It's difficult to even guess what the problem may be without having the locomotive to check.
As Bill mentioned, make sure all the drivers are in quarter. As an example all crank pins one side of the locomotive should be on the same plain. For example all crank pins should line up at say the 3 o'clock position. If one crank pin is higher or lower than the others then it would be out of quarter.
Did you tighten not only the side and connecting rod bolts but also the Phillips head screws that attach the counterweights and wheels to the axles?
Disconnet the connecting rod from each side of the locomotive. Take some fine wire and wire the connection rod up and out of the way so it will not hit on the crank pin. Run the locomotive to see if you still have the noise.
If so, the check the side rods since they could be bent, as Bill mentions.
If no noise with this test, then it could be a connecting rod hitting.
Other than that, without seeing the locomotive it's difficult to guess what the problem may be.
One of the "Enthusiastic Children"
JD
As Bill mentioned, make sure all the drivers are in quarter. As an example all crank pins one side of the locomotive should be on the same plain. For example all crank pins should line up at say the 3 o'clock position. If one crank pin is higher or lower than the others then it would be out of quarter.
Did you tighten not only the side and connecting rod bolts but also the Phillips head screws that attach the counterweights and wheels to the axles?
Disconnet the connecting rod from each side of the locomotive. Take some fine wire and wire the connection rod up and out of the way so it will not hit on the crank pin. Run the locomotive to see if you still have the noise.
If so, the check the side rods since they could be bent, as Bill mentions.
If no noise with this test, then it could be a connecting rod hitting.
Other than that, without seeing the locomotive it's difficult to guess what the problem may be.
One of the "Enthusiastic Children"
JD