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tachometer

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echristley(at)att.net
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Posted: Fri Oct 02, 2015 12:01 pm Post subject: tachometer

I've got a Van's tachometer that was in the partially completed project I bought.  Has anyone used one of these by tying the sensor wire to the negative side of the coil?

 [quote][b]

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John Pitkin

Joined: 13 Mar 2010
Posts: 6

Posted: Wed Oct 14, 2015 8:01 pm Post subject: Re: tachometer

Attaching anything to the negative side of the coil other than points and a capacitor adds another failure point. If the tach goes bad it takes your ignition with it.  



Electric tachs just need a simple trigger. Look or search for diesel tach sensors they have no ignition and therefore must use a sensor. It's nothing more than a small coil , a magnet, and a Hall effect transistor. 



[quote="echristley(at)att.net"]I've got a Van's tachometer that was in the partially completed project I bought.  Has anyone used one of these by tying the sensor wire to the negative side of the coil?

  	  Quote: 	
		  [b]

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echristley(at)att.net
Guest

Posted: Thu Oct 15, 2015 5:18 am Post subject: tachometer

There  are tachs that install in series with the coil.  One of those would be a  very bad idea, and would concur with what you say.



However, your statement concerning the ones that sense the current bounce on the negative electrode does not concur with basic electronics.  Unless a bad tach was somehow able to burn the short wire going from the coils negative terminal to the firewall, there is nothing it could do to affect the coils operation.

The diesel tachs are:

-more expensive

-require extra wiring through the firewall

-mounting sensors with a fairly tight tolerance to the flywheel or some other spinning part. 

 



  



     On Thursday, October 15, 2015 12:02 AM, John Pitkin <john(at)cedarcreekrun.com> wrote:

  

  



 --> CorvairEngines-List message posted by: "John Pitkin" <john(at)cedarcreekrun.com (john(at)cedarcreekrun.com)>



Attaching anything to the negative side of the coil other than points and a capacitor adds another failure point. If the tach goes bad it takes your ignition with it.  



Electric tachs just need a simple trigger. Look or search for diesel tach sensors they have no ignition and therefore must use a sensor. It's nothing more than a small coil , a magnet, and a Hall effect transistor. 



[quote="echristley(at)att.net"]I've got a Van's tachometer that was in the partially completed project I bought.  Has anyone used one of these by tying the sensor wire to the negative side of the coil?

 

 	  Quote: 	
		   [b]


	






Read this topic online here:



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 [quote][b]

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dlj04(at)josephson.com
Guest

Posted: Fri Oct 16, 2015 8:01 am Post subject: tachometer

On 10/15/15 11:56 PM, CorvairEngines-List Digest Server wrote:

 	  Quote: 	
		   Time: 06:19:00 AM PST US

 From: Ernest Christley <echristley(at)att.net>

 Subject: Re: Re: tachometer

 There are tachs that install in series with the coil.=C2- One of those wo

 uld be a very bad idea, and would concur with what you say.

 However, your statement concerning the ones that sense the current bounce o

 n the negative electrode does not concur with basic electronics.=C2- Unle

 ss a bad tach was somehow able to burn the short wire going from the coils

 negative terminal to the firewall, there is nothing it could do to affect t

 he coils operation.

It doesn't burn the wire, it shorts it to ground, bypassing the points. 

What's been seen is that a bypass capacitor fails, probably due to 

insufficient voltage rating or poor quality, and shorts the negative 

lead to ground, taking the points out of the circuit. If you must use a 

tach connected to the ignition primary, be sure you have two ignition 

circuits and connect the coil to only one of them.

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echristley(at)att.net
Guest

Posted: Fri Oct 16, 2015 11:34 am Post subject: tachometer

Aah!  Gotcha!  Thank you.



  



     On Friday, October 16, 2015 12:02 PM, D L Josephson <dlj04(at)josephson.com> wrote:

  

  



 --> CorvairEngines-List message posted by: D L Josephson <dlj04(at)josephson.com (dlj04(at)josephson.com)>



On 10/15/15 11:56 PM, CorvairEngines-List Digest Server wrote:

 	  Quote: 	
		   Time: 06:19:00 AM PST US

 From: Ernest Christley <echristley(at)att.net (echristley(at)att.net)>

 Subject: Re: CorvairEngines-List: Re: tachometer



 There are tachs that install in series with the coil.=C2- One of those wo

 uld be a very bad idea, and would concur with what you say.

 However, your statement concerning the ones that sense the current bounce o

 n the negative electrode does not concur with basic electronics.=C2- Unle

 ss a bad tach was somehow able to burn the short wire going from the coils

 negative terminal to the firewall, there is nothing it could do to affect t

 he coils operation.

It doesn't burn the wire, it shorts it to ground, bypassing the points. 
	


What's been seen is that a bypass capacitor fails, probably due to 

insufficient voltage rating or poor quality, and shorts the negative 

lead to ground, taking the points out of the circuit. If you must use a 

tach connected to the ignition primary, be sure you have two ignition 

circuits and connect the coil to only one of them.



_-========================gt; http://www.matronics.com/Navigator?CorvairEngines-Listhttp://forums.matronp;                     &n.matronics.com/contribution" target="_blank">http://www.matronics.com/con=================

  

 

  



 [quote][b]

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Ron Lendon

Joined: 10 Jan 2006
Posts: 685
Location: Clinton Twp., MI

Posted: Sun Oct 18, 2015 4:16 pm Post subject: Re: tachometer

Here is what I did 3 years ago and it still works after 460 hours of flight.



Contrex 

Accessory



ITEM # 5800-1412

MFG #	5800-1412



Magnetic Pick-Up, Smooth



From Galco

:

:

Stewart Warner 82636 - Stewart Warner Deluxe Series Tachometers



Click here for more information about Stewart Warner 82636 - Stewart Warner Deluxe Series Tachometers

Compare

Tachometer, Deluxe Series, 0-3,500 rpm, 3 3/8 in. Diameter, Diesel, Black Face, Each



Part Number: SWW-82636 



From Summit Racing

:

:



For less that a 30 gallon fill up of 100LL you have a proven method that won't interfere with your engines ignition.  I just checked the tach with a digital video method and it is spot on.  I have it counting the teeth on the flywheel and have had it set at .01 to .125 inches and it reads just fine at either distance.

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_________________
Ron Lendon
WW Corvair with Roy's Garage 5th bearing
CH 601 XLB
N601LT - Flying
http://www.mykitlog.com/rlendon
Corvair Engine Prints:
https://sites.google.com/site/corvairenginedata/

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