Author Topic: Turbine gearbox  (Read 2353 times)

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stofanel

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Turbine gearbox
« on: February 27, 2017, 09:47:04 AM »
I am ready to take plunge into a DIY turbine project, and I am considering a somewhat unconventional design (by DIY standards, anyway). The missing piece in all DIY turbines seems to be the gearbox. I have nothing against axial flux generators EXCEPT that they seem to be quite expensive and time consuming to build. My solution: hook up the wind turbine to an off the shelf 3600rpm generator via a 16:1 or higher gear box. Has anyone considered building such a contraption, and if not, what seems to be the challenge? Designing such a gearbox does not seem to be that difficult:  let's say, 2 sets of 4:1 or even 5:1 gears, two shafts, a few bearings and an enclosure. Full access to a machine shop is a must, but it seems to me that building a generator requires the same type of skills and tools.  Any thoughts?

I do have access to a full machine shop BTW.   
« Last Edit: February 28, 2017, 09:43:34 AM by stofanel »

super64

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Re: Trubine gearbox
« Reply #1 on: February 27, 2017, 11:47:19 AM »
you are trying to do what am trying to do  :D

well one member had a great success with geared wind turbine .ChrisOlson

http://www.fieldlines.com/index.php?action=profile;u=21517

my advice start small 1 kw and then scale it up .

from my understanding which is limited .

3600 rpm is a 2 pole generator so you are planning to use a generator head .

if yes , you should use a brushless type .brushes wear very fast and will risk a run away turbine.

anther down side wind is not constant so you should chose your location to suit such a wind turbine why, because if the speed drop below 3600 rpm as do voltage and if your turbine can get enough wind to get the 3600 rpm at the motor side of the tranny you need a way to deal with the extra wind to avoid over voltage .

axial flux have a larger range of wind input which make it a simpler machine to construct.


assumption is the mother all failure .

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joestue

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Re: Trubine gearbox
« Reply #2 on: February 27, 2017, 11:53:31 AM »
Off the shelf 3600 rpm generators say 10kw, Probably 1 shaft hp needed to turn them once you include the friction of a gearbox suitable for a 10kw max wind turbine.

If the average wind power available is 2-3hp, you just lost 30 to 50% of your yearly kilowatt hours.

I would suggest you use a vehicle differential as a single stage gearbox. Reduce the preload on the pinion tapered roller bearings, the ring gears bearings should be large enough to support the blades without any extra help. Wind a 4 pole synchrounous generator from an induction motor.

Use relays to cycle through the four standard voltages available, 138/240/277/480 , combined with variable excition to get optimum wind loading.

Brushless excition is just a few more machining operations away if you dont trust brushes

mbouwer

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Re: Trubine gearbox
« Reply #3 on: February 27, 2017, 12:21:19 PM »
In 1987 we made a two-stage gearbox for a 750 rpm generator.
In between you see the wiper motor for the active pitch.
« Last Edit: February 27, 2017, 12:26:21 PM by mbouwer »

Bruce S

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Re: Trubine gearbox
« Reply #4 on: February 27, 2017, 12:58:42 PM »
mbouwer.
Nice!!

OP, in the early days long before people had good speeds and Neos, people used ceramic magnets.
These of course needed a good high-speed. There was tons of ways people were using even the banjo style 3-members off old cars. I think even the owners of this website built them !!

Mother Earth News website might still have archives of them as well.
Hope this helps

Bruce S
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Mary B

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Re: Trubine gearbox
« Reply #5 on: February 27, 2017, 02:47:46 PM »
By the time you buy all the materials and do the machining it might be cheaper to adapt an off the shelf part like this https://www.mrosupply.com/speed-reducers/motor-multiplier/48101_hmf2-5k-b5-b5_boston-gear/ 1:5 multiplier gear box, 5hp input...

stofanel

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Re: Trubine gearbox
« Reply #6 on: February 27, 2017, 04:07:08 PM »
I have considered off the shelf gearboxes. There are no speed multipliers with gear ratios above 5:1 or so. For this contraption to work, I'll need to multiply 200-300 rpm to 3000+rpm. So the final gear ratio should be 10:1 to 15:1 or better. Cascading two off the shelf 5:1 gear boxes waste too much energy and cost too much.

People seem concerned about wasting 20%-30% of turbine power by adding a gearbox. This is the trade-off between mechanical power (wasted as friction) and electrical power (wasted as heat by the generator). I don't know the exact power dissipation of PMG's, but I would figure that I^2*R amounts to a lot of heat. By contrast, commercial 3000W-5000W generators can easily get 80% or better efficiency just because high rpms do not require as much copper windings as lowe rpm generators. So I would argue that the overall efficiency of a gearbox + commercial generator head is comparable, if not better than an axial flux PMG.   

