Tire Prop

I was wondering if you could give a rough order (or at least point out how one would approach it) recommendation on the approximate size of props to use if one were building the larger version using a car tire and an alternator. You could make whatever assumptions you wish. I am currently thinking along the lines of what will most commonly be found after the pole shift. For example say 100 amp alternator maximally capable of 1200 watts but under the circumstances say it will put out about 500 watts. 13 to 14 inch rim-tires. Average wind equal to average winds found today. Could use 3 or 4 propellers not sure the width of the most common molding. Not sure how to arrive at best angle to use based on wind speed. Some guide lines and considerations could be helpful.

Picture a tire mounted on a bearing on the end of a 2x4 using a angle iron to mount the tire bearing shaft to the board. A pipe flange with a stand pipe for the swivel mounts on the bottom of the 2x4 so that it can turn in the wind. You use 2 pipes. There are 2 where the outside diameter is the size to fit into the inside of the other. the larger one is fixed to the tower, house or whatever, the smaller one rotates inside the other mounted pipe and the wire from the generator can be passed through the center of the smaller pipe. On top of the 2x4 a block of wood with door hinge mounted on top and between a flat board mounted to the bottom of an alternator. The shaft of the alternator with a knurled knob replaces the pulley and rests on top of the tire with the hinge and board attached to the alternator holding it in place. A tension spring between the alternator and the 2x4 holds tension between the alternator shaft and the tire. A cowling cover is constructed over the alternator for weather.

Offered by Mike.

I would try to move away from the tire idea in this application for several reasons. It will require a larger than normal rotor area for self starting, complicating formulas used as we need to keep it as simple as possible. Used tires are usually hard and slick, making them difficult to mate properly to an auto alternator. An auto alternator needs to be extremely tight to operate properly under the heavy loads required for wind generation. With an auto alternator you would need to fabricate a collar, and then what would happen if the tire lost it's inflation? You would loose your generator mating, and eventually the tire would start to spin on it's rim. The gear ratio is important here, we need to be able to create a system that will have ease of starting at a very low wind speed. We usually try for a starting speed of 10 m.p.h..

Imagine yourself having to climb up or lower a 30 - 60 ft. tower just to air up a tire, are you going to use an air hose (you just lost your power) or are you going to use a bicycle pump on a car tire? I think I will avoid that possibility at almost any cost. Every time you have to do either you are creating a dangerous situation for yourself.

Offered by Jay.

After the pole shift, I think the tires we would find would have plenty of tread on them. Most likely being take them off the cars no longer running due to no gas in the area. I think the main problem is if these weren't taken off before the pole shift, they may get punctured during the high winds of the pole shift. A collar could be done with epoxy soaked into rope or string wound around the pulley to bring it up to just above the edge of the alternator pulley sides. If the tire lost it's inflation you would need to pump it back up or change it out. I think a heavy spring could be used to keep the generator in contact with the tire independent of inflation. I think even if almost flat in most cases the tire will be stiff enough to drive an Alternator. In high wind and high power usage situations I can see some potential slippage at the point of tire contact with the alternator modified pulley. I think spring tension to be the key.

To pump up the tire, I think a small pressure tank pumped up with a bicycle pump on the ground, strapped to ones back to climb the tower, would do it. I saw one at wall mark that would work (a couple of months ago) that was on sale for $20. I agree that a properly rain shielded chain drive would be better in the long run, if one can find the parts after the pole shift. If one left the chain unprotected in the rain, then I doubt it would last long. The near constant rain would wash off the grease and soon rust and/or collect grit mixed with the grease that will be in the rain-ash mix. I expect in this case it would soon ware out and the rubber tire approach to be a viable alternative. Climbing the tower to put grease on the chain has the same inconvenience as pumping up the tire occasionally.

Re the size of the tire blocking the wind. I think the formula would be accurate enough especially if one used a metal cone (made out of sheet metal) shape to deflect the wind to the edges of the tire. A large sprocket would also block the wind to some degree.

wind ----> <| 
< = cone
| = tire

Offered by Mike.