The Spares Company
Club Shop/Regalia
Parent Website
Contact Officials
Machine Registrar
Club Secretary
Membership Secretaries
MPH Editor and Forum Administrator.
Section Newsletters
Technical Databases
Photos
Home
What's new
Latest activity
Forums
New posts
What's new
New posts
Latest activity
Information
Bike Modifications
Machine Data Services
Manufacturers Manuals
Spare Parts Listings
Technical Diagrams
Whitakerpedia (Vincent Wiki)
The Club
MPH Material Archive
Flogger's Corner
Obituaries
VOC Sections
Local Sections
Local Section Newsletters
Miscellaneous
Club Assets
Club History
Club Rules
Machine Data Services
Meeting Documents
Miscellaneous
Essential Reading
Magazine/Newspaper Articles/Letters
Adverts and Sales Brochures
The Mighty Garage Videos
Bikes For Sale (Spares Company)
Log in
Register
What's new
New posts
Menu
Log in
Register
Install the app
Install
Home
Forums
Forums: Public Access
Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Magneto polarity
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Message
<blockquote data-quote="Magnetoman" data-source="post: 50914" data-attributes="member: 2806"><p>Yes, it does make a difference, but whether or not it is "a lot" is a value judgment. Because for a given voltage drop the local electric field (Volts/cm) is higher near a point than near a flat surface, it is easier to emit electrons from the central wire of a spark plug than from the earth electrode. So, the polarity does matter. </p><p></p><p>On a twin you have no choice since the plug on one side of the engine always will be at the "wrong" polarity. It's even worse with a Vincent twin since the magneto provides maximum output with the armature exactly 180-deg. apart, so not only will one plug always be at the wrong polarity, only one plug can be at the optimum point of the collapse of the magnetic field. That's why with a Vincent twin you at least want the plug on the non-optimum side of the magneto to fire when the central electrode is negative so you don't have two factors working against you.</p><p></p><p>While a single certainly will work with the "wrong" polarity (just as both cylinders on a twin do work), you will be better off it fires when the central electrode of the plug is negative, not positive.</p><p>As originally manufactured the cam had an indexing slot to make sure you couldn't put it in the wrong way. But, 60 years later, there's no telling what parts are in a given magneto. I've seen illustrations in books showing how to hold a sharp pencil tip between the electrodes to determine which way the electrons are flowing, but how one actually holds a plug and a pencil in a dark room while kicking over a bike and observing the tiny spark bounce off a pencil is a problem I've never had to solve, because I have electronic instruments to spare me from that pain and frustration.</p></blockquote><p></p>
[QUOTE="Magnetoman, post: 50914, member: 2806"] Yes, it does make a difference, but whether or not it is "a lot" is a value judgment. Because for a given voltage drop the local electric field (Volts/cm) is higher near a point than near a flat surface, it is easier to emit electrons from the central wire of a spark plug than from the earth electrode. So, the polarity does matter. On a twin you have no choice since the plug on one side of the engine always will be at the "wrong" polarity. It's even worse with a Vincent twin since the magneto provides maximum output with the armature exactly 180-deg. apart, so not only will one plug always be at the wrong polarity, only one plug can be at the optimum point of the collapse of the magnetic field. That's why with a Vincent twin you at least want the plug on the non-optimum side of the magneto to fire when the central electrode is negative so you don't have two factors working against you. While a single certainly will work with the "wrong" polarity (just as both cylinders on a twin do work), you will be better off it fires when the central electrode of the plug is negative, not positive. As originally manufactured the cam had an indexing slot to make sure you couldn't put it in the wrong way. But, 60 years later, there's no telling what parts are in a given magneto. I've seen illustrations in books showing how to hold a sharp pencil tip between the electrodes to determine which way the electrons are flowing, but how one actually holds a plug and a pencil in a dark room while kicking over a bike and observing the tiny spark bounce off a pencil is a problem I've never had to solve, because I have electronic instruments to spare me from that pain and frustration. [/QUOTE]
Insert quotes…
Verification
The Series 'A' Rapide was known as the '********' Nightmare?
Post reply
Home
Forums
Forums: Public Access
Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Magneto polarity
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.
Accept
Learn more…
Top