Talk:GWR 5600 Class

message: I've found a design modification:
*
It seems that the locos as built had the normal crank arrangement for inside-cylinder locos - that is, the inside cranks for the connecting rods were diametrically opposite the outside crankpins for the coupling rods. This helps with balancing the rotating masses, but As so often happened with high-powered inside-cylinder engines ... the driving axleboxes wore very rapidly. There were two reasons why this was inevitable. The bearings of the outside-cylinder GWR engines were 10in long. On the 56xx class there was only room for 7in between the wheel and the crank web. Not only were the bearings little more than half the area, but with inside and outside cranks set at 180° the fore-and-aft thrust on the axleboxes is greatly increased. Connecting and coupling rods are pulling in opposite directions, and all the force of this reversal has to be taken by the driving axleboxes, which are well suited to cope with vertical loads, but very ill-adapted to near-horizontal thrusts.In an attempt to reduce this heavy wear, which greatly reduced the mileage run between shoppings and so was very costly, a number of the class were after a time altered to have the Stroudley arrangement of cranks. In this the inside and outside cranks are in phase instead of opposite each other. It reduces the thrust by about half and so lessens wear, but since both cranks, big-end and coupling rod are on the same side, instead of largely balancing out, the balance weights have to be so large that they are difficult to accommodate in small wheels. They add very considerably to an already heavy axle load, and this is made more serious by the fact that this extra weight is unsprung. (the boldface is mine) I am of the opinion that this modification could easily account for a 15 cwt increase in weight. Gibson implies that the modification was post-construction, carried out as engines passed through shops for overhaul. Indeed, if this was a serious problem, there would almost certainly be a standing instruction to modify any engine showing such trouble. But it's difficult to see the problem as confining itself to nos. 6600-99, with 5600-99 being unaffected. It's possible, however, that 6600 onwards were built with the Stroudley crank arrangement, the earlier engines being so altered as necessary; this would account for certain publications showing the two number series with differing weights - they would be "as built" weights, not "as presently running".
Further information might be found in:
*
*
but I don't have those. --Redrose64 (talk) 12:06, 11 August 2010 (UTC)
replies: text: Altered crank arrangement described in  and the altered balancing (although not the full reason) in . Neither give any altered weights; Haresnape quoting 68t 12c as built. --Redrose64 (talk) 11:26, 19 August 2010 (UTC)
thread_title: Weights: crank arrangements

message: There is a rather partisan description of how this design came about, and particularly of early problems with hot boxes resulting from Swindon tolerances being too tight for twisty South Wales coalfield lines, under the heading "Collett's Folly" in:
http://www.nlsme.co.uk/Newsletters/NLSME-March-2003.pdf
http://www.nlsme.co.uk/Newsletters/NLSME-April-2003.pdf
http://www.nlsme.co.uk/Newsletters/NLSME-May-2003.pdf
Bill F (talk) 12:14, 5 March 2008 (UTC)
thread_title:  Teething Troubles