A Coarse Guide to the Steam Locomotive for ‘N’ Gauge Modellers

Started by Train Waiting, December 08, 2023, 09:15:27 AM

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martyn

After a little more research, hopefully the tail load for the Gresley long travel valves.

Long travel valves had in fact been fitted to the K3 (the first 3-cylinder GNR Moguls) class, designed in 1917, ie before the A1s. At 'normal' speed for a mixed traffic class, this was not a problem, but extended use on passenger trains meant that at higher speeds, due to various factors, the middle cylinder valve gear overtravelled, causing some internal damage and resulted in the middle cylinder doing more than its fair share of work. This was mitigated by reducing maximum cut off to 65% from 75%. Without getting technical, this was only a partial solution.

However, it did mean that when the A1s were designed, it was a deliberate policy to reduce the valve travel to avoid this problem, and hence they entered service with the short travel valves. The trials proved that the service running of the long travel valves were worth doing, as previously recorded.

Ultimately, the K3s had their valve gear altered to give longer lap, and this was successful, resulting in economies of coal and water, and making them freer running.

Hope this is of interest.

Martyn



 

fisherman

I'm another one really  enjoying this series and  learning a lot !

TY
<o({{{<<

crewearpley40

Quote from: fisherman on January 30, 2025, 02:15:08 PMI'm another one really  enjoying this series and  learning a lot !

TY
and I'm enjoying the series too with martyn 's ( and others) input. Long may it continue!

Southerngooner

I've spent a week or so reading this series of posts from start to finish and only have one word for them - Spiffing!

Keep up the good work

Dave
Dave

Builder of "Brickmakers Lane" and member of "James Street" operating team.

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