Pulley Setup and Fabrication

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Pulley Setup and Fabrication

Here are notes ont the pulley config and fabrication. As the the Rotrex is so new I will have t build the pulleys myself :)

Configuration

Below are two targets - low boost and high boost.

vespa Flywheel Diameter	118mm
Closest Pulley to Fit Diameter	130mm
Target RPM	9500
C8 Pulley Ratio (to 1)	12.52
Low Range Super Charger RPM	160,000
Low Range Super Charger Input RPM	12779.55272
Low Range Super Charger pulley diameter	~95mm
High Range Super Charger RPM	220,000
High Range Super Charger Input RPM	17571.88498
High Range Super Charger pulley diameter	~70mm

From the above the plan is to build 3 - 70mm, 80mm and 95mm.

These will have the ability to also be flexible in size (so I can make them smaller later if need be. So 95mm will have a inside diameter of 70mm, 80mm - ID 60mm, 70mm - ID 50mm.

Fabrication

Holding Tool

First step was to create a tool that mimics the Rotrex pulley adapter. This is so that I can have the pulleys I am making mounted in the lathe in the same way it would be mounted on the supercharger. The idea being that I can set up the pulley perfectly aligned in the chuck and the resulting poly-v grooves should be perfectly aligned also.

I made this with a combination of the CNC mill (for holes) and the lathe.

Step 1

Turn pulley blanks so that we have a flat surface and a centre hole for reference. Then set up the pulley in the CNC machine for drilling the 6 mounting holes (including counter sinks).

Note: The small one mounted is a test one

Step 2 & 3

Use g-code to drill out 6 holes.

Mount counterbore without moving blank and use more g-code to bore out the cap screw holes.

Step 4

Turn out the inside.

Note: I am finding issues with the pulley dimensions not matching what can fit on the C8-8. I will need to make the pulley thinner that what is specified in the technical manual (however I am only making it 6 rib instead of 8 so it should not be an issue).

Also note: I need to step the inside hole where the pulley nut goes. If I push it through 19.6mm all the way it takes the edges of the counter bores.

Warning!!!! The g-code files below are random uploads of g-code in various states of work in progress. Some are known to have serious errors (e.g. drill a hole and then try and move to another position while still in the hole - crunch!!!). As with everything on Vespa Labs if you you use anything, use it at your own risk! This is an extra warning as some of these will break your machine!