and I ran into a problem. I hopefully took care of the problem. Here is what I finished up this weekend. These are 14" rotors to be used in my new 16' diameter prop 24V machine. These use the same magnets DanB used in his 14' machine not too long ago. I am using .5" steel for the rotors. I cut them out of a sheet of steel and weld them together. I then drill out the center hole and all lug holes. The front rotor gets three additional holes threaded for the jacking bolts used to raise and lower the front rotor. Here is how the discs look after I clean them up on the lathe and sandblast them.
This is how it looks after its sandblasted. I think sandblasting the rotors prior to gluing, helps the glue stick better to the steel. Here you can also see the jacking bolt holes. I drilled and tapped these for 7/16" bolts. I think its adequate for raising the rotors. The magnets are very strong.
Here is the lugs I cut out of 5/8" allthread. I made them 8" long just to be sure because I am using thicker steel rotors than Dan used. Volvo hubs come in two sizes. The newer cars come with 1/2" lugs and the older ones with 5/8". I like the 5/8" because I feel its alot more sturdy and when it comes time for the hub assembly, its an easy job to drill out the 1/2" hub to 5/8".
Here is how I align my magnets. I take an aluminum ruler to substitute the steel one usually found in the square because it wont be attracted to the magnets and I wont be fighting it to get a measurement. :-) I basically glue all the magnets on the back rotor and then assemble the front rotor facing up and just transfer the alignment over to the front rotor. I make a pencil mark and then use a transfer punch to mark it on the outside edge. The marks and surface are cleaned off prior to gluing with acetone. After the magnets are placed roughly, I go around and use spacers between each magnet to make sure I have them all spaced evenly.
another shot of the alignment process.
Here, both rotors are ready for casting. All magnets, front and rear are aligned and glued. Again, all exposed surfaces are cleaned and scrubbed with acetone to remove any oils and to make it easy for the resin to stick. These magnets needed to be cleaned very good prior to gluing because I think there was some sort of residue from the plating process left on them. Not a big deal.
Here both rotors are cleaned and ready for resin casting. I used coffee cans to form the interior dam. It makes for a quick and easy pour. I bolted them down with the lug bolts and jacking screws to make a water tight seal so the resin would not leak out. I use duct tape on the outer edge as a dam. Resin is then mixed up and poured between the magnets.
Here is how they look after the resin cures. The coffee cans make for a very clean edge. Use the plastic cans because they can be bent in and removed easily.
This is what happens when you cure the resin too fast. It breaks when the temperature changes. If you try this, make sure you mix for a slow cure time (25-30 mins). This allows the resin to not cure so brittle. It was easy to fix this. I broke out the cracked pieces, cleaned it well, applied crazy glue to everything (this made me feel better hehe) and mixed up more resin (slower cure time of course) and repoured. hopefully this will not be a problem in the future, but time will tell.
Here is where Im at now. Its all assembled and ready for testing in the lathe. If you look in the vice, you can see the new hub I made to allow me to spin these in the lathe easily, without having to use a volvo hub. I have to order more magnet wire before I proceed with any further tests because Im running out. Ill be placing an order Dan!! :-P
Have fun!!
RoyR |
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