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tachometer

 
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echristley(at)att.net
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PostPosted: Fri Oct 02, 2015 12:01 pm    Post subject: tachometer Reply with quote

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

PostPosted: Wed Oct 14, 2015 8:01 pm    Post subject: Re: tachometer Reply with quote

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:
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echristley(at)att.net
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PostPosted: Thu Oct 15, 2015 5:18 am    Post subject: tachometer Reply with quote

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]



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[quote][b]


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dlj04(at)josephson.com
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PostPosted: Fri Oct 16, 2015 8:01 am    Post subject: tachometer Reply with quote

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
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PostPosted: Fri Oct 16, 2015 11:34 am    Post subject: tachometer Reply with quote

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

PostPosted: Sun Oct 18, 2015 4:16 pm    Post subject: Re: tachometer Reply with quote

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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