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Double-chuff?

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Double-chuff?
Posted by wobblinwheel on Friday, January 12, 2018 6:37 PM

I was just watching a video demonstrating a BLI Y6b locomotive, and it clearly had a "double-chuff" sound through out it's operation. I was wondering, since the Y6 was a COMPOUND locomotive, would you still hear the double-chuff?  Since the rear cylinders exhaust through the front cylinders, wouldn't you only hear ONE SET of chuffs? I know, on start up, the Y6 COULD be in "simple mode", but only for a short distance. Am I right on this?

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Posted by 7j43k on Friday, January 12, 2018 7:35 PM

They got it wrong.

And you are correct.

 

Ed

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Posted by gmpullman on Friday, January 12, 2018 8:06 PM

wobblinwheel
I was just watching a video demonstrating a BLI Y6b locomotive,

One of the downsides of many of the videos out there, weather on Youtube or a commercial DVD is that the sound has been dubbed from any number of sources, not always matched to the particular locomotive or scene being portrayed.

I had posted some old 8mm films that I shot back in the 1960s and '70s and some of the comments I got were, "Great video but the sound is broke".

Unless the photographer had "sound-on-film" or a recording engineer with synchronized sound recording equipment, chances are the video you saw had dubbed sound.

Better than nothing, I guess, but not necessarily accurate.

Regards, Ed

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Posted by Overmod on Friday, January 12, 2018 8:38 PM

wobblinwheel
I was just watching a video demonstrating a BLI Y6b locomotive, and it clearly had a "double-chuff" sound throughout its operation.

You are correct that the double-chuffs would only be heard during 'simpled' startup, and even then the ones from the lead engine would be different from the ones for the HP.  It might be interesting to consider the modifications to a sound chip to implement speed-sensitive simpling.

More likely, they simply (no pun intended) adapted the sound setup from their Class A, a prototype which is famous for producing desynchronized 'double licks' throughout its speed range.  (I have just bought one to test whether its setup actually reproduces the prototype or just has multiple chuffs timed off some sort of sloppy rotary encoder like the old four-sided nut cam)

 

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Posted by selector on Saturday, January 13, 2018 12:20 AM

Overmod, if it's an earlier version, say by BLI in their Paragon or Blueline versions, it will be strictly a BEMF-sensitive chuff that you can manipulate at a given speed and hope it stays relatively synched at higher speeds.  By the time they got around to Paragon 2 and beyond, I believe BLI resorted to a reed-switch and magnet arrangment which has an iffy reputation for robustness.  I mean, when it works, it's great, but quite a few failures have been reported, generally a couple of hours into its use.

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Posted by wobblinwheel on Saturday, January 13, 2018 1:27 AM

I sent the Loksound decoder from my original PCM version of the Y6 to a fellow with a "Programmer" to change the sounds. Using soundfiles from British, German, and who knows what else, we actually came up with a "compound" chuff that starts with a double chuff for around fifteen wheel revolutions, then shifts to a single chuff from then on. Then we changed the pitiful PCM whistle to a British "hooter" that sounds great, compared to the "moaner" originally installed! I dare say my PCM Y6 doesn't sound quite like any other out there.....

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Posted by 7j43k on Saturday, January 13, 2018 10:08 AM

That sounds like an interesting bit of work!  I think I would have wimped out and just put in a "non-articulated" sound.  I believe the compounds had a less-sharp exhaust, so, if I could pick-n-choose, I'd head that way.

The simple start is an intriguing inclusion.  I think it was switched on by intention by the engineer.  So it didn't always happen.

The ideal, for me, would be to have a function switch that could do what the engineer does/did.

I'm lucky, in a slightly disappointing way, to follow railroads that didn't have compound articulateds during my time period.  But I HAVE heard some really disappointing "regular" articulted sounds, where they emphasize the lack of engine "synchronicity" WAY TOO MUCH.  It sounds like one driver set has smaller diameter wheels, or something.

