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sks
Starting Member
United Kingdom
3 Posts |
 Posted - 10/12/2006 : 14:22:27
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Hi
I work for a school which has three cars entered for the Greenpower Electric Car racing series. www.greenpower.co.uk The cars are powered by two 65Ah batteries via a 260W 24v wheelchair motor. Recent changes to the race regulations have made carbon free charging of batteries during the races extremely advantageous.
The school has decided to approach charging in three different ways:
The first car will be solar charged. I expect this to be of limited use owing to racing in britain and the limitations of the panels we have available to us. It will however be a good educational exercise.
The second will be pedal charged. This will be a doddle as we have many keen and athletic volunteers who will happily crank away at a set of batteries for the duration of the four hour races. The generator we are building is based on four mountain bikes coupled to one of our spare motors. I do not forsee any problems with this.
The third car is to be thrown at the mercy of the winds as it were. Initialy, my plan is to stick a 4' diameter five bladed (soil pipe) rotor onto our second spare motor in a suck it and see fashion. I suspect that I may be a little naiive in thinking that this will yield a favourable result. If there's anyone there who thinks they can help spot pitfalls in this plan I'd really appreciate the input as this is all a bit of an unknown for us. Just incase it helps, here are the specs for the motor.
http://www.greenpower.co.uk/_code/download.php?extrapath=uploads%2F&file=GreenPowerF24MotorDrawing.pdf&a=&layout=
http://www.greenpower.co.uk/_code/download.php?extrapath=uploads%2F&file=GreenpowerF24PerformanceGraph.pdf&a=&layout=
Cheers 
Technology: The useful bits of art, the interesting bits of science.
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Edited by - sks on 11/12/2006 00:05:35 |
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gotwind
Forum Admin
United Kingdom
932 Posts |
Posted - 11/12/2006 : 10:09:06
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Solar is probably your most reliable method of power generation, remember that in January expect only a tenth of the power that July provides in the U.K
Your motor spec details 24v@2000 rpm, this is a bit too higher revs for a 4 Ft prop, suggesting a cut in speed of 1000 rpm, you would need a real gail blowing. My 100w plans uses an Ametek 30v DC motor that has a cut in speed of 350 rpm, but these motors are difficult to find - mainly found in the U.S
Treadmill motors have been used with some success in the past e.g 260v DC - try eBay
You could use the dynohub design with your 5 blade propeller design but don't expect much power, 5 Watts max.
Hope this helps and good luck.
Ben
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sks
Starting Member
United Kingdom
3 Posts |
Posted - 11/12/2006 : 12:27:31
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Thanks for the advice Ben
Our main races are in April, September and October  Not the sunniest, but we'll do the solar thing anyway just because we can.
I'm not locked into using a 4' 5 blade rotor, infact the research I did last night suggests that a two blade rotor might do the job better. What do you think? I'll get the kids to build a test tower that we can strap different options to and we'll have a good old experiment.
The only reason I suggested using the wheelchair motor is that we have two lying around. Eventually I would like to see a kid building an alternator as a GCSE project, that would be something
Technology: The useful bits of art, the interesting bits of science. |
Edited by - sks on 11/12/2006 12:32:52 |
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sks
Starting Member
United Kingdom
3 Posts |
Posted - 13/12/2006 : 17:32:43
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I managed to get some time for some experimentation today. My first,a 4' double blade turbine was rubbish, around 1.5v in a moderately srong wind. Not very scientific wind measurement going on but that will come. The second, a 3' soil pipe triple was ace. 13-16v in the same winds. That quite impressed me. Will let you know how things progress.
Just a thought, does anyone know if windscreen wiper motors have been tried yet? It just strikes me that there's a huge supply of them rotting away in scrap yards the world over. A wiper motor with a radiator fan? mmmmmm.....
Technology: The useful bits of art, the interesting bits of science. |
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gotwind
Forum Admin
United Kingdom
932 Posts |
Posted - 14/12/2006 : 15:27:37
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3 blader propeller is your best bet, most commercial machines run an odd number of blades, three, five e.t.c
I looked at useful bits from cars - all the motors require far too higher rpm's to be of use, you could use gears but that is wasteful.
Cars cooling fans are good and strong, but too smaller diameter, even the truck ones - don't worry I have considered most scrap sources for wind generation.
It is important to get your blades balanced properly especially high speed 3' ones - they could easily shake your generator to bits if not balanced.
My P.V.C propeller plans detail how to balance blades.
Ben |
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Greenpower Electric Car Racing
