Author Topic: Variable pitch turbine built...  (Read 2056 times)

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TrotFox

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Variable pitch turbine built...
« on: June 12, 2004, 11:09:35 PM »
Two blade, trailing rotor design.  Hub is made of two disks which act as though they were on a splined shaft sliding together and apart while rotating together.  The aft disk is compression sprung (pulled towards) the fore disk and has levers which act on the blades.  The blades are around 5 degrees at rest and are setup to move as the wind pushes them in order to prevent overspeed conditions while loaded.  They can move back to roughly 70 degrees.  Ideally, shorting the generator (not installed yet) will pull the speed way down and the wind will just push the blades back such that not much resistance is offered to the rig.  Under normal use conditions the spring would be adjusted such that constant power is delivered even though the wind speed is changing.  Setup on this part is adjustable to whatever the heart desired though with centrifugally actuated designs also possible.


I'm thinking a hybrid system with the blades sprung back for high starting torque but pulled forward by centrifugal force could be fun to play with.  Perhaps using a cam setup (lever that goes past center as the weights move farther out) it could be made to hunt the sweet-speed during high wind speeds?


Can't get photos of it tonight as my old digital camera doesn't work without really bright light (sunlight or bust!)  I'll try to get some tomorrow.


Trot, the tinkerin', fox...

« Last Edit: June 12, 2004, 11:09:35 PM by (unknown) »

TrotFox

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Re: Variable pitch turbine built...
« Reply #1 on: June 13, 2004, 05:20:09 PM »
Ok, some photos of the hub are now up at:


http://1stclass.mylargescale.com/trotfox/pix/windmill/


Seems like it wouldn't be too difficult to build in steel...


Trot, the idea-full, fox...

« Last Edit: June 13, 2004, 05:20:09 PM by TrotFox »

stop4stuff

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Re: Variable pitch turbine built...
« Reply #2 on: June 14, 2004, 03:20:06 AM »
Very neat use of Lego Trotfox ;)


If you've got a newer Technic motor, you could gear it straight on the fixed hub with an 8 tooth gear and get power out of your prototype. The motor puts out pulsed DC when spun up, and can be used for charging small NiCads (include a diode) or running similar Lego motors.


paul

« Last Edit: June 14, 2004, 03:20:06 AM by stop4stuff »

TrotFox

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Re: Variable pitch turbine built...
« Reply #3 on: June 14, 2004, 08:14:31 AM »
I either don't have any motors anymore (I know I burned one or two up in the past) or I've lost them.  I currently don't have any!  I plan to make a small axial-flux alternator anyway so this will make a good test stand.  I need to do some work on the blades though as it currently doesn't have enough surface area to turn itself over.  I'm thinking a little plastic-compatable oil will help this out though... just have to keep it out of the important bits!  That and trying to figure out a three-blade rotor will have me busy for a while.


Any thoughts as to the best pattern for pitch/RPM curves?  Seems like they may need to be swept way back for high starting torque and directional seeking at low RPM.  Maybe I should use weighted shafts to bring them into the wind on that cam system I was describing?


I don't know if you saw the link I put up before but I also have a stationary compressed air engine that was built completely from LEGO.  


Trot, the fox with too much yardwork to do... (wanna play!)

« Last Edit: June 14, 2004, 08:14:31 AM by TrotFox »

elvin1949

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Re: Variable pitch turbine built...
« Reply #4 on: June 14, 2004, 01:05:57 PM »
good afternoon Trotfox

looked at the pic's

varable pitch and simple

that is BEAUTIFUL

later

elvin
« Last Edit: June 14, 2004, 01:05:57 PM by elvin1949 »

TrotFox

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Re: Variable pitch turbine built...
« Reply #5 on: June 14, 2004, 05:48:22 PM »
Well, it worked...


(for a very short period of time...)


I re-worked for centrifugal adjustment but couldn't find anything to work as a compression spring or that was heavy enough to provide the fly-weight effect that'd be needed.  So I took the semi-finished rig out and help it over our AC unit's running condenser fan.  =D  It flew... apart... after shaking for a while.  Seems I had too much hanging off the front of it that wasn't directly supported by the mail axle. rolls eyes, shrugs  The pieces are all retrieved and still usable!  ;]


Time to work on a simpler 3-blade design.  No pitch adjust to start with, just for the fun of it this time.  I'll have to try building a real one with the results of this experiment once I figure out how to do a splined shaft...


Thanks for the comments!

« Last Edit: June 14, 2004, 05:48:22 PM by TrotFox »

stop4stuff

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Re: Variable pitch turbine built...
« Reply #6 on: June 15, 2004, 05:41:41 AM »
Hi Trotfox,


Here's a 12" dia 3 blade Lego turbine I made a while ago.

The blades are axles covered in paper, and they're mounted to 2 'Technic rotor 3 blade', part # 2712 (see http://www.peeron.com/inv/parts/2712 )

Using the older 1/2 bush (# 4265a) and 'Technic Plate 1 x 4 with Holes' (4263) , I got a twist to the blades too :)


For lubricating Lego, I use silicone grease, silicone oil, or my current favorite, PTFE/Silicone oil (available from RS Components in the UK)... any water/silicone based lube should be fine for Lego.


The pitch/rpm relationship is all to do with vector forces and how the blades 'see' the wind direction. Low wind speed = low rpm = steeper angle, High wind speed = high rpm = shallower angle (almost flat to the wind).


paul

« Last Edit: June 15, 2004, 05:41:41 AM by stop4stuff »

TrotFox

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Re: Variable pitch turbine built...
« Reply #7 on: June 15, 2004, 04:40:07 PM »
That's wonderful!  If you don't mind I might have to try and replicate that for my own enjoyment.  ; ]  I've got most of those pieces...


Trot, the impressed, fox...

« Last Edit: June 15, 2004, 04:40:07 PM by TrotFox »

stop4stuff

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Re: Variable pitch turbine built...
« Reply #8 on: June 16, 2004, 02:41:58 AM »
Hi TrotFox,


thanks :)

Sure you can replicate the turbine... be warned tho, the blades can fly off!

I'd recommend a spot of glue to hold them on.


Let me know how you get on. (email: paul at stop4stuff dot com )


have fun,

paul

« Last Edit: June 16, 2004, 02:41:58 AM by stop4stuff »