Click the film frame below to run a little QuickTime movie showing my 666 running full circle on Veijo Kivipelto's track:

Juhani Saloranta has made an ingenious little adapter, enabling him to run his 6" gauge O&K loco on 7-1/4" track:

It works splendidly, with virtually no slipping. The only "funny" thing is that in order for the train to run forwards, the loco has to run in reverse!