Thomas Modifications
When we first received the Bachmann Large Scale Thomas the Tank Engine, we were very disappointed in his performance. While we did not use the track that came with the original set, Thomas was put into operation on an oval of LGB track. 18’ x 8’ with 2’ radius curves for a Christmas display.
Thomas would run for a short distance and then stop. Give him a slight push and off he would go again only to stop a few moments later.
Before returning Thomas to the manufacturer. We thought that we would check some of the obvious reasons for this poor performance. Neither the wheels nor the connecting rods were binding, gears were well lubricated and the power pickup springs to the axle bushings were making good contact. Maybe the motor had a dead spot on the armature? Bench checks at very slow speeds with the power connected directly to the motor proved that the motor was working fine.
It was noted the main driving wheels were not with a polished surface as generally available on many G Scale locomotives. In fact these wheels appeared to be made of a coarse molded, low quality, metal with a blackened finish. Again, bench tests with power applied via stationary rollers show no hesitation in running.
While this form of contact spring riding on a metal sleeve is not considered as the best method of power pickup. It was decided to spot solder wires directly to the brass metal axle bearings to improve electrical continuity. This was applied to both front and rear axle connection points.
Running on a small 4’ x 5’ test track did appear to improve operation.
During the course of these tests and modifications it was found the wiring to the motor is reversed as compared to the majority of G scale manufacturers. This is really no problem when running one train on a single track but when attempting to run two engines on one track the vehicles will travel in opposite directions.
Thomas is wired to National Model Railroad Association (NMRA) standards and while a switch could have been installed to change polarity, similar to other Bachmann Large Scale locomotives, it was decided to change the wires going directly to the motor. This has also been discussed on other large-scale web sites and forums.
At our grand opening, National Train Day 2010, and his introduction to the Vines Garden Railroad. Thomas embarrassed us all by stopping every few yards around the main track.
Back to the drawing board!
It was going to take more than this individual to solve this particular problem.
Before deciding to return Thomas to the manufacturer. One of our members, R.J. DeBerg, offered to take a look This time all driving wheel tire contact surfaces were polished and electrical pickups added to the center axle. After total re-lubrication the engine was put back into service.
Thomas now runs without any hesitation at all speeds on all tracks!
Just what had been done to cure this problem?
It is now noted track wear is evident on all driving wheels, including those on the center axle. A metal straight edge shows all wheels are in very good alignment on both the left and right hand side of the gearbox. Further examination proved that while all six driving wheels touch the rail at the same time. The design of the motor block allows for no vertical movement for any axle (compensation) during operation. If there is any slight imperfection or elevation of the track, such as that may occur at a rail join, the center wheels can lift the front and rear wheels off the track, breaking electrical contact, causing Thomas to “stop dead on his tracks”. Adding the center axle electrical pickups finally cured this very annoying problem.
Norman Allum - 4/02/2011
JSE Designs, LLC