I just installed a Soundtraxx DSD-B280LC decoder into a Bachman Spectrum
Light Mountain 4-8-2 and I need to adjust the Chuff rate. Can anyone give
me an appropriate value for CV116?
I can adjust the rate by trial and error but I really don't know what the
rate should be. When exactly does a loco chuff?... every time the rod goes
into the cylinder? every time it comes out? both in and out?
Also, whenever the loco is on the track it makes an ideling sound whether
the loco is being addressed or not. That ideling sound is different from
the Chuff and goes CHA, cha, cha, CHA, cha, cha. Is there a CV that I can
use to turn that sound off, or at least turn it off when that loco is not
being addressed. I use the Atlas Commander so I don't have Function 8 to
mute the system.
Thanks/Carter
Carter,
The 'chuff' happens as used steam is exhausted from the cylinder. Steam is
admitted and exhausted on both the in and out part of the stroke(just from
different sides of the piston). Also most engines have two sets of
cylinders(the one on the other side of the engine) and they are 'quartered'(90
degrees out of sync). What this means is you get 4 'chuff's' for each rotation
of the drivers.
Run the engine real slow and time the 'chuff's - then adjust as needed. The
DSD-B280LC is adjusted for the drivers on he 2-8-0(63" IIRC). The 4-8-2 has
something like 72" drivers, IIRC....
The 'idle' sound is the air pumps - I would not try to adjust them.....
Jim Bernier
Carter Braxt> I just installed a Soundtraxx DSD-B280LC decoder into a Bachman Spectrum
A conventional two cylinder steam locomotive 'chuffs' FOUR times per
driver revolution. Such a locomotive is a two cylinder double acting
steam engine. Each cylinder/piston produces two power impulses per
revolution, one 'pushing', one 'pulling' (that's what "double acting" means).
A three-cylinder loco would have SIX 'chuffs' per driver revolution, and
so forth. A Shay (usually) has three cylinders AND is geared down, so it
typically produces something like 15 'chuffs' per driver revolution.
Articulated and 'Duplex' locos have FOUR cylinders, in two non
synchronized sets. Each set 'does it's own thing', making for a strange
(eight 'chuffs' per driver revolution) exhaust that goes in and out of
synch as one engine or the other slips or changes 'phase' with the
other. Sometimes railroads specified one driver set to be an inch or so
different in diameter than the other so as to FORCE a lack of
synchronization (which could result in some odd out of balance motions
hard on the loco or adversely affecting it's 'tracking' qualities)
An exception to the above were the "Mallets", which, though four
cylinder articulateds, only had a single exhaust from the front engine
(Four 'chuffs' per driver revolution). The rear (high pressure) engine
exhaust INTO the front engine, and hence had NO external 'Chuff'.
Then there were the Triplexes .... and other odd balls.
I've yet to see/hear anyone get the 'chuff' rate correct on a Soundtrax
unit without using the sound-cam option. It can be matched at some
reasonable running speed, but the acceleration rates of the actual loco
and the sound unit 'chuff' rate do not seem to matchable over a range of
speeds. I've seen several knowledgeable DCC types attempt this by doing
all sorts of things with the CV values, to little or no avail. I'm not
saying a reasonable job can't be done, but I've not seen (or heard) it done.
Having seen a LOT of real steam locos, and having long been installing
synchronized 'DC' sound units in my steamers, I've gotten used to how a
loco SHOULD sound at various speeds. The (usually) NOT synchronized
sound from most DCC sound units is REALLY annoying to me. Kind of like
an off-key note would be to a musician.
The best non-synchro (?) sound I've heard is from the new Broadway USRA
heavy Mikado. It is sufficiently good that I wonder if it IS
synchronized? Broadway's website does not mention this (actually, it
doesn't seem to mention the 2-8-2 at all?) If so, it's a BIG leap
forward in DCC sound.
Broadway's website DOES say their non-synchro sound can be closely
synchronized at LOWER speeds, but is purposely programmed to be too slow
at higher speeds. THEY think this sounds better. I feel this is
debatable, though it may be a quirk of how the sound unit functions or
sounds at higher 'chuff' speeds.
Broadway's sound unit in the N&W 'A" and 'T-1' DOES attempt to represent
the in and out of phase sounds of the simple articulated and duplex
locos. It's not real convincing from my experience, or the sound
recordings I've heard of the real locos. It's probably better than
ignoring the effect, however.
I HAVE seen/heard user-installed synchronized (sound-cam) sound using
Soundtrax decoders, and that's NICE! VERY nice!
Dan Mitchell
==========
Carter Braxt>
On of the things that bothers me about sound systems, other than I don't
like them, is that on real steam, the beats are (usually) not even.
If you listen carefully, as a two cylinder engine accelerates, it will beat
as follows.
CHUFF, chuff, chuff, chuff, CHUFF, chuff, chuff, chuff, CHUFF, chuff,
chuff, chuff............
