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torquillI have finished the blades for my wind turbine. Four 6' vanes, made of 12" aluminum flashing and held in a semi-rigid curve by two PVC ribs apiece. I spent much of this afternoon drilling the ribs, folding the cut edges of the flashing for stability and to get rid of sharp bits, marking them, curving them lengthwise (harder than it sounds!), tacking the ribs in place, and finally pop-riveting the ribs on the outside of each blade. The riveter was a bit fussy (it's old) and I had to drill out three rivets because of mistakes, but I got done before the light went.
They look quite good, if I say so myself. Fairly stable to handle, silver outside and gold inside (that's the flashing, not me), with teal ribs. I'd prefer BART blue to match the rest of the rig, but PVC is lousy at taking paint. It'll be covered in playa dust soon enough anyway.
As with any project, more steps end up appearing as you get to any given point in the process. The flashing wanted to curve widthwise rather than lengthwise, so I had to go on a tangent to make and attach the ribs. I need to take a little time to apply JB Weld to the wheel mounts I bought, as the center nut is only spot-welded and it wiggles. I diverted again to create a cross-brace on the base to keep the alternator and gear hub level under torque. Nothing that a little engineering and epoxy can't handle, but it's what makes for time and cost overruns on prototypes.
I should still be able to fully assemble it by the end of next weekend, which is the goal (testable by the end of July). At that point I bring in![[livejournal.com profile]](https://www.dreamwidth.org/img/external/lj-userinfo.gif)
foogod and zakipu, to look into the electrical aspects... zakipu and I have been nattering about possible solutions in case a combination of full batteries and high windspeed results in too many RPMs; that's much less likely than needing to take down the torque requirements for slower wind (which I expect to have to do) but it's still good to have some contingency plan. Even if it consists of only a long stick one can thrust aloft to wedge between the spokes. :)
At least we have a ready source of reliable wind for testing -- even in cooler weather, the wind-tunnel of the Pittsburg hills generates 15-20mph winds daily... which howl right across Greg's front yard. Set this thing on the sidewalk, and I can certainly do at least a basic test, if not a vibration check.
The assembly and disassembly should be manageable, though not exactly painless. I have yet to determine the order for mounting blades to wheels and spindle to frame, but that may become obvious as I do it for the first time. It will likely be a two-person job, for at least a couple of steps -- that's not a deal breaker, given that we're at least a two-person crew, and it's always possible to get somebody to help on playa if that were to mysteriously fail. (I still remember the poor guy down the street last year, who spent the better part of four days putting up a geodesic dome all on his lonesome, with a hand ratchet. No idea why he didn't recruit help.) There are eleven points of assembly for the frame, two each for the wheels, four for the blades, five for the alternator and gears, four guywires, plus looping the chain and doing the electrical connections... I expect full assembly could be done in under a half hour once I know the drill well enough. All points other than the blades, alternator, and guys are carriage bolts, which means I can go quite fast given a ratchet of my own. We'll see how I fare when moving the turbine from Concord to Pittsburg for testing.
I find I'm most paranoid about tearing the vanes, which is silly -- I know by now how tough even thin aluminum flashing is, and I've taken great care with the design not to stress it in any way that would promote tearing. Even the bases are supported 2/3 of the way by spokes, which will take a lot of pull off the single screw point at the outside corner, which is folded anyway for a bonus. Unless the torque is really excessive, it'll be fine -- and if it's that bad, I doubt the flashing will be my worst problem. Too much pull will misalign the gears and alternator, derailing the chain and dragging it all to a halt, unless my crossbrace is really, really good. We'll see.
Lots of this is wait and see... less and less waiting, now.
They look quite good, if I say so myself. Fairly stable to handle, silver outside and gold inside (that's the flashing, not me), with teal ribs. I'd prefer BART blue to match the rest of the rig, but PVC is lousy at taking paint. It'll be covered in playa dust soon enough anyway.
As with any project, more steps end up appearing as you get to any given point in the process. The flashing wanted to curve widthwise rather than lengthwise, so I had to go on a tangent to make and attach the ribs. I need to take a little time to apply JB Weld to the wheel mounts I bought, as the center nut is only spot-welded and it wiggles. I diverted again to create a cross-brace on the base to keep the alternator and gear hub level under torque. Nothing that a little engineering and epoxy can't handle, but it's what makes for time and cost overruns on prototypes.
I should still be able to fully assemble it by the end of next weekend, which is the goal (testable by the end of July). At that point I bring in
foogod and zakipu, to look into the electrical aspects... zakipu and I have been nattering about possible solutions in case a combination of full batteries and high windspeed results in too many RPMs; that's much less likely than needing to take down the torque requirements for slower wind (which I expect to have to do) but it's still good to have some contingency plan. Even if it consists of only a long stick one can thrust aloft to wedge between the spokes. :)At least we have a ready source of reliable wind for testing -- even in cooler weather, the wind-tunnel of the Pittsburg hills generates 15-20mph winds daily... which howl right across Greg's front yard. Set this thing on the sidewalk, and I can certainly do at least a basic test, if not a vibration check.
The assembly and disassembly should be manageable, though not exactly painless. I have yet to determine the order for mounting blades to wheels and spindle to frame, but that may become obvious as I do it for the first time. It will likely be a two-person job, for at least a couple of steps -- that's not a deal breaker, given that we're at least a two-person crew, and it's always possible to get somebody to help on playa if that were to mysteriously fail. (I still remember the poor guy down the street last year, who spent the better part of four days putting up a geodesic dome all on his lonesome, with a hand ratchet. No idea why he didn't recruit help.) There are eleven points of assembly for the frame, two each for the wheels, four for the blades, five for the alternator and gears, four guywires, plus looping the chain and doing the electrical connections... I expect full assembly could be done in under a half hour once I know the drill well enough. All points other than the blades, alternator, and guys are carriage bolts, which means I can go quite fast given a ratchet of my own. We'll see how I fare when moving the turbine from Concord to Pittsburg for testing.
I find I'm most paranoid about tearing the vanes, which is silly -- I know by now how tough even thin aluminum flashing is, and I've taken great care with the design not to stress it in any way that would promote tearing. Even the bases are supported 2/3 of the way by spokes, which will take a lot of pull off the single screw point at the outside corner, which is folded anyway for a bonus. Unless the torque is really excessive, it'll be fine -- and if it's that bad, I doubt the flashing will be my worst problem. Too much pull will misalign the gears and alternator, derailing the chain and dragging it all to a halt, unless my crossbrace is really, really good. We'll see.
Lots of this is wait and see... less and less waiting, now.
