I got this Mantua Mikado off of eBay that I’m interested in re-gearing and remotoring. However, it does not roll freely as is. There is “resistance” at certainpoints as the wheels turn. Any tips on diagnosising where the problem is?
Should I take the the side rides and valve gear off, get the wheels rolling smoothly with side rodes, then add eccentric crank and valve gear back? Very difficult to see where the problem is.
How about the eccentric cranks? Are there any rules on what their relative positions should be to avoid binding? Any tips appreciated.
Yeah, you should take off the valve gear and main rods, as they just (usually) go along for the ride.
The position of the eccentric cranks shouldn’t affect the binding. I am assuming the piece is simply captured under the head of the screw, when it’s tightened. The crank is usually 15 degrees “ahead” of the neutral position–best seen by finding a good photo and matching it.
After removing the “stuff”, the bind should still be there. Do a LOT of thinking before filing anything–you can’t put it back. One thing you might try is taking each screw out, one at a time, and seeing if just one of them is causing a bind. If so, some gentle filing should solve it.
Of course, this supposes that the bind is caused by the side rods. It USUALLY is. Unless it’s not. So I suppose, really, the first step is to eliminate that possibility by fully removing the rods and testing.
It could also be caused by friction at the drivers axles. I had that problem with a Mantua. I loosenned the screws of the underplate and that fixed the problem.
The “eccentrics” that need to line up are the connection points where the side rod connects to each driver. If one or more of those are not in line you’ll get the symptoms you describe. The crank pin eccentric only drives one driver axle. The drive is carried to each other driver by the side rod which must line up at each driver connection pin.
Its called quartering which is a misnomer for electric model locomotives but the term includes lining up the drivers. Quartering refers to the 90 degree (usually) offset between the left side and right side crankpins. Since our models aren’t actually driven by the pistons this aspect of quartering is aesthetic only. But the other aspect is real enough. Out of line driver connections will cause binding.
When you reach the binding point in driver rotation check the side rods on both sides of the drivers to ensure the rod looks straight (your model seems to have articulated rods which makes this issue a bit easier to identify and fix). As you move the drivers back and forth at the binding point does one connection point at a driver seem out of line with the others?
I would start by removing the screws that connect the drivers to the side rods, one axle at a time. Then install the screws before you disconnect the next driver axle.
If the binding goes away with one driver disconnected, that would indicate a quartering problem on that one axle.
Disconnect the driver that connects to the main rod last.
I would start by removing the bottom plate and check to see if some prior old dried lube is binding the axles, you can do that without removing the side rods.
Mel
Modeling the early to mid 1950s SP in HO scale since 1951
