Re: gEDA-user: Magnetic bike operation

["David C. Kerber" <dkerber@xxxxxxxxxxxxxxxxxxxxxxxxxx>]

Just attach a disk of some conductive material to the axle of the thing you want to brake, and mount a strong permanent magnet so that it's near but not touching the flat surface of the disk.  I think a C-shaped magnet with the opening just big enough to clear the disk would work even better, but it's not required.  I believe my trainer uses two magnets, one on each side of the disk, facing each other.  If you're putting any significant continuous load on it, you will need some cooling; my trainer's load box get pretty warm after I've been using it for 20 minutes or so, and it has fan blades to drive air flow through it whenever it's turning.



> -----Original Message-----
> From: geda-user-bounces@xxxxxxxxxxxxxx 
> [mailto:geda-user-bounces@xxxxxxxxxxxxxx] On Behalf Of Rob Butts
> Sent: Monday, March 29, 2010 11:15 AM
> To: gEDA user mailing list
> Subject: Re: gEDA-user: Magnetic bike operation
> 
> I've read about the eddy current breaks but it's still not 
> clear to me how to construct one.  The wikipedia talks about 
> a rotor connected to a spinnning coil.  I would think the 
> rotor would spin inside a coil.  Then wikipedia talks about 
> using electromagnets and varying the breaking force by 
> varying the magnetic field.
> 
> On Sun, Mar 28, 2010 at 8:03 PM, David C. Kerber < 
> dkerber@xxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
> 
> > My bicycle trainer uses an eddy current brake; there are no wires 
> > anywhere in the load; just a ventilated disk and a magnet 
> that I can 
> > move closer or further away from the disk by turning an 
> adjustment dial.
> >
> > D
> >
> >
> >
> > > -----Original Message-----
> > > From: geda-user-bounces@xxxxxxxxxxxxxx 
> > > [mailto:geda-user-bounces@xxxxxxxxxxxxxx] On Behalf Of Rob Butts
> > > Sent: Saturday, March 27, 2010 4:29 PM
> > > To: gEDA user mailing list
> >  > Subject: gEDA-user: Magnetic bike operation
> > >
> > > I'm having a debate with an ee friend about how the magnetic 
> > > resistance works on an excersice bike.
> > >
> > > It occurred to me this would be the best place to solve it.
> > >
> > > Does anyone know if it is simply an electro-magnet close 
> to a metal 
> > > wheel where the stronger the magnetic field the stronger the 
> > > resistance?  Or is it alternating magnets in a flywheel type 
> > > configuration with a toriodal coil surrounding the flywheel and a 
> > > variable resistance in the coil circuit resists the 
> induced current 
> > > providing the resistance to user who would be spinning 
> the flywheel?  
> > > (Sorry if I didn't describe that well).
> > >
> > > Or is it something completely different?
> > >
> > > Thanks
> > >
> >
> >
> >  _______________________________________________
> > geda-user mailing list
> > geda-user@xxxxxxxxxxxxxx
> > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
> >
> 


_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user