The day the designer figures out how to make the lamp work, I'll purchase one!

For the moment though, it looks as if there's need for some further development.

Feedback

Physics Don't Support 40 Watts-Equivalent for 4 Hours

On February 20, 2008 2:17 PM, Mountain time; Mike Bentley wrote:

Some back-of-the-envelope calculations by a couple of engineers indicate that this clock is in no way capable of shining as bright as a 40 watt incandescent bulb. They're thinking, in fact, that you won't be able to get 4 watts.

The comments below come from a mailing list of consummate techies.

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"They claim to be putting out 600 lumens for 4 hours by harnessing the energy in a 50 pound weight lifted about 1.5 meters.  Anybody who's ever wished for a 600 lumen bike headlight powered by a hub dynamo is going to get suspicious at this point.

The most efficient LEDs on the market put out about 135 lumens per watt, I think.  So they need at least on the order of 4 watts for 4 hours.  That's 4 * 4 * 3600 = 57600 joules.

E = mgh
(I think the units here are joules, kilograms, m/s/s and meters - if
I'm wrong, everything below this point is useless)
Solving for mass,
m = E/(gh)
m = 57600 / (9.8 * 1.5) = 3918 kilograms

So you need to lift a 4000 kilogram mass 1.5 meters to run this for 4 hours, and that's assuming a 100% efficient generator.  Either that or you need to lift the 50 pound mass 57600/(22.7*9.8) = 259 meters. Either way, you need something on the order of 175 times more energy than they have available.

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Going at it a different way: 50lb is 22.7kg.  At 9.8m/s^2 it exerts 222 newtons of force.  A watt is a newton-meter, so this weight must descend 4/222=.018m/s to produce 4 watts.  There are 14400 seconds in four hours. 14400*.018=259 meters."

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Inventor Concedes Error

One February 21, 2008 5:59 AM, Inventor, Clay Moulton, responded to the above as follows:

Good morning Mr. Allan,

If there's any question as to the legitimacy of the competition now, I have offered to graciously concede the 2nd place win, as well as any winnings. My job now is to figure out a better design, plain and simple. I made an estimation based on feedback I got during the design process, and that estimation was shown to be incorrect.

I proposed this design as a response to questions that arose during my thesis work - specifically about time in design. I met with my committee to discuss whether this could actually work, and after consulting with a few engineering friends, I was told it was not possible given current LED's, but given the rapid pace of innovation in low powered lighting, it would be a conceptual challenge - What if there's a lighting source that is efficient enough? Or a generator efficient enough? My committee and I both concluded that this was an okay thing - part of the responsibility of designers (in my opinion) is to provide applications for technologies that aren't yet mature, or aren't fully realized. If it stays as a concept, then so be it. The upside to this is that once I showed the design to the folks at VTIP, we concluded that, yes, there's something here - but it's not fully realized. The patent was filed with the notion that the mechanism from the Gravia lamp could be used to power low voltage, low amperage electronics.

At this point I'd like to apologize. Failure is an okay thing with a concept - it's how we make better decisions, better designs and smarter solutions. I just hope that this isn't associated with a general failure of the competition, or any other thing more "real" than a concept for a lamp.

I'd like to thank you, as well any everyone that has provided their feedback - without them, the process falls apart. I hope there is some levity I can bring to this, and it would actually please me a good bit to help show just how the design process CAN and SHOULD work.

With my deepest respect,

Clay Moulton