Warpspeed

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Re: Trubine gearbox
« Reply #7 on: February 27, 2017, 05:36:47 PM »
There are plenty of gearboxes around second hand at affordable prices rated to several horsepower.
Just remove the original three phase motor these gearboxes usually come with, and fit your own alternator to the four bolt flange. The original motor coupling can usually be reused, if not you can buy a replacement spare to suit any shaft diameter.
These gearboxes are super strong (and heavy) fully sealed and made to work completely exposed outdoors.

Ratios are all over the place, they come in either "straight through" or more commonly "right angle drive".
The input shaft and bearing will easily be strong enough to support a large diameter wind turbine rotor.
From machinery dealers the large ones can cost several hundreds of dollars.  On e-bay smaller ones can be found for a hundred dollars or less from private sellers.

A very quick look on e-bay turned up this:
http://www.ebay.com.au/itm/ABB-3-PHASE-MT199LB28-4-4-POLE-ELECTRIC-MOTOR-1430rpm-REYNOLD-12-5-1-Gear-Box-/122004676118?hash=item1c680b9e16:g:n~oAAOSwQItT6EMc
Its too expensive, but has continuous 3Kw rating and 12:1 ratio.

The straight through boxes are definitely preferred, especially as most of the right angle ones use a worm gear which will obviously not work when feeding power back the opposite way, so beware !
But the straight through gearboxes  have very large wide spur gears and turn very easily when driven from either end.


Be patient and something will turn up.
« Last Edit: February 27, 2017, 06:07:11 PM by Warpspeed »

bigrockcandymountain

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Re: Trubine gearbox
« Reply #8 on: February 28, 2017, 06:42:22 AM »
Check out breezy from prairie turbines inc. 

It does what your thinking.  I'm not saying buy the kit or anything, just look around their website.  They have some great ideas.

Harold in CR

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Re: Trubine gearbox
« Reply #9 on: February 28, 2017, 07:05:54 AM »

 I bought a 10:1 helical gearbox, brand new, for under $100.00. You just need to keep checking there.

 I built a 4KW alternator wind turbine, back in '77. I had an engineer do some complimentary figuring, and, he came up with a 16' dia wind turbine blade set up putting out 6HP in a 25 MPH wind. I bought a Browning helical gear gearbox and mounted it backward on the blade hub. Used a governing blade system and flew that machine for several years, until a tornado went by close enough to destroy the governing joints and throw the blades out into the brush.

 You won't lose enough power to notice using helical gears. I used a GE 1800 RPM alternator, self exciting. The prop would start to turn at 6 MPH and cut in at 8 MPH. I used a relay set to close and open where I needed, and an oversized diode and aluminum plate heat sink, all on one leg of the alternator. On the other leg, I used an old variac and a 36V Lester battery charger. It would trickle charge at 9 MPH and run full charge 25A at governed speed of 23 MPH and 1850 RPM.

 All this was done by "feel" adjusting things up on the tower, back when my knees would handle that.

 1800 RPM alternators are used on Diesel powered generation units.

 We had photos but they have disappeared over the years.

stofanel

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Re: Trubine gearbox
« Reply #10 on: February 28, 2017, 09:35:40 AM »
Thank you for the input. My first instinct was also to look for a reasonably priced reversible gear box. Unfortunately, most high ratio gear boxes are speed reducers (aka worm gears) which do not work as speed multipliers. If anyone knows of a supplier of such gearboxes (10:1 ratio or higher, approx 5hp), please let me know.

mbouwer

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Re: Turbine gearbox
« Reply #11 on: February 28, 2017, 10:00:06 AM »
We somethimes used a straigt through gearbox like Warpspeed mentioned.
Then we made a hollow axle with a sleeve in front of it to steer the pitch.


Adriaan Kragten

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Re: Turbine gearbox
« Reply #12 on: February 28, 2017, 11:23:40 AM »
In my free public reports KD 578 and KD 579 you find a lot of calculations for a 6.5 m diameter wind turbine with a 2-step standard gear box and a 3-phase, 4-pole asynchronous motor which is used as generator for (50 Hz) grid connection. In free public report KD 624 you find an alternative direct drive 46-pole PM-generator if the same wind turbine is used to drive the 2.2 kW asynchronous motor of a centrifugal pump but this generator can also be used for battery charging if it is provided with a low voltage winding (see www.kdwindturbines.nl). The problem with gear boxes is not only the efficiency but also the sticking torque, the noise production and possible oil leakage. Personally I favour direct drive even if it is more expensive.

