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Underground Ernie inspection car chassis - DCC fitting


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  • RMweb Gold

The chassis from the Bachmann 'Underground Ernie' inspection car is useful for critters in most scales for 16.5 mm gauge so here is a topic for DCC conversions.

 

The original model comes with an 8-pin socket - I removed this to save space when I built my model. I began with one of the DCC Concepts NANO decoders with a separate stay-alive unit. The stay-alive was just about made to measure to fit under the footplate, between the frames:

post-14389-0-60127100-1535133355_thumb.jpg

 

The associated decoder went in easily enough too, fixed with a blob of hot glue:

post-14389-0-25369900-1535133374_thumb.jpg

 

Unfortunately, there seems to be a big mismatch between the power requirements of the Bachmann and the delivery characteristics of the NANO decoder. The model would run at a happy crawl on notch 1 or 2, but would needed notch 8 to get going. I have had a brief but most helpful correspondence with DCC Concepts, and now swapped out the decoder for a Lenz Standard+ V2. The Lenz has more adjustments for motor drive characteristics. All the components are on the top of the pcb and I fixed mine down with Blu Tack:

post-14389-0-15133100-1535133383_thumb.jpg

 

The Lenz pcb carries a fair sized capacitor (yellow component in photo above) and I am not too sure whether an additional stay-alive is worthwhile. However with it glued into the frames I connected it up. The blue wire goes to V+ (accessory common) and I took the black wire to V- on the bridge rectifier:

post-14389-0-32457200-1535133391_thumb.jpg

 

The default settings of the Lenz yield a performance similar to that with the NANO, but improve a great deal after changing some of the CVs. I worked through the CVs in this sequence:

 

CV29 = 2 (disable DC running, disable Rail Com)

CV61 = 3 (control BEMF through a function button)

CV136 = 1 (use F5 to toggle BEMF)

CV50 = 5 (this is the sixth of the six motor profiles in the Lenz decoder, found by trial and error, the last one I came to)

CV2 =2 (motor start voltage)

 

This model always ran really well with my Kentrol Feedback analogue controller. Performance with DCC is comparable at slow speeds, better over points and crossings, and of course gives the ability to add inertia. I am keeping BEMF switched off, but I can experiment using F5.

 

I left the wires over length, coiled up inside the cab. Then I can reuse the decoder if (or when) I wear out the model. The dcc conversion actually cost a bit more than the original body and chassis.

 

- Richard.

 

post-14389-0-44723300-1535133405_thumb.jpg

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