[Andy Brockway]

The basic principle behind the dog shifter working is that the gears are free spinning on the shaft. The dog is mechanically engaged to the shaft so that when the dog rotates the shaft rotates. The shaft and dog have internal geometries for this engagement; a keyway for the Who'sCTEKS version, a hex shaft in the TechnoKats version, etc. The shifter is pushes the dog back and forth along the shaft, there is some clearance to allow the dog to spin on the shifter for outside shifters and the internal shifters spin with the shaft.

The mechanism works by the motors driving thru the gears. Both output gears are always spinning while the motors are turning. When the dog engages one of the gears, that gears RPM is transmitted to the shaft while the other gear free rotates. So the shifting is done to select the desired output speed range.

Because of the dynamics involved, there must be a 'neutral' between gears. This way you will not lock both speeds on while moving. This can cause the gearbox to break! The simplest way to achieve this is to increase the distance between the gears to the thickness of the dog plus .030+".

There is plenty of help available here at CD, your first gearbox should be a success!