Now got to the stage with the 2" Scale Clayton steam lorry with engine finished & in the chassis, when running on air the arm on the virbrating link moves backwards & forwards about 3/16" when running, this when to arm is connected to the forward & reverse lever.

Engines notches up OK, valve timing OK, any ideas as to why & how to correct?

Thanks

The movement of the vibrating link arm on your Clayton steam lorry could be due to a few possible reasons. Here are some things to check:

Check the alignment of the vibrating link arm with the forward and reverse lever. If the two are not aligned properly, it could cause the arm to move when running. Adjust the position of the arm and lever as needed to ensure that they are properly aligned.

Check for any looseness in the pivot points of the vibrating link arm. If there is any play or looseness in the pivot points, it could cause the arm to move when running. Tighten or adjust the pivot points as needed to eliminate any looseness.

Check the clearance between the vibrating link arm and the eccentric rod. If the clearance is too large, it could cause the arm to move when running. Adjust the clearance as needed to ensure that the arm is snug against the eccentric rod.

Check the fit of the eccentric strap on the eccentric sheave. If the fit is too loose, it could cause the eccentric sheave to move back and forth, which could in turn cause the vibrating link arm to move. Adjust the fit of the eccentric strap as needed to ensure that it is snug against the eccentric sheave.

Once you have identified the cause of the movement, you should be able to make the necessary adjustments to correct it.