Trigger Wheel Design & Fabrication
Crankshaft Trigger Wheel
I purchased a used Northstar crankshaft off eBay to get the measurements of the trigger wheel and create the wheel in CAD.
Here are the measurements of the Northstar trigger wheel:
Most measurements taken from the trigger wheel are giving in a range because measurements taken at different points of the wheel yielded
different results, this is due to machining tolerances of the wheel. The tolerances of the wheel do not need to be very close,
the notch position and size is what is important so the module can figure out where the engine is in rotation. Each of the 32
notches on the crank trigger wheel is about 15/64 (or 0.235 to be exact) of an inch in length and 3/16 - 13/64 of a inch deep. There
are 16 small raised areas which are about the same length as the notches, they are about 7/32 (0.21 - 0.215) of a inch. There are 16
large raised areas which are about 3 times the length of the notches and measure in at 0.66 - 0.665 of a inch. So calculating
in a percent of error for machining tolerances, each notch and small raised area are the same length. The large raised area is three
times the length of the notches.
The above broken down into degrees:
- 32 notches 3.75 degrees in length
- 16 small raised areas 3.75 degrees in length
- 16 large raised areas 11.25 degrees in length
The thickness of the trigger wheel is 9/32 - 5/16 of a inch thick, the thickness is different at different points around the wheel due
to the fact that one side of the wheel is un-machined cast and the other is machined flat.. The diameter of the trigger wheel is about
6 & 15/16 inches.
Northstar Crankshaft Trigger Wheel CAD
Here is the AutoCAD file of the Northstar trigger wheel, this can be scaled in size as needed:
Northstar trigger wheel (AutoCAD File)
Northstar trigger wheel (PDF File, only for viewing purposes)
Page created: January 2006
Page content last updated: 06-13-2009