4-12-2 double Walschaerts gear

[rockershovel]

I’ve been doing some background reading lately (oh all right, I ended up there having started some completely unrelated topic on Wikipedia) on the American three-cylinder types, and discovered that some were converted to two sets of external valvegear on one side, rather than the original Gresley conjugated set-up. 

 

Anyone?

[sncf231e]

The UP had 88 4-12-2 3-cylinder locomotives. Reduced wartime maintenance brought increased big-head heating and attempts were made to do away with the Gresley gear by adding a third set of Walschaert motion for the inside valve which was driven from a fly-crank on the right hand side. This was however only applied to seven of the 88 locomotives since the engines were transferred to another division were less speed and load was needed and the conversion was not necessary for all. If you really interested in UP's 4-12-2 Loco Profile 16 is a good read.

 

D&RGW railroad M75 Mountains also had 3-cylinders with 3 -sets of Walschaert; a model can be seen at 2:10 in this video I made:

 

 

Regards

Fred

 

[Adam88]

Here's another example.  This is the RHS of the Baldwin prototype high pressure three cylinder 4-10-2 locomotive no. 60000 of 1926 now on display at the Franklin Institute in Philadelphia.  There are many unusual features on this locomotive but the one which struck me immediately was its use of a water tube firebox - reminiscent of Gresley's Hush Hush in some ways, although the latter's whole boiler was water tube.  I saw 60000 in 2006 but it was not well displayed or interpreted, you could however 'ride the footplate' as it was periodically dragged a few yards up and down a short length of track - remember City of Birmingham?  There were a couple of other early 19C locomotives there too, both interesting survivors.

 

Edited April 22, 2022 by Adam88
restored lost photo