Bruce S

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Re: Turbine gearbox
« Reply #13 on: February 28, 2017, 12:31:14 PM »
stofanel;
Since you have access to a machine shop, why not cut your own gears?
IF you already have a mill you're ready to use, merely cut a gear that takes it up to your needs. Also you could even start with a bicycle gearing to test out the theory.
This should work with less loss than say going with a gearing that has pinion or sun gears to get it up to the speeds.

Just a thought.
Bruce S
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Warpspeed

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Re: Turbine gearbox
« Reply #14 on: February 28, 2017, 01:50:51 PM »
If you are going to home build something, commercial sprockets might be a lot easier than cutting your own gears.
The trick of how to make any speed increasing gearbox efficient, is to keep ALL the gear diameters reasonably large.
Think about it....

If you were building a speed REDUCING gearbox you can use an incredibly small pinion to drive a very large diameter gear all in one stage, and it will work fine.
But try driving the big gear, and it will not like turning a very small pinion.
A half inch fine tooth pinion cut directly into the shaft driving an eight inch gear for 16:1 will make a very poor speed increaser, but an excellent speed reducer.

A much better way would be an eight inch gear driving a two inch gear (4:1) followed by another eight inch gear driving a second two inch gear, also 4:1
none of the gears are really small and it will turn very easily when driven from the slow speed end.

stofanel

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Re: Turbine gearbox
« Reply #15 on: February 28, 2017, 07:30:18 PM »
stofanel;
Since you have access to a machine shop, why not cut your own gears?
IF you already have a mill you're ready to use, merely cut a gear that takes it up to your needs. Also you could even start with a bicycle gearing to test out the theory.
This should work with less loss than say going with a gearing that has pinion or sun gears to get it up to the speeds.

Just a thought.
Bruce S

I am actually researching this very same topic. Once one gets past the technical jargon, gears are easy to design and machine. I am considering cutting two sets of 4:1 gears that will allow me to build a 16:1 gear box. It turns out that youtube is full of videos on how to accomplish this.

joestue

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Re: Turbine gearbox
« Reply #16 on: February 28, 2017, 07:40:01 PM »
one option may be the final drive of a moped.

The relatively lightweight moped I found several years ago had a CVT transmission centrifugally controlled, followed by approximately a 6:1 transmission. spur gears, thick oil, difficult to turn backwards by hand, mostly due to the heavy gear oil, there were only two oil seals and the bearings were open race, ball bearings.

because the output shaft of the transmission supported the rear tire directly, on one side only, it would could probably support a 12 foot turbine directly with no modifications.

I would re-use the gears out of any small vehichle 4 or 5 speed transmission before cutting my own. easy enough to cut them off the secondary shaft (since you can't mix and match any of them) and bore a hole or grind the od of the shaft to fit a bearing on it. first gear multiplied by second should be in the range of 6 to 7:1. or use reverse gear.. 3.6 squared is about 13:1.


anyhow yes you can make your own gears quite easily but then you have to heat treat them. if you want to get linux cnc running you can use a stepper driven gear box to rotate the gear blank while you drive a hob from the spindle. allegedly there are several people on the various forums who have sucessfully done this. the encoder required for the spindle only costs a few dollars, or find one in a printer. no need for an expensive encoder, 500 lines is plenty.
« Last Edit: February 28, 2017, 07:46:40 PM by joestue »

stofanel

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Re: Turbine gearbox
« Reply #17 on: March 01, 2017, 12:53:10 PM »
It seems that it is quite easy to design gears for static and dynamic loading. There are plenty of formulas and online calculators that will do all the ugly math work. It is quite difficult to design for surface wear, so the preferred method is trial and error. I am being told, however, that stainless steel is relatively easy to machine and relatively inexpensive to procure, so I will be working on a 16:1 gearbox design (if I don't find a cheap used one in the meantime).

I do have access to a 4 axis CNC industrial spec mill, so the machining at least should be fun.

Bruce S

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Re: Turbine gearbox
« Reply #18 on: March 01, 2017, 01:59:20 PM »
stofanel;
If those are exciting to you, then maybe you could look into a type of Epicyclic gearing.
Everything would be enclosed in a nice small container that could be sealed to maintain longevity.
Along with only needing 3 gears, as the first could be the 4:1 multiplier then 3rd being the multiple of 2nd.
1st gear being 64tooth 2nd being 16 3rd being only 4, of course a 4 tooth gear would be horribly noisy , but you get the idea. Unless of course my graphite based math sucks...

