.


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## pogsteam (May 23, 2013)

Hi Reg 

I agree 100% that there were a lot of trains running fast back in the day, and on a level track, and in a way , with all your evidence, it doesn't seem fair that we, sorry I meant the Brits, 
have the official world speed record.......... (smiley face!)


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## Pete Thornton (Jan 2, 2008)

I agree 100% that there were a lot of trains running fast back in the day, 
And those Pennsy guys reckoned they had exceeded 100 mph regularly with the T1s, etc. I don't know why the steam record isn't the average of two runs in opposite directions on the same track, as it is for cars! 

So why doesn't someone try to beat it, I wonder...


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## bille1906 (May 2, 2009)

Pete 
You are absolutely right about the smaller the better for speed and in fact the Mallard and all of these fast runners had small crank radii and large wheels thus the 3.5 to 1 ratio where the freight haulers were normally at 2 to 1


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## zephyra (Jan 2, 2008)

There are entire websites (http://www.germansteam.co.uk/FastestLoco/fastestloco.html) devoted to who actually should hold the world speed record. The British tended to make up their own rules in the 1930s. The Hawker Hurricane was claimed as a 400mph aircraft based on a single run with a ferocious tailwind. 

Lots of coverage of Mallard in the UK this week. My sister just sent me this link from the UK Daily Mail: 

http://www.dailymail.co.uk/sciencet...75th-anniversary-126mph-landmark-journey.html 

Robert


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## AsterUK (Jan 2, 2008)

Last weekend at the National Railway Museum, York UK, members of the Gauge One Model Railway Association set up their portable track "Dobsons Bridge" with special high speed running straight to re-enact Mallards 1938 speed run with Gauge One live steam models.




























The Aster A4's put in the most consistent performance the aim being to match a scaled 126mph. My own A4 Golden Eagle (an Aster A3 / A4 hybrid) managed 122 mph and 143mph on the Sunday. The fastest A4 of the weekend was Alan's seen here backing down the straight after 155mph. Shown here is also a City of Truro and GWR train which managed 100mph fairly frequently.

Many nations claim their steam trains ran faster than Mallard but no one has a fully authenticated Dynamometer Car record proving beyond doubt that Mallard achieved 126mph on 3 July 1938.


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## zephyra (Jan 2, 2008)

Posted By AsterUK on 02 Aug 2013 01:59 PM 
Last weekend at the National Railway Museum, York UK, members of the Gauge One Model Railway Association set up their portable track "Dobsons Bridge" with special high speed running straight to re-enact Mallards 1938 speed run with Gauge One live steam models.



Was the gauge 1 track down hill









Robert


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## AsterUK (Jan 2, 2008)

Robert, I was told it was flat!

The biggest problem is that the train was accelerating all the time. Hitting a scale 126mph between the markers was the real challenge.

Andrew


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