Marcellus Jacobs: Wind-Power Generating Inventor
(Page 4 of 12)
November/December 1973
By the Mother Earth News editors
PLOWBOY: But we're still using two-bladers on airplanes!
RELATED CONTENT
John Shuttleworth discusses his experiences living the self-reliant life that Mother Earth News is ...
A Plowboy Interview with Shuttleworth, who discusses everything from the business of the magazine i...
The Plowboy Interview with Amory Lovins, author of the 1976 essay, "Energy Strategy: The Road Not T...
The Plowboy Interview: Frank Herbert May/June 1981 SCIENCE FICTION'S "YELLOW JOURNALIST" IS A HOMES...
JACOBS: Not always. When Curtiss-Wright developed some of that company's first really big engines at the start of World War Two, they found that the powerplants tore themselves right out of their mounts when the planes were kicked into an abrupt turn. I won't go into a long, confusing explanation of why this happens. It's enough to say that the Curtiss-Wright engineers and test pilots wrecked a bunch of aircraft before they finally solved the problem by going to three-bladed propellers...something I had done years earlier with my windplants.
See, this potentially destructive situation always exists with propellers that have two blades. It's always there but most of the time it doesn't give airplanes any trouble. I mean...when you make a turn with a plane, how large a curve do you usually fly? A quarter mile? Half mile? That's not nearly sharp enough to cause a problem. But a windplant supported in its center on a bearing whips right around, doesn't it? There just isn't any way to make a two-bladed wheel hold up on a windplant. Sooner or later—and probably sooner—it'll snap off at the hub...or one of the blades will let go.
PLOWBOY: But a three-blader won't.
JACOBS: No.
PLOWBOY: OK. Why wouldn't four blades be better yet?
JACOBS: Well, there'd be no object in going to four.
Look. It doesn't matter if you have one blade or a dozen...if you design them right you can make that wheel catch all the wind that comes through it. You can stand behind those spinning blades and strike a match and it'll hardly blow out. You're catching all the wind, you see, and slowing it down and changing its direction. One blade is just as good as four or five or more.
The only trouble with one blade, however, is that you can't balance it...and two blades have the vibration problem I've mentioned. A wheel with three blades nicely solves both these problems and you'd be foolish to add any more.
PLOWBOY: Why?
JACOBS: Because the tips of that wheel are moving through the air at 125 mph and every time you put on another tip you're adding unnecessary drag. It takes a lot of energy to push something through the air at 125 mph, you know. That's a waste of power.
There's another factor involved too. We wanted our windplants—which had 15-foot-diameter propellers—to develop their maximum charging rates in a wind of, say, 20 mph...but we didn't want their tip speeds to exceed 125 mph. A three-bladed prop met these requirements admirably.
PLOWBOY: All right. This takes us up to about 1927. What happened next?
JACOBS: Well, once we had the propeller design worked out, we still had two main problems: speed and pressure. If you want to get as much power as you can from a light breeze, you've got to have a propeller of large diameter. But when you have a large diameter, you've also got something you can't control in a high wind. You need some way to regulate your propeller's speed and you want to be able to take the pressure of the wind off your blades during a real gale.
Page:
<< Previous 1 |
2 |
3 | 4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
Next >>
