Wind power!
Jul. 9th, 2009 21:43![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
torquillSo, the project I'm working on is a small wind turbine for Burning Man, to power the RV's battery bank and supplement (or replace) the onboard gasoline generator.
The plans I came across that seemed the most complete -- and which matched the power scale I was going for -- were those for the Chispito wind generator. I started hunting around for a suitable treadmill motor, and discovered that not only are they pretty difficult to lay your hands on for less than $100, if I did get one (as I managed to, thanks to a friend with a disused walking unit) there was no guarantee that it would have the right specs... and the numbers varied so widely that I would have to make calculations based on the label for each motor. Sigh.
It was at about this point that I consulted![[livejournal.com profile]](https://www.dreamwidth.org/img/external/lj-userinfo.gif)
zakipu, and he threw several ballpark figures my way... and noted that a car alternator might do well. I said that the main problem was having to gear it down (as the Otherpower "motors" section mentions), which I had discarded as an option (thinking of motorcycle/car transmission type meshing gears). Then I realized, hey, bicycles have gears too, and the torque shouldn't be too bad...
So, since the top performance that can be expected out of a decent windmill is about 600 RPM, and most car alternators get the listed voltage at about 6,000 RPM, I'd need to gear down substantially. That's ok, there are lots of bicycle gears to choose from. I started revamping my designs to have an offset turbine/generator arrangement. One advantage to a car alternator is that it's already set up (complete with internal rectifier) to produce current/voltage suitable for charging 12V car batteries, so I didn't have to worry so much about whether it had the right ratings.
I got myself an alternator from McHugh's Dismantlers here in Concord for $25, and rustled around Recycle Bicycle in Berkeley for gears and wheel hubs (yay bearings). The current design calls for three gearsets linked by two chains, which should give me enough power with a good transfer rate.
So, in order of power transfer, I need to have:
Three PVC blades, bolted to a round metal rotor (I picked up a 6" flat pulley wheel, quite light and sturdy); that rotor is welded to a 3/8" allthread "axle", much like the wheel axles in bike wheels but much longer. Then there is a wheel hub, or two, which carries a bracket to bolt the axle assembly to the support and stabilize it. At the other end is the gear(s), welded to the other end of the axle; the hub(s) allow the axle to be repositioned forward or back as needed for chain/gear alignment, and the length of the axle should be chosen for best balance. Everything there rotates except the hubs.
The chain goes to a back-wheel hub/gear set bolted to the side of the support, which helps the gear ratio and guides the chain out of the way of the support bar. The second chain leading from that goes to the smallest gear I have, connected to the alternator bolted to the vertical post, further down. Lower than that is a pivot (I got a nice Volvo engine pulley wheel with a sealed bearing which should do nicely). The end of the horizontal support carries the tail fin.
If it all works out, I can enclose most of it to keep out (most of) the playa dust, grease the chain with dry lube, and have a nice turbine which spins the alternator fast enough to generate plenty of power for the batteries.
I still need to: cut the blades (not sure whether I want 3' or 2' blades, but I can do a set of each) and sand them to shape; get a piece of 3/8" allthread; weld a mounting nut to the end of the allthread for the rotor; make brackets for mounting all three hubs and the alternator; test the alternator on the lathe to check its stats; make the tail; assemble everything to find the balance points and weld the supports together; make the loops of chain; experiment to find the best gear ratios... there are also things like adjusting the intermediate gearset (on two axes) to make sure that the chains are on the right gears and have good tension.
After that, I turn my attention to the mast -- since we could be closer to the center of the city this time, I may need to plan a taller mast than "just above the RV". That gets us into assembling a mast, getting it upright, and probably putting in at least a couple of guywires. Whee!
The plans I came across that seemed the most complete -- and which matched the power scale I was going for -- were those for the Chispito wind generator. I started hunting around for a suitable treadmill motor, and discovered that not only are they pretty difficult to lay your hands on for less than $100, if I did get one (as I managed to, thanks to a friend with a disused walking unit) there was no guarantee that it would have the right specs... and the numbers varied so widely that I would have to make calculations based on the label for each motor. Sigh.
It was at about this point that I consulted
zakipu, and he threw several ballpark figures my way... and noted that a car alternator might do well. I said that the main problem was having to gear it down (as the Otherpower "motors" section mentions), which I had discarded as an option (thinking of motorcycle/car transmission type meshing gears). Then I realized, hey, bicycles have gears too, and the torque shouldn't be too bad...So, since the top performance that can be expected out of a decent windmill is about 600 RPM, and most car alternators get the listed voltage at about 6,000 RPM, I'd need to gear down substantially. That's ok, there are lots of bicycle gears to choose from. I started revamping my designs to have an offset turbine/generator arrangement. One advantage to a car alternator is that it's already set up (complete with internal rectifier) to produce current/voltage suitable for charging 12V car batteries, so I didn't have to worry so much about whether it had the right ratings.
I got myself an alternator from McHugh's Dismantlers here in Concord for $25, and rustled around Recycle Bicycle in Berkeley for gears and wheel hubs (yay bearings). The current design calls for three gearsets linked by two chains, which should give me enough power with a good transfer rate.
So, in order of power transfer, I need to have:
Three PVC blades, bolted to a round metal rotor (I picked up a 6" flat pulley wheel, quite light and sturdy); that rotor is welded to a 3/8" allthread "axle", much like the wheel axles in bike wheels but much longer. Then there is a wheel hub, or two, which carries a bracket to bolt the axle assembly to the support and stabilize it. At the other end is the gear(s), welded to the other end of the axle; the hub(s) allow the axle to be repositioned forward or back as needed for chain/gear alignment, and the length of the axle should be chosen for best balance. Everything there rotates except the hubs.
The chain goes to a back-wheel hub/gear set bolted to the side of the support, which helps the gear ratio and guides the chain out of the way of the support bar. The second chain leading from that goes to the smallest gear I have, connected to the alternator bolted to the vertical post, further down. Lower than that is a pivot (I got a nice Volvo engine pulley wheel with a sealed bearing which should do nicely). The end of the horizontal support carries the tail fin.
If it all works out, I can enclose most of it to keep out (most of) the playa dust, grease the chain with dry lube, and have a nice turbine which spins the alternator fast enough to generate plenty of power for the batteries.
I still need to: cut the blades (not sure whether I want 3' or 2' blades, but I can do a set of each) and sand them to shape; get a piece of 3/8" allthread; weld a mounting nut to the end of the allthread for the rotor; make brackets for mounting all three hubs and the alternator; test the alternator on the lathe to check its stats; make the tail; assemble everything to find the balance points and weld the supports together; make the loops of chain; experiment to find the best gear ratios... there are also things like adjusting the intermediate gearset (on two axes) to make sure that the chains are on the right gears and have good tension.
After that, I turn my attention to the mast -- since we could be closer to the center of the city this time, I may need to plan a taller mast than "just above the RV". That gets us into assembling a mast, getting it upright, and probably putting in at least a couple of guywires. Whee!
