Following several weeks experimenting, and lots of discussion with jbkiwi, the exhaust smoker is now installed in the Crash Tender.
The heart of the device is an e-cig tank and coil. This was adapted with an acrylic end piece to allow connection of power and air. The 2ml capacity of the e-cig is a bit limiting so an expansion tank made from acrylic tube was added to give a fluid capacity of around 10ml. The smoker fluid is 75% vegetable glycerine.
The coil in the e-cig is designed to work from a single cell LiPo battery. A power converter drops the voltage from the boat's 2S battery down to 3.5V with a claimed efficiency of 98%. This voltage is adjustable which allows control of the amount of smoke produced.
Forced air is provided by a small diaphragm pump salvaged from a defunct blood pressure monitor. This pushes air through the e-cig. The resulting smoke is fed into the cooling water line between the ESC and the exhaust ports.
As the smoker is most effective simulating the engine 'ticking over' a water pump is used to create some water flow when the main propulsion motor isn't running. This adds more realism to the effect.
An electronic controller based on PIC microchips connects to the throttle channel and pulses the air pump at a rate determined by the throttle setting. It also runs the water pump at a slow speed, and controls the power to the
smoke generator
coil. If the throttle is held at maximum for a couple of seconds, the smoker pumps and coil are switched off to save on battery consumption. With the throttle at idle, a quick blip forward on the throttle will start the smoker again. Power consumption is around 0.7A on a 2S LiPo.
The two pumps are mounted below the footwell floor and the
smoke generator
is fixed to the bulkhead at the rear of the engine room.
My thanks go to jbkiwi for his encouragement and suggestions during the development of this feature.
Graham93