Sound systems don't do this.
--
Cheers
Roger T.
Home of the Great Eastern Railway
I agree, the syncronized chuffing is the only way to go. Without the
syncronization, you can have a loco sitting there chuffing along without
movine or the other side of the coin, moving without ever making a sound but
then again, when a loco is drifting, there is no sound from the exhaust.
The Shay gives a whole bunch of chuffs and, at anything over a very slow
speed of maybe 4 mph, the exhaust tends to blend together for both the
reason that there are so many chuffs and that the exhaust pipe is so long
that it acts more like a minimal muffler.
I've done sound systems on a number of locos and have dealt with both the
remote PFM style sound systems and local to the loco sound modules and none
of them have been that great as the real sounds from a loco are quite varied
from the starting long chuffs to the running choppy chuffs when the Johnson
Bar is in the company notch to the absolute silence when the throttle is
closed. Unsyncronized chuffs from a DCC system would just be a cartoon of
reality and I'd rather not hear such nonsense.
I'll also note that most sound systems that I've heard have been way too
loud.
--
Bob May
Losing weight is easy! If you ever want to lose weight, eat and drink less.
Works every time it is tried!
"T> On of the things that bothers me about sound systems, other than I don't
"T> like them, is that on real steam, the beats are (usually) not even.
"T>
"T> If you listen carefully, as a two cylinder engine accelerates, it will beat
"T> as follows.
"T>
"T> CHUFF, chuff, chuff, chuff, CHUFF, chuff, chuff, chuff, CHUFF, chuff,
"T> chuff, chuff............
This might be due to variations in the actual distance between you (the
listener) and the *four* different exhaust ports.
"T>
"T> Sound systems don't do this.
"T>
"T>
"T> --
"T> Cheers
"T> Roger T.
"T>
"T> Home of the Great Eastern Railway
"T>
formatting link
"T>
"T>
"T>
"T>
"T>
\/
Robert Heller ||InterNet: snipped-for-privacy@cs.umass.edu
Real steam locos should not make such sounds either ... but, yes, they
often do. Such a non symmetry denotes either some malfunction, or, more
likely, a minor valve timing issue. Steam locos are meant to be 'square'
(railroad shop term), meaning all beats SHOULD be equal, denoting proper
valve timing. Perfection rarely happens, however.
And a minor discrepancy can result in a nice 'beat' to the exhaust, as
you describe. The old" I think I can" ... etc. exhaust.
Dan Mitchell
==========
"Roger T." wrote:
Perhaps. But experience in the cab also shows that the fire and everything
else rattles with the same syncopated rhythm..
CHUFF, chuff, chuff, chuff, CHUFF, chuff, chuff, chuff, CHUFF, chuff,
chuff, chuff............
--
Cheers
Roger T.
Home of the Great Eastern Railway
I don't agree. In my experience, the "chuff" sound originates at the stack.
I can happily recall several Burlington trips behind 4960, 5632, etc.
leaning out the baggage car door listening to the echo of the locomotive off
the walls of the warehouses south of Chicago Union Station. The echo was
louder than the direct sound path from the front of the loco to the side of
the baggage car. I heard all four chuffs per revolution of the drivers
about equally, which would not have been the case if the sound originated at
the valve ports in the cylinder block on the two sides of the locomotive.
The sound also distinctly changed as we passed under the many street
overpasses, which would not be the case if the sound was originating low on
the locomotive. I do agree there was an unevenness as one "chuff" always
seemed louder than the other 3, and I concur with other posters that this is
due to minor differences in the mechanical features of the exhaust steam
paths. GQ
The "chuff" on the prototype begins at a variable point in the movement of the
piston, adjusted by "cutoff". The beginning and end can be almost the moment
when the piston begins to move (rod across the centre of the wheel) to almost
half way through the movement where the rods are top or bottom.
At slow speed and heavy load, the cutoff is adjusted for the longest power
stroke and at moderate speed with a light load the cutoff is at maximum with
the shortest power stroke.
A two cylinder locomotive has four beats per revolution.
That noise is the Westinghouse brake pump - it works on the prototype like that
to counter any leaks in the brake pipes, of which there are many in a long
train. So long as the pump can keep up with maintaining brake pipe pressure
there is no problem.
One more sound would be the steam powered generator for the lights which
maintains a constant hiss - generally turned off when the lights are
extinguished.
:
:
: > This might be due to variations in the actual distance between you (the
: > listener) and the *four* different exhaust ports.
:
: I don't agree. In my experience, the "chuff" sound originates at the
stack.
: I can happily recall several Burlington trips behind 4960, 5632, etc.
: leaning out the baggage car door listening to the echo of the locomotive
off
: the walls of the warehouses south of Chicago Union Station. The echo was
: louder than the direct sound path from the front of the loco to the side
of
: the baggage car. I heard all four chuffs per revolution of the drivers
: about equally, which would not have been the case if the sound originated
at
: the valve ports in the cylinder block on the two sides of the locomotive.
