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IndustryArena Forum > Hobby Projects > Hobby Discussion > balancing machine for turbine shaft!!!
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  1. #21
    Join Date
    Jun 2008
    Posts
    2
    Hey guys,

    Let me first introduce myself. I'm Rik Hermsen, 22 y.o. student Elektrotechnics at university of Eindhoven (Holland). For the hobby I am building a MW54 turbine turboprop engine. To balance the shaft i build a balancer tool, and developped electronics for it. This last part, i'm still working on that. Here in Holland there are also serveral builders that were interested in the electronics.

    I have a website (in dutch, i'm sorry about that) were i post photo's of recent projects were i am working/worked on.

    You can find the website here!

    My way of balancing (at least i hope to do so) is by driving the shaft with a motor and an elastic cord. Then the electronics (microcontroller) measures the speed and regulates the shaft to a constant speed at frequency of the band pass filter. I am still working out the desing, so it's not finished yet. The hardware (i.e. balancer mechanics) is finished and has all sensors needed.

    On my website you cay also find pictures of the MW54 i'm building, as well as the building planns on that same page.

    Cheers,

    Rik

  2. #22
    Join Date
    Jan 2006
    Posts
    481
    would be nice to have one of these machines $$$$$$$$ High-speed turbo balancing machine [nomedia="http://www.youtube.com/watch?v=TMA5RFpGRbg"]YouTube - High-speed turbo balancing machine[/nomedia]



    Amazing with all that technology they still remove metal filings of rotating assembles being balanced and it mixes with the return oil lubrication system while the shaft assembly is being spun to operating speeds to be filtered.

  3. #23
    Join Date
    Jun 2007
    Posts
    3757

    Cool It is now a digital world.

    Rik.

    Most of the noise comes from the drive system.
    The old analogue bandpass filter suffers a large phase shift for a small change in frequency. The phase gives you the position which once the Q is high enough to get rid of the noise, the angular error is significant.
    A small angular position, once the balance becomes finer becomes an error at close 90 degrees.

    Don't worry about speed regulation.
    Just spin it fast, release the drive belt and process on the spin down.

    You can use a Kalmen filter http://en.wikipedia.org/wiki/Kalman_filter to resolve signals at 0 and 90 degrees, say, call them X and Y.

    I reality you simply multiply the signal by plus/minus 1 at the correct times for 0 and 90 degrees, and save them, along with the current speed.

    sqrt(X^2 + Y^2) gives you the vector for each measuring plane.
    Multiply X and Y by 1/(speed squared), to get rid of the speed problem.

    Stuff all the vectors in and array for discrete speed steps, and process as percentiles, and throw out the wild values caused by silly resonances.
    You need 0 and 90 degrees signals optically from the shaft, and the signals for each measuring plane.


    For this to work it needs to be a high tune system where you measure the unbalance FORCES. Not deflection.
    Piezoelectric transducers against a large mass, work well.
    You can resolve the vector to the balancing plane(s) from the measuring planes by simple moments about the measuring points treating the shaft as a beam.
    Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.

  4. #24
    Join Date
    Jun 2008
    Posts
    2
    Hi Neil,

    Tnx for your reply.

    I tried to do build it in digital environment, but it introduced even more phase lag. The idea was to use a DSP, and implement a 100th order low pass FIR filter in it, convoluted with a delta pulse ( in order to get a band pass) and then multiply the samples with that filter. In this system the phase shift was not constant, so that was the big issue, and the reason why I got back to analog domain.

    The first thing I did was making the signals visible, so i can see all the frequencies present:

    picture1

    and then zoom in on the frequency of interest:
    picture2


    I measured the signal with an usb Handyscope, and plotted the signals with Matlab. This is the FFT at 7800rpm, where i got the best result.

    Then, i made a simulation of a band pass filter in LTspice
    picture
    I took as example a LT1363, and made a band pass filter with it at 130 Hz (i.e. 7800rpm). The red line is 1st order, de green one 2nd.

    Some people here in holland drive the shaft first with a compressor. Disadvantage is that u will always need a compressor. So that's why I thought to hold the turns stable, and make a band pass filter on that stable frequency.

    The method you described we here know as the least squares method, where you draw an optimal line trough points (correct?). The question i'd now like to ask is why you use this theory/method. Can you show some measurements and analysis you did? It looks very interesting, but also quite complex(). Do you have pictures of set-ups? I wonder why you use such a complex method, and what the information is you get (because that's not quite clear to me).

