71000

The issue with any twisting forces or slight non-alignment is that the piston rod gland will wear oval in the direction of the misalignment. The result is that the gland (and ultimately the piston heads and cylinder bores) starts to leak steam, which leads to higher than desirable water (and coal) consumption, but doesn't particularly present an increased risk of things breaking. As is always the case with steam locos, they can get pretty run down and nonetheless keep doing useful remunerative work, provided you are happy to put up with the clanks and increased water consumption and lack of visibility round the front. The trick is knowing for how long you can tolerate it, before the problem gets bad enough that the subsequent overhaul becomes much larger.

Tom

 

Get that...but there was no FEA in aircraft design in 1954.. people still flew....some didn't survive...

 

Where would be without the legendary clanks of the WD's up the Calder Valley hauling "coil" to our poor Lancastrians to feed their steam mill engines... magical.

 

The answer iirc is ‘yes’. The Advanced Steam Traction Trust looked at this as part of the design study for Clan Hengist, prompted by the uneven cylinder wear experienced on DoG where the inside cylinder had significant less wear than the outside cylinders (might have just been rings, I forget).
The analysis showed that the outer cylinder crosshead described a very flattened figure of eight with significant deflection at the front and rear of the stroke.
Based on this the Clan has adopted the rear cylinder cover slide bar support as well.
Edit : I’ve now had chance to go back through the ASTT / Clan websites and found the relevant item, see screenshot below.
https://advanced-steam.org/wp-content/uploads/2017/10/CLAN-General-Presentation-v3-for-ASTT-Bury.pdf

 

There are indeed many forces at play. The biggest ones are those reciprocating steam hammers which start knocking a locomotive to bits from day one.

 

Thanks for that I'll have to run my eye over it

 

Sorry my thermal expansion concerns were in the horizontal plain perpendicular to the frames and in hind sight would affect all similar locomotives regardless of the slide bar type.
The slidebar arrangement is to my mind a bit like the frame spacing , another inapropriate borrowing - no bother on a Bulleid (24 inch stroke) not so clever with a 28 inch stroke.