It looks like we've finally got to the bottom of what was the matter with Merddin Emrys.
You may remember a couple of weeks ago I posted about how Himself was going to remove and refit the power bogies and the drive shafts to see if that was the explanation for its increasingly arthritic performance.
Initial performance on Dduallt at the exhibition last weekend was promising, with it having a fair turn of speed again, but as the show wore on it slowed down to a crawl again.
Himself decided that he could no longer avoid opening it up to take a look at the motor.
This is not a simple operation on a Backwoods Fairlie.
As you can see from the picture above he had to remove the boiler / smokebox castings, the cab roof and the firebox wrapper to get at it.
He tells me that what he found under there was a motor caked in filth.
By twisting the motor around in its mount he could get to the brush holders, and having removed them, discovered there was barely anything left of them!
Fortunately there was just enough meat on them that the commutator had not suffered any damage.
Our Merddin must be at least 15 years now, and has run many thousands of scale miles on Dduallt and Bron Hebog, so I suppose we shouldn't be surprised.
He recovered some spare brushes from a disused motor and has fitted those and reports that it appears to have revived the locomotive, although it has yet to have a proper run on a test track because both the layouts are still packed away.
It says a lot for the regard in which Backwoods designer, Pete, held Mashima-san, that he was prepared to trap the motor in the firebox cradle on these engines so as to make it virtually impossible to remove them again.
He always said the only maintenance you'd ever have to do was possibly replace the brushes - let's hope he was right.
Himself is making noises about getting in a stock of spare brushes in case the Earl and DLG begin to show similar symptoms.