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Helper Disassembly instructions The SHS Smoke unit is tiny. It's small size means only 10 drops of smoke fluid fills it to capacity. The element is a glass bulb wrapped in wicking and once the wicking carbonizes the element is shot and needs replacing. It is so fragile that removing the wicking usually breaks the bulb. It is also a power hog at only 4.5 ohms. With the working voltage of 4.5 volts is consumes one amp cold. |
| So we looked into making a more conventional type
element used in many smoke units. A nichrome wire wound element that
rests on a heat resistant replaceable packing that stores the smoke
fluid. By using an open winding it is more efficient and draws half the power of the original type and produced much more smoke. I found a good core for winding the element from a 5 or 10 watt power resistor. Breaking the power resistor's ceramic case by crushing in a vise reveals the resistor core components. The 1/8" diameter core is cleaned up and holes drilled for attaching the new leads. |
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Here is results of testing different element
values. Voltage to elements was 4.2 to 4.5 volts depending on element resistance. There was some voltage drop in the loco wiring depending on element load. The original type smoke unit: Resistance cold 4.4 ohms, Hot 8 ohms. Using 10 drops of Anormal1 smoke fluid. Time of smoke run was 12 minutes. Amount of smoke was adequate but not great. The nichrome wire was 37 gauge, 32ohms/Ft. My test element #1: Resistance 7.7 ohms. Using 10 drops of Anormal1 smoke fluid. Time of smoke run was 5 minutes. Amount of smoke copious. My test element #2: Resistance 11 ohms. Using 10 drops of Anormal1 smoke fluid. Time of smoke run was 12 minutes. Amount of smoke light to adequate. My test element #3: Resistance 9 ohms. Using 10 drops of Anormal1 smoke fluid. Time of smoke run was 9+ minutes. Amount of smoke generous like a good AC Gilbert smoke unit. |
| Also see Al
Castellani's Article on repairing elements for the SHS smoke unit Here is Al's type element that I added a couple of ceramic Indian beads to for stand off insulators to keep the element off of the circuit board and to help penetrate into the wick packing more. This one is wound with 37 gauge Nichrome at 9 ohms. 
Don Thompson at S helper Service says that they are looking at a similar design for replacement elements. |
You can see that version 3 seems to be the best
compromise with a value of 9 ohms. The smoke unit cranks out a generous
volume of smoke for a reasonable time considering the small capacity of
the fluid reservoir.
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