This type may seem horribly inefficient, but it stuffs the gears into each other; lending stability to the system and less mess.

 
Just a thought
Bruce S
 
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Warpspeed

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Re: Turbine gearbox
« Reply #19 on: March 01, 2017, 02:14:17 PM »
Epicyclics would certainly be the ultimate in every way, but in practice about 5:1 would be about the highest practical ratio per stage.
Way beyond cutting your own gears at home I would think.

But I wonder if some very nice epicyclic parts could not be salvaged from dead automatic transmissions ?


stofanel

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Re: Turbine gearbox
« Reply #20 on: March 01, 2017, 04:58:24 PM »
I have plenty of dead transmission parts. Some of the planetary gear assemblies are relatively cheap and easy to obtain. However, gear ratios top at about 3:1, and they are a pain to mount properly. Planetary gears rely on reaction points to hold one of the gears in place while trying to couple with the remaining two. Machining such contraptions is beyond what I care to do.

The Professor

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Re: Turbine gearbox
« Reply #21 on: March 02, 2017, 12:05:25 PM »
Here's my take on a single stage speed up from the propeller to a automotive alternator. A 47" laminated wooden propeller hub with a 6 grove automotive serpentine pulley and 2 V belt groves lathed in the circumference, (to have a choice). There will be a spring loaded smooth idler pulley to make the belt wrap further around the  driven pulley. Ratio about 47:2.5.
Several pictures of the temporary lathe set up spun by a washing machine motor to turn the pulley groves, suspension from a cable to check balance (it will need some lead
on the rim of the hub, and the painted hub and 8' blades.
This is the extent of my progress. Video: https://youtu.be/h002s6fx0oU







« Last Edit: March 02, 2017, 03:37:25 PM by The Professor »

mbouwer

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Re: Turbine gearbox
« Reply #22 on: March 02, 2017, 03:09:26 PM »
T.P.

The design is a bit like Mega-Windforce-68
The advantage of making spokes in the pulley would be that the wind could go through there less disturbed.

Cheers Rinus
« Last Edit: March 02, 2017, 03:14:27 PM by mbouwer »

Warpspeed

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Re: Turbine gearbox
« Reply #23 on: March 02, 2017, 03:47:55 PM »
The grooved belt is an excellent idea, it should work fine even if the large pulley is completely smooth.  With about ten feet of belt wrap its not going to slip even when wet.

But the grooves are definitely required on the alternator pulley, and that is easy.
Flat belts are also very flexible, and it will need to be where it wraps around the alternator.

I see a potential problem with not enough belt wrap around the alternator pulley, especially if the two pulleys are located very close together, but it may be o/k .
A solution might be a spring loaded idler on the outside of the belt to provide more belt wrap around the alternator.  Pretty easy to add later if required.

Mary B

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Re: Turbine gearbox
« Reply #24 on: March 02, 2017, 04:36:53 PM »
If my poor memory serves me Chris Olson did a chain drive with an oil bath case on his turbine... far as I have heard it is running well.

george65

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Re: Turbine gearbox
« Reply #25 on: March 02, 2017, 06:51:40 PM »
Quote
The grooved belt is an excellent idea, it should work fine even if the large pulley is completely smooth.  With about ten feet of belt wrap its not going to slip even when wet.

I have a Lister CS Diesel engine with  24.5" smooth flywheels. I drive an 80A 12V alternator (2 actually) off the flywheels with a serpentine belt ( as do many others) and they never slip wet or dry.  The alts are quite close as I can just get a car belt to work and I'd guess the belt contact area is only around 30% of the pulley (2") circumference and they never slip either. I don't have a tensioner, I just use a turn buckle to pull the belt taught.

I think the idea of microgroove serpentine belts is the huge increase in driving area and the lower tensions that can be run with them.
There are all sorts of formulas and measurements for working out belt tension but I work to a very simple one, just enough tension to prevent slip under full load and that's it.  Anything above that is just extra friction and strain on bearings and shortens belt life.  I just run the alts at full load and adjust the turnbuckle till the belt stops  slipping then back off a bit. I never really need full power out of each alt and it's no effort at all to nip the buckle up a bit if they do start to slip. I just secure the position with a bit of stiff wire and that's it.

 You don't need near as much tension as with a V belt and microgrooves have far less transmission losses partially due to that.