    Please let me know what u think, i could use some help

    Cheers,

    Rik

    p.s. turbinecrazy: If u like me to start me a new topic, please let me know. i don't want to "steal" your topic or something like that.

  5. #25
    Join Date
    Jun 2007
    Posts
    3757

    Phase lag?

    Rik,

    Don't process in real time. You have got no hope.

    I see you said you 'tried' to do it digital. This definitely needs planning and no trial and error stuff.

    In real time, about all you need do is sum the X and Y data, in the correct sign and multiply by 1/speed squared, which filters it, and store in the correct array for each speed interval. Needs heaps of memory.

    Now when you process each speed interval, use percentiles, to toss out the wild data.

    Better still store ALL the RAW data and process it later. You can get rid of wild rubbish better that way.

    Process it ALL LATER, when you apply the brake, if there is one.
    You can't get phase lag if you time tag it properly, which is how it is filtered too.

    A comment: If your web pages were simple, without all the fancy stuff, it could be translated by Babelfish by just pasting the links.
    Be really nice if http://babelfish.yahoo.com/ worked on your web pages. I use it all the time, for non-English stuff, but it won't work past your home page.
    You can't expect a translator to process silly embedded stuff, and a whole heap of your page is lost by the fancy, useless menu stuff.
    It is getting rid of the silly stuff why all my projects work properly.
    Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.

  6. #26
    Join Date
    May 2006
    Posts
    343
    You guys should look into this Data processing with DEWESoft 7

    How would you hook up the accelerometers and speed sensor, and or strobe?

  7. #27
    Join Date
    Jul 2005
    Posts
    302
    When I was building my own balancer, I got many helps and enlightenments from Mr. Miklos Koncz from Hungary, [email protected] ,
    Hereby his earlier turbine balancer [nomedia="http://www.youtube.com/watch?v=uRHvW_A-DSA"]YouTube - Phoenix Mk4 turbine balancing by Dynams (Original bench)[/nomedia]

    Soft and parts from Mr. Andy Paul,
    Affordable dynamic balancing ,
    got a lot of teachings about dynamic balancing.
    cheers,
    herbert

  8. #28
    Join Date
    Apr 2006
    Posts
    3498
    Hi Herbert,
    Thanks for the links. Really informative and interesting work.
    Regards
    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/

  9. #29
    Join Date
    Nov 2009
    Posts
    1

    Balancer

    Hi

    Lots of info and help with building a balancer and turbines with the GTBA

    GTBA - The Gas Turbines Builders Association

    Built a KJ66,Balancer,Spotwelder etc with the help of these guys

    Ray

  10. #30
    Join Date
    Jun 2005
    Posts
    32
    Quote Originally Posted by neilw20 View Post
    Rik.

    Most of the noise comes from the drive system.
    The old analogue bandpass filter suffers a large phase shift for a small change in frequency. The phase gives you the position which once the Q is high enough to get rid of the noise, the angular error is significant.
    A small angular position, once the balance becomes finer becomes an error at close 90 degrees.

    Don't worry about speed regulation.
    Just spin it fast, release the drive belt and process on the spin down.

    You can use a Kalmen filter Kalman filter - Wikipedia, the free encyclopedia to resolve signals at 0 and 90 degrees, say, call them X and Y.

    I reality you simply multiply the signal by plus/minus 1 at the correct times for 0 and 90 degrees, and save them, along with the current speed.

    sqrt(X^2 + Y^2) gives you the vector for each measuring plane.
    Multiply X and Y by 1/(speed squared), to get rid of the speed problem.

    Stuff all the vectors in and array for discrete speed steps, and process as percentiles, and throw out the wild values caused by silly resonances.
    You need 0 and 90 degrees signals optically from the shaft, and the signals for each measuring plane.


    For this to work it needs to be a high tune system where you measure the unbalance FORCES. Not deflection.
    Piezoelectric transducers against a large mass, work well.
    You can resolve the vector to the balancing plane(s) from the measuring planes by simple moments about the measuring points treating the shaft as a beam.

    I have read at places about wattmetric instrumentation for balancing machines. It is claimed that it given most accurate results. Please let us know more about it, if somebody has some information.

  11. #31
    Join Date
    Apr 2006
    Posts
    3498
    Rik...great work
    http://free3dscans.blogspot.com/ http://my-woodcarving.blogspot.com/
    http://my-diysolarwind.blogspot.com/

  12. #32
    Join Date
    Mar 2003
    Posts
    6855

    Re: balancing machine for turbine shaft!!!


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