The video review of the BLI Pennsy H-10s offers me an opportunity to raise an issue without, I hope, sounding too critical. I have the company’s earlier Decapod, and I sent it back three times because it seemed to me to “stutter” in its chuff. Let me emphasize that the people at Broadway were consistently helpful, polite, and timely; they wound up giving me a whole new chassis (since I thought I could actually see a little bind that might account for the syncopated chuff) AND a new decoder. That’s one of the reasons I was happy to buy another of their offerings.
But as Dana is running this new Consolidation in the review, I can hear places where the same off-beat chuff is audible (it is, I believe, the same decoder as in the Decapod). Sometimes it sounds as if the sequence of chuffs has a slight delay in the onset of the second beat (i.e., one…two-threefour); sometimes it sounds as if the main beat is the second rather than the first (i.e., one-TWO-three-four instead of ONE-two-three-four).
I won’t be offended if anyone responds by saying I’m hearing things. That will at least balance the times I’m told that I DON’T hear things. But it occurs to me that even at my age, and having grown up in Lima, and having ridden a number of steam excursions, I may simply not be familiar with the whole chuff repertoire. Maybe these are authentic Pennsy patterns. Maybe the regular (even rigid) rhythms I’m accustomed to are the result of listening to movie soundtracks. Maybe those rhythms depend on the age and maintenance schedule of a loco. If anyone has wisdom on any of this, I’d appreciate hearing from you.
No BLI experience, but there are two basic kinds of chuff. The best is driven in some way by sensing the actual rotation of the driver. This can be done magneticaly, photo-optically, etc.
Most chuff is synthesized in the decoder. There are chuff adjustments that can help keep it in time with actual driver rotation, but these are alays off at some point in the throttle range. The trick is usually to set it so that at a typical low speed it’s more or less in synch. When running faster, it won’t be, but faster tends to blur the sound we hear together and its less of an issue.
Blackstone locos, for instance, use synthesized chuff, although I would’ve thought it would have been easy enough to upgrade to a sensor driven system.
Keep in mind usually every 4th chuff was a touch louder, especially noticeable at slow speed. So it wasn’t “chuff chuff chuff chuff” but more like “CHUFF chuff chuff chuff” (or “BRO mo selt zer, BRO mo selt zer”) [;)]
I think it had to do with the side rods being quartered, so that as wheels rolled each rotation there’d be a point where both the siderods on both sides would be going up, and then both going down as the wheel rolled. Takes more energy to lift the siderods, less when gravity is pulling them down.
This is exactly it. The synchronization of this should be as the rods rotate from 9 o’clock position to 3 o’clock position (seen from engineers side train moving forward).
The piston thrust is heavier sounding as it lifts the rods over the apex of the rotation. The weight is dead weight. As it passes the apex, the dead weight becomes a help (with gravity) and thus the pulse of the thrust is a bit lower… cha CHUFF chuff chuff… cha CHUFF chuff chuff.
Is this what your hearing? Its natural for steam locos and not at all out of place.
While I understand what you guys are saying about the weight of the rods and the chuffing, in actual operation, the weight of the rods is insignificant in relation to the mass of the train and has a likewise insignificant effect on the chuffing. Also, the balancing of the rods with the counterweights will further negate any effect on the operation of the locomotive, as far as how the exhaust sounds. A locomotive that is properly timed will have four equal “chuffs”. As a locomotive wears, the slop in the valve gear tends to make them run out of square, resulting in some chuffs that are stronger than others. While this might be prevalent on smaller operations, an out-of-square locomotive would be an anomaly on a Class 1 railroad in the heyday of steam. They had a vested interest - as well as the personnel and shops - to keep the mainline locomotives running as close to perfect as possible. They had the setting and adjustment of valves down to a science, as can be seen in the technical books of the day such as Johnson’s “The Steam Locomotive”, McShane’s “The Locomotive Up to Date” and Grimshaw’s “Locomotive Catechism”. A properly timed locomotive runs more efficiently, will make the maximum amount of power when needed, and won’t wear out as quickly as one that is out of time (or “lame” as the crews would call them). Now, all that has really nothing to do with how BLI’s locomotives sound… except that I would think, to be prototypically correct, a Pennsy H-10 would be square. “The Standard Railroad of the World” knew a thing or two about maintaining steam locomotives… - James
Funny, but I head the same thing with most sound decoders. The chuff just sounds out of time, kind of like band with one instrument not in the same beat. Just barely noticable, but there.
Likewise the bell sound with most decoders just seems too fast for a bell clanging. The timing of a gravity driven bell would be slower. Instead the timing seems more like a mechanical clapper. While it sounds appropriate on a modern locomotive, it just seems out of place to my ear.
