Monobloc Cylinders

[ahardy]

Evening all,

Can anyone tell me please, what was the first locomotive/class on the LNER to carry monobloc 3 cylinder?

Many thanks

Andy

[Chris Grouse]

Think it was the V2, the other 3 cylinder locos used separate castings for each cylinder. Shame Green Arrow didn't receive the modification in BR days, it might still be running....

[60800]

One of the main factors in the preservation of 60800 was her monoblock casting. So if BR had changed it for three separate cylinders, we may not have her at all

[61962]

The V1s were the first pure LNER locos to have monoblock cylinders followed by the P2s, both classes being earlier than the V2, which were followed finally by the V4s. The LNER already had large numbers of three cylinder locos with monoblocks inherited from the NER. Class Z (C7) 4-4-2, S3 (B16) 4-6-0, T3 (Q7) 0-8-0, Pacific (A2)4-6-2, and H1 4-4-4T rebuilt to A8 4-6-2T , some of which were built post grouping. Technically the first LNER monoblock locomotive was the NER Class X (T1) 4-8-0T which was the earliest of the NER monoblocks

Eddie.

[richard]

I wonder if the P2 people are ordering a monobloc, or splitting it into three to ease maintenance?

[2392]

I wonder if the P2 people are ordering a monobloc, or splitting it into three to ease maintenance?

Be interesting to see if they do go for the monbloc, as it would provide information as to any problems from a casting/production point of view, for the possiblity of casting a new 'bloc for 4771 Green Arrow.

[1H was 2E]

I would be interested in the reasons for casting all three cylinders in one piece. I can see a number of obvious disadvantages in both production (e.g. very large casting requiring very complicated pattern; likelihood of blow holes with such a large amount of metal being poured; achieving parallel when machining bores) and in service (e.g. one defective cylinder requires replacement of whole casting) but I'm struggling to think of a single advantage.

[61962]

I would guess the main driver was weight. By removing the bolting flanges and designing the single casting to distribute the loads from the three cylinders then there must have been a substantial weight reduction over three separate castings, Another advantage was to cast in the steam passages for the outside cylinders. With individual cylinders an internal steam passage had to cross the joint and it would have been difficult to make steam tight so it was necessary to use external steam pipes with the additional problems of movement between the boiler and the cylinders. The monoblock was also a stiffer structure with reduced likely hood of the frame bolts working loose or breaking.

In terms of manufacture, I don't thick the foundries would have any greater problems with castings of this size, than the individual cylinders. Just another day at the foundry. There was actually less machining required as the bolting faces were smaller and only needed on one face each side where the castings were attached to the frames. The separate cylinders were bolted together before the cylinders were bored. They had special boring machines that had three boring heads set to the require inclinations for the cylinders, and the valve bores would also be done at the same time to ensure correct alignment.

I don't suppose the designers ever really considered the costs of replacing a monoblock at the time. Bear in mind that labour was cheap, and the cast iron was recycleable in the company's own foundry. Locos went in for an overhaul and came out with whatever refurbished or new parts that were needed. The important thing was meeting the civil engineer's axle load limits. Three cylinders reduced hammer blow, and what would appear to be minor frame cut outs were made to reduce weight. Nickel chrome steel in side and connecting rods to save a few pounds weight. Every little helped.

By the time the V2s started to have problems with cracked castings, there had been a lot of changes in the way the railway was run, and accounting was one of those changes. The other was improvements in the load capacity of the permanent way, so the substitution of separate cylinders was perhaps an economy measure. Interestingly I don't think the V1/V3 tanks were troubled so there might also have been a design issue on the V2s.

Eddie