Steam Engine Valve Gear driven by Steam Pressure?
 

I bought an old model steam engine at an estate sale today, and I am
puzzled by the valve gear. There is no mechanical connection between
the crankshaft and the valve!

The steam chest has a shaft protruding from the fore and aft - these
will slide in and out. Haven't gotten it to run yet - I would like to
try to find out more about it before dis-assembling.

Can anyone fill me in on this beast?

TIA,
Wally

pictures?

Rich

http://www.wallyblackburn.com/engine.html

In article s.com,
Jon Elson wrote:
wrote:
I bought an old model steam engine at an estate sale today, and I am
puzzled by the valve gear. There is no mechanical connection between
the crankshaft and the valve!

The steam chest has a shaft protruding from the fore and aft - these
will slide in and out. Haven't gotten it to run yet - I would like to
try to find out more about it before dis-assembling.
I'm no expert on steam, but I get the strongest feeling that there is
SUPPOSED to be a link to that shaft on the steam chest. Is there
anyplace on the flywheel or the crosshead that the valve could be linked
to? Is there anyplace on the mounting board where something else once
went, like the reversing gear?

I have to agree. Your angles for your photos make it more
difficult to determine whether there is an eccentric on the flywheel
shaft -- perhaps between the flywheel and the crankpin.

It *looks* as though the shaft in the steam chest needs to move
the opposite direction of the piston in the main cylinder to switch
steam to the proper place. But what appears to be missing is anything to
accomplish this.

You could experiment with powering it from compressed air as
being a little less likely to cause serious problems than steam would
be. I'll bet that as it sits, it will rotate to TDC or BDC and stay
there, unless you flip the valve in the steam chest at just the right
time.

It just might be that there is some way that the main piston
valves steam to a smaller piston in the steam chest to shift the valve.

The best thing would be to find what model this was -- perhaps
find it in an *old* issue of Model Engineer (in the UK), to find out
what it was supposed to look like when complete.

But it *might* have been a patent model, which means that
finding the right patent to examine would be the only real solution.

Good Luck,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"DoN. Nichols" wrote: (clip) But it *might* have been a patent model, which
means that finding the right patent to examine would be the only real
solution.
^^^^^^^^^^^^^^^^^
This engine may be a hand-built that was never finished. You may have to
invent the missing linkage. I would look at other engines to see how it is
usually done.

Isn't there a steam newsgroup?

wrote:
http://www.wallyblackburn.com/engine.html

Is the shaft that appears to be attached to the valve spring-loaded? Is
it a single shaft or two that stick out opposite each other? I assume
there's no internal linkage or you'd have turned the flywheel and seen
movement at the valve chest..

I wonder about the fact that steam can't be gotten to both ends of the
cylinder (assuming double-double acting) I see what looks like a tube
going to the head opposite the shaft, but it's quite small to be feeding
steam to that end of the cylinder. Is that a tube connected to the
center of the head and the flange? If so, I could see that having
something to do with working the valve.

I can imagine a couple of methods of valving an engine like this with no
linkage, but they wouldn't be very ideal..

As Jon says, it could be missing valve gear, but I just don't see any
room on the crank for it, unless the counterweight worked as a cam, but
I just don't see that happening..

Regardless, you've got a nice little engine and I'll bet someone here is
going to know what the score is.

John

This link shows how the linkage in a locomotive works.
At the bottom of the page are links to animations.
http://home.new.rr.com/trumpetb/loco/wdiagram.html

Art

"Leo Lichtman" wrote in
message ...

I would look at other engines to see how it is
usually done.

Here's a site that shows a number of stem engines in animation. This will
give you a few ideas
http://www.keveney.com/Engines.html

"Wood Butcher" wrote in message
...
This link shows how the linkage in a locomotive works.
At the bottom of the page are links to animations.
http://home.new.rr.com/trumpetb/loco/wdiagram.html

Art

"Leo Lichtman" wrote in
message ...

I would look at other engines to see how it is
usually done.

You can do a valve gear system by having the piston move the valve gear back
and forth. This will make an engine which is rather wasteful of steam but
it will work.
The piston approaches the end of it's stroke and hits a pin that moves the
valve from the position where the steam is entering one side of the cylinder
to the other side of the cylinder. Inertia and the steam pressure on the
bottom side of the piston allows the piston to top out on the stroke and
start back with the pressure now on the topside of the piston while the
bottom side of the piston is vented to the air.
That system doesn't make use of the expansion properties of the steam but it
does work and requires no valve gear beyond what is in the piston head
stuff. I'll also note that steam passages from the cylinder to the valve
can also do the movement of the valve.

--
Why isn't there an Ozone Hole at the NORTH Pole?

wrote:

The steam chest has a shaft protruding from the fore and aft - these
will slide in and out.

As far as I can see on the pictures, there is nothing that could be used
to fasten some kind of rod to that shaft (hole, thread, whatever)?
Right?

Nick

--
WDR Fernsehen:
"Ein Computer arbeitet so lange Befehle ab,
bis keine mehr vorhanden sind."
Muss ich die dann irgendwie nachfüllen?

Nifty site!!!

Tom Miller wrote:
Here's a site that shows a number of stem engines in animation. This will
give you a few ideas
http://www.keveney.com/Engines.html

"Wood Butcher" wrote in message
...