I certainly agree with everything you point out in your reply, James, and in an ideal world the pristine maintenance scenario would hold true but quite a few stories I’ve read in the PRRTHS Keystone tell a different tale, at least in the later days of steam. There were scores of engines that had been mothballed and ready for scrap when they were needed for an up-turn in traffic, was it late '56 or '57? Anyway, there were some stories from crews that would make any road foreman hit the roof.
As for the BLI “chuff sensor” I have had to replace a few on some of my NYC Hudsons. It is a small, glass reed switch and, as such, is a mechanical device with moving parts inside the glass envelope. The magnet spinning on the flywheel, especially at higher RPMs doesn’t have a perfect alignment with that reed switch. As the thrust of the motor shaft varies fore and aft—there’s always a little play there—the magnetic field will vary slightly.
I’m no electronics expert but I believe a Hall effect device or an optical sensor would probably work better.
Personally, I LIKE to have a little variation in the exhaust sound, especially with the Paragon II because after 20 minutes of constant running the exhaust sounds more like a motor boat with a bad muffler than a steam locomotive. BLI’s chuff intensity sounds pretty lame as well.
I have an H10 but haven’t had a chance to give her a workout. Guess I’ll have to see how mine runs…
Interesting reading and a great discussion. I have to go with JamesP here, what he says makes the most sense. However, my Walthers Proto USRA 0-8-0 and the echoes in my mind from seeing steam in operation when very young and the sound tracks from countless railroad movies have always had one chuff “accented” out of the four. If the goal was that the chuffs be square, it would appear to me that would not have occurred very often.
In fact, I rode the Durango & Silverton, two months ago and heard this exactly the same as it was in the movies and back in the 50s.
All of this discussion (I think) has little to do with the O.P.’s question, which I believe has to do with a flaw in his BLI locomotive.
Yeah, that could be it. Thanks to you and David B. I know what’s in the BLI now. There the possibility that an issue like this could be caused by a bit of fuzz or something else that was picked up. Might be worth taking a peek at.
The thing about the reed switch is it’s essentially a binary device - eithr the magnet is close enough to make it open and close or it’s not, so any variation within the range of an operating magnetic field isn;t going to alter the output of the switch. If it does move far enough out that it doesn;t activate on a paricular rotation or two, that will throw the count off and create a lag between chuffs - say it’s set to chuff ever 16 rotations, and it missesd 4, so between the previous chuff and the next chuff you get 20 motor shaft rotations.
A Hall sensor would be better, just for reliability over the long haul. Optical is out, because that’s how MTH does theirs, and if BLI did that, they’d get sued (again).
One thing I notice in a lot of the reviews where they run the loco - there is a pretty heavy hand on the throttle. That too will distort the sounds vs starting up slowly in a more prototypical fashion.
This was a valve event timing problem. Each set of running gear on either side of the locomotive gets its own adjustments. For the strong exhaust to take place, it’s opposite must be that much less strong. However, our ears don’t hear that weaker exhaust, only the stronger one.
The stronger blast is the result of a valve not sliding over the exhaust port at the correct time such that the exhaust, when it does happen, is stronger than the others due to the piston still at the extent of its stroke instead of already commencing its return down to the other end of the cylinder. When the piston gets to the other end and just begins to return once again, the valve has already begun to bare the exhaust port on the far end of the cylinder in which it travels, so the steam still expanding against the piston begins to exhaust early…meaning less overall pressure/expansion as exhaust takes place. Means a quieter exhaust at that end of the stroke. That’s the one our brains don’t want to perceive.
Even a perfectly squared running gear could have that accented fourth chuff because the volume of steam in the space ahead of the piston is greater than that behind it, due to the presence of the piston rod. Some engines were equipped with balance rods, which were just forward of the piston and extended through the cylinder head. I’ve seen pics of these on some PRR engines, but they were probably removed because the maintenance wasn’t worth it.
This is great stuff in response to my query/comment. I’ve learned a good deal about prototypes and models alike. I apparently didn’t choose a clear enough term (stutter) to describe the tiny halt that produces an uneven rhythm. I thought that my ONE two three four notations would convey the BRO mo selt zer idea, but perhaps not. Using that method, what I’m hearing is sometimes bro mo selt ZER and sometimes (depending on speed) BROmo selt zer–I’m trying to indicate pauses with extra space between syllables. At some speeds it sounds like one pair of chuffs being echoed by another; put another way, there’s a slight pause between the second and third chuff. At other speeds, as I said in my post, it sounds as if there’s a pause (stutter? stammer?) between the first and second, with the remaining chuffs closer together, as if making up the “lost time”: BRO…moseltzer.
What I appreciate most, as is so often the case at this forum, is being taken seriously. Considering what an unserious issue it is–it’s only a little noise coming from a toy, after all–that’s a great tribute to the respondents. Either that or we’re all a little obsessive.
- James