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#271028 - 08/19/09 8:52 pm Bizzar electrical question for the day: 12volt bulbs in 6volt bike.  
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Ignoramus Online content
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Auckland NZ
OK why would anyone run 12 volt headlight bulbs in a 6 volt bike? Allow me to explain. The government here in a futher move to oppress silly old fools on ancient motorcylcles have, in their wisom, made it law that you have to ride with headlights on during the day ($100 if you dont, revenue gathering anyone?).

I mean DURRRRRRRRRRRR if turkeys in cars cant see a bike its becasue they arnt ****ing looking and lights will only be one more thing not to look at.

I digress:
Since 6v prefocus bulbs are quite hard to get here (and they are not realy an item I would want posted) and I have loads of 12 volt headlight prefoucus bulbs my question is:

Will running a 12volt bulb place undue strain on a 6 volt charging system?

I have been told it will place LESS strain on charging system becasue 12volt bulbs have higher resitance??....I dont get it...can someone explain....

I have tried a 12volt bulb and they are plenty bright enough to give the illusion of complying with the stupid law during the day. I dont want to burn out my one 6volt bulb AND I will never be using this old 6volt bike at night. Thats what 12 volt A65's are for!

Thanks guys (and yeah i know its silly)


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
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#271031 - 08/19/09 9:25 pm Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: Ignoramus]  
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hh Offline
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The 12V bulb will be fine in a 6V system, just dimmer. It won't harm your electrical system in any way. It will draw half the current compared to running it in the 6V system. V=IR, so if the R goes up (double in this case), the current must go down, given constant voltage.


"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
#271032 - 08/19/09 9:36 pm Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: Ignoramus]  
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Alex Offline
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Yes, a 12V bulb will place less of a load on your system and here's why:

Incandescent bulbs are generally rated by their power consumption. Power consumption is generally proportional to brightness. Hence, a 6V hi beam rated at 30 Watts will be dimmer than a 12V hi beam rated at 45 Watts. Now, if we use Ohm's law we can figure out the filament resistance since R=V^2/P. This leaves us with a resistance of 1.2 Ohms and 3.2 Ohms for the 6 and 12 V bulbs, respectively. If you were then to only supply 6V to the bulb with 3.2 ohms of resistance, it will only consume 11.25 Watts of Power and your bulb will be REALLY dim.

Make sense?


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#271049 - 08/19/09 10:35 pm Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: Alex]  
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hh/Alex:
Cheers...i kind of get what you mean....will study it latter..just as long as it wont make the generator struggle im happy.

Like i said i have a load of 12v fog lamp tinted bulbs and they look just as bright in daytime on 6v as they do on 12. If i burn afew of themn out and save my 6v bulbs for "warrent of fittness" (no idea what you call vehicle inspections in USA)checks every 6 mounts its all good


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
#271138 - 08/20/09 11:26 am Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: Ignoramus]  
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I doubt that you will have much luck running the 12V globes.
Incandescent glob filaments are not particularly strong when glowing red hot.
So you will most likely find that they will break quite frequently.


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Trevor
#271142 - 08/20/09 12:04 pm Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: BSA_WM20]  
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If you fit 12V bulbs all round, 12V coils , and a 12V battery, you will have a 12V charging system.

You'll have a better 12V system if you connect the alternator for permanebt full output and use some kind of regulator.


Amateur Loctite enthusiast.
#271177 - 08/20/09 3:40 pm Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: triton thrasher]  
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hh Offline
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BSA_WM20: how exactly is the 12V incandescent filament going to be glowing red hot when it's running at 1/4 its rated wattage with half its rated voltage across it? If it weren't for vibration, it would likely burn forever.

triton thrasher: your solution is the best one for a three wire alternator currently configured as a 6V system, like in a TRW. It's easily reconfigured for 12V with a regulator and will work just as well or better than any British factory 12V system.

But if it's a 6V generator, converting it to 12V is a poor solution since the RPM required to achieve 12V is considerably higher than 6V. You end up with a charging system that is struggling to maintain its nominal voltage for a greater percentage of running time, and a greater likelihood of a discharged battery and weak lighting and ignition below about 2000 RPM.





"Beer is proof that God loves us and wants us to be happy" - Benjamin Franklin
#271197 - 08/20/09 5:18 pm Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: hh]  
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So it's not an A65 then?

If it's a dynamo (DC generator), just stock up on 6V bulbs off the internet.


