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38 Ton Shay Sound System problem

Started by Mt Beenak, January 17, 2008, 05:24:07 AM

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Mt Beenak

I have a 38 ton, two truck shay. (1:20.3)  Added new style trucks after two years running, goes better than ever.  (Love the shay and the climax!)
I used a simple 'chuffer' sound circuit for years which reacted to track voltage.  I have tried upgrading to a unit which is activated by the Shay piston activated switches, but no luck.  I get a permanent closed circuit on the board.  I loosened the two screws beside the cylinders and it works intermittently, but I cannot get it to work properly.  Any ideas would be appreciated. 
Are there quality sound boards which work off track voltage, or do I go back to the 'chuffer'?

Matthew (OV)

Try this:

With a small flat bladed screwdriver, gently pry off the cylinder heads (3) on your Shay.  The chuff contacts are little copper fingers found directly below.  As each piston rises, it pushes the two fingers together.  The three cylinders are wired in parallel, so that closing any of the three sends the "chuff" signal to your sound board.  Often, these fingers will be bent so that one or more are stuck together permanently, resulting in the problem that you have.  You can use your screwdriver to GENTLY lift the top finger up a bit, bending it slightly until it's no longer permanently in contact with the one below it.   You can test it by disconnecting the drive shaft at the square universal joint, turning on the sound, and slowly rotating the crank to see that all three are hitting.  The chuff is triggered when the piston approaches the top of its travel, so if one isn't working you can tell which one it is.

Some people have the opposite problem, where you get a "chuff chuff (blank)" pattern ... in this case the fingers (on one cylinder)  are bent too far the other way and aren't making contact at all ... or in some cases have had one finger break off.  (if it's two, it'll be "Chuff-blank-blank" or three "blank-blank-blank" ... get it?) The same kind of bending (except in this case down instead of up) can be applied to fix this, unless it's broken off, in which case you have to get a set of "sound breaks for a shay" from Service, and change them out. 

The important thing is to be very gentle and judicious with your bending so you don't fatigue and break the finger you're adjusting!  This is a very thin piece of copper, and just a little pressure will do it!

If you're using a phoenix, there is an adjustment that automatically doubles the chuff for the prototypical six exhaust beats per revolution of the crank ... or you can leave it at three, and hear more distinctive chuffing at normal operating speeds if you like. 

The transistor fix for the K27 simply inverts the chuff from "normally closed" to "normally open" for the way most large scale sound systems see their chuff pulsing....  with the Shay it's a lot simpler fix, and not related to the transistor discussion at all.

Matthew (OV)

PS.  Oh, and tighten up the screws you loosened!

Mt Beenak

Thanks for the advice.  I had already tightened the screws, and i had found the cylinder caps and tried adjusting them.  The caps seem to force the top contact down a set amount.  The system worked intermittently with the caps off, but not at all when I replaced them.  Again the only way to get them going was loosening the screws and holding the cylinders away from the body. 

In relation to replacing the contacts, I cannot figure how to remove the cylinder assembly from the cabin.  I could not find any further screws to remove, and one of the screws up throught the ashpan has been put in cross threaded and refuses to come out!  Is there a trick to taking the cylinders off?

Mick (Mt Beenak) in Oz.

Matthew (OV)


Matthew (OV)

PS.  If putting the cylinder head on is causing the problem, they're probably both bent up too high.  Press the bottom one down, then the top one, so that they're not touching, but still bent down a bit.  It may be that the whole sound break is loose or misalligned on the back of the cylinders, so if you follow the above instructions to remove the engine assembly, you'll be able to see and correct it.

Mt Beenak

 ;D After viewing the web site suggested by Matthew (OV), I took the plunge and fully dismantled the ashpan and cylinder gear.  I found at least three obvious but simple problems, fixed them all and re-assembled.  IT WORKS!  Thanks for the help guys!  :)

Mick of Mt Beenak, Down Under.

Matthew (OV)

You're welcome... glad I could help!

One of the best things about the large scale community here, and places like  and is that everone is generally willing to help each other out, and share the "how we did it" parts of our railroads.

Now, let's see some photos of your Shay at work!

Matthew (OV)