Cast frames vs built-up?

[Pneudyne]

 

I imagine that if one surveyed all American steam locomotives built since 1930 or thereabouts, then over time there would be a steadily increasing incidence of cast beds, with such being the clear majority choice, particularly for heavier locomotives, by around 1940.

 

In particular, I’d expect that very few 4-8-4s and 2-10-4s were built without cast beds after 1930.

 

Some notable exceptions amongst heavier locomotives of the period are the early Alco Challengers (UP, SP and probably WP) and the Baldwin 2-6-6-4s built for P&WV and SAL, all with built-up frames.  In respect of the WP 2-8-8-2s I don’t know, but would guess built-up frames for the 1931 batch and just possibly cast beds for the 1938 batch.

 

In the medium-weight range, the early NKP 2-8-4s had built-up frames.  An interesting case in the same timeframe was the B&M design pair, the 4-6-2s, with built-up frames, and the 4-8-2s with cast beds.  Evidently the putative extra cost of the cast beds was seen as justified for the latter, but not the former.

 

 

Cheers,

[Pneudyne]

I should not necessarily expect cast frames (beds) on mine run locomotives as such.  What was more surprising was the use of a single-plane articulation in combination with built-up frames.  That form does place a lot of longitudinal stress on the front unit frame, to the point where the built-up type might be marginal.  The Alco damping arrangement as used on the early UP (and NP, I think) Challengers was something of a halfway house, and that did overstress the built-up frames.

 

On frames generally, I suppose that a very coarse classification would have three levels, namely plate, bar and cast bed.  Plate frames were the UK norm for domestic production until the end, and used on exports where customers did not specify something better.  Bar frames, generally much better, became the North American norm early on, and were used on some UK and other exports, particularly where the customers so specified.  In the basic bar frame, the siderails were usually flame cut from bar, but later North American practice favoured cast side rails.  At the top level in North American practice were cast beds.  It would appear that the cost and in some cases, weight penalties deterred their universal use.

 

Cast beds had some application outside of North America.  South African Railways (SAR) was an enthusiastic user of GSC cast beds on post-WWII steam locomotives supplied by UK and German builders, including on its later Garratts.  There was some use in Australia, as well.  Apparently, Beyer Peacock was against the idea, regarding it as an unnecessary and costly complication.  Thus, for example the Rhodesian 20 and East African 59 class Garratts were built with bar frames, which were troublesome in both cases.  The 59 was also very hard on the track, and had to be speed restricted.

 

 

Cheers,

[Backshop]

Weren't they just copies of earlier C&O 2-6-6-2's built in the Teens?  If so, maybe they didn't want to pay for redesigning them?

[BaltACD]

timz

In the other thread, Pneudyne said

"A perhaps surprising application was on the final Baldwin 2-6-6-2 batch for the C&O.  Way back when (late 1980s, I think), I was looking at the example in the Baltimore museum, and did a double take when I saw the articulation joint.  And this was with built-up, not cast frames."

So those last 2-6+6-2s did not have cast frames. Us fans tend to think of cast frames as mandatory for any self-respecting halfway-big engine. So why didn't C&O want them on these last engines? Two possibilities come to mind:

Cast frames cost more?

Cast frames are heavier?

For all I know, both could be true, and C&O figured engines that were going to spend their lives rooting around in the woods for a few hours a day wouldn't need inordinate wiring-together. And maybe they figured the engines' lives would be too short to justify the extra initial cost?

The C&O 2-6-6-2's were mine run engines, not really Main Line engines.  They were purchased to service the many coal mine operations on the C&O.  Take empties to the mine to be spotted and loaded and the pull the loads back to the marshalling yard for the area and then switch the coal into Main Line trains to be hauled to either the Export Coal dock at Newport News or to the Lake Dock at Presque Isle in Toledo.

Western Maryland Senic 1309 is the operating example of the C&O 2-6-6-2.

[Overmod]

Keep in mind that 'cast frame' is not the same thing as 'cast engine bed'.  The former refers to one-piece longitudinal 'bar frame' section, with no joints and possibly with integral pedestals, but it still has bolted crossmembers and other parts of the frame.  One of the Canadian large-locomotive production videos (either the CP 4-8-4s or the TH&B 2-8-4s) shows the cast frame fabrication graphically.

I don't have time to find it now, but I'm sure there are lavish pictures of 1309's frame during its restoration to operation.

 

[timz]

In the other thread, Pneudyne said

"A perhaps surprising application was on the final Baldwin 2-6-6-2 batch for the C&O.  Way back when (late 1980s, I think), I was looking at the example in the Baltimore museum, and did a double take when I saw the articulation joint.  And this was with built-up, not cast frames."

So those last 2-6+6-2s did not have cast frames. Us fans tend to think of cast frames as mandatory for any self-respecting halfway-big engine. So why didn't C&O want them on these last engines? Two possibilities come to mind:

Cast frames cost more?

Cast frames are heavier?

For all I know, both could be true, and C&O figured engines that were going to spend their lives rooting around in the woods for a few hours a day wouldn't need inordinate wiring-together. And maybe they figured the engines' lives would be too short to justify the extra initial cost?