X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com X-Authority-Analysis: v=2.0 cv=adbjbGUt c=1 sm=0 a=6jktZp3dcHAl1vye2O6wCg==:17 a=jl9P3j1e7_0A:10 a=PAbBOzD169AA:10 a=yRlGJCGbHvAA:10 a=6WB07kdHjWAA:10 a=8nJEP1OIZ-IA:10 a=wR-FlJDvAAAA:8 a=mVJ64cV3UQEA:10 a=HCPz85UZZ8MxPB3J3m8A:9 a=wPNLvfGTeEIA:10 a=6jktZp3dcHAl1vye2O6wCg==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 70.113.67.117 Message-ID: <51505B7A.8060202@ecosensory.com> Date: Mon, 25 Mar 2013 09:13:14 -0500 From: John Griessen User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130307 Thunderbird/17.0.4 MIME-Version: 1.0 To: geda-user AT delorie DOT com Subject: Re: [geda-user] Magnetic Exercise Bike design with a stator and rotor References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Reply-To: geda-user AT delorie DOT com On 03/24/2013 03:58 PM, Rob Butts wrote: > One plastic disc is fixed and the opposing plastic disk is allowed to rotate 30 degrees providing the variable magnetic field and > variable resistance. I have not been able to simulate the resistance I believe because I'm not providing the same rotational > velocity of the aluminum disc. Sounds like the out of alignment of the discs makes the field vary from weak to strong. To have strong fields, each magnet needs to be straight across, (through the aluminum disc), from another with same polarity direction. Then induced currents flowing in circles around the strong field area counter subsequent motion by a force of their own. I've never quite grasped how that force stays local to any place in the aluminum plate though...perhaps inertia of electrons? Else moving the path of the high eddying current is more resistive than the eddy path? It's all so circular! I feel like researching and reading about it instead of doing my taxes... What do you mean by simulate? What velocity can you get? Some decent velocity is needed for small inexpensive magnets. I've seen a demo of eddy current braking done with a pendulum hung plate, then a slotted plate for comparison, where the opposing magnets were very massive and with iron looping around to make a complete magnetic circle path with two short gaps, ( where the aluminum plate moved). It would slow the pendulum in one stroke by 4/5ths. It must have weighed 80 lbs. An alternator will need velocity also. Bicycle gearing can get you velocity.