Adding inertia to DCC locomotives

DCC chip Bachmann 36-566One of the smarter features of DCC locomotives is the ability to simulate inertia.

If you want to improve the realism of your locomotives operation, the starting and breaking delay CVs – numbers 3 and 4 – are worth exploring.

These variables for locomotive DCC chips and determine how quickly the locomotive accelerates and how slowly it stops.

To simulate a heavy train, with slow acceleration and deceleration, program these with higher values, up to 255. For lower weight loads, passenger cars etc, that get up to speed faster and equally come to a halt sooner, reduce the value. 1 being the lowest, giving quick, low inertia stopping.

Remember however having slower acceleration and deceleration times mean it’ll take more time and track to either reach the speed wanted or come to a stop. Don’t do what I did and set a high  breaking delay and then watch your loco run off the end of the track because.

I’ve now set my 0-4-0 small shunting locos that typically pull wagons that would be heavy to 60 for both CVs and it makes a much more credible operation while still giving me time to stop them.

Being an NMRA Recommended setting it should work on most decoders, it works on my Zimo chips and apparently also works on Gaugemaster and Zen chips including others, although on some Lenz chips the range is limited (check with your manual first).

Set both CVs to 0 to disable inertia control.

> A final, personal, note: I spend a huge amount of time testing, photographing, writing and researching techniques for these articles and pay for all the running costs of MRE out of my own pocket. If you found this article useful you can support me by making a donation on my fund-raising page. Thanks and happy modelling, Andy.


Founder of ModelRailwayEngineer, Andy Leaning

Andy is a lifelong modeler, writer, and founder of He has been building model railways, dioramas, and miniatures for over 20 years. His passion for model making and railways began when he was a child, building his first layout at the age of seven.
Andy’s particular passion is making scenery and structures in 4mm scale, which he sells commercially. He is particularly interested in modelling the railways of South West England during the late Victorian/early Edwardian era, although he also enjoys making sci-fi and fantasy figures and dioramas. His website has won several awards, and he is a member of MERG (Model Railway Electronics Group) and the 009 Society.
When not making models, Andy lives in Surrey with his wife and teenage son. Other interests include history, science fiction, photography, and programming. Read more about Andy.

Afflliate disclosure:The links on this page may take you to carefully selected businesses, such as Hornby, Amazon, eBay and Scale Model Scenery, where you can purchase the product under affiliate programmes. This means I receive a small commission on any orders placed although the price you pay does not change. You can read my full affiliate policy here. I also sell my my own ready to use, pre-made and painted buildings and terrain features. browse the range.

Add Comment

Required fields are marked *. Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.