|Diodes are neat as
they only allow current to flow in one direction and they have an
internal voltage drop of .7 volts. (some do have different voltage drops
but I am not sure which ones)
I used groups of 1N54004 diodes which are
rated at 3 amps. I purchase these from AllElectronics.com As you can see
the following diagram and photos, I grouped 4 diodes together for a
total of 2.8v drop at the first slow down point and 5.6v drop at the
second slow down point. You can have as many slow down points as you
For the return I used 2 diodes for a 1.4v
increase at the two speed up points. This helps to ensure the loco has
enough oomph to get started.
Here is the diagram I drew showing the placement
of the diodes.