How to slow a locomotive
Seuthe smoke units run best at about 8 -10 volts which means that if you fit one to a standard UK RTR loco, it's got to be doing a scale 100mph before you get any smoke. Not much use!
There is a fix, however... But I have to say that this is not meant to be the best or the only way but it IS a way of generating smoke at low speeds.
My experience is with 2 types of Hornby locos. The 0-4-0 tank engine and tender drive XPs (namely GWR King class and LMS Duchess).
You will need:
Seuthe Smoke unit - No 22 for narrow chimneys or No 100 for the standard 5 mm chimneys found on most UK outline locos.
0.6 ohm resistor (or two if you want to really slow the motor down! Just wire them in parallel.).
Soldering iron and solder
Asbestos fingers (you WILL burn yourself!)
And the usual screwdrivers, craft knife etc.
0-4-0 Tank engine
The problem here was that there was no room under the body for smoke unit, resistor and all the insulation. I also wanted Dave to stand still whilst emitting smoke so I came to the conclusion that he needed an independent power source for the motor. I reckoned a permanently attached wagon could hold the batteries for the motive power and the smoke unit power could come direct from the tracks via the normal pickups. 3v is ample to give an 0-4-0 a scale speed and enough power to pull several carriages.
2 AA batteries were mounted in a wagon with leads to the motor - worked a treat. (Pic 1) The Mk11 version has Dave being an auto-coach with 2 x AAA batteries and a switch underneath so I can change direction. (pic 2)
For the smoke unit you will need to insulate the motor from the chassis (I used black insulating tape) and solder the smoke leads to the brass pickup on either side of the chassis. (pic 3)
The Duchess was much easier.
There was already a power pickup for the lights so all I had to do was solder the Suethe lead to the brass plate. The chassis provided the neg. so there was no need for the brown lead on the Seuthe unit. (pic 1)
Fitting the 0.6w resistor to the motor pickup was also easy - plenty of room (pic 2)
KE1 was a bit more of a problem:
Not having lights, she had 1 pickup from the loco and 1 from the tender. This meant that the wire from the smoke unit had to run to the tender which meant a permanently attached tender. Not much of a problem, just a pain.
All this effort is well worth it if you want to give your locos an extra dimension. OK, not actually prototypical but who cares?