Sound synchronization

[Mike]

With the Spectrum locomotives  (and for that matter, for BLI or others) equipped with sound, is there any synchronization of the chuff rate with the movement of the train? I was watching a friend's C&O Spectrum DCC equipped locomotive last night, and it was not synchronized. However, he was running it on DC (the layout isn't finished yet.) I was wondering if the synchronization might be tied in with the DCC. I guess I would have to say that I was surprised that such a nice looking and running loco was so "out of synch". Any info would be appreciated.- Mike S

[SteamGene]

Normally factory installed sound decoders have the chuff synchronized with the valve movement.  When you install a sound decoder, you have to synchronize it yourself.  The freeware software makes that a piece 'a cake.
Gene

[Mike]

That's what I thought, Gene. Since the locomotive I was watching was a new out-of-the-box Spectrum C&O DCC, I was surprised that it wasn't synchronized. Maybe the owner needs to contact repair?!- Mike S.

[Jim Banner]

Are all of these soft synchronization or does anybody use hard synchronization in H0?  By hard sync, I mean a sound cam or a reed switch and a magnet or something similar so that if the axles do not turn, there is no chuff, no matter how much voltage is applied.  Soft sync implies that the cuffing starts at some motor voltage, and hopefully the locomotive starts at the same voltage.  I am wondering what happens with soft sync when more load is applied - starting up hill, starting with a long train, etc.  Do you reach a point where the chuff starts but the train is still sitting still?  With DCC, I would think back emf speed stabilization would help.  But what about dc?

[Nigel]

.....I would think back emf speed stabilization would help.  But what about dc?

The bemf works with DC too.  The decoder's control circuitry is not bypassed when operated on DC, rather the decoders control signal is the analogue voltage rather than the digital signal.

[Jim Banner]

Thanks, Nigel.  That has got to make installing synchronized sound a lot easier to install, including in dc.

[Mike]

OK- For clarification for me... you're saying that all Bachmann factory sound equipped HO locomotives have synchronized sound...  Correct? And, if you're saying that, is the synchronization controlled by back emf or by a physical trigger?- Mike S.

[Nigel]

Hi Mike;
By the bemf, there is no "physical" trigger like a switch or magnetic sensor on Bachmann sound equipped locomotives.

[Mike]

Ok, Nigel. Are you saying that the Bachmann locos have BEMF? Also, if they do, does that mean they should be synchronized correctly. I hate to sound so ignorant here; but I really am just try to find out if the Spectrum I saw had a problem... or if all of them are just synchronized poorly. The chuffs were nowhere near coordinated with the piston/rod movement. Thanks for your thoughts.- Mike

[Tim]

Hi Guys

A point of clarification on sound sync.

The syncronization on a new sound equiped loco will be close but not exact
for the following reasons. 

1: The decoder is tuned to a basic standard that represents the loco it is to
be used in, example 4-4-0.  All 4-4-0's will not operate exactly the same, so
some will be well synced others will not.

2: The mechanism will free up as it gets more running time an a loco that was
in sync when new will slowiy get off sync.

Just as you have to change the loco number from 3 to the cab number, you
have to tune the chuff to the proper sync.

BEMF decoders are less prone to changing over time because tjhey monitor
the speed of the motor, and can compensate.

Other Non BEMF decoders monitor the voltage fed to the motor, and can't
compensate for motor speed changes.

All decoders sound or not have to be tuned or set up by the owner for
best performance.

The sync of the chuff is your responsibility.

Tim Anders
Souderton,Pa

[Jim Banner]

Mike, being "synchronized" in this case means the cuffing starts when the wheels start turning and speeds up as the wheels turn faster.  There is no implication that the chuff occurs at the correct part of the cycle, i.e. at the point where an exhaust port opens, nor even the implication that there are exactly four chuffs per wheel revolution (for two cylinder engines.)  In fact, most model locomotives  are set up for two chuffs per revolution, otherwise they "don't sound right."

Even when the chuffs are synchronized with a cam or switch they are usually set at two chuffs per revolution.  It is a little unnerving when the locomotive is moving slow enough to observe the action while listening to the sound.  It is like watching a locomotive that has the valves and cylinder on one side removed.  Using this two per revolution gets even worse when you have a three or four cylinder locomotive.  A Mallet, for example, really needs two sound systems to sound anywhere near right. 

[morrisf]

The chuff rate is not controlled by an electrical contact. It is controlled by throttle setting, but is adjustable.

To adjust the chuff rate, change the value of CV116 until it is four chuffs per driver revolution at the speed normally run for the locomotive.

This will affect the operation on analog DC somewhat (particularly slow speed control), as you will experience.

If you get everything all messed up, you can reset the decoder to factory values (including the address) by setting CV30 to 2. Then you can start all over again.

Remember to change only one setting at a time and then test, so that you know what does what; otherwise, you'll lose track of what settings have an effect on things.

Morris

[ebtnut]

FWIW, I have not yet seen ANY loco with factory sound that had the chuff rate synced anywhere close to the driver revolutions.  Many seem to come close to 2 per rev, but not 4.  All DCC locos have the chuff generated electronically, increasing as the voltage increases.  They are not directly synced to the drivers.  While you may not get the chuffs to "fire" exactly at each 90 degree point, if you get them close to 4 per rev you'll be fine.  When you do try to set the sync, do it at low speed, where the effect is much more noticable to the eye.  At moderate to high speeds the chuffs begin blending together, and you can't really tell by eye whether there are actually 4 beat per rev or not.

[Mike]

Thanks, guys. Those last few posts got down to answering my questions. I guess the bottom line is that I'll probably just stick with my DC non-sound engines. (The only possible exception which I might make would be the 2-10-2 model of #5044 which BLI is going to release inlate 2007. Since I have the bell from that engine, I might just have to find a way to get the model!) Thanks again- Mike S.

[Virginian]

Okay, I have to weigh in here.  I have 6 sound steam locos.  3 are articulated.  The two cylindered locos are synched at 4 chuffs per revolution and were that way from BLI.  And they are not close to 4 chuffs per rev, they are at 4 chuffs per rev.  Two simple articulateds slowly go in and out of synch between 4 and 8 chuff per rev at relatively low speed.  At higher speed who can tell?  They came that way from BLI.  The compound Mallet has been set to start in simple at 8 chuffs and switches to compound and 4 chuffs about 8 MPH.  It came set up compound from PCM and I changed it per the instructions.
I do not see how 2 chuffs per rev could sound better when that is wrong.
I am ALL DC, but I have a BLI box and a PCM box and I passed reading comprehension.