Spectrum Decapod "Jamming" in FWD. Ok in Reverse

[Capt. Grimek]

All of a sudden my HO/DCC sound equipped Spectrum Decapod (Russian) is acting up and I can't figure out why. It runs fine in reverse. IN forward it runs one half revolution of the driver(s) and stops and vibrates/grinds lightly. When I put a tich of weight with my hand on top of the boiler it will go forward slowly for a bit. The driver is not 90 degrees apart (less) but then this loco ran fine for hours without wobble etc. It runs fine in reverse so figure quartering is not the problem. I took off the gear plate to see what's what but the gears are clean and greased (this loco has only been run for a couple of hours-4 hrs.) I see a slight "cupping" or U shaped area on the rear of the white plastic gear (left to right not fore and aft) is that "cupping"? and a little bit of "fuzzing" or angel hair standing up from the teeth. Is ANY of this normal wear even relatively quickly? No shavings. Got this in 2008 so not an early model with known cupped gear problems. Anybody got pics or a link to see what that looks like? I have NOT tried turning analog operation CVs to off yet. But this loco has always run fine although a little grindy which I assumed was it's five wheels in a rigid frame/track noise. All drivers wiggle freely, all screws are tight, have lights, etc. Any ideas what to try next. This is my very lst loco troubleshoot/repair. I'm using the Kalmbach book maintating and repairing by Jim Vollhard. I haven't run it upside down yet have to make up some clips but I don't see anything binding other than maybe (?) the gear. Thanks!

[Capt. Grimek]

http://www.modelrailroadforums.com/forum/showthread.php?t=11415&page=3 Just found this fantastic thread (page 3 by cjcresent) on another forum. I haven't had the nerve to tear things down this far but after removing the gear plate I couldn't see any flash on the axle bearings. Would the loco have run fine previously if there was any? I got a pretty good view from the underside only through the gear plate. Anyway the great step by step pics should help others so wanted to share it. If anyone can make the link live, feel free.

[richg1998]

 http://www.modelrailroadforums.com/forum/showthread.php?t=11415&page=

rich

[locoi1sa]

 Capt.

  It runs fine in reverse but not in forward? Remove the main rods to the cylinders and slide the piston rods from the cylinders and leave all the other links on the loco and run it again forward and reverse. I suspect you have a rod or piston rod jamming or a cross head that has become dislodged from the slides.

         Pete

[cacole]

 Run the engine very slowly forward and watch the drive rods, fist one side and then the other, for any binding or rods catching on bolt heads.  It's possible that one or more side rods have been bent inwards through handling, and are binding on each other or on the bolts that hold the rods to the wheels.

 

[Capt. Grimek]

Hi Pete and cacole, Thanks. All rods and other linkage are free to move and jiggle when wiggled lightly with a pair of tweezers. I can't see any bolts,screws, etc. protruding and catching on anything. I can rotate the drivers a bit before they stop which I presume is fine as they do stop (can hold on a down grade). I'd think they'd catch when the loco is in reverse as well if that were the case? Would any of this be caused by having the analog CV on if there wasn't trouble running in the past? If the gear's little hairy teeth were the cause (some kind of gear binding) wouldn't there be the same behavior in reverse as well? I have not yet dismantled the valve/driver linkages as they don't seem to be binding anywhere. If I take this loco apart and have trouble reassembling it completely, will Bachmann still honor the lifetime warantee or do I need to keep it assembled/whole? Thanks.

[Capt. Grimek]

Oh yes, thanks Rich for bringing the link to life for us all. Check it out, it's a great guide-if I get up the nerve. If I can send a partly re-assembled loco back to Bachmann I guess I'll have more nerve. Cheers.