QUOTE (Ed Allen @ 14 Jul 2008, 22:12)
<{POST_SNAPBACK}>.. Some weeks later I called back and was told that the wheels were coated with a hardened sticky substance which he was having trouble cleaning off. ... He said that only petrol would clean the muck off, and then with a lot of effort. .. anybody out there had a similar experience ?
The solvent required to shift the 'muck' is a good clue to what type of compound was on the wheels: most likely a lubricant residue (waxes and lacquers are also possibilities). Here's a surmise on how it got there: the factory machinery on which the wheels were made has to be lubricated, and small (invisible) quantities of that lubricant will be found on the wheels. A subsequent 'degreasing' stage should clean it all off, but it is only too easy for the first few items at the start of the day's production run to go through a cold degreaser, and not get efficiently cleaned. When the loco with those wheels is run it will pick up general track dirt, and the 'muck' becomes visible, and as it collects dirt it interferes with current conduction.
I had a similar experience a few years ago, the mechanism of the new loco worked the dirt into a dotted pattern on the driven wheel tyres, corresponding to the slight cogging of the somewhat stiff new drive. If the loco stopped with metal wheel surface in contact with the rail it would restart, but if it had only dirt in contact with the rail - no go! I had to use acetone to get the muck off, another aggressive solvent.