The MintakaFulcrum

Mk 1.0

July 2001

Building Instructions, Photos, and Schematics

• Materials and Tools List

• Stator Construction Details
  
  
  • I wound my primary coils with AWG 22 with and equal number of turns for each core made. You want them to match. Try to use the exact same length of wire too.
  • I wound them with a conical winding technique that I found at Don Adstt's page. This in not necessary. You can simply wind back and forth. The URL is: www.theverylastpageoftheinternet.com.
  • You Can also get some great information and tips about DC pulsed motors at Konehead's website here: http://www.geocities.com/koneheadx/
  • For this design, only two stators are needed but can accommodate as many as eight.

• Stator Update

1. It appears that since my rotor magnets are 1" in diameter, this would allow my maximum drive coil diameter to be no more than 1/4" in diameter in keeping with Dr. Adams rule of one quarter ratio of core to magnet.
2. The best material for cores according to Dr. Adams is, pure iron and then next relay cores.
3. When using bolts as cores, it is a good practice to grind down the heads of the cores to as thin as possible. This is will help to maintain maximum flux concentration.

• Rotor Construction Details
  
  
  • I drew up a some plans for the disk and spindle, and then took them to a machine shop.
  • The only problem with these plans is that the disk thickness is smaller than my "new" magnet diameter... I would go with a 2" thick rotor and drill 8 one inch dia. holes for the magnets.
  • Here is drawing #1.
  • Here is drawing #2.

• Rotor Update

1. I now have 8 times 4 magnets on my disk. I have found that by using lots of hot glue and some filament tape, I have a very nicely balanced rotor that I have used safely up to almost 2500 rpm.

• Schematic for Switching Coil Circuit
  
  
  • Here is a schematic of the circuit I am using. It does not show the the secondary circuit pickup windings. Also the 1 K trim pot is not needed unless you want to control the speed of your motor. I am still determining weather this is an easy and effective way to control the duty cycle or not.

• Switching Update

1. Transistors are only good for running the motor and not so great for recharging the supply battery. Dr. Adams still uses commutator type of switching even on his latest designs. It is possible to use electronic switching, but it has do be done with a mosfet to keep the supply battery recharged.

• Construction Details for Rotor Base and Coil Support.
  
  
  • It is important to get your bearings to fit snugly into the two supports for them. You want to keep the shaft as perpendicular as possible.
  • The L-brackets are just screwed into the wood with small screws and this leaves a small amount of movement for adjustments later.
  • Also, you will have to drill a 3/8" hole in the L-bracket for your stator bolts to fit through. Do not do this until the rotor is mounted in its fixed position and you are happy that it is sturdy. Then measure from the top of the mounting platform to the middle of where the magnet is on the disk to get your proper height to drill your hole.

• Construction Detail Photos
  
  
  • Click on any picture for a bigger view.

Two holes must be drilled. One for the bearing and one for the shaft. Drill the bearing hole first.	The bearing is seated in the top support bracket.	Here is the bottom bearing seated in its support and held in place by screws from underneath the board.	The L-bracket that I used to mount my coils. A new hole must be drilled to accommodate the stator bolt. Notice washers under bracket for spacing of stator to rotor magnet.
Here is the mounted coil with some washers for spacing.	Here is the read switch mount. The switch cannot be seen as it is buried in styrofoam and tape to protect it.	Here is another view of the reed switch mount.	This is the transistor and heatsink.
View of the Base assembly ready for rotor.	The rotor has been put in place.	The top bearing mount is now ready to be secured in place.	This is my primary coil before I wrapped a secondary around it.
Here is my secondary coil over my primary. It is secured in place to the L-bracket in this photo.	This is the "safe" air gap that I use.	Note: The protruding part of the stator being the head of the bolt should be ground down as flat as possible to the surface of the coil retention disk... you want the magnets as close as possible to the stator core and the coil of wire when it swings by.	Other Note: It can be seen by looking at the way the magnets are held on... ie. hot glue and tape, that it would not be a good idea to take this model much above 2000 rpm or so. I have limited myself to using 12 volts for this reason.

CAUTION: The information here is for educational purposes only. Any attempt at replication is done at full liability of the one replicating it. These motors can develop high rpm and high voltage depending on how they are designed. Build and operate at you own risk!

email me: motorlab@shaw.ca

For the copy-right/claim© 2001-3 by: Ian Coke-Richards and The MintakaFulcrum and may be freely distributed with due respect. Not for commercial purposes without permission and licence from the author. All commercial uses are subject to the terms of the user licence.