| 49# 发表于 2010-8-30 13:22 | 只看该作者
Now to begin the second magnet rotor. Put the template on it so that the 4 holes line up and one of the slots lines up with the marks we made earlier. This assures us that the magnets we place will be facing each other when the rotors are assembled. The top of the first magnet on this rotor must be the opposite pole as the top of the first magnet we placed on the first rotor. In other words, the two surfaces facing one another must attract one another. Once you get the first magnet down, follow the same proceedure as you did with the first magnet rotor.
Check your work! You can easily double check your work now. Find a small magnet and hold it in your hand (dont turn it over - hold it in the same position always for the testing). Each magnet rotor has one magnet (the 1st one we placed) between the marks we made. The test magnet should attract this magnet on one magnet rotor, and repel it on the other. Then we can go around each magnet rotor and the test magnet should attract one magnet, repel the next one, attract the next one etc. If you made a mistake, you need to knock loose the offending magnets, put the template back on and get them right. Once all the magnets are placed and the tape is wrapped around them it's a good idea to clean the magnets and the rotors one more time with laquer thinner to make sure there's no grease. This will help the resin stick to the magnets.
Cut out two rings from fiberglass mat, or fabric. They should be 12" in diameter, with a 6.5" diameter hole in the center.
Grease the mold everywhere (Except on the bottom - that's not necessary). A good mold release is car wax, or Johns** wood wax. We've also used shortening from the kitchen and axel grease (axel grease is kind of gross and messy but it works). Grease it really well especially the first time you use the mold. The first coat tends to soak into the wood but after several applicati** it gets better. The point here is to make the mold greasy so the resin won't stick to it. Once all the parts are greased well then run a bead of caulk around the outside of the 12.5" hole in the mold. Also run a thin bead around the outside of the 1/2" thick 6.5" diameter disk. If it's not still there, stick the 1/4" drill bit in the center hole, we'll need this for alignment. |
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| 50# 发表于 2010-8-30 13:22 | 只看该作者
Drop one of the magnet rotors into the mold carefully. It fit nicely on the smaller 2.75" disk in the center of the mold so that the magnet rotor is a good fit and about pefectly centered.
Put the 6.5" diameter disk down. The drill bit will serve to center it on the disk. The side that we've run caulk around should face down and we need to press it down onto the magnet rotor. The caulk will assure that no resin can run under it.
We use polyester resin to cast the rotors. We get this stuff from almost any autoparts store. It's best to buy it by the gallon (it takes about exactly one gallon to build this whole machine). It comes with hardener in small plastic tubes. |
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