Tony K
Elder Statesman
Posts: 1,573
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Post by Tony K on May 20, 2008 16:28:07 GMT
Mr. Alan, I know he is experienced, what I meant was, he did not tell us what his experiences were with superheaters. Something like "when I fitted a superheater, my loco performed markedly better than before and disappeared over the horizon" would have been a useful addition to the argument. ;D
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Post by alanstepney on May 20, 2008 18:50:21 GMT
Ahhh, I see what you mean.
I'll stick to Jim Ewins views as he did so much both practical and theoretical on loco efficiency.
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Post by baggo on May 20, 2008 19:07:34 GMT
The gist of Doug's letter was that he originally ran his Y4 with the standard type 'flue only' superheaters with brass return bends which proved to be satisfactory. The loco was used continuously as a 'works' engine during the construction of Doug's own railway. Eventually the superheaters failed and due to lack of time the superheaters were bypassed and the cylinders connected directly to the regulator. All the drivers noticed a marked increase in coal and water consumption.
Eventually the superheaters were replaced with one piece elements bent from 5/32" dia. stainless tube which extended to the back of the firebox. The elements are 'double' i.e. they leave the wet header, go to the back of the firebox, return to the tubeplate and are then bent back again to the firebox and return again before connecting to the dry header, similar to full size practice.The first steaming of the loco after fitting these new elements showed a significant decrease in the coal and water consumption compared to the original ones. He found that, whereas before he could only manage 15 to 20 minutes on one fill of water in the tanks, he was now getting 35 to 40 minutes per fill.
It is also interesting to note that he did try some coaxial (tube in tube) type a la Don Young and found them to be a "real disappointment" and " were little better than nothing"!
The letter also contains a couple of photos of the superheaters and headers for the 2-6-4T and they are a work of art!
John
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Post by havoc on May 20, 2008 19:43:23 GMT
Another problem when evaluating superheaters is that the performance of the superheater can be masked by inefficiency of other pieces of the engine. IF you have such a low efficiency to start with then it won't make much difference. While if the rest of the engine has already a decent efficiency, the additional gain might be more noticable.
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