Cylinder fitting

[Garry Coles]

Hi everyone
Still cracking on with the building of my 3 1/2" William, but have a question about the fitting of the cylinders to the frames. The plans have marked on them a center line of motion. This I understand is the line that the wheel centers and piston rod should line up with, but what if the finished loco weight is greater or less, and the center of the wheels rest above or below this. How critical is it.
Garry

[AndrewP]

Hi Garry,
I'm on with Rob Roy which is a close relative to William and I don't believe it is critical. The suspension is going to deflect anyway, in fact my frame holes didn't exactly line up with the cylinders so I have had to, err 'adjust' them.
If it's way out then you might have more problems with connecting rod fouling the end of the slide bars which is a known issue anyway - solution is more 'adjustment' with a file!

Cheers, Andy

[baggo]

Hi Garry,

the usual thing is to set the ride height of the axles by altering/adjusting the springing once the engine is finished so that the axleboxes are in the middle of the horn slots when the engine is full of water etc.

Adjustment on William is fairly simple as you can easily change the springs if necessary or just screw the spring pin nuts up or down the threads.

The design on Rob Roy (with the springs on top of the axleboxes) is a pig to adjust as it means removing the springs to alter them. Not an easy job

One thing that seems to be rarely mentioned is the importance of getting the weight on all the driving wheels the same for maximum traction. Some loco designs tend to be very front heavy and it's easy to finish up with most of the weight on the front axle. It's not easy to do but there have been a few articles in ME outlining methods using spring balances, digital scales etc.
John