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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.

construction

Decisions were made. This would be 0-2-4 configuration. Four LGB loco wheels were picked up via eBay – a pair of these will become the driving wheels of this vehicle. The bogie is from an LGB bogie stake wagon – acquired via eBay for a very reasonable price, else this would be a rather expensive way to acquire just one bogie. In the event the chassis of the stake wagon was adapted to form the chassis of this railbus and part of the floor of the stake wagon was used for the floor of the bus.

A chassis was made incorporating a 30:1 geared motor block from I P Engineering. Tricky to do as there is minimal provision for bolting the motor block to the chassis. (Why?) Things were almost all together when the plastic housing (seems to be a nylon casting) holding the gears in place broke. The fracture revealed that the cross-sectional area would have been fairly minimal – even if there hadn't been significant voids in the cross-section. In a word: 'Rubbish'.

One option was to rebuild a new chassis around the unbroken I P Engineering parts. But I also had a 30:1 geared motor from Essel Engineering sitting around. This has a 6 mm shaft so is compatible with the chunky moulded nylon bevel gears available from Motion Co (though strictly the gears are only compatible with 6 mm shafts by inserting metal bushings, but that's fine by me). The LGB driving wheels were moulded for axles a tad under 6 mm but were simply drilled out.

The Motion Co bevel gears have a 3:1 ratio (or thereabouts – I've not counted the teeth) bringing the overall reduction down to about 90:1. 'Way too much!' I hear you say. Not so, as this model aims to emulate Stephenson's Rocket so the driving wheels are the biggest I could get my hands on. And I'm not a fan of model trains haring around at ridiculous scale speeds. (Plot spoiler: seems 90:1 does indeed give about the right sort of slowish speeds.)

So a new chassis was constructed from brass strip, held together with M3 and M4 bolts. This time more care was taken designing and engineering a pivot between where the firebox of the Rocket will be and the front of the bus body. The wheelbase of this model is simply absurd so without it being a 'bendy bus' there is no way the tight radius of LGB track could be negotiated, even with a bogie on the back. Anyways, a good friend of a good friend used to drive twelve inches to the foot bendy buses in America, so it just seemed right…

On the front of the chassis a cow catcher (removed from the LGB 'Rio Grande' loco used to make Nellie) was mounted. And on the underside of the cow catcher a combination of sticky-back copper tape and Scalextric metal braid was configured to provide the electrical contact with the track.



 

 
Two views of the chassis before painting.


Once the chassis was more or less completed construction commenced on the locomotive parts. The firebox was adapted from the LGB 'Rio Grande' loco left over from the making of Nellie. The boiler emulates the construction of the Occre kit, but is twenty percent bigger and uses coffee stirrers for the cladding, glued to the bottom parts of two small plastic bottles which came with vitamins in. Inside the boiler is the cast metal 'deadweight' from inside the LGB 'Rio Grande' loco.

Diecast parts from the Occre Rocket kit were used for the cylinders and 'motion', augmented with brass tube and assorted other parts.

The 1:24 scale Occre B-type bus kit does seem too small after all. So the laser-cut sheets were scanned and enlarged by twenty percent. Printouts formed the construction drawings for a scratchbuilt body using the same construction method pioneered for the coaches inspired by the Giant's Causeway tramway.

 



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Images and text copyright Bob Trubshaw 2018–2021