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balancing.

Nice article, but it's about torsional dampers and specifically says "not harmonic balancers".
As pointed out in the article, to control torsional vibration you need some sort of frictional device. The stock 16V has one of these, but a light weight aluminum pulley does not, so if you need to control torsional vibrations the aluminum pulley is the wrong way to go.
If you're not using a torsional damper and just changing the weight of the pulley, then all you're doing is changing the location of the "nodes". A node is a position on the crank that is static relative to the vibration. i.e. on one side of the node the crank will be twisted on way and on the other side of the node the crank will be twisted in the opposite direction. The node is also the location of highest stress.
So, if you change pulley weight (or flywheel weight) you will change the position of the node. If you change it to a weak location on the crank the crank will break sooner. (provided you're operating at its resonant frequency)  Or you may change it to a stronger location on the crank. The node's location can be calculated. I can't do it. I'm pretty sure your machinist can't do it ;^). So, the only way he's going to know if he has a problem is if he's breaking cranks.
Sounds like your machinist is mostly concerned about weight and rotational inertia as opposed to "retuning the harmonics", although he is telling you a good story!
Dan

----- Original Message ----- 
  From: Adrian 
  To: 'Dan Bubb' ; 'Mark' ; 'shawn f' ; 'scirocco list' 
  Sent: Wednesday, October 29, 2003 1:17 AM
  Subject: RE: balancing.


  Here u go .. hope this article will clear it up for you.

  http://www.grapeaperacing.com/GrapeApeRacing/ttramblings/dampers.pdf

   

  Adrian C.

  Project Scirocco R2.oT - "The Turbocharged 16Valves of Fire Breathing Fury"

  ( 2.0L 16V T66 )

   

  -----Original Message-----
  From: Dan Bubb [mailto:jdbubb@ix.netcom.com] 
  Sent: October 28, 2003 4:10 AM
  To: Adrian; 'Mark'; 'shawn f'; 'scirocco list'
  Subject: Re: balancing.

   

  Can you explain what "retune the harmonics of the crankshaft" means?

  Or was he just appalled that you'd put a heavy stock pulley on his beautiful lightened crank?

  Dan

    ----- Original Message ----- 

    From: Adrian 

    To: 'Mark' ; 'shawn f' ; 'scirocco list' 

    Sent: Tuesday, October 28, 2003 4:24 AM

    Subject: RE: balancing.

     

    The reason why they need the pulleys is that need to retune the
    harmonics of the crank shaft once its been balanced.
    My machinist after he knifeedged my crank he took a look at my pulley
    and looked at me and said:
    This is garbage... if I put this back up we didn't really accomplish
    anyhting cuz were just putting back some more weight.
    So I guess he got me aluminum one. From where he got it, I have no clue.

    The engine is almost complete.
    Rods and pistons are still back ordered (dammit why do they have to
    always give you a hasle with custom stuff!  

    Head will be done soon and will post pictures of it :)
    - Ported and Polished ( 2.0L 16v ) 
    - Head Converted to Solid Lifters 
    - Black Nitrided SS intake Valves and Inconel Exhaust Valves
    - Valves are .5mm oversized and 1mm back cut for better flow.

    Now I'm a bit confused on whatever I should wait for UMS or get the DTA
    unit.
    Either way I will have to look at fitting the Gm sensorsso it's a toss
    up between the $2500 CAN ECU or the $250 Can ECU ;)

    Adrian C.
    Project Scirocco R2.oT - "The Turbocharged 16Valves of Fire Breathing
    Fury"
    ( 2.0L 16V T66 )
     

    -----Original Message-----
    From: scirocco-l-bounces@scirocco.org
    [mailto:scirocco-l-bounces@scirocco.org] On Behalf Of Mark
    Sent: October 27, 2003 9:25 PM
    To: 'shawn f'; 'scirocco list'
    Subject: RE: balancing.

    I don't think they'll be grinding any metal off of the pulleys...  My
    guess is that they bolt it together with the crank and material gets
    taken off of the crank if it's out...

    Mark.
    80 S
    81 S  ABA/JH/4K

    > -----Original Message-----
    > From: scirocco-l-bounces@scirocco.org [mailto:scirocco-l-
    > bounces@scirocco.org] On Behalf Of shawn f
    > Sent: October 28, 2003 12:09 AM
    > To: scirocco list
    > Subject: balancing.
    > 
    > Well since my engine build got delayed i decided i should get it
    balanced.
    > They (the machinist) want my Rod, one set of con rod bearings, one set
    of
    > rings, The crank, flywheel and bolts, cluch, pressure plate, front
    srocket,
    > with bolt and pulley. I was wondering i sanblasted (another get air
    tool i
    > got recently, sand blasting cabinet) the parts pulley and sprocket
    that is
    > and was wondering if it would be ok to paint these parts. Just
    wondering
    > if they mind i guess it doesnt matter. Problem i was thinking is if
    they
    > have to grind some of the parts there goes the paint. I guess i can
    touch
    > any areas ground down. But then that may throw it out of balance
    again.
    > Anyone know how much redline i can expect. I relize that i still need
    a
    > better cam and stronger springs in the future, but when i get some
    good
    > springs what redline can i expect. Any things i should stress with the
    > machine shop? Any advice would be great...
    > 
    > Shawn F
    > _______________________________________________
    > Scirocco-l mailing list
    > Scirocco-l@scirocco.org
    > http://neubayern.net/mailman/listinfo/scirocco-l


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