Longer term, I have ambitions to dabble in custom chassis. I've seen a few people on here who designed them to be 3D printed, although little evidence, one way or another, to suggest whether they have ultimately proven successful or not. I have my reservations, but also no experience, so I'll reserve judgement for now. The sensible option for project number one seemed to be to design something to fit to a commercially available chassis - walk before you run, etc.

Browsing through Nile's excellent thread lead me to the Electrotren 0-6-0 chassis. To my eye, it looks rather alien in most instances where it's been used to represent British outline stock, but it does bear a passing resemblance to the underside of the Swindon, Marlborough and Andover Railway - the predecessor of the MSWJR - Nos. 1-3:

From the excellent Swindon's Other Railway site.

Despite resembling shunting engines, they were diagrammed on passenger services for the SMAR for four full years despite a maximum speed of just 30mph and a frequent inability to match the published timetable. Eventually, in 1885, they were designated as goods locomotives. No.1 continued in service for the MSWJR until 1916, when it was sold on; Nos. 2 and 3 were sold together in 1906.

Measurements provided in Nile's thread, and elsewhere in the forums, suggest the Electrotren chassis has 14mm drivers, set to a 20+24mm wheelbase. This equates to 3'6" at 5'0"+6'0". The SMAR locomotives, had slightly larger wheels, set slightly closer together (4'0" at 4'9"+5'9") - two discrepancies that will likely visually highlight each other on the eventual model - but I hope the combination will still be passable. We'll see.

The chassis is available for just under £50 from Rails of Sheffield, brand new (or a little bit more second hand on ebay if you want to battle it out with the 0-16.5 modellers). I have one ordered, which should arrive next week. In the mean time, I thought I'd set to experimenting with modelling software. In my school and university days, I was spoilt rotten with ProDesktop and Solidworks, neither of which are a realistic proposition to have at home now. With that in mind, I've downloaded free copies of Sketchup, Blender and 123D Design. My initial impressions are that Sketchup doesn't provide nearly enough control, and Blender perhaps has exactly the opposite issue - I didn't make much progress with it before deciding to sit on it for a while... 123D Design was also a little frustrating, but feels the most promising of the three at the moment. There are still some fairly fundamental features that I've not been able to intuitively uncover, as yet, but I expect they will exist somewhere. And I have found it possible to fudge around these gaps to continue making progress, although it's very unsatisfying.

This is where I've got to to date:

I anticipate this model probably won't ultimately be used - once I've refined my techniques a little, I think I'll want to start it afresh and I've not had a first-hand look at the chassis I'm designing for as yet - but it's progress to share.

Thanks,
Mpeffers