Re: [z_scale] Mallets - ome more time attn Bahl - slider.jpg
- Ole Rosted schrieb:
> On Sat, 2 Dec 2000 15:06:24 +0100, you wrote:Hi Ole,
> Hi Michael,
> The attached pic of a steam cylinder is NOT a compound then? Right?
> The small "cylinder" is there to only to lead the steam to the right
> side of the piston? In a compound there would be an extra cylinder for
> the first expansion?
> regards Ole
the four pictures show the working principle of a normal cylinder,whereas the
first two pictures depict a slide valve equipped cylinder,and the other two show
the same arrangement with a piston valve.
The steam from the boiler (yellow) is distributed by the valve gear (those funny
miraculous smaller rods in the above region of most steam locos).The valve gear
itself is not shown in the pictures,this might have made it a bit more
In pic 1,the steam comes from left and enters the valve chest(the pressure of
the steam is keeping the slide valve tight to the cylinder,by the way).The
opening,which is not covered by the slide valve is used for the steam to enter
the cylinder and to move the piston in the depicted direction.
Picture 2 shows the way to the steam "out" (now brown).The slide valve now has
been moved in a position,where it lets new steam enter from the other side
(white),and the decompressed (brown) steam leaves the cylinder by an opening in
the middle of the valve chest,which,sadly,is not shown,which might lead to
confusion.It is right in the brown space,which is covered by the slide valve in
any position.For this is the task of it - build a kind of "escape tunnel" for
the steam after work...;-) )
Slide valves were later replaced by piston valves,as latter proved to be more
steam-tight and less maintenance-prone.
You can easily distinguish a real steam loco,if it has slide - valves or piston
- valves,if you look at the cylinders.If the upper parts are rounded,as with the
Märklin US-Mikados or Pacifics,they are piston - valves.If the upper parts look
box-like,(ooops,no Märklin-example found),it is a loco with slide-valves,and
most certainly(as these two things often go together) with unsuperheated
Now as to pictures 3 and 4:It is the same principle as above,just with a piston
A clearly visible difference is the way for the steam to and from the valve box.
In a compound locomotive,the principle of the cylinders is the same,and
compound designs exist with slide or with piston valves.But the steam does not
escape from the Hp cylinder to the smokebox,but comes into a combiner;a chamber
to house the steam until it has access to the low-pressure cylinder.Of
course,this access is being distributed by a valve..
- Dieter_Mac_Nolte@... wrote:
>Yes this is an actual loco. Can be seen at
> 'Amtrak Acela', is this a real new development? My information on Amerikan locos
> ends with 1998, sorry. So, any info?