Improving the Running of a Lima Class 73
Some years ago, I decided to try and improve the running qualities of one of my Lima class 73 models by replacing the Lima armature with a ModelTorque motor (available from the manufacturer just a couple of kilometres up the road from me at the time - sadly no longer available since the passing of the man responsible for them). This was almost a drop-in replacement but promised much better, smoother and more responsive running. It still used the Lima gearing and did deliver what was promised, although the Lima gearing did it no favours, but it would go from a crawl to around 350 mph. The top speed was later tamed a little with a diode pack supplied by the manufacturer. At this time I was still using analogue DC.
It was still totally dependent on the Lima brass wheels and dodgy electrical pickups, however. That remained the achilles heel for running qualities. Hard-wiring a Bachmann decoder allowed much finer tuning for the motor speeds and also tamed the acceleration and deceleration using the inertia/momentum settings, but still those brass weheels and poor electrical characteristics prevented reliable running, with the occasional prod from a large finger being needed.
A partial solution has since become available in the form of a Hornby dummy bogie from Peter's Spares. The Hornby bogie not only has better wheels but also picks up from both sides of the bogie, where the Lima one only picked up from one side. Fitting the bogie required the hole in the chassis for the original Lima one to be enlarged a little, using a round file. The Hornby bogie could then be clipped in, after first threading the two wires through. When I originally rewired the Lima chassis for DCC, I followed the convention of using a red wire for the right-hand track feed from the power bogie (which is always the number 2 end of the Lima/Hornby models). Hornby have very kindly marked one of the two black wires from the new bogie with a red patch - this also goes to the right-hand side of the bogie. I simply soldered the red-patch wire to my existing red connections, and the black wires together, then tested for short-circuits before putting the loco on the programming track and double-checking that all was well.
Doing this modification means that I have electrical pickup from four decent quality wheels on the dummy bogie, and two (on one side only) through the Lima brass driven wheels. I could wire up extra pickups for the remaining two wheels on the motor bogie but these also have traction tyres, so the benefit would be marginal, to say the least. Anyway, the running, while not perfect, has improved considerably, to the point where 73 142, Broadlands, can now rejoin the main fleet and not be parked languishing at the back of the drawer.
In the photos, the motor bogie looks like it has a standard Lima 'pancake' motor, whereas, in fact, the ModelTorque motor is installed from the other side, away from the camera. The first photo shows the new bogie clipped in place after opening out the hole, with the two wires floating loose, and the original Lima clip arrangement also detached, awaiting removal.
The second photo shows everything soldered in place and all joints covered with heat-shrink tubing. I had to use a short stretch of red decoder wire to extend the reach of the Hornby wire to the original wiring.
I'll post a short video to demonstrate the improved running in a short time - I'll edit this post to include it.
EDIT: OK, video delayed - it ran smoothly enough until I got the camera out, then the main drive gear started slipping! I'll try again when the glue has set properly.
2nd EDIT: I finally got the video, edited it and then uploaded it to YouTube (even that took ages, for some reason).
I may have to consider putting a newer, better decoder ... I'm not even certain that the existing one has BEMF facilities, it's that old!
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