Ron v. Sommeren

The e-mail group for help and discussion on construction and design (English), monitored by yours truly:
http://www.yahoogroups.com/group/LRK-torquemax
You’ll find more links there and you will get more links upon subscription.
To join the list, click ‘Join This Group’ in upper-righthand corner, or send an empty message to [email protected].

These diy high-torque/high-performace brushless outrunners can be made using a relatively simple lathe. One has to be capable of making a press-fit ball-bearing seating though. They have a high torque at lower rpm than a conventional high-revving brushless layout. SPS is the electro-mechanical principle used in these motors: every other stator-tooth is left empty. SPS was originally designed for magnetic levitation trains! There's no need for a gearbox, which means less weight, less losses, lower costs and no gear whining. It can be tailored to the application by choosing the stator diameter and magnet length and the number of windings you want. It's possible to rewind the motor (or even swap the complete stator) for a different type of application.

The LRK is an inside-out motor, the coils are stationary, housing and magnets rotate. This has the additional benefit of good magnet cooling and the coils are not stressed by centrifugal forces. The magnets must have at least a magnetic strength of 1.1 Tesla (Neodymium, NdFeB, magnets). The motors built to date, range from slow-flight 20Watt to 2kW versions, development for 3kW versions is underway. Efficiency is in the 80-85% region and still increasing, slowly moving to 90%. LRK motors operate with normal brushless controllers. ESC manufacturers have already updated or are in the process of updating their controller software to make the controllers suited for this type of motor.

You can use an old brushed motor or gut your CD-ROM player, harddisk, wife's blowdryer (or your own , (cordless)powertools or fanmotor for stator material. Check the bin of a motor/transformer rewind shop for material. You can do a little dumpster jumping at metal stampers, scrap yards, the local dump. Use shafts from VCR’s or broken drills. Or you can buy the parts.

If you can read a bit of German, check out the German LRK forums, they are *very* good:
http://www.rcline.de >> rc-forum >> elektro-motoren
http://www.rc-forum.de >> flug >> LRK
http://www.rc-network.de >> forum >> E-Motoren & LRK-Technik