Hi guy’s,
Back in 2009 I decided to make a start making my own motor conversions for a wind generator.
This post will detail the build where the magnet arrangement is in the Offset pattern. The Offset pattern is where the 8 magnets, 4 south facing and 4 north facing are spaced at less than 45 degree angle to eliminate the cogging. Now if the magnets were placed at 45 degrees they would all be aligned and it would need a huge set of stilsons just to move the shaft.
So after talking with online colleagues I settled on a 43.75 degree spacing which after drawing the setup in autocad it turned out to just about right.
Now rather than machine the existing rotor I decided to machine a new one out of a steel shaft to the dimensions I designed in autocad.
I machined the smaller diameter on the left which holds the dual ball bearing longer than needed to allow for a fan to put at the rear of the motor. The output shaft was machined to 25mm for the conlock fitting for the blade mount.
This conlock fitting is designed to clamp shaft and bore where both are parallel. Thus not needing a keyway and the lock is easily broken using the cap screws.
For extra safety a 10mm tapped hole and cap screw is used just for piece of mind.
Now in order to machine the flats on the rotor I setup my Bridgeport milling machine with my rotary table and used a 5/8″ slot drill to machine the flats. For the 43.75 degree spacing used 43.75, 87.5, 131.25, 175, 218.75, 262.5, 306, 349.75 which was easily dialed in as the rotary table does have have a vernier scale.
The magnets I used were 2x1x1/2″ N42 epoxy coated with a 3mm countersunk hole which I bought from America. Each magnet lightly screwed in then I poured some Stupid glue (superglue for the many) under each magnet then tightened it down. The next job a casting the rotor in epoxy to totally seal the magnets and also allow me to fully machine the casting to ensure the rotor shaft was balanced.
I machined the OD for a total of 2mm clearance on the ID of the motor housing, put the bearings on then using a chain block on my 2 tonne engine hoist (with several large steel billets positioned to counter act any pull from the magnets) and lowered the rotor home.
Now for the blades I decided to make a 3 metre set for my first real attempt at wind turbine blade. At the local scrapyard I came across some old Oergon posts then after making some templates for the angles got stuck into carving out the excess.
Here is a pic of the first blade under way.
Here is a picture of the project finally finished and up and flying.
This my first motor conversion is still up and working today and recently it was brought down for a bearing replacement. It has seen many 100+ K winds and loves them and when it’s doing 500+rpm in high wind a small noise can be heard from the blades over the noise of the wind, where at lower speeds they are silent.