Prototypical CV's

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Prototypical CV's

Postby kingmi53 » Thu Jun 10, 2021 7:57 pm

I have a large number of loco's, steam, diesel, electric etc. which I'm now ready to run on my layout and wondered if anyone has or has seen a list of typical cv''s that cover acceleration, deceleration, top speed etc. for the various loco categories. I know some will depend on what they haul but it would give me a basis on how they generally perform in real life.

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Re: Prototypical CV's

Postby RAF96 » Fri Jun 11, 2021 11:48 am

One of those ‘how long is a piece of string’ questions unfortunately.
Each loco mechanism is likely to be different as will be their train load.
You are going to have to experiment on the basis of CVs 3 (accel) and 4 (decell) are usually default at value 5 to preclude dead stop/starts. Value 255 will allow you to build a layout as they get up to speed and stop. Value 25-50 is a good starting point then you can refine up or down from there. The higher the value the more apparent inertia to overcome.
CV5 V-max and associated CV6 V-mid are not supported by all decoders, so if you need to tame a racehorse then choose a decoder that does.
The only other adjustments you are likely to use are BEMF (cruise control) and motor algorithm (PID). The associated CVs may vary decoder make to decoder make. These are however basic refinements for smooth running and once sorted can be ignored.
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Re: Prototypical CV's

Postby Bigmet » Fri Jun 11, 2021 5:08 pm

Do you have a circuit of track (of known length) would be my first question. If you do, or can create one temporarily, then it all becomes much easier. For speed setting because you can time the loco over a decent distance, and for seeing the effect of acceleration and deceleration rate.

By one of those weird coincidences, if you have an oval of track on an 8' by 4' board (possibly the most common size for a UK layout) it's conveniently near enough a quarter mile. So if your loco goes round in 15 seconds, that's equivalent 60mph.

Your slow unbraked steam powered heavy mineral train will need 45 seconds to get around one circuit, once it has grafted up to the 20mph that was the typical safe maximum speed. It will need a mile if handled briskly- four circuits - to get up to that speed, and probably half a mile - two circuits - to stop. I use values up in the hundreds in CV's 3 and 4 to get this effect; there's no point giving exact values as the time constant on the decoder varies from example to example, and varies yet more significantly between different decoder makers. Depending on the length of run you have available, you may want to decide how much you are going to scale down these values...

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