in the first picture below, presumably taken soon after the engine was built, there is a pipe running between the firebox and the rear cylinders. In 2nd picture, that same pipe is rerouted up near the top of the firebox and then back down, and is this way is most pictures of the engine taken in the field.
what is this pipe, high/low pressure steam? and why is it rerouted?
Greg,
The 1st picture(builders photo) shows a ‘compound’ engine. The high pressure steam is routed from the super heater to the rear high pressure cylinders(small). The exhausted steam is then routed to the large front cylinders before being exhausted.
The ‘in service’ photo appears to be of an engine that has been converted to ‘simple’ operation. Note that both cylinders are about the same size and are both being fed high pressure steam. The reason that the new connection is on top of the smoke box may be that a new super heater or a feed water heater has been installed so that the boiler can keep up with the increased demand for high pressure steam.
Jim
I think Jim’s got it right. The Reading had 31 2-8-8-2’s used mainly for pusher service. Numbers 1811-1830 were built by Baldwin in 1918-1919 as compounds, subsequently rebuilt to 2-8-8-0 simples, with both front and rear cylinders the same size. In the second photo of 1817 it appears to still have the trailing truck under the cab.
On looking at the second photo again I wonder whether those front cylinders are not in factl the original large size, despite a loss of efficiency. These were slow-speed pushers and coal was cheap!
And then the RDG took some of the 2-8-8-2’s and rebuilt them into 2-10-2’s which were used with the kitbashed 4-8-4’s.
Look again. This time, check the height of the bottom of the front cylinder against the center of the pilot axle.
Also, from the Reading Company’s point of view, coal was not cheap. They had Save a Lump stencils all around the firing deck.
I won’t go into the weight distribution vs. piston thrust thing - except to mention that the N&W had to put fourteen tons of lead into the front frames of their Y6 locos when the ‘booster’ (extra steam when running compound) was installed. Even the prototype added weight to prevent driver slip.
Chuck (Modeling Central Japan in September, 1964)
Between 1927-1930 30 RDG 2-8-8-2’s were rebuilt as 2-10-2’s and between 1930 and 1934 the remaining compound engines were rebuilt as simple engines all with the same size cylinders.
The Reading Steam Roster ( http://www.northeast.railfan.net/rdg_steam1.html ) has a photo from Joseph a. Smith’s collection, of 2-8-8-2 Number 1821.
The undated photo shows 1821 with rerouted steam lines to the two sets of cylinders, but with what appears to be the original jowly-looking low pressure cylinder set, certainly larger than the rear cylinder set.
Were these engines originally built with the capability to switch between simple and compound mode, still retained up to this time, before replacing the low pressure cylinders? Or did they operate this engine with high pressure steam to both cylinder sets?
The ‘re-built’ engine appears to have new ‘piston’ valve front cylinders. The original ‘delivery’ photo show slide valves - not compatible with superheated high pressure steam. The rebuilt engine appears to have direct high pressure steam from the same location as the rear cylinders - If it were to run ‘compound’, it would need to get the ‘used steam’ from the exhaust of the rear cylinders, and route that to the front pair(as in the delivery photo). The N&W Y Class were the only steamers I am aware of that has the capability to run ‘simple’ at start-up and switch to ‘compound’ after getting the train moving(at least in N/A). The boiler was not capable of supplying steam in simple operation for any length of time.
Jim
ALL Mallet compounds were designed to start in ‘simple’ configuration - it’s part of the original patent. (If they weren’t, the front engine would have been dead at start - no exhaust steam available.) The LP cylinders were fed boiler steam through a pressure reducing valve.
What made the later N&W Ys unique was their ability to:
To compensate, the front engine had to be loaded with 14 tons of lead to keep slippage under control.
If the cylinders of a simple semi-articulated are of different sizes, either the weight on axles or the admission steam pressure has to be reduced for the larger cylinders. Since pressure reducing valves are much simpler than playing with locomotive weight and balance, reducing pressure would seem to be the preferred method.
Chuck (Modeling Central Japan in September, 1964)
Looks to me like the front cylinder assy has piston valves in both photos. Roger Huber
Reading’s 2-8-8-2’s were built in 1917-1919, well into the superheater era and the declining use of compounding and of slide valves. Builder’s photos of 1805 taken in 1917, and of 1817 above, certainly show piston valves- no box-like slide valve on top of the cylinder.
It looks to me that the original front cylinder “castings” were re-used. Note that the dimensions are different between the front and rear cylinder casting even for the conversion.
Ed
According to the RDG specs, the cylinders were the same size for both engines, front and rear, Same diameter, same stroke. I don’t have access to the exact size right now, but they were the same.