Thanks for the advice.
I did remove the cover on the axle gear and saw that the nylon gear looked in good shape, possibly a little dry so I put a small amount of labelle lube on it.
Ed, I see that there are 2 screws on the back of the cab and I assume that there is a long one under the pilot truck. If I remove these will the boiler, cab and pilot just come off in one piece? I have taken the 'boilers' off of plastic locos, e.g. replacing a chuff sensor on a BLI mikado, but have no experience with brass. With plastic, the pilot usually stays with the chassis. I don't want to damage anything.
I will look at getting a set of rollers. I have considered doing so before.
By the way the engine does smooth out going forward at a high throttle setting.
CN Charlie
One of the best diagnostic tools I have for locomotive "tuning" is a set of these roller stands:
IMG_6625 by Edmund, on Flickr
I connect a DC supply directly to the motor and allow the drivers to turn at various speeds.
https://www.walthers.com/display-test-stand-rollers-e-z-riders-tm-rolling-w-ball-bearings-for-powered-axles-pkg-4
This allows me to "poke around" and look for binding, stiff springs or thrust washers worn or out of place. Sometimes I have diesel drive trains that have a "squeak" or a rubbing sound that I can't locate. These stands allow me to try to pin-point the source of the friction.
In your case of running well in reverse but not forward, you might have to look at the condition and positions of thrust washers in the input shaft of the grarbox mounted to the driver.
If the locomotive has spent a majority of its life running forward, that will put a lot of friction (wear) on the rearward set of thrust washers. This also has the effect of mis-aligning the worm gear to the spur gear. Does your loco have an actual gearbox or is it open gear/worm?
This can also transfer the thrust to the motor shaft and if the thrust bearings in the motor shaft are worn you will get increased friction, thus current draw.
Using a DC power source with an amperage readout can help so you can witness the current draw while you look for binding or friction:
Meter-A by Edmund, on Flickr
Some locomotives should have a "torque arm" in order to avoid having the rotational force of the gearbox transmitted to the motor. This reduces the chances of the force or pull being applied to the drive shaft and then to the motor.
I'll try to find a "clinic" I came across once that had some good information in this regard and update mthis reply when I find it.
[edit]
Here it is. (eat the meat, spit out the bone)
http://schutzer.net/Brass_Clinics/RebuildingBrass2008a.pdf
Good Luck, Ed
If nothing is bent or cracked inside, it might be the quartering. You'd think the bind would work both ways, but perhaps not.
There should be a gear cover held on by two screws under the frame. Remove that and clean out the old grease and lubricate with two drops of clean oil.
.
If that does not fix it, remove the boiler and the motor and see it it rolls freely by hand.
Also inspect for any dust build up inside the gears.
-Kevin
Living the dream.
CNCharlie I'm thinking it could be the gearbox is gummed up. CN Charlie
I'm thinking it could be the gearbox is gummed up.
That would be my first thought as well. Another thought would be to disconnect the motor, and try rolling it on a straight piece of track to see if there's a bind in the drivers. If there is indeed a bind in the drivers, start disassembling the rods until you can isolate the bind.
Recently I purchased my first brass loco. It is a CNR Hudson manufactured by Samhongsa in 1978.
While it is a very nice looking loco with rare factory paint, its running quality leaves a lot to be desired.
It runs fairly well in reverse but has a hesitation going forward with each revolution of the drivers.
I gave it a light lube and checked the drive axle gear which seems ok. I also cleaned the wheels. I have been running it back and forth on my workbench as my layout is DCC. It is running somewhat better now.
Perhaps someone here can give me some guidance as to why it runs fairly well in reverse but not the other direction. I'm thinking it could be the gearbox is gummed up.
I'm aware that Samhongsa locos of this vintage don't have a reputation for great running, but if you want a CN Hudson they are pretty much the only option. Yes I'm aware that Hobbycraft Canada did get BLI to do a run of them about 2005 but just try to find one. If you do the price will be very high.
Anyway thanks in advance for any suggestions.