Members Models
These pages show model boats under construction or completed and useful tips by members of the Sedgemoor Model Boat Club
Want to know how to measurer your motors RPM?
Bob Bryant shows a simple way to build your own DIY tachometer
DIY Tachometer
A dc motor can be used as a tachometer. Any motor could be used but calibration is a problem without another tachometer and many motors do not give the same output in both directions. A 385 motor is a convenient one to use because it gives an output of approximately 1volt for every 1000rpm in each direction. I tested mine using a lathe with a nominal speed of 550rpm and got an output of 0.55 volt. For many applications this is accurate enough. The photo shows a basic set up which could be improved if desired. Masking tape will hold the motors in place but it is advisable to hold the rig in a vice. A digital multimeter is ideal for the readout as the speed will be volts x 1000rpm.
