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The Rand Cam Engine

Cams

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The cams are the center piece of the engine.

They provide movement for the vanes.

Timing of engine is controlled by this part.

4vane4camsolutionvariant.jpg

The original design that Jim (James McCann) made called for a cam pressure angle of almost 30 degrees.

This is fine for slow moving mechanical devices - approximately 50 to 250 rpm.

However as the rpm starts to increase the pressure angle causes too much impact loading on the face of the cam and the vane tips.

This was the major reason for failures of early prototypes.

The addition of a transition area reduces impact loading but doesn't eliminate it.

camprofile01.gif

The above graph of the cam profile shows the enlarged transtion areas. This graph was made from the following;

* Trig

* Algebra

* Geometry

* Calculus

The result is an algorithm that describes precisely the part shape.

When Jim was trying to cut the part on a CNC machine he could not communicate the proper program to the CNC programmer. The programmer gave up after two weeks. Jim showed me the way he calculated the part manually and I drew it up on my graph paper.

I mulled over the problem for a bit and when we were supposed to go to a meeting it came to me.

I grabbed a piece of paper and wrote it down. I grabbed my 80 dollar radio shack programmable calculator and plugged in my algorithm.

Low and behold when I punched in the degree - it spit out the correct x y z coordinates.

From the time the algorithm popped into my mind and verification on the calculator was half an hour.

It took 4 days to actually hand plot the cam profile down on graph paper.

I had access to state of the art CAD/CAM programs but you know the old saying - garbage in garbage out. (are you listening John)

velaccjerk.jpg

Velocity - Acceleration - Jerk.

These are the most critical design parameters that the cam profile has to produce.

If the Acceleration and/or Jerk is to high - the engine will fail...

Dale Robinson * Box 196 * Waglisla * BC * V0T 1Z0