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Old 02-03-11, 10:14 PM   #1
regnof
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Magnetic resistance exercise bike head-scratcher question!

Hi everyone,

I recently lost 20 pounds (158 lb down to 138 lb) riding an exercise bike; it is a nothing-too-fancy Proform 920 S EKG that I bought used on Craigslist for $50. I wasn't exact overweight to start with. I'm male, 5'8"; was just carrying a little spare around the belly. My body fat went from 18% to 11%.

Since I've been riding the exercise bike a lot, I'm starting to notice a few things malfunctioning on the exercise bike. The digital display is totally shot/illegible, but I can still control the intensity level from 1 to 10. Then I got to thinking, since the difficulty of the machine is controlled by the position of the magnet to the flywheel - closer, more difficult to ride; farther, easier - why do they still need to build exercise bikes with a chainring connected to the flywheel via a belt? That is, why don't the maker just have the user pedal directly onto the flywheel, saving parts and money, reducing the number of things that can go wrong? The rider should be able to pedal, as usual, except the crank is built into the flywheel, and the magnets are positioned just the same as before to control the difficulty. Less part to worry about, less things that can go wrong, smaller and more compact machine, win-win for everyone...

Can anyone tell me why?

Last edited by regnof; 02-03-11 at 10:29 PM.
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Old 02-04-11, 01:32 AM   #2
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but then it wouldn't be an exercise bike, it would be an exercise Big Wheel!


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Old 02-04-11, 06:51 AM   #3
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Aesthetics sell products; no matter how sensible from an engineering standpoint, if it doesn't look right to a consumer, it won't sell.

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Old 02-04-11, 06:51 AM   #4
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Take off your back wheel and drop your bike frame right onto this baby. Of course, Lance fans might choose to boycott the product...

http://www.lemondfitness.com/product...ond-revolution
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Old 02-04-11, 07:59 AM   #5
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Originally Posted by regnof View Post
Then I got to thinking, since the difficulty of the machine is controlled by the position of the magnet to the flywheel - closer, more difficult to ride; farther, easier - why do they still need to build exercise bikes with a chainring connected to the flywheel via a belt? That is, why don't the maker just have the user pedal directly onto the flywheel, saving parts and money, reducing the number of things that can go wrong? The rider should be able to pedal, as usual, except the crank is built into the flywheel, and the magnets are positioned just the same as before to control the difficulty. Less part to worry about, less things that can go wrong, smaller and more compact machine, win-win for everyone...

Can anyone tell me why?
Easy Peasy. How fast is that wheel rotating? Probably faster than 1:1 with your pedal stroke. The more frequently the magnet on the wheel passes the magnets and sensors on the frame, the finer control you can achieve with regard to resistance.
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Old 02-04-11, 01:00 PM   #6
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Easy Peasy. How fast is that wheel rotating? Probably faster than 1:1 with your pedal stroke. The more frequently the magnet on the wheel passes the magnets and sensors on the frame, the finer control you can achieve with regard to resistance.
Not sure about your theory, Artkansas, the flywheel and the chainring are roughly the same size, so I would assume that the pedal stroke and the flywheel are rotating at about the same speed.

However, I did find a very attractive stationary bike with what I described previously, pedaling directly onto the flywheel.


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Old 02-04-11, 01:05 PM   #7
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"but then it wouldn't be an exercise bike, it would be an exercise Big Wheel! "


Cyclaholic, that picture is totally hilarious!
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Old 02-04-11, 02:35 PM   #8
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Having the Mag unit spinning much faster than your pedal rpm allow the mag unit to be much smaller and less expensive to build. I pedal at 100 RPM and my mag unit magnets spin at about 6000 RPM....
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