And, as long as I'm whining/complaining:  I'm not too fond of being forced to have sounds coming out of MY steam locomotives that indicate the valve timing is off.  I like to think that my shop crews are on top of the matter.  It may sound "cute" and "clever", but it gets old.

 

Ed

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Posted by wobblinwheel on Saturday, January 13, 2018 11:06 AM

Ed, when you say "valve timing is off", what do you mean? What does that sound like? Is that something some manufacturers "incorporate" into their sounds?

Mike C.

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Posted by 7j43k on Saturday, January 13, 2018 11:30 AM

A properly timed steam locomotive will have four indistinguishable chuffs for every driver revolution.  There should not be one that is louder or "different" than the others--no "I think I can" with the emphasis in "think".

 

Yes, they do incorporate it.  That's why I'm hearing it.  All too often.  

It's just fine to have it in a back-woods 2-8-0.  I guess.  But in a modern 4-8-4--I don't think so.  

PERHAPS some of them give you various sound options, and you can pick a different (better) one.  No problem here with that.  But it's ridiculous to offer that as the only one.  For that matter, it's ridiculous to offer that particular choice on an engine where it's inappropriate.

 

Ed

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Posted by rrinker on Saturday, January 13, 2018 11:48 AM

 I think more often than not, that is an artifact of recording the sounds and getting them set up to play with some amount of attack and decay and not just a sudden burst of sound, and then stringing it together to play a 4 chuff sequence. Since the samples can'e be a whole cycle (how would you change chuff rate for speed then, make 60 sets of samples, from 1 mph to 60mps in 1 mph increments?) what you get are 4 distinct chuffs with just the slightest gap which gives the cadence you end up hearing. It would, I expect, take an outstanding sound engineer to get it so that at no speed throught the loco's range, there is zero gap, especially before the first chuff. Some people have learned the hard way that editing sounds for a sound decoder isn't all that easy, as they end up with an audible 'click' in their whistle sequence or similar. 

                            --Randy

 


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Posted by Overmod on Saturday, January 13, 2018 12:32 PM

7j43k
It's just fine to have it in a back-woods 2-8-0. I guess. But in a modern 4-8-4--I don't think so.

You hear it all the time when the steam tract isn't maintained properly or one of the valves has more 'blow' than the others.  I've always thought that a good sound system ought to be able to be 'tuned' to produce a variety of typical failing-maintenance effects (I may be one of the few modelers who actually loved the idea of the 'failing F unit' that was marketed a few years ago) since a perfect foursquare exhaust with equal beats is something unlikely to persist long without periodic (and by the late '40s, increasingly expensive and specialized) maintenance.

With respect to 4-8-4s, and one locomotive in particular, I remember a comment in Trains many years ago now about some C&O power that had a very different sound on every fourth exhaust beat -- the prose described it as "chow-chow-chow-wheep".  They didn't know the reason for that, and I still don't, but I suspect it would be clearly audible in sound samples.  And once we figure out what causes it, perhaps in other applications as well.

Of course it's also ridiculous to use the same sample for multiple speeds: as the locomotive reverser is notched up, a number of characteristics of the exhaust will be changing.  In a sense this is more important than 'synchronizing' the sound with the mechanical motion, as most people won't be able to figure this out considering the relatively high cyclic rate of the motionwork at any meaningful road speed plus the effect of 'speed of sound' over typical model viewing distances.

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Posted by 7j43k on Saturday, January 13, 2018 2:36 PM

Overmod

 

 
7j43k
It's just fine to have it in a back-woods 2-8-0. I guess. But in a modern 4-8-4--I don't think so.

 

You hear it all the time when the steam tract isn't maintained properly or one of the valves has more 'blow' than the others. 

Well, yes.  But you don't hear it with a properly maintained locomotive.  I have nothing against having and running "ragged" exhaust sounds.  I just don't see them as a logical first choice.  Just as I don't see the sound of a nearly dead F unit as a first choice.  Or, worse, the ONLY choice.

 

Ed

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Posted by selector on Saturday, January 13, 2018 5:46 PM

Overmod

 

 

With respect to 4-8-4s, and one locomotive in particular, I remember a comment in Trains many years ago now about some C&O power that had a very different sound on every fourth exhaust beat -- the prose described it as "chow-chow-chow-wheep"...

