building a wind turbine using a bevel gear.

[Faolan]

I asked my instructor about this but he doesn't have experience in wind turbines. would it be possible to build a wind energy generator using a set of angle gears so the motor sits on the vertical axis and doesn't spin?
I've tried to draw it out but I don't think I can get the proper support in my design. My thought is that the blades will turn a shaft sitting on bearings with a 45 degree bevel gear at the center of balance, the motor is housed in a pipe (the mast) connected to the second bevel gear. the turbine rotates around the gears on a bearing, with support wrapping around the mast a few feet down also on a bearing.
basically I don't want to worry about the power cord getting wrapped up, twisted. Any thoughts I can get on this would be awesome. thanks.

 

[magoo2]

You might check out Darrieus wind turbines. It has the generator at the bottom of a vertical shaft. The turbine is vertically mounted and looks a lot like an old egg beater.

It's not your gear idea but it might expand your horizons on the topic.

 

[MikeHalloran]

The only drawback of the bevel gear arrangement is that the torque being transmitted to the motor will try to swivel the turbine out of the wind. It might have some interesting stability problems.

I suppose it could work with an unusually large rudder, or one that was set up like a sailboat autopilot to provide correction for the yaw torque not due to wind direction.

Alternatively, you might use two bevel gears on the turbine shaft, driving a shaft and a tube in opposite directions, driving two generators on the ground by another two pair of bevel gears. That's a lot of mechanical complexity to deal with, especially as the tower gets taller and critical speeds become important.

;---

WRT excessive twisting of the power cables for a generator driven directly by the turbine, one of my former professors told an interesting story about that.

It seems that a company in Bethpage, Long Island, New York, built a wind turbine for a limited test run in Potsdam, New York.
It was equipped with mercury slip rings to carry the power from the generator to the tower.
Mercury freezes at around -40F.
It never gets to -40F in Bethpage.
It gets to -40F in Potsdam, pretty near every winter.
Sure enough, the slip rings froze, and there was some collateral damage.

It happened that the turbine/generator assembly was also equipped with a trailing rope inside the tower, for use when the turbine had to be manually slewed out of the wind.
Someone noticed that the trailing rope never became knotted, suggesting that the turbine never yawed more than one-ish revolutions from its initial position.

The slip rings were removed and replaced with long dangling cables, which allowed the turbine to yaw freely, and the generator was returned to service.

I suppose you could add mechanical rotation stops if you are really paranoid.




Mike Halloran
Pembroke Pines, FL, USA

 

[GregLocock]

Each gear pair will lose ou 2% in efficiency.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[racookpe1978]

There is a little bit to gain by moving the heavy generator stator down to the foundation level.

But....

The wedging force of the bevel gear up (and sideways) requires a substantial strength and mass up at the top of the mast anyway.

Also, that force needs to be reversed (supported) at the bottom with a massive gear/bearing assembly to absorb the weight and inertia of the 300 foot long, 12-16 inch diameter vertical drive shaft now required to transmit the torque from the stationary bevel gear mount at the top through the shaft to the generator and its (now vertical) bearings down low.

The generator rotor now needs the same treatment against axial movement to resist the rotor weight (some 15,000 lbs to 35,000 lbs total vertical weight for a large wind turbine), but with thermal issues and oil temperature differences added between a 120-130 degree mid-summer heat bath and a -40 deg mid-winter cold spell.

The original yaw and feathering controls are still needed to prevent wind damage, so there is no savings by eliminating those hydraulic motors and drive gears.

The upper turbine housing can be lighter however because it can be smaller. This helps, but doesn't replace cost of the the massive shaft and its radial and axial bearings.

 

[MikeHalloran]

OR, you could use contra-rotating turbines on concentric or colinear shafts, each driving a bevel gear, with a single bevel gear at the top of a single long shaft driving the generator.

You'd probably take a lot of crap over increased bird strike probabilities.


Mike Halloran
Pembroke Pines, FL, USA

 

[waross]

Cost, complexity, higher maintenance, torque issues, added failure modes; there may be some reasons why no-one uses right angle drives with bevel gears.
Interestingly in the early days of farming when windmills were common, there was a system for direct driving or pulling the sucker rod of a water pump.
The blades or turbine were mounted on the input shaft of a reduction gear box.
The output shaft had a bell crank positioned over the center of a hollow main pivot bearing.
The sucker rod had a swivel joint and was suspended from the bell crank.
A counter weight could be fixed below the swivel joint to balance the weight of the sucker rod.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[racookpe1978]

It is refreshing to be able to relate the info I got after a couple of trips to Lubbuck's wind energy museum - It covers the history of the orignal European rotating house-mills and pump stations, the 1800's-1950's US-Western flat-blade windmills, and the more efficient lifting blade electric generatrors very well with hundreds of models of blades, pumps, and generators of all sizes.

the flat blade, "wind resistance" western windmill is characterized by tremendous torque at zero rpm (large lifting force at near-zero rotation speed when starting, but poor efficiency and lower torque at high speeds. This fits their intended application exactly: They need to lift the 150-300 foot pump rod, the foot valve at the bottom of the well, any water trapped above the foot valve, all the water column from foot valve to top of well, and all of the resistance of the (rusted) arms and linkages at the top of the windmill.

Once at speed, the inefficiency of the flat-blade windmills could be basically ignored. There was no alternative to the windmill, so ANY power available at the top of the windmill was useful.

Even the earliest electric generators in the 1930's found that their application needed almost no starting torque (electric power can be tapped only after the machine was at speed) but high-speed efficiency was essential. So the three-blade lift-profile became common for power production almost immediately.

The flat-blade old windmills are good for irregular intermittent water pumping at any convenient time the pump can be run and refill the animal's water tank, but not much else.