PIETECH V.1, P. 2: Redesigned Sun Gear Makes This Model The “PIE 4.3”:


Inverted Chain Sun Gear

I am really pleased with the raw power that the PIE 4.0 exhibits. This power is still quite wild and unrefined, but it is impressive, nonetheless.

I was happy with the inverted chain design, but I quickly saw some issues that would give me trouble keeping the PIE running. Mainly the width of the chain is too narrow to allow for wheel run-out and axle deviations. The main wheel is expected to deflect some and I am not using a precision sun gear axle so I have no realistic expectation of it being perfectly straight.

Narrow Chain/Gear Mating Area

Now the sun gear has now been redesigned/improved. It still functions as an inverted chain but rather than roller chain, 8mm (5/16”) rods are used. The new sun gear width is 30mm (1-3/16”) so there is plenty of room to change designs.

Redesigned Sun Gear

The new sun gear is made from two #40-26 tooth sprockets with the teeth cut nearly off and 8mm (5/16”) rods welded into the remaining tooth divots. A piece of 1” steel rod with the center drilled to 5/8” is used for the center of the gear. The sprockets are welded to the center rod and the 5/16” rods ae then welded in place.

Bench testing is showing that adjusting the sun gear’s timing by as little as 1 or 2 teeth (13 to 23 degrees) changes the direction of thrust dramatically. 

Below is a video of the new sun gear set for forward motion and PIE clamped firmly to the bench.

I am planning on doing more extensive testing in the next days and weeks, including the use of an inverter to make the drive portable for vehicle testing!

It has occurred to me that since the PIE 4.0 has already gone through 2 gear redesigns and a motor swap that this is truly the PIE 4.3, so that is what it shall be known as… PIE 4.3!

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