Monday, August 10, 2009
Does any other word strike so much fear in the model locomotive builder ? Walschaerts valve gear is wonderful stuff on an engine, it adds complexity and detail under the footplate. All those rods form a natural focal point. Built properly, every modeller will ohh and ahh over it.
And joy of joys, the Garratt has four sets. To be fair, if you ignore the connecting rods then the complexity is formed of only 6 parts. OK, so all of these are double thickness lamination's but that's not too bad.
No, the worst bit is jointing the parts. Most of mine are done with brass pins or in one case, a brass rivet. All are soldered. Some days this works, some days it doesn't. The first day I tried to build up the valve gear, I made the first joint 5 times before it flexed. The next day everything went perfectly. To stop the solder running I used the tin-foil method and it worked a treat.
One issue I did find was that the unit where I had fudged things to get enough clearance between cross head and front crank pin didn't work. The joins were too small and kept breaking so I had to bit the bullet and dismantle it, rebuilding with the cylinder faces moved out to gain space. It just shows you need to do each step properly before moving on or it will come back to bite you.