It's sort of pointless to sync typical model articulated locos with a cam, because they usually have a single motor and are driven by a system similar to many diesels - so there is absolutely no way for the two engines to get out of sync, unless you stripped a gear. Adjusted close at slower speeds and it will be hard to tell there isn't a cam in it.
The ideal, for non-compound articulateds, would be two motors, two cams, and not have perfect balance so that the weight on both engines would not be indentical. And of course no traction tires. So one engine might slip while the other doesn't. Dunno if anyone actually makes a 2-cam input sound decoder, so maybe 2 sound decoders, one for each engine.
A compound articulated that doesn't have a bypass for starting will always be in sync, with only 4 beats, so a single cam, or just timing it to be 'close' is fine.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I just put a Soundtraxx in my older Big Boy. But a lot of the following will apply. Since the Big Boy is a two engine loco synchronization with a cam is not as critical. I don't know about Digitrax, but with Soundtraxx I just programmed the chuff rate for the 4 per revolution while on speed step 10 and then changed the sound to set up for the two engines, which in effect gives you 8 chuffs per rev. But the engines go in and out of phase so you get that really neat sound effect. To do that you need to set it up to asynchronise chuffs engine to engine, there may be something about setting up for articulated locos. I have seen videos of articulated locos where one truck(engine) spins and the other has traction which makes for really neat sound. I don't know if Digitrax gives you all that flexibility however.
Richard
As noted earlier, Digitrax has a thing called Auto chuff which is a programable chuff rate when a cam is not available. Some decoders allow you to use an optical cam where you glue a paper pattern inside one of the drive wheels. An opto sensor then picks up the pattern which basically does the same thing as a cam. I can tell you though that once you have the auto chuff set up correctly, people will have no idea unless they happen to stare at the drivers for a period of time.
Springfield PA
I believe the CAM wire is a lead from the back of a locomotive driver where the driver has been 'surfaced' to create "noise" as a follower (the cam) passes over the marks on the driver giving instant syncronization to the 4 'chuffs' per driving wheel revolution. This is a system of providing sycronization that has been around since before DCC. If the term 'CAM' means something else now; you have my apology.
Broken Tie
Look in the decoder literature to find what CVs to change for chuff intervals. You can get them close but not exact. On my locos I set the throttle at speed step one and program on the main to get 4 cuffs per rev of the wheels as close as I can get. Once its under speed then who cares how many a rev.as long as it sounds good.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
I just bought a digitrax DCC decoder with sound for my older HO big boy. The manual says something about the CAM input wire. The big boy doesn't have a CAM wire or at least I dont see it. Does anyone have any experience with the older big boy as far as syncing the chuffs for the DCC system?