Adjusting timing on Stephenson valve gear - myLargescale.com > Community > Forums

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Old 08-22-2013, 10:34 AM   #1 (permalink)
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Default Adjusting timing on Stephenson valve gear

I just acquired a Catatonk Shay that had been ignored but apparently not significantly miss-used for a few years. All the parts look good and no sign of significant issues with the running gear. The problem I am having is when I fire it up, after clearing the cylinders, I can't get the Johnson bar positioned for forward running. It seems to run in reverse quite well, all the way from high speed to fairly slow. Switching the gearing from reverse to forward seems to bind the lift rod, and it seems that it is not positioning the link correctly to get the eccentric cranks in the correct position.

The bar moves back and forth, with due care since it appears to bind at the valves. In the past I know that if the links of this type of gear are not positioned right it will not time correctly. That is what it feels like as I try to rotate the drive shaft, it feels like the timing is way off in forward gear.

Does anyone have links to good setup procedures for this type of valve gear? I would like to fiddle with it a bit myself, but would not be against sending it to someone skilled with this machine who could give it a tune-up.

This is one of Mike Chaney's models. s/n 14

Joel
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Old 08-22-2013, 12:00 PM   #2 (permalink)
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Default RE: Adjusting timing on Stephenson valve gear

Hi Joel:

I have owned on of these Chaney Shays....once you get them sorted out they are good runners, one nice thing about them is the valve gear is true Stephensons rather than modified piston valve gear.

But be aware there are a few issues you'll need to sort through...the first is the crankshaft itself...this is not one piece but rather built up and held together by Locktite....it is entirely possible that something could have slipped on the assembled crank....Silver soldering is the ultimate answer and what I did to prevent any problems there.

On my Chaney Shay I had regular issues with the valve gear linkage slipping...there is a main shaft that the reversing lever attaches to...it is held tight by grub screws that can loosen....causing the two cylinders to get out of sync with one another....you'll need to look at the set up carefully and check to see if the two sides of the engine are operating in unison or out of sync. Solution here is get timing set up and then file a small flat on the shaft to give the grub screw something to bite into...problem of course if is you file the flat in the wrong place.

It is a great looking engine in operation when properly set up...just takes a bit of fiddling.

Mike Chaney lurks and occasionally speaks on this forum...add the phrase "Chaney Shay" in your subject line and you'' probably get a response from him with additional solutions...

Best Regards,
Cliff
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Old 08-22-2013, 02:55 PM   #3 (permalink)
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Default RE: Adjusting timing on Stephenson valve gear

Thanks Cliff, I went ahead and reposted. Probably get shot for it, but I agree, needed to attract other Shay owners.

I had heard about the crank shafts, and did notice the grub screws on the reverser lifting link arms. After looking carefully at the engine, I have no doubt it will run again, in fact it runs great in reverse. Just a bit of TLC is all she needs.
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Old 08-24-2013, 10:14 PM   #4 (permalink)
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Default RE: Adjusting timing on Stephenson valve gear

Hi Joel,
Back in 2004/2005 Paul and I sent our older Chaney Shays SE to Norm Saley for the replacement of the two-piece-glued-together-crankshafts with one [one each] of his one piece units. Paul's locomotive was so loose in the crank halves, that a local Mexican band wanted to use it as castanet backup for their ensemble gig on Friday nights! Paul also had big time going ahead problems [the castanet cycle], while going astern was lacking guts. Mine was OK, but the Locktited crank interface worried me. Norm fixed us both up with one piece crankshafts, and we are both happy campers.
The byproduct of his crankshaft replacement was that both locomotives were timed, locked down, and all the adjustment fasteners were Locktited in place at the time of final assembly. This is Locktite's design purpose; to keep machine threaded fasteners from vibrating loose. It is not a glue nor an error eradicator.
Norm hangs out at [email protected] .
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Old 08-25-2013, 09:23 PM   #5 (permalink)
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Default RE: Adjusting timing on Stephenson valve gear

Thanks for the clue. Yes, the more I look at it, the more it appears to be loosy-goosy around the cranks. Each cylinder has it's own idea of when it wants to be somewhere.

I will give Norm a ping to see if he still has the jigs and fixtures. Sounds like a worthwhile rebuild.

Joel
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Old 08-23-2014, 01:21 PM   #6 (permalink)
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I have built one of the two cylinder 7 1/2" gage Shay engines designed by Bill Harris in the seventies. I am totally confused as to how to time the eccentrics for the valves. As it sits now at 75spi the engine will if turned by hand pop over about 3/4 of a revolution. That is all.
I have messed with the eccentrics and gotten that much.
Can anyone out there provide some guidance for this total novice?
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Old 08-23-2014, 02:19 PM   #7 (permalink)
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Welcome, Bruce!

Probably best to launch a new thread, it's pure luck for someone to find your topic within another.

By asking "how to time the eccentrics," do you mean make the necessary mechanical adjustments to produce correct timing for the valve events, when those events should occur, or both?

Does your engine turn freely by hand?
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Old 08-24-2014, 10:42 AM   #8 (permalink)
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John Frank and I have Chaney 24 ton Shays. He has run his for many, many scale miles and I have run mine for quite a few too. Nothing has ever come loose. Beautiful engines.
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