For the high pressure cylinder receiving pressure from both ends; did they come up with a solution to dissipate pressure from the unwanted side? Or was it not a big enough problem in the grand scheme of things to worry about? Secondly, even if they were hitting their limits, were there cross compounds being purchased for their ease maintenance over any gains seen on the systems you described in this video?
Ta for your comment. To answer your second question first, roads bought what worked for them, but with first-tier tonnage the use of cross-compounds pretty much ended by 1900, when the tonnage-hauling ability of Tandems could keep up with tonnage demands. Having said that, Soo Line was buying them up to at least 1907. But the AT & SF tandems, the biggest locomotives of their day produced prodigious rated tractive effort compared with the cross-compounds - as expected by being four-cylinder instead of two-cylinder. And they were a bit quicker across the road - albeit peanuts to the roads speeds expected in following decades. The water and fuel savings, the greater efficiency of a bigger locomotive, and the greater ability to haul (i,e, less need for double heading and double crewing) - and thus they were prepared to carry the complexity. Still, superheating eventually won the day. To answer your first question, no. Dissipating the pressure acting against the non-working face of the H.P. piston would also dissipate the pressure acting against the working face of the L.P. piston. This applies as much at start-up as it does in normal operation - as there's open communication between the faces through the receiver. This is the fundamental reason why steam in a compound is not used 'twice,' but used more like 1.4 times.
Vauclain and Tandem compounds suffered from cranked and narrow inside steam passages between the cylinders, so there was no "internal" streamlining. So their efficiency was well beyond a well designed cross or balanced compound and maybe only slightly ahead of a saturated steam simple locomotive. With the advent of the superheater there was no advantange at all in comparison to a superheated simple locomotive. There was nobody in the USA, who wanted to try superheated cross or balanced compounds. Everybody was happy to get rid of complication. However in the end N&W proved the effectiveness of the superheating and compounding combination.
I think it had something to do with hauling more, faster - as well as complication. The notion of building an extremly efficient super-heated compound would have, in North Ameria been a small locomotive for secondary duty - and with the plethora of 2-8-0 locomotives perfectly servicable and knocked-off front-line road service would have meant that no market could have been found. In the New Zealand experience it was the onset of WWII that coincided with our two classes of de Glehn's being rebuilt as (mostly) two-cylinder simple.
I'd only known of compounds for articulated locomotives prior to this, I didn't realize it had been tried so early and with non-articulated examples. It seems like a lot of the headache of a compound valve arrangement goes away with an articulated unit since it's basically two engines with a common boiler anyway.
I'm currently editing the next in the series, with thye final iteration of single engine compounding in North America. Interestingly, such compounding contined onwards and upwards in France. Whereas the Americans adopted compound articulateds. Interesting stuff.
@@theimaginationstation1899 If you ever get a chance. Visit the Museum of Transportation in St. Louis MO, (USA) they have the last surviving Y6a (N&W 2156) which was a true Mallet (compound) and I belive it's the largest and most powerful surviving compound locomotive. They also have 4006, a UP Bigboy (considered a simple Mallet, so not a compound), they are stored very close together. They have a decent sized collection so you can easily spend an entire day or two looking over everything. And that's without including what isn't open to the general population (you have become a volunteer).
In Europe 2 cyl cross compounds in passenger service were quite successful. The most well known example was the prussian S3 which was THE standard passenger locomotive at its time. en.wikipedia.org/wiki/Prussian_S_3
I'm interested where you found the formulas for stated tractive force. I've never much thought about tandem compounds, but I have dabbled in 4 cylinder compound steam locos, and I'd found a far more complex formula. I tested the results of both and the formula you had found gives a different result to the one I tend to use (yours is a hell of a lot nicer looking!) I had used (4*low pressure bore^6 * stroke * boiler pressure)/(10*driver diameter*high pressure bore^2*low pressure bore^2 + 5*driver diameter*high pressure bore^4 * 5*driver diameter*low pressure bore^4)
Hi radio, do you mean bore squared or bore to the six to start with? Anyway... The two-cylinder simple locomotive formula I use is from the Locomotive Dictionary (1916) - a standard North American trade reference. From memory, it didn't state a formula for compounds. My compound formula comes from Swengal (1967 - IIRC) "Evolution of the American Steam Locomotive." Swengal cautions that roads and manufacturers were free to go their own way with calculating Rated TE. So it may be that you're looking at a specific manufacturer's equation. Since it's convoluted, I'd say Baldwin. Swengal goes no to say to exercise caution when using published Rated TE to compare locomotives - and to put the geometry into a standard equation in case the different roads used different fomula. Interestingly (or perhaps not), in NZ we used 80% as the Mean Effective Pressure modifier instead of 85% - but with our four-cylinder comdounds (Vauclain and de Glehn) we used the 120% modifer. I'm not sure of the reason for the deviation to 80% while also adopting the 120% without deviation.
