Hot Water posted this helpful explanation on another thread...
OK, the Wilson Blowdown Separator System, has a "turbine housing" mounted on the top, just forward of the cab. There are two remote valves on either side of the firebox, mounted down low (mud ring area). Instead of those remote operated blown down valves simply shooting the boiler water horizontally out the side, the water is piped upwards towards, and into the base of that large "turbine housing". When either the Engineer or Fireman opens his respective "mud ring blown down valve", the VERY hot and dirty boiler water enters the inside of that "turbine housing", and at that point the hot boiler water is exposed to atmospheric pressure, and rapidly turns to steam and exits vertically out of the center of the round "turbine housing", while the remaining dirty water is "spun" to the outer portion of the inside of the "turbine housing". The remaining dirty liquid is subsequently piped downward to an exit chute, located directly under the cab on the Engineer's side.
When using the Wilson system, the Engineer can simply look downward and watch the condition of the sludge that is exiting the discharge chute, down onto the ballast. If the discharge gradually turns to cleaner looking water, the "sludge removal" process can then be ended. The Engineer will also indicate to his Fireman to continue to operate his blowdown valve until both sides of the firebox mud ring has been "cleaned out".
Depending on the quality of the water used in whatever part of the country that water has been taken on (filling the tender), the blowdown or "sludge remover" was used VERY regularly.
In conclusion, the Wilson Blowdown System would have a visible steam exhaust at two locations: 1) from the round "turbine housing" on the top, forward of the cab, and 2) fro the sludge discharge chute located below the cab on the Engineer's side. Obviously this arrangement would be pretty difficult to accomplish on a model steam locomotive.
I have the JLC Big Boy at home and I am pretty sure that the turbine housing that HW referenced is molded into the boiler just in front of the cab. I am also pretty sure there is a round "opening" cast in the center of the housing.
I have a Pentrex Big Boy DVD and in most of those videos steam is streaming up from that location. I thought that the dynamo was under that shroud. It seems like it may have been coming from the Wilson Blowdown Separator Turbine Housing. I will post pics later for reference, but I am curious if this detail is in the casting of the JLC/VL Big Boy. Then where is the dynamo on the Big Boy? I know it is not an exposed appliance like on the Challenger. In the Pentrex videos multiple streams of steam are shooting out of the top of the boiler.
Visually, I would have preferred the smoke come out of the area just in front of the cab on the VL Big Boy as opposed to the sides. Having seen the inside of the VL Big Boy, it appears to me a single tube for the blow down could have been run up to the top of the boiler shell rather than running two tubes along the sides. Maybe the motor did not allow adequate clearance for that. I have only seen the inside of the VL Big Boy, but it was not mine so I did not mess with it.
HW is, as Marty stated, a wealth of knowledge. Having said that, pointing out "perceived flaws" of a new purchase for which many are so excited in a thread simply asking who bought one did come across like rain on their parade. Hopefully HW will chime in on this thread.