 

I noticed that 'squeak' sound on the xth chuff of WP&YR's #73 in the summer of 2016.  It was also picked up by my Panasonic camera's mikes.

As you describe it...

"Wheeep, chuff, chuff, chuff, wheep, chuff, chuff, chuff..."

My suspicion is that the disparate chuffs we hear of various types may seem louder, but really they're just different, and are perceived as more salient and more energetic/louder solely because of their difference.  Like you, though, I am stumped by this squeak.

Meanwhile, I have an emailed inquiry sent to the scenic railway.  We may get lucky if the hogger replies.

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Posted by Virginian on Saturday, January 13, 2018 8:04 PM
On Simple articulateds the double chuff would go in and out of synch as the front engine would almost always slip more than the rear under load.
What could have happened.... did.
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Posted by 7j43k on Saturday, January 13, 2018 8:35 PM

Virginian
On Simple articulateds the double chuff would go in and out of synch as the front engine would almost always slip more than the rear under load.
 

 

 

What I hear is a continuous slip, then.  I hear it coming in and out of phase.  It sounds exactly like one engine has smaller drivers.  All the time.

 

Is that what you're describing?

 

Ed

 

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Posted by wobblinwheel on Sunday, January 14, 2018 12:10 AM

I really can't stand the constant "NOT random" slipping in-and-out of the sound-equipped four-cylinder locos that have. After having some of these locos for years, and not liking that aspect of the sound, AND the fact that at higher speeds, the out-of-sync chuffs sounded like a jumbled up MESS! I finally decided to remove the axle covers under one set of drivers, and reset the driver position to match (or very close) the position of the other drivers. I then adjusted the sound to eliminate the double-chuff. I'm much happier now with the sound, and they clearly sound better at higher speeds! No need to have the SOUND go out of sync, when the drivers DON'T... EDIT: I forgot to mention, those who may have the "old" BLI locos with the QSI decoder, you might think you can't disable the second chuff. Well you can, using the CV that controls the volume of the SECOND chuff. On mine, I adjusted the volume of the second chuff very low, until it sounded like a slight "echo" that would drift in and out. Very neat effect....

Mike C.

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Posted by BigJim on Tuesday, January 16, 2018 8:45 AM

Virginian
On Simple articulateds the double chuff would go in and out of synch as the front engine would almost always slip more than the rear under load.
 

Hopefully in the near future the tapes made by Bud Swearer will be made available again. If and when they are, I am guessing that you will be very surprised at how generally wrong you are. Time after time, Class A locos are heard for long stretches of time ascending the Blue Ridge grade with their exhuasts synchronized with absolutely no slipping at all. In fact, it is quite amazing that in none of the recordings made on Blue Ridge did any slipping occur other than the one where the Y6 is starting heavy loads switching the rock quarry at Blue Ridge. That is not to say that the double-chuff didn't occur. However, I would venture to guess that on well over 95% of the recordings, there was no "double-chuff" from a Class A.

I am not sure if the recording "Extra 1235 East" is available. It contains other good recordings of the same.

Two other things are interesting. When the Class A was starting a train, the double-chuff was very noticable, but, it didn't take very long before the two exhuasts synced up. Also, when the Y6 locos were "simpled" while running, at first you could hear a double-chuff, but again, it would not take very long for these two exhausts to synchronize. It is quite a treat to hear a long sequence where the Y6 pusher goes from compound to simple and then as it speeds up, goes back to compound.

 

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Posted by Overmod on Tuesday, January 16, 2018 2:06 PM

Ryan Hoover has a page with some relevant sound clips, including 1202 on the Blue Ridge grade from Al Sherry's album...

http://www.columbusrailroads.com/new/?menu=05Steam_Railroads&submenu=14Norfolk_%26_Western&submenu4=13Sounds_of_the_N%26W

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Posted by wobblinwheel on Tuesday, January 16, 2018 5:28 PM

To be honest, I think the sound systems on articulated, or four cylinder model engines should only have a "double-chuff" at startup, and for a short time at SLOW SPEED. The double-chuff does NOT sound good at higher speeds. Ever...!

