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engine noise

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pj.ladd(at)btinternet.com
Guest

Posted: Sun Apr 11, 2010 2:54 am Post subject: engine noise

Hi All,

  

 following the chat here about supressing radio  noise.

 I have been digging through the usual pile of `may  come in handy one day` equipment and I found a block of plastic about (1" 3/4  X3/4"X1/2") with a wire protruding. The packet is  marked `Suppression  capacitor 4.7mFD for Alternators`

 The plastic block has a fairly substantial metal  tongue with a hole in it. About quarter of an inch dia.

 The protruding wire is green and has, on the end, a  metal tag of much thinner material , also with a hole  through it.

  

 Apart from the fact that it obviously meant to be  bolted to something at either end and that at a guess mFD means microfarads i am  totally at a loss.

  

 Does this sound as though it might be what is  needed to cut engine noise.?  i have a 4 stroke Jabiru. If it will  work , where do I fit it?

  As you may have guessed I am totally ignorant  of electrical stuff, and most engineering if it comes to that.

 Help!

  

 Pat

   [quote][b]

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rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Sun Apr 11, 2010 6:46 am Post subject: engine noise

Pat, It sounds awfully light. Rotax recommends 2000 micro farads, I use a 20000 micro farad on my Mk III based on the recommendations of the Aeroelectric connection which is also here on the Matronix forums. I'd recommend you do some research on the Aeroelectric Connection. Bob Nuckolls has been doing avionics for the major general aviation manufacturers here in Wichita, KS for decades. If anyone can explain the ins and outs of why a capacitor is necessary and what it does, it's him. 



Rick Girard

do not archive



On Sun, Apr 11, 2010 at 5:54 AM, pj.ladd <pj.ladd(at)btinternet.com (pj.ladd(at)btinternet.com)> wrote:

 [quote]       Hi All,

  

 following the chat here about supressing radio  noise.

 I have been digging through the usual pile of `may  come in handy one day` equipment and I found a block of plastic about (1" 3/4  X3/4"X1/2") with a wire protruding. The packet is  marked `Suppression  capacitor 4.7mFD for Alternators`

 The plastic block has a fairly substantial metal  tongue with a hole in it. About quarter of an inch dia.

 The protruding wire is green and has, on the end, a  metal tag of much thinner material , also with a hole  through it.

  

 Apart from the fact that it obviously meant to be  bolted to something at either end and that at a guess mFD means microfarads i am  totally at a loss.

  

 Does this sound as though it might be what is  needed to cut engine noise.?  i have a 4 stroke Jabiru. If it will  work , where do I fit it?

  As you may have guessed I am totally ignorant  of electrical stuff, and most engineering if it comes to that.

 Help!

  

 Pat

    	  Quote: 	
		  



get="_blank">http://www.matronics.com/Navigator?Kolb-List

tp://forums.matronics.com

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[b]

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_________________
The smallest miracle right in front of you is enough to make you happy....

R. Hankins

Joined: 18 Jan 2006
Posts: 185
Location: Grants Pass, Oregon

Posted: Sun Apr 11, 2010 1:50 pm Post subject: Re: engine noise

Pat,

That little "m" stand for "milli". What you have is a 4.7 milliFarad (4.7mFD) capacitor.  This equates to 4700microFarads (4700ÂµFD), still shy of the 20,000ÂµFD recommended above.

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Roger in Oregon
1992 KXP 503 - N1782C

pj.ladd(at)btinternet.com
Guest

Posted: Mon Apr 12, 2010 1:24 am Post subject: engine noise

still shy of the 20,000ÂµFD recommended above.>>



Thanks for your help.



Pat

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by0ung(at)brigham.net
Guest

Posted: Wed Apr 14, 2010 6:50 am Post subject: engine noise

If anyone can explain the ins and outs of why a capacitor is necessary and what it does, it's him.   

   

Rick Girard  

   

   

 	  Quote: 	
		  >>>>>>>>>>>>>>>>>>>>>>>>>   

   
	


 I see that no one else has given this a go,,,,  so I’ll try!!!  

   

a capacitor  is made up of 2 metal plates separated by a non conducting film,,, with 1 plate Pos and 1 plate Neg..     When attached to a voltage source that is not regulated ( moments of voltage spikes followed by moments when there is no power)     when hit with a voltage spike works much like a battery to absorb  the spike and the associated current, but it works a bit different.  In a battery the voltage  in the circuit has to rise in order for the excess of  electrons to enter the battery and cause a chemical reaction ( charges the battery).     But in a capacitor the current will flow into the plates before the voltage has time to peak.      The capacitor stores the electrical charge much like a battery.  But it acts much quicker.    And during a moment when there is no power from the source, the capacitor gives up its stored energy to keep the current flowing smoothly.  During this time the capacitor is partly  discharged creating room to absorb the next spike.      

   

   

If I could use my plumbing experience ….    And make an analogy that is all wet, it may paint a better mental picture.      

   

Suppose we have a garden hose shoved down an over flow pipe.   If the hose is turned on to  half speed,     The amount of water in the overflow  is equal to the water in the hose..   If someone starts to turn the hose faucet  on, off, on, off, on, off, on, off.   the water flow in the overflow will follow the surges.      

   

Now lets take the hose out of the overflow and place it in a tank with a overflow,        with the hose at half speed the water in the tank will rise and the amount of water going down the overflow will be equal to the flow from the hose,      now if someone starts to turn the hose on and off ,   the excess water in the tank will cause the level to rise slowly and it will slowly increase the amount of water in the overflow, and if you turn the hose off for a moment, the water in the tank will  continue to run down the overflow  at a slightly slower rate.   All this time the outlet flow in the overflow will go up and down but  it  will be more constant.         

   

Now increase the size of the tank to say a swimming pool.   ( a larger capacitor)   and the surges in the overflow will be  even less.    

   

Now how does this affect us in our kolbs.     Lets compare the flow of water in the overflow to the volume of our radios.   A constant volume   is much easier to listen to.    

   

   

Told you the analogy  was all wet.  

   

Do not archive.  

   

Boyd   

   

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williamtsullivan(at)att.n
Guest

Posted: Wed Apr 14, 2010 7:10 am Post subject: engine noise

Boyd- Does this mean that using an oversize capacitor won't hurt?

  

                                            Bill Sullivan

                                            Windsor Locks, Ct.

                                            FS 447

 [quote][b]

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by0ung(at)brigham.net
Guest

Posted: Wed Apr 14, 2010 1:35 pm Post subject: engine noise

Boyd- Does this mean that using an oversize   capacitor won't hurt?   

    

                                             Bill Sullivan   

                                             Windsor Locks, Ct.   

                                             FS 447         	  Quote: 	
		   	
  

 	  Quote: 	
		  >>>>>>>>>>>>>>>>>>>>>..  

   
	


No it will not hurt.  The installation manual on the 912 says to install a 22,000 uf 25 volt capacitor  between  the positive output on the voltage regulator and ground.   That  should be enough to smooth out the power…   if you went 40,000 uf    it  would it make it smother than smooth,,  it wont hurt  but it may not do any additional good…,    going too large should not hurt unless you are cramped for space and weight.  If a person wanted  he could install one near the voltage regulator and one near the radio.    If you can only find a capacitor of half the desired amount,,,  put two in parallel,  that will cause the values to add.    On the electrolytic type capacitors they are marked with a + and -   make sure they are installed correctly.  

Two capacitors of the same rating mounted  in series will give you the value of 1/2  of a single capacitor.    

Boyd Young  

   

   

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