Please do read these notes - this is a Technical Video 3 of 3 on model railways.

When running in multiple some of the EMUs are suffering cyclical surging issues. This is covered in detail within the notes accompanying Technical video 1:    • Ewhurst Green Technical video 1 of 3 ...   and Technical video 2:    • Ewhurst Green Technical video 2 of 3 ...  

Following these videos a comparison on the BR(S) EMUs on Ewhurst Green was undertaken in order to ascertain which were affected.

Conclusion
With matters such as controllers (including the load thereon), track /track feeds and so forth the conclusion was reached that the causation appears to be different characteristics in the motors used for (say) the original 2010-build of 4 CEP units (etc) and the current 2023-build of 4 BEP and refurbished 4 CEP units.

The term 'characteristics' is used as it may not be quite as simple as motor speed as (according to the helpful staff at Bachmann) these could still be affected by different components in the PCB board. So it looks as though a little more investigation may be needed....

Of possible interest
Ewhurst Green's fleet of 2 EPB /2 HAP /4 CEP /4 BEP and MLVs were renumbered and weathered by The Model Centre near Whitby. https://www.themodelcentre.com/
The Blue /Grey and 'Jaffa Cake' livery units are currently visiting the layout.

Information on the 12"=1' versions of these EMUs can be found on my BloodandCustard webdite https://www.BloodandCustard.com/

For more information on Ewhurst Green model railway please visit www.EwhurstGreen.com