It has been a couple of weeks since my last post regarding the Mallard Duke. You may recall I had a bit of a problem with it that meant a slight rebuild and some remedial actions. That complete I have now done a bit more detailing, but more importantly I decided it was time to have it move itself along the rails. So I completed the task of making up the cranks, reaming them out and fitting them. After a bit of tinkering I had the cranks in place and quartered.
I then looked at fitting the coupling rods. I decided I would used the Alan Gibson crankpin system, but instead of screwing into the wheels the screws go into the back of the cranks, a bush sits on the front, onto this is fed the coupling rod and then a nut added. Once the nut was tightened down it gave a fairly rigid fit, but I did have to countersink the cranks - somewhat hard after I had force fitted them on and quartered them. I did it with a burr in my mini drill without removing the cranks. I careful created a depression into the back of the cranks into which the Gibson crankpin sat. Partly this was required as if I left the screws proud of the back of the crank they caught on the rivet detail of the outside frames. It is all very tight in OO, I hate to think what it would be like in EM or P4 - lucky I don't work to those more exacting standards.
After more tinkering it ran reasonably, I did have to replace the pickups again, the little sprung loops were exerting too much pressure on the wheels, so I went for more springy wire and reduced the drag the pickups placed on the wheels. Setting up the wheels on the axles was a bit of a chore, clearances are very tight and getting the same amount of axle either side of the frames was difficult.
The next thing was to solder in the subframe that holds the inner frames in place and setup the fixing method for the frames. I also took the opportunity to add some lead in the firebox, the loco now sits happily on its wheels without the need to hang the tender off the back and will actually run as an 0-4-0 if the front bogie is removed.
Other little jobs including tender handrails, vents, fixings and lamp irons. Both the loco and tender now have turned brass buffers, the sprung heads will be fitted after painting.
The loco needs a top feed, pipe works for the top feed, clack boxes, lamp irons and the rest of the smokebox dart - once I make the part of have fitted no longer point at the sky! Not to mention of course the handrail, once the positions of rat handrail knobs have been marked out and drilled.
Below is a video of it running, it is not perfect, there is still a slight tight spot I think, but it runs reasonably well.