This link shows how the linkage in a locomotive works.
At the bottom of the page are links to animations.
http://home.new.rr.com/trumpetb/loco/wdiagram.html

Art

"Leo Lichtman" wrote in
message ...

I would look at other engines to see how it is
usually done.

Right. I remember seeing an article in one of the model magazines
about an engine that used the steam pressure to operate the valve, but
I can't remember where.

wrb

I think it must have originally been designed to have some sort of drive to
the valve gear other than steam. No one smart enough to design an engine,
would be dumb enough to bring the shafts through the end covers of the steam
chest if they didn't have to. Gland are a never ending source of
annoyance,so if you didn't need them , why make them?



wrote in message
ups.com...
I bought an old model steam engine at an estate sale today, and I am
puzzled by the valve gear. There is no mechanical connection between
the crankshaft and the valve!

The steam chest has a shaft protruding from the fore and aft - these
will slide in and out. Haven't gotten it to run yet - I would like to
try to find out more about it before dis-assembling.

Can anyone fill me in on this beast?

TIA,
Wally

It's getting stranger. I took the outboard head off - it has a tube in
the center that goes through a hole in the middle of the piston -
apparently to feed pressure/vacuum from the cylinder at the inboard
side of the piston. This is fed out through the top of the head and
back into the valve block.

The "shafts" protruding from fore and aft on the valve block are
actually just pins. The butt against the top of a valve, allowing it
to be pushed in with the pin.

I *know* I've read about this recently, I just can't remember where!

wrb

wrote:

I *know* I've read about this recently, I just can't remember where!

Somehow this looks like a Ringbom stirling. No it ain't, I know. But
maybe you have that picture in your mind?


Nick
--
WDR Fernsehen:
"Ein Computer arbeitet so lange Befehle ab,
bis keine mehr vorhanden sind."
Muss ich die dann irgendwie nachfüllen?

Tom Miller wrote:
I think it must have originally been designed to have some sort of drive to
the valve gear other than steam. No one smart enough to design an engine,
would be dumb enough to bring the shafts through the end covers of the steam
chest if they didn't have to. Gland are a never ending source of
annoyance,so if you didn't need them , why make them?



wrote in message
ups.com...

I bought an old model steam engine at an estate sale today, and I am
puzzled by the valve gear. There is no mechanical connection between
the crankshaft and the valve!

The steam chest has a shaft protruding from the fore and aft - these
will slide in and out. Haven't gotten it to run yet - I would like to
try to find out more about it before dis-assembling.

Can anyone fill me in on this beast?

TIA,
Wally




I don't know what kind of valve gear this engine has, if any. He says it
doesn't run, which may be enlightning.

But ... Extended, or 'balanced' piston rods were very common on steam
engines (including locomotives) at one time (up to ablout 1900 anyway).
Early crossheads, or what passed for them, were NOT good, and allowed
the pistons to tip in the cylinders. This wore both the piston and the
cylinder into elliptical shapes. NOT good. The simple solution was to
extend the piston rod through the piston and out through the cylinder
head. This, of course, added another packing gland which was a source of
different problems as you allude to.

Dan Mitchell
============

It does reach more than halfway through the cylinder. Makes me wonder
how the rod is connected to the piston. Maybe I'll dis-assemble that
end tonight...

wrb

I hooked up compressed air and experimented with the pins. You can get
erratic movement by pushing the pins in. It *seems* that, if you could
get the timing of the "pin pushing" right, you could cause the engine
to run.

I may dis-assemble further.

Thanks so far,
Wally

Actually, I forced myself to stop messing with it. I bought it to
resell and I already have too many projects going. If I get
interested, I will want to keep it, my wife will kill me, and someone
will buy it at *my* estate sale and be asking you guys about it.

It's on eBay: 5977782177

JohnM wrote:
wrote:
I hooked up compressed air and experimented with the pins. You can get
erratic movement by pushing the pins in. It *seems* that, if you could
get the timing of the "pin pushing" right, you could cause the engine
to run.

I may dis-assemble further.

Thanks so far,
Wally


I was thinking the pins were for starting it, but that's a tough call.

Did you get any further on it? That's an awful nice engine, I didn't see
the 6" rule the first time I looked at the pictures (it looked like a
smooth spot in the casting, with something stamped into it), the engine
is bigger than I first thought. Very cool..

John

Hey Guys,

I'm going to see the Milton Steam Era show on Sunday, as I'll already
be in Toronto for Friday and Saturday. I'll stay over just for that,
as I have not been there for many many years, so it's a bit of a
nostalgia trip for me. If it's really good, I may even go back
Monday!

Anybody else going, or have "best things to do or see"
recommendations?

Brian Lawson,
Bothwell, Ontario.

Drat -- you got me all excited -- we have a "Milton" down near
where I work here in western Washington. Then I realized it
was the wrong Milton. Hmpfffff.

mikey

"Brian Lawson" wrote in message
...
Hey Guys,

I'm going to see the Milton Steam Era show on Sunday, as I'll already
be in Toronto for Friday and Saturday. I'll stay over just for that,
as I have not been there for many many years, so it's a bit of a
nostalgia trip for me. If it's really good, I may even go back
Monday!

Anybody else going, or have "best things to do or see"
recommendations?

Brian Lawson,
Bothwell, Ontario.