Hi Paul,
My experiences in dealing with Mamod haven’t been to good either. I have spoken to them asking about buffer beam overlays for my Boulton, the chap on the phone didn’t know what I was on about. I also emailed them on this and other enquiries and never received a reply.
I am surprised at the chassis failing as I know it is made by Essel, I have several Essel locomotives and they have all performed (and still do) very reliably indeed.
Having said that, the roundhouse chassis certainly suits the loco, you have done a superb job.
Regards Alan.