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Post Info TOPIC: Torque measured or calculated?
Lynx


Senior Member

Status: Online
Posts: 344
Date: January 29th
RE: Torque measured or calculated?
 

To calibrate I am thinking about a bucket on a rope tied to the pull side.  Add a pint of water for a Lb and a gallon for 8 Lbs pull.  A five gallon bucket holds 40 Lbs.

Mark each weight on a visible scale lined up with the marker.  Then just video to get the torque, rpms, (or use the HZ meter), real time volts (calculate amps through the resistor).

As long as we hold wind constant we should learn a lot about the turbine blade setup and alt efficiency and any difference.



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Marcus
sjh7132


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Posts: 3176
Date: January 28th
RE: Torque measured or calculated?
 

I wasn't paying much attention to this thread because I've been busy with other things, but I think using the alt as a PRONY brake is a great idea.   It will let you measure the actual mechanical power and compare it to the electical power.



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Steve
brother paul


Senior Member

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Posts: 226
Date: January 28th
RE: Torque measured or calculated?
 

marcus

 

to know the efficiency of your windmill you have to PLOT

 

1° WINDSPEED > ENERGY from the wind with the classic formula

F = ...V3  i cant write it here since there are exponents and so on

 

2° YOUR measured Force or kWh

 

and indead your 36% will diminish to 30% possibly with all the inefficiencys of converting motion in electricity etc



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fluitic


Senior Member

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Posts: 185
Date: January 28th
RE: Torque measured or calculated?
 

I think its a great idea to build a prony break into the test stand. The alt. with a variable resistor and Hz meter makes a great brake and RPM meter. Lots of good easy to use data can be obtained.

I think I will copy the idea for my firts test stand.

Thanks



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Dan
itsandbits1


Guru

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Posts: 1757
Date: January 27th
RE: Torque measured or calculated?
 

well it would be interesting to have a mechanical measurement to back up the theory. If the wings are thrusting with ? pd,s or whatever the measure and you are getting ? watts out, the difference is calculated in your turbine somewhere and then you can localize it by  taking a reading of just the wings with the alt freewheeling but snubbing the shaft to measure output. It would pin things down pretty well.



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I will only try to build the best. If it ends up looking like yours, take it as a compliment. I am always in the developement stage
Lynx


Senior Member

Status: Online
Posts: 344
Date: January 27th
RE: Torque measured or calculated?
 

Don't worry so much about the mechanics or if Torque can be calculated from watts.  I am hoping you guys can think about the concept of whether there is a significant difference between actual and calculated torque.

Is it just the difference between a 90% efficient alternator at that speed vs. true torque? And if it is, how will I know if the VAWT is 36% efficient or 80% of 45% effcient?    80% x 45% = 36%

I am trying to figure out if it is worth the trouble to build the torque meter into the test stand.



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Marcus
Bob Mann


Senior Member

Status: Offline
Posts: 248
Date: January 27th
RE: Torque measured or calculated?
 

We are back to a dyno

here is aEbay link for a small digtal scale that will work.

http://www.ebay.com/itm/10lb-Scale-Kit-/350523006299?pt=LH_DefaultDomain_0&hash=item519ccc9d5b

than all you will need is to record the RPM.

You mount the PMA in a way so it can spin freely add a 1 ft arm on to the PMA set up the scale at the 1 ft mark. use a small car or bike shook to keep it a smooth reading. You now have a FTLB reading times RPM you have HP per RPM.

Bob Mann



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itsandbits1


Guru

Status: Offline
Posts: 1757
Date: January 27th
RE: Torque measured or calculated?
 

I don't know if the base scale lever could be set tight enough to let the alt float yet not bounce too much from the harmonics you get from the wing thrust. I guess you could put a damper on it and once it reaches full rotation, loosen it off and just stop it from bouncing too much with your fingers so it doesn't set up a resonance.



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I will only try to build the best. If it ends up looking like yours, take it as a compliment. I am always in the developement stage
brother paul


Senior Member

Status: Offline
Posts: 226
Date: January 27th
RE: Torque measured or calculated?
 

your torque will vary during rotation and average out
anyway the simplest is to measure your watt in function of a resistance.. and measure the Kilowatth versus the theoretical kilowatth from the wind touching your windmill

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Lynx


Senior Member

Status: Online
Posts: 344
Date: January 27th
Torque measured or calculated?
 

I am setting up a wind turbine for testing various blades.  At the bottom of the VAWT there is a Boreas 3 style alternator.

Wind will be controlled to a certain speed.  The load will be a fixed resistive load to match that wind speed.

The varaible will be the blade setup.  

If X number of output watts are observed at that windspeed and at a measured rpm we should be able to calculate efficiency, hp, and torque. 

Question?  Would that calculated torque be the same as the actual torque?

I am thinking about attaching the alternator to a moving base that is calibrated to show ftlbs.  If the alternator wastes heat the true torque might be higher than the calculated torque from output?  Not sure.torque vawt.jpg



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Marcus
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