while the small 2-8-0 i have can move pretty slowly, about 1 in per 5 seconds, it has a bit of a “gallop” at higher speeds (maybe 5 in / sec). The gallop occurs once per driver rotation. Hope gallop is a reasonable explanation and is familiar to some experienced modelers.
is this a quartering problem?
how far out of quarter can the driver be to have such a problem?
is the only recourse to disassemble the wheels and re-quarter all of them, or can the problem wheels be identified and just those re-quartered?
Most HO steam locos have enough slop in the mechanism to tolerate drivers which are slightly out-of-quarter. When out-of-quarter begins to cause problems, you can usually spot the problem driver(s) simply by noting which driver counterweights don’t line-up with the others. The easiest way to check this is to run the loco until the counterweights on one side are at the bottom (or top) of their rotation. If they all line up, then check the position of the counterweights on the other side of the loco - they should all be vertical, either at the front or rear, depending on how the loco is setup.
The usual cause of out-of-quarter is one wheel slipping on its axle, and usually it’s enough to correct only that particular wheel.
I won’t go into the particulars of correcting it right now, but it’s not especially difficult in most cases.
Your “galloping” is more likely caused by a bind - perhaps the siderods striking a counterweight, or some part of the valve gear - sometimes such trouble spots can be detected by areas where the paint has been worn off.
Quartering (out of) can be one thing that will cause the gallop you describe. Another can be a valve control rod binding. Make sure all the valve gear rods are clear of all obstructions, and can move slightly beyond their proper travel throw in both directions. That’s probably the easier place to start looking.
I had one engine where the piston rod sliders were hitting the yoke, another where a valve rod was hanging up…
You can do an eyeball check of the drivers quarter by setting the loco on a flat surface, and make sure the counterweights on one side are all flat level to the surface. On the other side of the loco, all counterweights should be perfectly 90 deg to the surface. Ise a small square or some item you know is square to eyeball it against. Sometimes, this will reveal a set is out of quarter. Works best if the counterweights have a flat side on them. This may help save you some trouble of a complete teardown, maybe-maybe-maybe…[:S]Dan
If your engine behaves well at low voltages/speeds, it is not experiencing a quartering problem. Not even a cracked gear problem. My bet would be that you have a bent axle.
It happens. The engine moving slowly won’t show the wobble or yaw, but speed it up and the amplititude will become more noticeable.
Would this galloping loco be a Bachman 2-8-0? Very common for this loco to hunt from side to side at speeds above switching speed. Mostly caused by the light weight of the locomotive and the Unbalanced drive train.
You can spend days working on this loco but I am speaking from experience that it will always hunt somewhat. I had quartered my wheels, soldered the oversize holes in the stamped out side rods, clamped them together and used the frame spacing/axle bearing holes to ream the side rods to the right size to fit the crank pin screws. I cut out some of the split frame and filled the cut outs with lead wrapped in electrical tape to add more weight over the drivers. I got it to run fairly decent until the plastic gear broke between the motor and flywheel that drives the cogged belt. It is still waiting for shop space to open up.
I think that a bent axle would be very unusual, as axle stock is very similar to music wire in its hardness. You’d likely have to stand on the loco to bend it, and chances are it would spring back . [swg]
Probably the most common cause of irregular running of brass locos is interference between the side rods, or between the side rods and counterweights on the wheels. This can usually be corrected by either bending to various components to gain clearance or by inserting spacers to remove the interference.
If the previous owned has had the wheels and/or gears off the axles, look for them to possibly be not running true on the axles. Another problem area is tires loose or misaligned on the wheels. I recently repaired a 2-8-0 for a friend who thought that the wheels were out-of-gauge, but all eight wheels had the tires loose or misaligned.
If the worm is mounted on the motor shaft, as on some older models, the gear mesh may need adjustment - sheet(s) of paper or thin styrene is often useful for this.
Another area that may cause problems is the valve gear - usually this is from parts misaligned or not properly seated in the valve gear hanger, but I have seen misaligned cylinder castings causing binding, and piston rods or valve rods too long, and bottoming-out within their respective guides.