Joy's Valve Gear for an LNWR Precursor Tank

Joy's indirect valve gear module.

The removable valve gear unit seen here is built from a set of nickle silver castings produced by LGM. The mechanism is non-working or cosmetic, it does not include a crank axle nor the connecting rod big-ends, though the front parts of the connecting rods, which attached to the piston sliders, are present as the swing links and their dependant linkages are attached to them below the radius block. Only the "front end", that is the parts of the valve gear that can be seen below the boiler, has been modelled. The jointed, pivoted and sliding parts of the valve gear do indeed move, they're not soldered solid, so it's as near working as possible and everything moves in an appropriate manner if you tweak the connecting rods. I think with what I've learned making this model I might be able to build an actual working set for a future project. Laurie's instructions are helpful though I found the best guide to building Joy's valve gear was Geoff Holt in "Locomotive Modelling" Part 1.
The centre frame member, which protrudes to the rear of the motion plate, provides a third point of support to the crank axle in the prototype. In the model the inverted "U" shaped cut-out provides clearance for the front axle.




It's a busy place between the frames under the boiler and rather murky too!

If you peer carefully under the boiler you'll find that quite a lot of the valve gear is in evidence, in addition the anchor link and its supporting stirrup are visible below the frames, behind the front brakes and below the sand boxes. The brackets which carry the transverse shaft, on which the anchor link is mounted, are attached to the lower slide bars, these are out of site though they have been situated and designed so as not to foul the bogie wheels on corners.







Joy's Indirect Valve Gear in situ.

Joy's indirect valve gear adds another layer of complexity to an already fiddly business by the inclusion of rocking levers, seen here between the curved radius rods and the valve spindles.

The red electrical wire that can be seen is a pick-up wire, which is struggling to find a way through the valve gear to its connection on the front bogie.