The lurching (speed changes) that are being observed at low speed operation is probably not mechanical. Everyone is so focused on mechanical issues, that nobody apparently noticed that the speed-up / slow-down is synchronized with the activation of the smoke fan.
I have observed this same nuisance issue on some Lionchief Plus locomotives like the Mikados. At low voltages, the drive motor RPM's can be significantly impacted by the current drawn as the smoke fan motor cycles on and off, causing this "jerking" issue. As the locomotive speeds up, the issue tapers away as the fan motor operation transitions to continuous.
This problem goes away on the LC+ locos if the smoke unit is turned off. Has anyone actually turned off their smoke unit to see what effect it has on this slow speed issue?
