Rabbit                                                                                                                      

The Rabbit engine layout

The Terrapin project was so slow and bulky it would not run. I hope the single engine Rabbit project runs a little faster. I may add a second engine and call it Jackrabbit,  Lepus californicus.

Click images for bigger views.

Piston and Cylinder

The piston cylinder is made from a 12 inch piece of ABS 4” drain pipe. I picked a pipe that was fairly smooth on the inside. I glued a ½” PVC barbed fitting into the 4” cap and pushed a 5” piece of 13/32” brass tubing though holes drilled in the cap’s sides. The cylinder will pivot about this point on a 3/8’ steel axel as the connecting rod moves on the crank.

Piston Seal

The piston head is made from three Plexiglas discs (turned on a router table) and a 4” o-ring sandwiched together. The o-ring is held to the cylinder wall by the pressure (or vacuum) inside the piston and it slides well with the help of a slathering of petroleum jelly. The o-ring seal is the only moving part of the project where I have to contend with air leaks. If the finished piston leaks, then the project will be postponed until I can make a functioning piston.

SMPP-03 Calibration Graph

I ordered several pressure sensors and temperature sensors from Mouser electronics. I mounted a SMPP-03 sensor ($4.50) and a small op-amp board ($0.49) inside a PVC fitting.  At ambient pressure, the unit outputs 1.85 V. The voltage changes linearly from 0.5V to 3.75V over the entire +7 PSI range. I am working on PVC overpressure and underpressure relief valves. I have $5 worth of 5/8” rubber balls, coming from Smallparts.com.

PVC Parts

Ardunio Uno R3

I ordered an Ardunio Uno R3 micro controller on eBay for $16.49. With it, I should be able to control and monitor the engine by way of a USB cable to an old desktop XP computer. I will be attempting to write a VB6 interface program to send engine commands and collect data. I have a steep learning curve ahead, but I have wanted to learn about this supposedly excellent product for a long time, and this project is a good fit for this device. Even if the engine does not run, I will have learned something new.