Saturday 26 January 2008

... Loco Motion

Motion: Part the Second.

On the right hand side of the D49/2 is the valve-gear; slightly different in that it has Lentz rotary poppet valves. A crank on the foremost driver rotates bevelled gears which drive through a shaft into the cylinder. Further gears and shafts operate the valves in the two cylinders.

Whilst relatively straightforward, the model set-up involves the mock gearbox "floating" on an etched arm and the drive shaft. The bracket, which in real life is attached to the footplate, serves no use in the model and the lining up of the components requires a fair degree of care.

There are no joints to manufacture on this side other than to solder the crank onto the crank-pin capturing the coupling and connecting rods and ensuring that the other end of the crank corresponds to the centre of the wheel. This was done by eye and I think is reasonably successful. If there is any slight misalignment, it is not obvious especially behind the gearbox.

The gearbox is manufactured from a fold up etch onto which we solder a small tube, to take the shaft, and a piece of 0.3mm wire to attach the arm that holds it. This seemed to be going swimmingly until I came to attach the whole to the chassis. On trimming the wires, I loosened the shaft tube; obviously the soldered joint was poor! Reattaching it, now that the gearbox was in-situ and the wires had all been trimmed, proved to be somewhat testing. Eventually I was happy that all was secure and in the correct place. Files and abrasives cleaned up the assembly before the whole chassis was given a thorough wash in the bathroom basin.

I consider the last few days work a success; despite all the gubbins which now adorns the chassis, it still runs very freely - better than I could have hoped for. I have learned some new techniques and pushed back my own modelling boundary a little further. Truth be told, despite the setbacks the motion has actually gone together much less painfully than I thought it would; I guess I can still surprise myself.

Now onto the bogie/pony (?) and then lets get some power to those wheels!


Anonymous said...

Well done Tony!
I've been following your blog account, though lurking somewhat, and letting you get on with it.
I've always said a lot of the fears that put people off, are all in the mind.
In 'having a go' you have taken that step that can lead to success if you keep at it.
Knowing the designer, who can supply back up replacement parts if required, can also boost confidence!
Still a little way to go yet, but it will be worth it when she starts rolling along on her own.
I await the day you show it off the finished model at Bournmoor.


Yorkshire Square said...

Thanks for the kind comments, Bob.

I'm certainly enjoying building the kit. I know I've made mistakes, but that's half of the fun sometimes!

I'd maybe not suggest this particular loco for a beginner, but for anyone who has done a couple of kit/scratchbuilt 2mm locos, it should be more than achievable.