Having got the Hunslet as far as I could without the boiler, I started to think about what to build next. Initially, I decided to build an 0-4-2 tinkerbell for personal use, because it would give me a reasonably powerful, self-contained engine. It wouldn’t be up to lugging big trains round Swanley park, but that wasn’t something I was interested in. Discussion with various people came up with the following:
· Make the cab longer so that ordinary people can drive it without toasting their knees (3” longer)
· Use smaller (8”) driving wheels to get more power
· Use the locomotive rather than the marine boiler (steams better and provides more steam)
· Using the above, bore out the cylinders to 2.75”
· Roller bearings wherever possible (axleboxes, motion etc.)
I sketched out various options with several wheel arrangements, from the standard 0-4-2 up to a 2-4-4:
In the end I decided to go for an open cab 0-4-2 as this would make keeping watch over the passengers on the portable track much easier. I was undecided about Heywood valve gear – experience with Rosie shows that although it is simple to build, parts of it wear alarmingly quickly. I had part-designed a replacement Walschaerts gear.
I turned wheels for the rear pony and built it, then got blanks for the driving wheels. I started to turn them at the SNBR workshops when a fellow member (who is Rosie’s regular driver) asked me what I was doing. We spent a long while talking it over, and he persuaded me to make it a little bigger – to give the SNBR another large steam engine. Everything I had done so far could be used in such a project. I immediately decided on the name Jim as it was to be a friend for Rosie (ask your children/parents to explain if you don’t get it).
So, I decided to ask Jim Haylock for some advice (who else would you ask about big sit-in engines ??). A visit to the MVR and Jim’s helpful advice made me decide to make the engine a 2-4-4T, like Jason and Hartfield. She is to have 3.5” bore x 4.25” stroke cylinders, with one of Jim’s standard boilers. I took lots of photos of Jason, and returned home to think.
I ended up with a bit of a cross between the two engines, 90” long (yes, a 7'6" long tank engine in 7.25" gauge. . .), 26” wide, and 48” high. Walschearts valve gear was a must, using Charlie Dockstader’s program to calculate an optimum setup. Laser cutting is to be used to make life as simple (and accurate) as is possible, with many MVR-like parts, sourced either from or via them or their suppliers.
A half day spent driving Jason during the summer showed me just how good an engine she is – easy to drive and fire and with enough power to pull a couple of houses down. In fact, everything you need for a big, commercial steam engine. Oh yes, and the cab is a delight to sit in – comfortable, spacious and sheltered from the sun on what was a very hot day. I just couldn’t find fault with her as a driver.