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A typical exercise treadmill consumes about 1500 watts of power to move the tread; this is mostly due to the large amount of friction between the moving belt and the stationary platform beneath it.
If the platform beneath the belt were eliminated, the friction would be gone. Of course, the tension
of the belt would need to be increased to prevent the belt from sagging from the weight of the person walking on it, but this could easily be done if the belt were made of strong enough materials (carbon fibre reinforcement, perhaps?).
Once the treadmill's belt is able to turn freely, even with the weight of a person walking on it, it would be trivial to change the motor into a generator, allowing the exerciser to produce electricity.
To allow even more electricity to be generated, the person exercising could wear a harness, with a tether attached from the harness to some sort of post behind the treadmill; this allows the runner to push back on the tread at any given speed without running forward off the treadmill.
the laundry bike...so cool!
http://blogs.discov...2/laundry_bike.html
[xandram, May 12 2009]
[link]
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The first two paragraphs could be interesting. If you scrapped the bit about power generation and changed the title this might get a bun from me. |
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What about the varying reactive load as soon as you attempt to draw current from your generator? A very unpleasant exercising experience for someone who just wants to go for a run.
I can't quite see how the belt could be rigid enough to support a running person and yet flexible enough to bend round the rollers at either end. |
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//If the platform beneath the belt were eliminated, the friction would be gone.// |
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//Without the supporting platform, the tension required to support the weight of a very large man trying to lose weight would vastly increase the risk of belt failure, not to mention a trampoline effect, which is difficult to run on, and at that level of tension a belt failure would be incredibly dangerous. // |
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hmmmmm, maybe if the running surface were made from a thixotropic polymer then vibrations in the end rollers could possibly deform this flat sturdy surface only at the point of flexing. |
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Best of both worlds.
hmmmm. |
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21Q, /You also seem to forget the friction required to power your generator. You don't get energy from a generator without putting energy, in this case friction, into it./ |
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The friction I want to eliminate is that which occurs between the belt and the platform, which is a pure energy loss (motion is converted to useless heat). |
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The generator requires *work*, since you can't get something for nothing, but it doesn't require *friction* (parts rubbing and dragging against each other). |
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I realize that it won't be effortless for the runner, but "effortless" running is not the goal ... the goal is to convert the runner's efforts into useful electricity, rather than into wasted heat. |
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And as for searching... I have searched, and every I've looked, one person suggests generating power from a treadmill, someone else responds, "treadmills can't generate electricity, because treadmills consume electricity to operate." |
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skegger, with the proper controller, we can start off by drawing a very tiny current from the generator, then gradually increase it. |
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As for the belt, it shouldn't be inherently rigid; it's firmness should come either due to being pulled very tight, or as 2fries suggested, by using a
thixotropic material for the belt. |
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The main problem with this is that it would generate a pathetic amount of power, even if you are an exercise freak, or run a commercial gym. Something on the order of 100W. |
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You'd save far more energy by running round the block instead of driving to a gym. And if you have it in your home you wouldn't use it enough to generate significant power. |
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I commited this faux pas on my very first post- but I thought that everyone had seen this before. |
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This is going to require a new miracle-material be developed for the belt.
I made you an equation to find the belt tension: T=(W/2sin(arctan(2D/L))). T is the belt tension and will be in the same units as the person's weight (ie pounds). W is the person's weight. L is the length of the treadmill and D is the amount of belt sag you feel is acceptable (L and D must be same units).
There HAS to be some belt sag or the tension will be infinitely high (and your calculator will give an error). Play around with and you'll see that this belt is going to be under a LOT of tension. |
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how about a belt consisting of slightly wedge shaped elements? the smaller side would face inward, sitting on a belt. This would make for a slightly arched running surface. |
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Apart from that: there is no real challenge in constructing a friction-reduced belt system, otherwise tanks would use wheels instead of tracks. the reason treadmills skip this construcional part is that friction is perfect fo their application. |
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Apart from all that: gyms that produce electricity? [-] |
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It's not really a stupid idea- see link for bicycle-washing machine. |
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Can it be used to electrocute the person generating the
current? |
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[xandram]: the laundry bike skips the eletrical part, and uses mechanical energy for mechanical work - it doesn't get much more efficient than that, which is the good part. On the other hand, not using electricity robs this machine of just about every finer point of current washing machines, and reduces the current high-tech products to a rotating water-filled drum. (Current washing machines pull ~3000 watt peak, no use trying to pedal those) |
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