Author Topic: Jury Rigging  (Read 1031 times)

Offline Stu55Flash

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Jury Rigging
« on: 19.08. 2010 00:22 »
Has anyone tried to "jury rig" their ignition to improve it using an AC coil as: 170523598139. I did this on my Fanny B. The biggest problem with high tension coils is that they breakdown with age and do not generate a high enough voltage. You simply connect the HT lead to the input of the coil and it generates a higher voltage at the plug - a good hot blue spark instead of yellow one. The mag is still used to generate the spark at the correct time. On my Fanny B I hid the coil under the tank. I had loads of starting problems before using this idea and non afterwards.

Stu
"Keep a distance from lady "L" drivers in cars. Some are not mechanically minded, are slow to acquire road sense, an are apt to panic..." The Pitman Book of the BSA Twins.
Golden Flash Plunger 1955, Francis Barnett Falcon 67 1954, Ferguson TEA Tractor 1951. Looking for another project!

Offline wilko

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Re: Jury Rigging
« Reply #1 on: 19.08. 2010 09:40 »
I'm confused? We talking about  maggy's?

Offline lawnmowerman

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Re: Jury Rigging
« Reply #2 on: 19.08. 2010 10:39 »
Interesting concept. We are looking to use the coil as a step up transformer. May work in theory but not sure about the insulation resistance of the coil's primary winding which is only designed for 6 or 12v - it may leak to earth losing some of the mag's voltage and dissipating some power as heat in the coil. Also, increasing the voltage proportionately decreases the current - not sure what effect this may have on the spark but there is only a finite amount of power (voltage x current) available from the mag.
IMHO, at the end of the day you would probably be masking a mag problem and adding more components and potential for problems.
If you try it I would be interested to know the result.

Jim
1959 A10 SR
1938 Wolseley 14/60
1955 Ferguson TEF20 tractor
1965 Ferguson 135 tractor
1952 Matchless G80 rigid
1960 BMW R60
1954 Matchless G80S
1955 Ariel 500 VH
1951 Sunbeam S7DL
1960 Matchless G12 with Watsonian Monza
......and loads of lawnmowers

Too old to Rock and Roll but too young to die  (Jethro Tull 1976)

Online chaterlea25

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Re: Jury Rigging
« Reply #3 on: 20.08. 2010 22:49 »
Hi All,
I googled the number Stu gave and it comes up as a coil for pazon or similar types of electronic ignition
(not 6 0r 12 volt) in these systems a pulse is thrown at the LT side of the coil and is transformed into a high voltage for the plug!!
IF you connect a lead from your mag to earth via the coil windings you do not get a high voltage into the LT it is simply converted (shorted) into a current pulse (very small)
I have never heard of doing this before?????
30 or so years ago I converted a couple of mags to work with a remote coil, (energy transfer) it works well if you use an AC coil from a scooter or honda 50,
The slipring and brush have to be kept clean and free from oil, as they now have to crry a current pulse from the LT winding.
I even got a V twin BSA running well on this setup using 2 coils
Back then mag rebuilds were as about as expensive as they are now??? so I think in real terms a lot cheaper now???
Or maybe I can afford it nowadays??????

Recently I was at a Steam Fair  and had a wander through the stationary engine exhibits
One engine was running away happily with a flourescent light choke acting as a kind of coil ???? ???? ????
I couldnt find the owner to ask how it worked, maybe it was a booster for the LT magneto some of these engines had
??????????????
Cheers
John O R
1961 Super Rocket
1963 RGS (ongoing)

Offline lawnmowerman

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Re: Jury Rigging
« Reply #4 on: 21.08. 2010 20:52 »
Good point John. I thought there must be a reason why it would not work or everybody would be doing it and the mag rebuilders would go bust.
I have just remembered the way a coil works - the voltage via the closed points is applied to the primary through to earth while the points are closed (dwell). This allows a considerable build up of flux in the coil primary and it is only when the points open that a back emf is produced, instantly releasing all the stored energy in the coil primary. It is then magnified by the many more turns on the secondary winding to produce a short duration spark at the plug. Although many thousand volts - very little current and short duration.
A similar high voltage short duration low energy voltage pulse is produced by the mag and would not be enough to fully flux a coil primary.
Sorry if I have repeated what you said but I am just trying to get it right in my head. It is many years since I studied telecommunications principles as an apprentice and the theory is very similar to electromagnetic relays and switches.
Quite interesting to hear about the remote coil set up - I guess that this replaces the "coil" in the mag to step up the voltage to spark levels, but as you say, means that the slipring and brushes have to carry more current.

Jim
1959 A10 SR
1938 Wolseley 14/60
1955 Ferguson TEF20 tractor
1965 Ferguson 135 tractor
1952 Matchless G80 rigid
1960 BMW R60
1954 Matchless G80S
1955 Ariel 500 VH
1951 Sunbeam S7DL
1960 Matchless G12 with Watsonian Monza
......and loads of lawnmowers

Too old to Rock and Roll but too young to die  (Jethro Tull 1976)

Online chaterlea25

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Re: Jury Rigging
« Reply #5 on: 22.08. 2010 00:26 »
HI Jim and All,
I'm not saying it doesn't work, just that I have not heard of it or tried it!!!
I know that many mag windings lose resistance as they age and the insulation breaks down between the adjacent windings, this makes them lose voltage for the spark, the voltage will only rise enough to jump the gap in the plug
the bigger the gap you make the spark jump the bigger the voltage needed,
This is bad news for the poor windings as the "stress " on them is increased considerably
It is bad practice to spin over your bikes mag without the leads grounded or connected to the plugs
Modern coils used in transistorised ignition or CDI are a different animal,!!!
They are fired by a voltage pulse (spike) As the Pazon boys state the wattage needed to fire the coil is minimal
This has set me thinking ???? ???? ????
On the mag remote coil conversions the current is generated by the LT windings in the mag, this is in parallel with the second coil primary, when the points open the mag coil discharges its current into the second coil, this change is enough to generate the spark in the secondary coil

HTH
John O R
1961 Super Rocket
1963 RGS (ongoing)

Offline Stu55Flash

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Re: Jury Rigging
« Reply #6 on: 22.08. 2010 00:39 »
The system works fine on the Fanny B in this case its a single cylinder. First a tried a new HT coil, these fit inside the flywheel and therefore get hot. When hot, the spark is was not hot enough to ignite the fuel - oil mix. OK when running not good enough to restart. I gave up with this and stripped the HT windings off the old coil - which were green and shorted. I then connected this to the input of an AC coil which is what I think the Pazon coil is but for a twin. These are different to the DC coils. In effect instead of generating a pulse electronically you are generating it mechanically. The system works even if you don't remove the knacker ed HT windings as these are shorted out and therefore won't transform up to the required voltage.  The mag output is effectively the output of the HT coil on the villiers engined Fanny B. I am hoping my mag works ok, if it doesn't I will give it a try. Just wondered if anyone had tried.
"Keep a distance from lady "L" drivers in cars. Some are not mechanically minded, are slow to acquire road sense, an are apt to panic..." The Pitman Book of the BSA Twins.
Golden Flash Plunger 1955, Francis Barnett Falcon 67 1954, Ferguson TEA Tractor 1951. Looking for another project!