Ignition switch/barrel

[Mosin]

It would appear that during the great engine demise of January 2010, my magneto has been damaged beyond all economical repair. In the interests of useability over originality I have decided to fit a new pazon kit. However, a couple of questions arise from this...

• The wiring diagram for the pazon clearly shows a fuse in the circuit, but does not give any indication of what size fuse to use (I am running 12v)
• The diagram also shows that some form of ignition switch is required. Does anyone have one on their bike? If so, where is it fitted? Is it preferable to just go with a basic on/off switch, or one of the many keyed ignition barrels that are available? And if so, is there an "accepted" position for mounting such a thing?

As ever, any thoughts anyone might have would be most welcome...

[brackenfel]

Hi Simon,
Sorry to hear of the continuing fallout from that day...  To my (limited) knowledge ignition switches were not fitted to the pre-unit bikes as they all had magneto ignition..
The later A50 / A65 etc ones had coil ignition and an ignition switch fitted, although I don't know exactly where - it would be worth looking at a parts list for these models, especially the early (post '62) ones.

Good luck with the Pazon, I'm sure many of us will be curious to know how you get on..

Cheers,
Adrian

[BSA_54A10]

Coil draws around 5 Amp (cont ) and a 60W headlamp will add another 5 Amp, 1 for the instruments lights & tail lamp and 2 more for the stop lamp which makes 13 make allowences for bad joints and you end up with 20 A continious. I think it equates to a 35A instant ( USA ).

Now here is the trick, fit 2 fuses, one on the battery and one on the regulator out put.
If you have an Amp meter then you simply fuse both wires that go to it.

We used to fit push/pull switches into the tool boxes in the 60's with the business end pointing out through the back so it was hard to find. The again I had thinner and far more nimble fingers in those days.
Put the fuses right next door.

[trevinoz]

And where are we going to get all of these amps?
Trev.

[BSA_54A10]

Not from a standard dynamo thats for sure

[Dynamo Regulators Mike]

Lucky that current estimate is way off beam (no pun intended).
How would bad joints conceivably add to the current drain, or am I missing the point? Surely draw would be less, but ought to be near negligible if connectors in reasonble.
Another estimate:
Coils 2A average, 60W headlight 5A, 1A other lights plus occasional 2A from stop bulb
So 8 Amps total. Similar to rated current output of E3L (at 2,000 dynamo rpm) at 7V. It is the current which heats the winding whatever the voltage as resistance is fixed.
Interested to know what 35A instant is, are US Amps short measure like US gallons?
So Mosin a 10 or 15 Amp fuse (normal slow blow auto types) gives good protection.
My Flash has a simple on/off keyswitch from an electrical catalogue (RS components). Has been ok for 10k miles to date but feels a little sloppy. Fitted to front of tool case. Adds a bit of security. But a heavy duty switch as fitted to my B50 isolates all electrical loads so less chance of flat battery from sticky stop switch or whatever. Lock & key & switch part nos. Lucas 1-80 + 39565, BSA 82-6981 + 19-1904
Mike

[muskrat]

G'day mosin,
                 I run Boyer and DVR2 on both my A's. I use a 10A fuse on the main power wire and a cut out switch (keyed), and an ignition toggle on the bars.
I think Pazon is similar to Boyer in that it turns it's self off in 5 seconds if no pulse is detected, and back on when one is.

[A10Boy]

You know, those DVR2 jobbies are the dogs dodahs---------

[Richard]

Mike,
I think what was meant about bad joint is that if you have a poor joint the resistance is greater therefore the circuit would then draw more current due to the higher resistance and as you know this in turn would lead to a fuse blowing due to more current being used.
pretty unlikely on a bike as if it was that poor it would more than likely fail, but it could happen!!
Richard
ikba rules
PS A10boy, now don't over do it about the DVR2

[chaterlea25]

Hi Richard,
You arnt quite right there with your theorie!!!
A poor joint increases resistance, to increase current you need less resistance or more volts
since voltage is fixed 6 or 12 then a poor joint will reduce current (like a kink in a garden hose)

Quote:
"Coils 2A average, 60W headlight 5A, 1A other lights plus occasional 2A from stop bulb
So 8 Amps total. Similar to rated current output of E3L (at 2,000 dynamo rpm) at 7V"

ManorMike is also mixing up some 6 and 12 volt values!!
60watt headlamp takes 5 amps with 12 volts, 10 amps with 6 volts
8 amps at 7 volts will only give 56watts ?????

Over to you Mike??

Cheers
John O R

[Dynamo Regulators Mike]

Current loads are approximate for a 12 V system.

Any confusion over voltage comes from dynamo output figure. I was quoting Lucas spec. for the 60 W E3L: 8.5 Amp with 0.8 ohm load at 1,850-2,000 rpm at 7 Volts
(tolerance of resistors back then was not so good as today, calculated current is: 7V / 0.8 Ohm = 8.75 A).
Power into load is: 7V x 8.5A > 59.5 W
The point is that the armature is safe from overheating whilst supplying 8 A whether in a 6 or 12 V set-up. Need higher revs to get up to 12 V of course.

Cheers
Mike


PS: Mosin hope you get a switch sorted out


PPS: tempted to say there's no such thing as a bad joint, just that some are better than others but . . .                      (please enjoy in moderation)

[Richard]

John,
not sure I quite agree,if a poor joint increases resistance, then lets say for a given ampage on a lamp circuit with a poor joint and increased resistance it will have to draw more from the power supply which in turn increase the current as ohms law must apply, with the possibility of the cable getting hot or the fuse blowing due to the higher draw through it.
or am I just missing your point?
Richard

[trevinoz]

Richard,
 
                 You are missing the point.
A high resistance joint is the same as having a resistor in series with the load which will limit the current in the circuit.
The load cannot demand a higher current as it can only draw what ohms law allows as current through a resistance is dependent on the voltage drop across the resistance.
When you have a high resistance joint, there is a voltage drop produced across that joint which will then limit the voltage across the load.
The sum of the voltage drops across the resistances equals the applied voltage.
Are you totally confused now?
   Trev.

[bsa-bill]

Hi Richard, I had have very limited experience with the electrickery stuff although I did start out working life as an apprentice Electrician and then a spell in TV and Radio before becoming a son of the soil.
I understand what Trev is saying, think of a bad joint as a partially blocked artery it restricts the flow of blood so less blood is pumped around that artery but the heart has to work harder to push blood past the blockage - have no idea what Mr Watt and Voltaire would think of this analogy  ???

all the best - Bill

[Richard]

ok so let me put this to you,
A 12volt circuit with a 60watt lamp will draw 5amps
a 6volt circuit with a 60watt lamp will draw 10amps
so if we have a 12volt circuit with the 60watt lamp and it has a bad connection and restricts the volts as it is acting as a resistor then lets say the volt drop will then only give you 8volts then the lamp will draw 7.5amps causing a 5amp fuse to blow (assuming it is a quick blow) also if the cable is only rated for 5amp then that to will start to get hot,the resistance increases the voltage decreases the ampage goes up and so on, so where am I incorrect in what I said in the first instance?
I know that the cable is not likely to get hot as we are not talking big currents here but the theory as far as I can see is ok