Joined
·
494 Posts
The Biles Coleman 2-6-6-2 as proposed would have been a compound locomotive, hence the differently sized cylinders.
A compound locomotive has a bypass valve in the cab (sometimes called an "emergency valve" ) that allows the engineer to temporarily run the locomotive as a simple articulated locomotive. This feature was designed to provide a means of running the locomotive in the event of a failure, or in certain situations where more power was require to start a train moving, or on a heavy grade. The advantage was lost above just a few miles per hour.
When operating as a compound locomotive, the only exhaust to the blast pipe comes from the low pressure cylinders. As such, it would have the standard four beat pattern common to most rod type steam locomotives. In simple mode, you would hear the syncopated rhythim Bob refers to, as all four cylinders are then exhausting to the blast pipe.
Most locomotives designed to be simple articulated all the time had two smokestacks up front, and exhibited the syncopated chuffing all the time.
Those particularly interested in this topic might consider a good cup of coffee and this article: http://www.catskillarchive.com/rrextra/mallet.Html
There is also some other related information here: http://www.catskillarchive.com/rrextra/blwmal00.Html
Matthew (OV)
PS. I agree ... there IS a lot of stuff out there to sort through regarding the proposed Bachmann locomotive. I am aware that there are reports the locomotive will never actually be released. Note that its accompanying D&RGW caboose release has ALREADY been pushed back to "first quarter of '09", and that only selected folks (and no dealer I'm aware of) have the Davenport, which was supposed to have been released when "Now" was two months ago... which may be the source of some of those ideas. There are also rumors that it's been designed to make various common control and sound systems incompatible (I'm not sure where that rumor might have been formulated; perhaps someone on this board knows.) These two rumors have been discussed by Bachmann people on the Bachmann board itself, and they reassure us that they are both "ridiculous" ... so taking that at face value, if the locomotive IS actually released, and it IS NOT made in such a way that adding my choice of sound and control is impossible then I'm looking forward to installing a mechanical chuff timer on both sets of drivers, and making the locomotive selectable remotely between simple and compound, just as its larger cousin would have been. Otherwise I suppose, it may become the most perfect model yet: A theoretical proposed model locomotive that was never built of a theoretical proposed 1:1 locomotive that was never built.
A compound locomotive has a bypass valve in the cab (sometimes called an "emergency valve" ) that allows the engineer to temporarily run the locomotive as a simple articulated locomotive. This feature was designed to provide a means of running the locomotive in the event of a failure, or in certain situations where more power was require to start a train moving, or on a heavy grade. The advantage was lost above just a few miles per hour.
When operating as a compound locomotive, the only exhaust to the blast pipe comes from the low pressure cylinders. As such, it would have the standard four beat pattern common to most rod type steam locomotives. In simple mode, you would hear the syncopated rhythim Bob refers to, as all four cylinders are then exhausting to the blast pipe.
Most locomotives designed to be simple articulated all the time had two smokestacks up front, and exhibited the syncopated chuffing all the time.
Those particularly interested in this topic might consider a good cup of coffee and this article: http://www.catskillarchive.com/rrextra/mallet.Html
There is also some other related information here: http://www.catskillarchive.com/rrextra/blwmal00.Html
Matthew (OV)
PS. I agree ... there IS a lot of stuff out there to sort through regarding the proposed Bachmann locomotive. I am aware that there are reports the locomotive will never actually be released. Note that its accompanying D&RGW caboose release has ALREADY been pushed back to "first quarter of '09", and that only selected folks (and no dealer I'm aware of) have the Davenport, which was supposed to have been released when "Now" was two months ago... which may be the source of some of those ideas. There are also rumors that it's been designed to make various common control and sound systems incompatible (I'm not sure where that rumor might have been formulated; perhaps someone on this board knows.) These two rumors have been discussed by Bachmann people on the Bachmann board itself, and they reassure us that they are both "ridiculous" ... so taking that at face value, if the locomotive IS actually released, and it IS NOT made in such a way that adding my choice of sound and control is impossible then I'm looking forward to installing a mechanical chuff timer on both sets of drivers, and making the locomotive selectable remotely between simple and compound, just as its larger cousin would have been. Otherwise I suppose, it may become the most perfect model yet: A theoretical proposed model locomotive that was never built of a theoretical proposed 1:1 locomotive that was never built.
