# 3 Truck Shay Chuff Seneor Question



## Bill Swindell (Jan 2, 2008)

Has anyone figured out how to use the chuff sensor in the Bachmann 3 truck Shay? I have tried several times to get it to work on Phoenix sound systems and nothing happens.


----------



## K27_463 (Jan 2, 2008)

Bill 
I have always mounted 3 magnets 120 degrees apart on the solid disc wheel and set the Phoenix up for 2 hits per pulse to give that classic shay whirring chuff. There is no other way to get the correct sound with the installed trigger as it will not correlate to the correct 12 chuffs per crank shaft revolution of the prototype. 

jonathan/EMW


----------



## Bill Swindell (Jan 2, 2008)

I have found that the factory chuff sensor doesn't seem to do anything at all. So far, I have just given up and used the auto-chuff.


----------



## artgibson (Jan 2, 2008)

In my post above, would making the chuff doubled make it more like the real thing. Using the interface with Phoenix. I disconnected the chuff on the Bachmann also.


----------



## Greg Elmassian (Jan 3, 2008)

I haven't looked at the chuff hardware on a 3 truck.. I know the 2 truck has 3 switches, one on top of each cylinder... not the same arrangement on the 3 truck? 

Regards, Greg


----------



## David Buckingham (Jan 2, 2008)

The Shay does six beats from the engine and mine (Accucraft} is geared 2 1/2 to 1 so 2 1/2 times 6 equals 15 beats 
for every rev of the driving wheels. 

This is a lot but Shays run slowly and using Jonathans method magnets on the rear truck wheels and multiple hits from the Phoenix works very well in my case. 

Dont know the arrangement on the Backmann rear truck. 

Dave


----------



## TonyWalsham (Jan 2, 2008)

As far as I know the chuff arrangement on the cylinder heads is the same for the two truck and the three truck. 
I would have thought there should be 6 beats per shaft revolution. Two per cylinder.


----------



## Greg Elmassian (Jan 3, 2008)

According to George Schreyer, (and TOC has confirmed also), there are "leaf" switches at the top of each of the 3 cylinders, so you should get 3 beats per crankshaft revolution. 

Bill, did you find and test the chuff switch wire? No result? As I remember, all three switches are connected in parallel, and reference to the frame as ground, but I could be in error here. George or TOC will know for sure. 

Regards, Greg


----------



## Bill Swindell (Jan 2, 2008)

on 2 separate 3-truck Shays, I have measured the continuity between the 2 wires that are from the chuff sensor. In each case, there appears to be some resistance between the 2 leads with no change as the cylinder shaft is rotated.


----------



## Anthony Duarte (Dec 27, 2007)

Posted By TonyWalsham on 27 Oct 2009 01:22 AM 
As far as I know the chuff arrangement on the cylinder heads is the same for the two truck and the three truck. 
I would have thought there should be 6 beats per shaft revolution. Two per cylinder. 
You are right, there should only be 6 chuffs per revolution. 12 chuffs per cylinder would mean we're dealing with a 6 cylinder shay


----------



## David Buckingham (Jan 2, 2008)

As I said above six from the engine but dont forget in my Accucraft loco it is geared 2 1/2 to 1 

So 15 chuffs per WHEEL revolution 

Dave


----------



## Greg Elmassian (Jan 3, 2008)

Talked to TOC today. The switch is shaped like a capital E made of 2 pieces of brass with a plastic separator. Each of the three fingers of the "E" is closed by the pin in the cylinder. Apparently you pull the cylinder caps off to see the switch for that cylinder. The contacts can get bent so there is no contact, or always contact. They take periodic looking at. 

You might want to pop the ends of they cylinders off to inspect them. Apparently the operation then becomes clear. 

If you do so, I'd like a picture, I recently sold my shay. 

Regards, Greg


----------



## TonyWalsham (Jan 2, 2008)

The wafer contacts are notorious for breaking where the wires are soldered to them. 

Remove the two screws holding the engine to the frame. Then remove the ash-pan and you can see where two plastic eccentric spacers behind the engine are turned to hold the engine to the frame. Align them with the slots and the motor will drop out with the wafers in place. 
I bend the bottom contact at an angle at the end so that it makes better contact with the wafer above. Leave it gapped slightly so that it goes open circuit when the push up plunger on the pistons drops down. 
I would re-solder the chuff wires to the wafers and anchor them to prevent them breaking.


----------



## Bill Swindell (Jan 2, 2008)

Thanks for all of the help. I will have to wait for the next project since I already gave the latest one back to the customer.


----------

