- #1
JustRob
- 5
- 0
I am an electrical engineer disabled in a snow sking accident and am now a quadriplegic. I'd like to design an exercise arm bike and make it magnetically resisted because friction resisted is not conducive to minute changes in resistance.
I have a magnetic resisted trainer for a road bicycle where you take the front wheel off of a road bike, fasten the forks in the trainer frame and the back tire sets on a roller. At one end of this roller is a small aluminum disk roughly 1/8" thick and 4" in diameter and attached to the spinning roller. On one side of the spinning disk is a disk the same diameter with six 3/4" diameter magnets (appear to be ceramic) arranged around the perimeter of the 4" disk evenly spaced (as if every 10 minutes around a clock). This disk is fixed and cannot move.
On the other side of the spinning aluminum disk is an identical magnet disk with magnets configured the same way but allowed to rotate 30 degrees. The strength of the magnetic field is varied by rotating one magnet disk causing the magnets to more eclipse the corresponding magnet on the other side of the spinning aluminum disk.
I can't find good information explaining the theory behind this. I have read all of the wiki pages on eddy current brakes. I'd like to see an equation that would explain what is going on. I got 1" neodymium magnets and positioned them around a 5" disk with a 1/8" thick disk between but the resistance is minute. I suspect it is because the rotational velocity is no where near as fast as the road bike trainer. I have also been told that the thickness of the spinning disk between is too thin.
Any help or direction is GREATLY appreciated!
Thanks
I have a magnetic resisted trainer for a road bicycle where you take the front wheel off of a road bike, fasten the forks in the trainer frame and the back tire sets on a roller. At one end of this roller is a small aluminum disk roughly 1/8" thick and 4" in diameter and attached to the spinning roller. On one side of the spinning disk is a disk the same diameter with six 3/4" diameter magnets (appear to be ceramic) arranged around the perimeter of the 4" disk evenly spaced (as if every 10 minutes around a clock). This disk is fixed and cannot move.
On the other side of the spinning aluminum disk is an identical magnet disk with magnets configured the same way but allowed to rotate 30 degrees. The strength of the magnetic field is varied by rotating one magnet disk causing the magnets to more eclipse the corresponding magnet on the other side of the spinning aluminum disk.
I can't find good information explaining the theory behind this. I have read all of the wiki pages on eddy current brakes. I'd like to see an equation that would explain what is going on. I got 1" neodymium magnets and positioned them around a 5" disk with a 1/8" thick disk between but the resistance is minute. I suspect it is because the rotational velocity is no where near as fast as the road bike trainer. I have also been told that the thickness of the spinning disk between is too thin.
Any help or direction is GREATLY appreciated!
Thanks