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Reply to "671 Repair Questions - 1946 turbine"

@Ted S posted:

Regarding your angular measurements... If I understand you correctly, you're saying that there's enough "slop" in the side rod holes, that the next tooth in the worm wheel will ALWAYS be picked up by the thread of the worm, before the outside of the wheel is pulled forward by the rod.  YEP!! This is an amazing discovery, because it pretty much busts my theory that different "timing" between the front & rear worm wheels is the reason why some of these locos run very well while others are noisy and balky.  Maybe someday the true cause of the widespread variation in running quality will be found! As in ALL theories, the proof is in the pudding. It wouldn't surprise me for somebody else to challenge my conclusion and provide a more accurate one!

I'm not surprised at your 23-tooth count.  There's a design philosophy that says if you want the mechanism to be long-wearing, use prime numbers for tooth counts so that over the life of the mechanism, wear is distributed evenly over the whole gear.  In this case, it looks like it worked! Did not know that! Now I have to forget something else to make room for that new found bit o' knowledge!

One more thing-- you don't necessarily have to pull the driver.  Try wedging a slippery plastic "bread clip" between the wheel and the frame, or even inside the chassis between the worm wheel and the frame on the opposite side.  (You can also use material from a plastic milk jug, etc.  Cut it into a circular shape smaller than the driving wheel.)  Among Berkshire owners this is known as the "bread clip mod."  Do this as a temporary fix to see if it improves performance.  And take comfort in knowing that If you do have to remove the wheel, you have at least 7 degrees of forgiveness when it comes to re-mounting it "in quarter." Too late for that, I have one wheel off already! As I pulled it, I realized I don't have wheel cups for this puppy!! A quick call to Jeff and he had a remedy in hand before I could even blink. He has a single set of universal wheel cups for my press - fits all 5 wheel variations. I will be using 671M-23 thin washers, about 0.010" thin to be specific. That way I can easily stack them to get the fit I want to reduce lateral play, eliminate the flange from rubbing on the frame, and help to keep the worm centered on both axles. I will be pulling all wheels before I'm through 

Great discussion here!! Yes it is! And BTW, that horizontal e-unit is the best thing since sliced bread. The spring resolves a couple of issues - horizontal mtg to reduce overhead, it eliminates the unsightly lever stick up through the boiler, and it would seem to eliminate the "hanging pawl" syndrome where the e-unit remains stuck in a gear until thumped or tapped - my experience with that is that the drum gets a single groove carved into it by the snapping action of the pawl - kind of cuts into the plastic a bit and leaves a very narrow "shelf" for the pawl to rest in when the power is cycled. A single edge razor blade cleans that up easily, just got to cut slowly!

A  

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