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Posted by LogginLocos on Wednesday, January 17, 2018 11:30 AM

Even on curves locomotives like articulated will chuff in and out of sync. 

On steam locomotives, the wheels are rigid on one axle, keeping every wheel at 90 degrees apart for the engine quartering. The reason why older cars would screech on curves was because the wheels were single cast and then machined. one wheel would slip and thus the wheel would screech. The same effect would occur on locomotives, the slip on a curve would force the wheels into and out of sync.

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Posted by Bayfield Transfer Railway on Wednesday, January 17, 2018 12:06 PM

Who made a "failing F unit?"  I could use a few.

 

Disclaimer:  This post may contain humor, sarcasm, and/or flatulence.

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Posted by selector on Wednesday, January 17, 2018 1:55 PM

LogginLocos

Even on curves locomotives like articulated will chuff in and out of sync. 

On steam locomotives, the wheels are rigid on one axle, keeping every wheel at 90 degrees apart for the engine quartering. The reason why older cars would screech on curves was because the wheels were single cast and then machined. one wheel would slip and thus the wheel would screech. The same effect would occur on locomotives, the slip on a curve would force the wheels into and out of sync.

 

I'm afraid you are mistaken.  All rail wheels are machined to have a truncated cone profile.  This conical geometry allows the axles to center themselves when on tangent rails, and to ride up to accommodate the disparate radii on curves.  The squealing you hear is about flanges vibrating as they repeatedly scuff the inside bearing surfaces of the rail heads on sharp curves, or, as wheels wear and their conical surfaces deform, some minor upper bearing surface scuffing causes the wheels to sing.

The synchronisation changes takes place because of wheel slip, that's true, but it's rotational wheel slip due entirely to two factors...weight distribution vs. piston thrust.  Or simply, the disparate adhesion of steel tires on steel rails from engine to engine under the one boiler.  Assuming each set of cylinders gets the same boiler pressure at the work surface of the piston, it's the engine with the least adhesion that will begin to slip when the other engine retains its purchase on the rails.

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Posted by wobblinwheel on Wednesday, January 17, 2018 7:16 PM

Well, as a result of this conversation, I watched several YouTube videos last night on the 1218 as well as the UP 3985, both being simple articulated locos. The MAJORITY of the time, the 1218 exhibited DISTINCT double-chuff on start up and slow speed, while the 3985 seemed to have it's drivers in sync (sound wise) MOST of the time! While the wheels did not always "appear" to be in the same position, the chuffs sounded like they were. Obviously, the drivers don't have to be synchronized, in order for the chuffs to be...? Neither of the locomotives sounded out of sync at higher speeds. I guess it's just too hard to tell...

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Posted by 7j43k on Wednesday, January 17, 2018 8:23 PM

For simple articulateds, the exhausts are directly linked to the driver positions.  If the driver positions happen to be "in sync", then the exhausts will be.  If not, they won't.

I would expect driver positions in each engine of an articulated to be randomly chosen.  There is no "linkage" between the two driver sets or valve sets.

However, it is certainly conceivable that the engines could get themselves into a synchronized pattern, by use of minute amounts of wheel slippage.  I'm not going to try to describe what I'm talking about.  But I'll call it "getting into a sweet spot".

Whether that happens or not is a matter of fact.  I doubt anyone has made an effort to do the research, so it remains only speculation. 

 

Ed

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Posted by PRR8259 on Wednesday, January 17, 2018 9:24 PM

Articulateds did routinely slip on startup and thus would work themselves both into and out of time as the front and rear engines synchronized.

I cannot stand the bad narration but the Sunday River videos of N&W steam do reflect a huge variety of Y Class sounds.  I am pretty sure they have recordings of engines drifting in and out of time.

