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Rocket-powered B-type railbus


As a teenager one of the management's few ventures into 1/32 scale modelling was to adapt the Airfix kit of a 1910-era B-type bus into something more like a tram body. This ran behind a scratchbuilt tram locomotive running on a Triang Big Big Train wheels and motor. However these fell victim to a major 'decluttering' exercise when the management's parents moved house a couple of years later, just prior to setting off for art college.

When the management acquired a substantial amount of Hornby track and rolling stock late 2016 and early 2017 then memories of this juvenile kit bashing came, somewhat unclearly, to mind. After all, about 45 years had flowed under the proverbial bridge in the meantime. Much to the management's surprise the same kit was available at a reasonable price via eBay, and duly acquired. However, as recounted elsewhere, trying to model 1/32 scale rolling stock on the Hornby track proved to be a dead end.

But when Whittlecreek and Eaton St Torpid Heritage Railway came into being late 2018 then the B-type bus once again came to mind. Lo and behold, there's a 1/24 scale laser-cut wooden kit made by Occre. Who also make a model of Stephenson's Rocket to the same scale. Why not combine the two, creating a Rocket-powered B-type railbus?



 

 
How the Occre kits are supposed to be built.


Those who have been paying attention will recall that there's already been a Rocket-powered model from the Jackdaw Works, so combining the B-type bus with the Rocket might seem a tad déjà vu. Although, pedantically, the Rocket-powered hot rod came to mind after the inspiration for the version of the B-type railbus. And the hot rod is only a static model transported on a flat bed – there may well be a different load for the wagon to transport in due course. Indeed, there's already the Nukiller Waste Transporter.

The management realised that a railbus based on the B-type bus would be ideal for pulling the Lazybeach Special, although Nellie could also do the job too. In a moment of rash expenditure (neither are cheap!) the management acquired both the Occre kits. (Yes, Whittlecreek and Eaton St Torpid Heritage Railway is modelled at 1/20 scale, but hopefully the twenty percent difference in scale won't be too noticeable!) While the kit bashing required to combine the two laser-cut kits is not overly intimidating, this could only sensibly proceed once the chassis was constructed. And constructing a chassis required linking up a motor with the necessary gears and wheels.

But the management, ever prone to prevarication, couldn't decide whether this should be powered by a two-axle bogie (configured as either 0-4-2 or 2-4-0 – i.e. bogie under the boiler or bogie under the back end of the bus) or by actually driving the Rocket-like wheels either side of the boiler. As the Rocket-like wheels would need to be connected to con rods to make the pistons seemingly work, then it made more sense for these wheels to be powered (i.e. 0-2-4 configuration, with the bogie under the bus unpowered). This would require scratchbuilding the gears and axles. Not something the management initially felt confident to take on.

However, six or seven months later – after completion of both Sir Toby (which used a rather expensive bought-in motor-gears-and-wheels subchassis) and OctaVee (which didn't, and was the management's first attempt at scratchbuilding a motor-gears-and-wheels subchassis) – then the necessary mechanics seem within reach. The plan is to construct the 'first Porsche' next – as this also requires a scratchbuilt motor-gears-and-wheels subchassis – to gain a little more expertise.

But all the necessary parts are coming together as, while at the National Garden Railway show in April 2019, the management discovered some smallish geared 12–24 volt motors on sale from Essel Engineering for the reasonable price of under 12 (including a fixing bracket). These are small enough to fit inside the firebox of the Rocket and have the right sort of gear ratios. One has been acquired and looks the biz, although no attempt has yet been made to assemble with axles and wheels. A few months previous, four LGB loco wheels were picked up via eBay – a pair of these will become the driving wheels of this vehicle. The bogie will no doubt be based around Whittlecreek and Eaton St Torpid Heritage Railway's 'standard issue' Binnie Engineering's axles, axle boxes and wheels, held together with a scratchbuilt chassis.

update:

Contrary to previous reports that progress was deferred, in practice this project is progressing at the expense of the 'first Porsche' – though not at the expense of the 'Doof Wagon' or a Valkyrie speeder.

The interminable thoughts about which way to configure the motor and gears were finally terminated in favour of bevel gears from Motion Co on the output end of the the Essel Engineering motor's integral gearbox. Even though the Essel gearbox has a 30:1 step down (typical for model railway motor blocks) I opted for a further 2:1 step-down on the bevels. Not because I want the railbus to crawl along spectacularly slowly but because the driving wheels need to be quite large to emulate the Rocket. Large driving wheels are necessary on steam locomotives designed to pull express passenger trains but nothing like what would be fitted to a real-life railbus, steam-powered or otherwise.

The boiler is from the Occre Rocket kit. However the firebox is from the LGB 'Rio Grande' loco left over from the making of Nellie.



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Text and previously unpublished images copyright Bob Trubshaw 2018–2019