I have an old PCM 4-8-4 where when it runs the engine will hop about once a wheel revolution. What is causing this to happen and is there any fix for it?
sfb
Sounds as if the drivers of the loco are not properly quartered. This causes the side rods to “bind”, affecting this “hitch in the gitalong”.
Top of the morning to ya.
Your problem could be a lot of different things. From a chunk of crud on a wheel to a gear with a busted tooth. I would start by carefully taking the loco apart one piece at a time. eventually you should find what is making it bind up.
It could also be a bent side rod or a binding siderod, which can possibly be fixed before tearing it apart.
I would first Put it upside down in a cradle and connect it to power and watch carefully to see if the siderods appear bent or to bind when it “hiccups”.
If it appears a side rod is bent, you can bend it back to a straight position carefully with pliers.
If the siderods appear to bind, try a TINY drop of Labelle oil {on the end of a toothpick} at the connecting points of the siderods to help lubricate them.
If That fails, then you can proceed with tearing it apart if you desire to look for cracked gears or change out of quarter drivers.
just a suggestion. Others may vary.
[8-|]
Does it have those hard plastic traction tires?
Pete
I don’t know, I will check.
sfb
Another possibility is something interfering with the crosshead or piston rod. Maybe see if a fastener in that part of the mechanism is loose or out of alignment?
I have had a couple of locos with this thumping problem and in each case it was an out-of-quarter driver - I have been lucky so far avoiding the cracked gear problem on steam locos. (Oh dang, now I have to find some wood to knock).
Running the loco real slow might show a driver that lifts slightly or the side rod will move differently when it binds.
If the out-of-quarter condition is slight, and if there is a way to remove the fastener holding the rod to the drivers you can use a small round file to slightly enlarge the hole. You can’t do this too much or you create too much looseness in the mechanism. I have done this with a couple of kit-built locos.
My 2 cents…
George V.
Nope, no traction tires.
[sigh]
sfb