To answer your question, it is meant to be raised to the sixth power. Secondly, it's not actually based off of Baldwin research, it's based off of Porta's research in steam technology, a lot of it having come from the mathematics he used to define his locomotive "La Argentina" as it's most commonly known. I've tested it against the stated tractive effort of various 4 cylinder compound locomotives and it's seemed to me to be an incredibly reliable and close measurement. The inly thing I take from baldwin is a recommendation that the ratio of volumes should actually be near 3 to one, so when I do my own modelling work I try to have the low pressure bore be the square root of 3 times larger than that of its respective high pressure cylinder. I the history of tractive effort calculations is rather incredible as a whole, maybe I need to go on a hunt for more railroading related engineering books (as many as my wallet allows, haha)
@@radioisotopics The 2nd hand locomotive engineering book market in NZ is pretty slim, and postage from overseas is prohibative - so it might be a while before I get a copy of Porta. But if you want to start from the beginning of locomotive mathematics de Pambour's 1836 work is on Hathi Trust - it's several hundred pages of pre-Victorian description - but his development of the TE equation is interesting. Ralph Johnston's "Steam Locomotive" is also on Hathi - and it is very interesting.
For the high pressure cylinder receiving pressure from both ends; did they come up with a solution to dissipate pressure from the unwanted side? Or was it not a big enough problem in the grand scheme of things to worry about?
Secondly, even if they were hitting their limits, were there cross compounds being purchased for their ease maintenance over any gains seen on the systems you described in this video?
Ta for your comment.
To answer your second question first, roads bought what worked for them, but with first-tier tonnage the use of cross-compounds pretty much ended by 1900, when the tonnage-hauling ability of Tandems could keep up with tonnage demands. Having said that, Soo Line was buying them up to at least 1907. But the AT & SF tandems, the biggest locomotives of their day produced prodigious rated tractive effort compared with the cross-compounds - as expected by being four-cylinder instead of two-cylinder. And they were a bit quicker across the road - albeit peanuts to the roads speeds expected in following decades. The water and fuel savings, the greater efficiency of a bigger locomotive, and the greater ability to haul (i,e, less need for double heading and double crewing) - and thus they were prepared to carry the complexity. Still, superheating eventually won the day.
To answer your first question, no. Dissipating the pressure acting against the non-working face of the H.P. piston would also dissipate the pressure acting against the working face of the L.P. piston. This applies as much at start-up as it does in normal operation - as there's open communication between the faces through the receiver. This is the fundamental reason why steam in a compound is not used 'twice,' but used more like 1.4 times.
@@theimaginationstation1899 Very nice and clear explanation, Thanks
Vauclain and Tandem compounds suffered from cranked and narrow inside steam passages between the cylinders, so there was no "internal" streamlining. So their efficiency was well beyond a well designed cross or balanced compound and maybe only slightly ahead of a saturated steam simple locomotive. With the advent of the superheater there was no advantange at all in comparison to a superheated simple locomotive.
There was nobody in the USA, who wanted to try superheated cross or balanced compounds. Everybody was happy to get rid of complication.
However in the end N&W proved the effectiveness of the superheating and compounding combination.
I think it had something to do with hauling more, faster - as well as complication.
