Step 6: Applications
Perhaps our favorite application of an Easter engine is in the toy Jeepster SUV illustrated in Step 3. A thin plywood bottom was cut to fit the body, and large foam wheels were made to give it a "Monster Wheel" look, but in operation it is quite docile. The underside is shown in the photo below. The axles are set to make the car run in a tight circle (because we have a small living room) and the front wheel drive setup greatly helps it stick to the intended circular path. The gear train was taken from a commercial hobby motor unit shown in the next photo, but it was fitted out with a 13 Ohm motor.
A 1 Farad super capacitor gives the car about 10 seconds of run time each cycle, which takes it almost completely around a 3 foot diameter circle. It takes a while to charge up on cloudy days or when the car happens to stop in a dark spot. Anywhere from 5 to 15 minutes is usual during the day in our living room. If it finds direct sunlight coming in a window, it recharges in about two minutes. It travels around in a corner of the room and has logged many revolutions since being built in 2004.
Another amusing application of the Easter engine is "Walker", a robot-like creature that waddles along by means of two arms, or rather, legs. He uses the same motor and gear train setup as the Jeepster with the same 76:1 ratio. One of his legs is purposely shorter than the other so that he walks in a circle. Walker also carries a blinking LED so we know where he is on the floor after dark.
An simple use for a solar engine is as a flag waver or spinner. The one shown in the 5th photo below can sit on a desk or shelf and every now and then it will suddenly, and rather wildly, spin a little ball around on a string thereby attracting attention to itself. Some embodiments of these simple spinners had a jingle bell on the string. Others had a stationary bell mounted nearby so that it would get smacked by the flailing ball - but that tends to become annoying after a few sunny days!