locomotive that has a smoker

[bigred1379]

i have a smoker that only works at full speed can anybody tell me why or give alittle advice thanx bill

[ABC]

That's just how the Bachmann smoke machines are, all of mine are the same way. If you are willing to pay more money MTH and BLI have better smoke machines that work at slow speeds too.

[Jim Banner]

Why does this happen?  When you run on dc, you increase speed by increasing voltage on the rails.  That means as you go faster, more voltage is available to the smoke generator.  More voltage means more heat.  In fact, if you double the voltage, you get four times the heat.  More heat means you can vaporize more oil.  And more vaporized oil means more smoke.

The only way to keep the smoke output constant is to somehow apply a constant voltage to the smoke unit.  One way is to use a low voltage smoke unit, say a 5 volt one, and regulate the dc track voltage to 5 volts.  This is often done in large scale.  So any track voltage from 7 volts up to 20 or 22 volts will send the same 5 volts to the smoke unit.  In small scales, this systems has problems.  Most voltage regulators are linear devices which means they get rid of the extra voltage as heat, in amounts that are hard to get rid of in small locomotives.  There are voltage regulating modules that control the heat by pulsing the power on and off but they tend to be expensive and occasionally troublesome.  A more satisfactory method in small scale is to use constant voltage on the rails.  This could be either DCC or high frequency ac superimposed on dc.  The latter has been used for constant lighting for many years.

My advice - if constant smoke production is enough of a concern, convert to DCC and enjoy the many other benefits as well.  A much cheaper alternative is to accept what the smoker does now, which is not all that different from the prototype.  Firemen were proud of how little smoke they could make - less smoke means more heat from the same amount of coal.  And the fireman who could do the same job with the least amount of coal was considered the best fireman.  There are only two times you will see a steam locomotive produce smoke - one is when they are pushing the locomotive to its limits and the fireman ends up crowding the firebox.  The other is to impress the tourists.  Also remember that smoke is black.  The fluffy white clouds pouring out of the stack are steam which shows up when the humidity is high, the air is cold, and the engine is being worked hard.  Running easy on the flat, it is not unusual to see no exhaust (smoke or steam) at all.  At least with steam locomotives.  Diesel locomotive smoke behaves rather differently.

Jim