The notion of building an extremly efficient super-heated compound would have, in North Ameria been a small locomotive for secondary duty - and with the plethora of 2-8-0 locomotives perfectly servicable and knocked-off front-line road service would have meant that no market could have been found.
In the New Zealand experience it was the onset of WWII that coincided with our two classes of de Glehn's being rebuilt as (mostly) two-cylinder simple.
I'd only known of compounds for articulated locomotives prior to this, I didn't realize it had been tried so early and with non-articulated examples. It seems like a lot of the headache of a compound valve arrangement goes away with an articulated unit since it's basically two engines with a common boiler anyway.
I'm currently editing the next in the series, with thye final iteration of single engine compounding in North America. Interestingly, such compounding contined onwards and upwards in France. Whereas the Americans adopted compound articulateds.
Interesting stuff.
@@theimaginationstation1899 If you ever get a chance. Visit the Museum of Transportation in St. Louis MO, (USA) they have the last surviving Y6a (N&W 2156) which was a true Mallet (compound) and I belive it's the largest and most powerful surviving compound locomotive. They also have 4006, a UP Bigboy (considered a simple Mallet, so not a compound), they are stored very close together.
They have a decent sized collection so you can easily spend an entire day or two looking over everything. And that's without including what isn't open to the general population (you have become a volunteer).
In Europe 2 cyl cross compounds in passenger service were quite successful. The most well known example was the prussian S3 which was THE standard passenger locomotive at its time.
en.wikipedia.org/wiki/Prussian_S_3
Ta.
Interesting locomotive.
I'm interested where you found the formulas for stated tractive force. I've never much thought about tandem compounds, but I have dabbled in 4 cylinder compound steam locos, and I'd found a far more complex formula. I tested the results of both and the formula you had found gives a different result to the one I tend to use (yours is a hell of a lot nicer looking!)
I had used (4*low pressure bore^6 * stroke * boiler pressure)/(10*driver diameter*high pressure bore^2*low pressure bore^2 + 5*driver diameter*high pressure bore^4 * 5*driver diameter*low pressure bore^4)
Hi radio, do you mean bore squared or bore to the six to start with?
Anyway...
The two-cylinder simple locomotive formula I use is from the Locomotive Dictionary (1916) - a standard North American trade reference. From memory, it didn't state a formula for compounds.
My compound formula comes from Swengal (1967 - IIRC) "Evolution of the American Steam Locomotive." Swengal cautions that roads and manufacturers were free to go their own way with calculating Rated TE. So it may be that you're looking at a specific manufacturer's equation. Since it's convoluted, I'd say Baldwin. Swengal goes no to say to exercise caution when using published Rated TE to compare locomotives - and to put the geometry into a standard equation in case the different roads used different fomula.
Interestingly (or perhaps not), in NZ we used 80% as the Mean Effective Pressure modifier instead of 85% - but with our four-cylinder comdounds (Vauclain and de Glehn) we used the 120% modifer. I'm not sure of the reason for the deviation to 80% while also adopting the 120% without deviation.
To answer your question, it is meant to be raised to the sixth power.
Secondly, it's not actually based off of Baldwin research, it's based off of Porta's research in steam technology, a lot of it having come from the mathematics he used to define his locomotive "La Argentina" as it's most commonly known. I've tested it against the stated tractive effort of various 4 cylinder compound locomotives and it's seemed to me to be an incredibly reliable and close measurement. The inly thing I take from baldwin is a recommendation that the ratio of volumes should actually be near 3 to one, so when I do my own modelling work I try to have the low pressure bore be the square root of 3 times larger than that of its respective high pressure cylinder.
I the history of tractive effort calculations is rather incredible as a whole, maybe I need to go on a hunt for more railroading related engineering books (as many as my wallet allows, haha)
@@radioisotopics The 2nd hand locomotive engineering book market in NZ is pretty slim, and postage from overseas is prohibative - so it might be a while before I get a copy of Porta. But if you want to start from the beginning of locomotive mathematics de Pambour's 1836 work is on Hathi Trust - it's several hundred pages of pre-Victorian description - but his development of the TE equation is interesting. Ralph Johnston's "Steam Locomotive" is also on Hathi - and it is very interesting.