'I am just about to start cutting the cylinders and valve chests for my Rob Roy so can you point me in the right directioon to moify the above error before I start.
Thanks Bob'
Bob,
I've looked at the list from Andy and there are a few mods mentioned in the book 'Rob Roy & William' by Martin Evans. Some might be repeated but thought they were worth mentioning.
1. Check the height of the horizontal stretcher. The book suggests raising this by 1/16" to give more clearance to the eccentric straps.
2. Cut a 'U' in the upper left vertical stretcher to give clearance to a possible blowdown valve.
3. It suggests using cast bronze for the connecting rod big end bearings instead of drawn bronze to give a longer life.
4. The flange on the valve crosshead is removed and its boss increased by 1/32" giving more support to the valve spindle?
5. The oil check valve is fitted with a plunger instead of the spring bearing directly on the ball.
6. Bushes are used on the backplate and smokebox plate instead of threading the plates themselves.
7. The safety valve vent holes are increased in size from No 55 to No 52. The spring locating pin or spindle is reduced in diameter to accomodate the above mod.
I think I saw a string on this issue somewhere else and these changes are a puzzle to me i.e., I have worked in a design office for 30 years. All the mods would take less than a few hours to correct including a mod record (either electronically drawn or by hand). I wonder why we don't do it?
Phil H