Wind Turbine Project
I thought for sure I had posted about this project, but I went looking for it and could not find it. So I guess this is a new topic for the blog (albeit over a year old).
This is a project I worked on last year some time at school. I can't remember what class it was for now, it was either a custom production class or an electronics class (I know I got credit for at least the custom production class with it, but I think I just did it on the side).
The wind turbine is a crude machine, but there is a reason for why it looks the way it does. It uses a DC motor as a generator (an Ametek 30v). The motor needs around 2000 RPM to generate voltage in the 14+ voltage range (enough to charge/maintain a 12v battery system). I tested the motor on a lathe before I assembled this (that is what lead to the design). In order to get this voltage from the motor running as a generator on the turbine it required a 1:10 step up drive system, so for every 1 turn of the prop the motor spins 10 times.
The turbine borrows ideas gathered from the folks over at www.otherpower.com This includes the design of the tail. It is designed as a furling turbine. The theory behind this is that if the turbine gets in high winds the force of the wind on the turbine will push the turbine out of the wind and keep the turbine from over speeding, which would lead to destruction. How this works is both the tail and the hub are on opposite sides of the azimuth rotation axis and the tail is angled outward (as opposed to being perpendicular to the turbine). The angle on the tail ensures that the normal force on the rotor will hold it in to the wind. Once the wind speed reaches a certain point the force on the rotor will push the tail against the wind and the tail will actually rotate, holding the rotor at an angle to the wind. The tail hinge point is angled so that gravity holds the tail "down" when it is in the normal position. Then the tail will rotate "up" when the force gets too high.
Here are a couple pictures of what I mean:
You can see the angle of the tube hinge where the tail attaches to the turbine frame. I made it like this so the turbine breaks down, as opposed to permanently attaching the tail.
This is a front-on view where you can see the angle of the tail, it isn't straight in line with the rotor. The actual angle may be "tuned" by grinding down the tube the tail hinge sits in. I won't know until I get it up exactly where it needs to be.
Here are some pictures of the main hub. The part where the blades attach is not quite done yet, I need to get it spinning as true as I can get it before I finish weld it. Then welding is sure to cause some movement so it will be a challenge for sure. The final balance will be once the blades are on, that is the most important part as long as the wobble is held to an absolute minimum.
The main bearing block here was a major pain to machine. The stock wasn't thick enough to provide good support (at least that's how I felt) for the shaft so, not only did I have to cut out the recesses for the bearings (which took about 15 hours by itself on the machine I used) the outside had to be machined down so I could get a tube collar on the outside - pressed on tight and welded in place.
Things left to do - make some blades, true up the main hub, mount the blades, tune the mechanics and function of the tail, then hope for the best!
This is not an "ideal" design, it was making do with what I had on hand in the school shop with materials and tools, plus a few extras like pulleys and belts that I bought. I am sure you can spot a few design flaws. If I can get it up and running for Field Day or some other demonstration that would be great. I don't think this one would hold up to continuous use in a permanent installation.
This is a project I worked on last year some time at school. I can't remember what class it was for now, it was either a custom production class or an electronics class (I know I got credit for at least the custom production class with it, but I think I just did it on the side).
The wind turbine is a crude machine, but there is a reason for why it looks the way it does. It uses a DC motor as a generator (an Ametek 30v). The motor needs around 2000 RPM to generate voltage in the 14+ voltage range (enough to charge/maintain a 12v battery system). I tested the motor on a lathe before I assembled this (that is what lead to the design). In order to get this voltage from the motor running as a generator on the turbine it required a 1:10 step up drive system, so for every 1 turn of the prop the motor spins 10 times.
The turbine borrows ideas gathered from the folks over at www.otherpower.com This includes the design of the tail. It is designed as a furling turbine. The theory behind this is that if the turbine gets in high winds the force of the wind on the turbine will push the turbine out of the wind and keep the turbine from over speeding, which would lead to destruction. How this works is both the tail and the hub are on opposite sides of the azimuth rotation axis and the tail is angled outward (as opposed to being perpendicular to the turbine). The angle on the tail ensures that the normal force on the rotor will hold it in to the wind. Once the wind speed reaches a certain point the force on the rotor will push the tail against the wind and the tail will actually rotate, holding the rotor at an angle to the wind. The tail hinge point is angled so that gravity holds the tail "down" when it is in the normal position. Then the tail will rotate "up" when the force gets too high.
Here are a couple pictures of what I mean:
You can see the angle of the tube hinge where the tail attaches to the turbine frame. I made it like this so the turbine breaks down, as opposed to permanently attaching the tail.
This is a front-on view where you can see the angle of the tail, it isn't straight in line with the rotor. The actual angle may be "tuned" by grinding down the tube the tail hinge sits in. I won't know until I get it up exactly where it needs to be.
Here are some pictures of the main hub. The part where the blades attach is not quite done yet, I need to get it spinning as true as I can get it before I finish weld it. Then welding is sure to cause some movement so it will be a challenge for sure. The final balance will be once the blades are on, that is the most important part as long as the wobble is held to an absolute minimum.
The main bearing block here was a major pain to machine. The stock wasn't thick enough to provide good support (at least that's how I felt) for the shaft so, not only did I have to cut out the recesses for the bearings (which took about 15 hours by itself on the machine I used) the outside had to be machined down so I could get a tube collar on the outside - pressed on tight and welded in place.
Things left to do - make some blades, true up the main hub, mount the blades, tune the mechanics and function of the tail, then hope for the best!
This is not an "ideal" design, it was making do with what I had on hand in the school shop with materials and tools, plus a few extras like pulleys and belts that I bought. I am sure you can spot a few design flaws. If I can get it up and running for Field Day or some other demonstration that would be great. I don't think this one would hold up to continuous use in a permanent installation.
posted by Steve at
5:18 PM
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