Most extant recordings of UP 3 cylinder 4-12-2 engines reflect engines that were poorly maintained at the end and thus are badly out of time.  So their already offbeat exhaust is worse than railroaders claimed it actually was, and has been poorly modeled or replicated in ho.

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Posted by 7j43k on Wednesday, January 17, 2018 11:10 PM

PRR8259

Articulateds did routinely slip on startup and thus would work themselves both into and out of time as the front and rear engines synchronized.

 

We are not talking about engine slip on startup for articulateds.

 

3-cylinder engines are also outside of the topic.

 

Ed

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Posted by wobblinwheel on Thursday, January 18, 2018 12:30 AM

Not sure I entirely understand that. It seems that looking at one side of an articulated loco, and the EXHAUST is pretty much in sync, couldn't one set of drivers be, say, 180° out of position to the other set, yet the exhaust still be "in sync"? You don't mean that if the front engine is "rods down", then the rear drivers also have to be rods down in order for the exhaust to be synchronized? If each engine group exhausts 4 times per rev, that changes the opportunity for "exhaust synchronization" considerably! It seems that one driver set has four positions per revolution for the exhaust to actually be....."synchronized"? I think I noticed that several times in the videos....

Mike C.

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Posted by selector on Thursday, January 18, 2018 1:50 AM

We need Overmod or Juniata to rescue us here.  I think they'd introduce backpressure and exhaust nozzles as part of their explanation.

"You don't mean that if the front engine is "rods down", then the rear drivers also have to be rods down in order for the exhaust to be synchronized?" -wobblin

If the front engine is rods down, it's only on one side.  Walk around the boiler and you'll find the left side with the cranks rearward to 3 o'clock...or the other way around to 9 o'clock, depending on which side 'leads'.  This would be true for the rear engine as well.  So, whether all cranks on one side are down or rearward/forward, those on the other side would also be fully aligned, but displaced by 90 deg.  In that case, all you'd hear would be four perfectly timed chuffs as the locomotive moved.  If either engine is out of phase, you'd hear multiple exhaust noises, as you can hear plainly during the Class A accelerations on various youtube examples.

Listen to the first 30 seconds of this video...it's all it will take.  Watch 3985 go in and out of synch, and try to tell, with your eyes closed, when it's in synch.  I'll bet you can't.

https://www.youtube.com/watch?v=XhgHrDbN4EU&t=52s

 

Now watch this test of 3985, but scroll the cursor on the video timebar to at least the 2:30 minute mark or you'll die of boredom. Get some volume going....you'll want the full experience. Stick out tongue The locomotive is clearly in full synch, pulling hard against two modern diesels in 'full setup', meaning both have their dynamics fully engaged for resistance.  What does the sound of the chuff tell you?

https://www.youtube.com/watch?v=9alWb5KI5Uo&t=296s

 

 

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Posted by PRR8259 on Thursday, January 18, 2018 8:24 AM

7j43k
 
PRR8259

Articulateds did routinely slip on startup and thus would work themselves both into and out of time as the front and rear engines synchronized.

 

 

 

We are not talking about engine slip on startup for articulateds.

 

3-cylinder engines are also outside of the topic.

 

Ed

 

 

I completely disagree for the following reasons:

When the front or rear engines did slip a little bit, the articulateds would work their chuff both "into" and "out of" what some hear as "relative" chuff synchronization, which is what this topic, I thought, was all about.

Also, the thread specifically discussed models whose chuff does not synchronize with the drivers and/or whose sound system design approach (sound cam) does not survive in actual use--of which the 4-12-2's are absolutely the worst offenders.

Having spent many hours watching articulateds from all roads on video (a little of which was actually live recorded and not dubbed), having played with my friend's multiple sound systems, and many sound equipped HO models subsequently, I was trying to contribute something of value here.

Having already sworn off posting on other MRR forums due to the attitude of certain folks, I am now utterly done here too.

Have a great day.  You absolutely will not hear from me again.

John

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Posted by LogginLocos on Thursday, January 18, 2018 9:28 AM

Perhaps your not considering the way two race cars on the same loop of road tend to be quicker on The inside opposed to the car on the outside 

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