: The sound also distinctly changed as we passed under the many street
: overpasses, which would not be the case if the sound was originating low
on
: the locomotive. I do agree there was an unevenness as one "chuff" always
: seemed louder than the other 3, and I concur with other posters that this
is
: due to minor differences in the mechanical features of the exhaust steam
: paths. GQ
:
Somewhere I got the impression that most engines exhausted the steam out of
the stack - perhaps to assure draft. I'm not able to find a reference on
the subject - anyone know?
Here's a reference on the basics of a steam engine FYI:
The exhaust ports all feed into the one blast pipe that exhaust up the
same chimney. Even with double chimneys and multiple blast nozzle
systems the chimneys are so close together that they are, in effect, one
chimney.
Robert Heller wrote:
snip
snip
And the problem with Soundtraxx Steam sound units. They should have
some way to sync with a wheel instead of trying to do it electronically.
We spent an entire evening doing it by trial and error because every
locomotive is going to be just a bit different.
This would be the air compressor or air pump sound. Try setting CV123
to zero.
For a good understanding of when the "chuff" occurs, run the simulation for
your model's type of valve gear as found at Charlie Dockstader's super site:
"KTØT" wrote in
news:nvENb.26350$ snipped-for-privacy@twister.rdc-kc.rr.com:
According the the MR Cyclopedia, vol. 1, the cylinders exhaust
into a Venturi tube in the stack. That creates a suction that
provides the draft needed for the firebox and boiler. That
suction pulls air into the firebox to help combustion of the
fuel and then pulls the hot gasses on through the boiler tubes
and into the smokebox in front of the boiler. I suspect that
some earlier engines did not have this arrange which may be
one reason why they had such tall smokestacks. Look at some
of the earliest engines, like the DeWitt Clinton, and you see
a stack that is almost as tall as the engine is long. The
tall stack was partially to provide a draft for the fire in
the boiler and partially to try to carry sparks over the top
of the train. (It didn't work so well at that, since many
early RR passengers who rode on the car tops complained about
sparks burning holes in their clothes. Look at illustrations
of the earliest RR's in this country and you see seats on top
of cars and the cars converted from Concord Coaches.)
: "KTØT" wrote in
: news:nvENb.26350$ snipped-for-privacy@twister.rdc-kc.rr.com:
: > Somewhere I got the impression that most engines exhausted
: > the steam out of the stack - perhaps to assure draft. I'm
: > not able to find a reference on the subject - anyone know?
: >
: > Here's a reference on the basics of a steam engine FYI:
: >
formatting link
: According the the MR Cyclopedia, vol. 1, the cylinders exhaust
: into a Venturi tube in the stack. That creates a suction that
: provides the draft needed for the firebox and boiler. That
: suction pulls air into the firebox to help combustion of the
: fuel and then pulls the hot gasses on through the boiler tubes
: and into the smokebox in front of the boiler. I suspect that
: some earlier engines did not have this arrange which may be
: one reason why they had such tall smokestacks. Look at some
: of the earliest engines, like the DeWitt Clinton, and you see
: a stack that is almost as tall as the engine is long. The
: tall stack was partially to provide a draft for the fire in
: the boiler and partially to try to carry sparks over the top
: of the train. (It didn't work so well at that, since many
: early RR passengers who rode on the car tops complained about
: sparks burning holes in their clothes. Look at illustrations
: of the earliest RR's in this country and you see seats on top
: of cars and the cars converted from Concord Coaches.)
Thank you Woodard!
Bob
"Woodard R. Springstube"
That's called the blast pipe. It's position in the smoke box and its
diameter all have a strong bearing on how well a kettle does, or doesn't,
steam.
--
Cheers
Roger T.
Home of the Great Eastern Railway
Except that what you hear as "chuff" is the exhaust steam leaving the
orifice(s) at the top of the blastpipe. The beats are an indication that
the valves are not set absolutely square.
Yairs! It's amazing how critical a seemingly minor misalignment of the
blastpipe and petticoat can be. Or carbonisation of the blastpipe
orifices. Or simply not having the smokebox door shut TIGHT!
Very few people apart from engineman appreciate just how important the
front end is to steam loco performance.
[ ...]
The idling chuff is the air pump. Air pumps had a governor, and did not
run continuously. When air pressure dropped the pumps started and worked
to get pressure back up, then slowed down as pressure neared the desired
level, then stopped. So, you should turn it off after a while to make it
sound right.
Another idling sound is the blower. That is a ring of pipe around the
blast nozzle that directs a number of small steam jets up the stack to
maintain the draft when the engine isn't moving. This would be a mild
hiss when the engine is just sitting and the steam pressure is high
enough. It would increase to a bit of a roar when the fireman needed to
raise the steam pressure. You should hear some blower whenever and while
the engine is stopped.
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