Having played around with my early issue Hornby Hogwarts Castle by converting it to DCC and adding headlamps and flickering firebox glow, plus a crew, I was less than satisfied with the running qualities of the Airfix-derived chassis.

Someone on these forums mentioned that the newest Hornby RailRoad County 4-6-0 chassis would be a good DCC-ready substitute, so I duly ordered one from Rails of Sheffield.

The wheelbase is spot on, but on comparison of the two chassis side by side, I discovered that there are several discrepancies that would make the swap slightly more difficult, with the two major problems being the cylinder positions and the position of the rear combined tender drawbar and body mounting screw, which was slightly further forward on the County.

After much head scratching, I decided that using the cylinders in the position of the County would be better as it more closely resembles that of a Hall, which is what the 'real' Hogwarts Castle is (Hornby didn't have a Hall model at the time, so used the Castle). I had already worked out that the chassis differences would not allow for an easy swap of cylinders and connecting rods. Allowing for the cylinders to fit under the Castle body meant filing down the depth of the footplate towards the front, which means that my Hogwarts Castle now has a shallow valance extending back to where the old cylinders sat. The repositioning of the cylinders also meant the 'S' shaped steam pipes were now leading from the smokebox to empty air, so they had to come off too; fortunately, they are separate mouldings which plug into holes in the smokebox and footplate.

In the meantime, I pulled the TCS M1 decoder back out of the old chassis and resoldered the main track pickup wires (black and red) and the brush feed wires (grey and orange) back onto an 8-pin plug, but left the white, yellow and blue wires from the decoder soldered to the 3-pin connector plug I used to allow separation of the body from the chassis before. A quick test of the chassis showed that this was all successful.

Back to the adaptation, I decided that the tender coupling should remain where it was on the Castle body, which meant that it didn't line up with the hole at the rear of the County chassis; I milled away a crescent shape at the rear of the metal County chassis to clear the screw while allowing it to set the chassis height at the rear, being hard against the rear of the chassis. The front mounting screw actually does most of the work of securing the chassis to the body.

A few minor adjustments to the footplate, mainly involving drilling holes to clear bits of the County cylinders and valve gear, saw everything sitting nicely and running well.

In all of this, I managed to dislodge the Hogwarts Express headboard, one of the headlamps, and the fireman I had previously glued in, so a quick session with the superglue saw all of those things restored to their 'correct' positions. I found some plastic tubing that was approximately the right diameter for some new straight steam pipes (maybe a teensy bit anaemic!), so set about trimming and fitting those by trial and error.

I'm not too worried about accuracy: we are talking about a fictional engine on a fictional train, running on a fictional line from a fictional platform at Kings Cross to a fictional destination! With that in mind, a hybrid locomotive with an identity crisis really fits in! Poor old Hogwarts Castle doesn't know whether it is a Castle, a Hall or a County!

Here are a couple of photos of it with the County chassis fitted but minus its headboard and steam pipes, no fireman, and with one headlamp pointing off into the scenery.

And after the fixes were applied.

The Knight Bus is one I hacked from two EFE models bought cheaply with the conversion in mind.

I think I'm happy with it now, although I may restore the valance depth a little behind the cylinders at a later date ... much, much later.