Amateur Loctite enthusiast.
#271242 - 08/20/09 9:16 pm Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: triton thrasher]  
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Ignoramus Online content
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Trevor:
I have tried one 12 v and it is surprisingly bright on 6v (am using tinted fog lamp amber bulbs so its not the kind of brown light you get of a weak battery and std white bulb)....gives a very respectable looking light in day time, if for example, viewed by a cop car comming in the opposite direction looking to give out $100 fines. I have plenty those 12v bulbs so if i pop afew in short order I will give up on the idea. I was only concerned about any harm to my generator.

HH:
Its a 1952 6volt generator bike and i wouldnt convert it to 12v even if i could for the sake of originality (12 volt "consumables" dont count). I think Trevor means glowing red hot (as in pathetic light) as opposed to glowing white hot as in good light. I think resistance wire is more brittle at lower temepertaure.

TritonTrasher:
yep magneto ignition,6 volt generator (which was what i was worried about damaging with a higher resitistance bulb) I dont fancy my chances of the bulbs arriving unbroken by mail to NZ. No doubt I will get some somewhere but for now dont want to burn out my one 6v bulb by having lights on all day just for some stupid revinue gathering schemme targeting bikes.

thanks all


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
#271275 - 08/21/09 12:28 am Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: Ignoramus]  
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If globes can take Pommy vibration they could stand postage travelling!!

#271331 - 08/21/09 11:34 am Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: douglas]  
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Originally Posted By: douglas
If globes can take Pommy vibration


Quite often they can't.

I simply don't believe that no-one in NZ supplies 6V bulbs. Or that shipping would break many of them.


Amateur Loctite enthusiast.
#271414 - 08/21/09 7:25 pm Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: triton thrasher]  
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Ignoramus Online content
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Auckland NZ
TT;
you can get them by mail, thing is i ordered 3 12v ones a while back and 2 were broken in transit and they only came from south island (about 1000miles)..doesnt exactly inspire confidence.

Like i said its a temporarary fix to avoid a $100 ticket untill some 6v turn up (and i would also need tail light and speedo light.....now 6v speedo light realy are hard to come by localy)

Dont confuse parts avalabilty in UK or USA with here,,,damm near everything is a mission to get here and postage ex UK is prohibitive on anything other than real small bits. My mate was quoted 150 POUNDS postage for an exhasut system.


"There's the way it ought to be and there's the way it is" (Sgt Barnes)
#271447 - 08/21/09 10:54 pm Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: douglas]  
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Quote:
BSA_WM20: how exactly is the 12V incandescent filament going to be glowing red hot when it's running at 1/4 its rated wattage with half its rated voltage across it? If it weren't for vibration, it would likely burn forever.

triton thrasher: your solution is the best one for a three wire alternator currently configured as a 6V system, like in a TRW. It's easily reconfigured for 12V with a regulator and will work just as well or better than any British factory 12V system.


I hope you were trying to be funny with this post, but just in case you were not.
Incandescent filaments do not BURN, they are a resistance wire which prevents the flow of electricity through it by the generation of heat.
The heat generated by the electricity in the wire causes two things to happen. Firstly the nickel tungsten steel goes through 4 phase transformations.
Secondly the wire glows, white hot to be specific from where we get the light.
It is exactly the same as a resistance wire in a heater which glows red because we want the hot infrared radiation to come out to keep our bums warm.
In a globe we do not want the heat output we want the light so we up the level of heat from the red part of the spectrum to the white part of the spectrum this is done by using a material with more resistance than for you heater or toaster and further enhanced by making it much much thinner.

Now the actual strength and in particular the shear and fatigue strength of the metal used for the filament is different in each of the 4 different phases ( crystal structures ) and it is highest at its full operating heat ( white hot) other wise every time your bike went over a bump the globe would blow.
Now a lot of metallurgy has gone into filament materials to taylor an alloy with maximum strength from cold all the way through to white hot and the modern materials are 1000 times better than those of yesteryear .
However miracles do not happen in real life and to obtain maximum strengths at both working temperatures ( white hot ) and idle temperatures ( ambient). The current alloys are the best compromise between these two extreames but the down side is that during the phase change from the Etta to the Delta phases tha material is very weak and this phase change occurs at temperatures that corrospond to the medium to bright red range.

When you turn on a globe the filament will go from black to dull red to bright red to orange to yellow to white and now days to ultra white.
However all this happens so fast they all your eyes see is a light that goes from dull to bright.

The speed of this transformation in a particular piece of wire will be dependent upon two things, the thickness of the wire and the force of the electricity ( voltage) applied across it.
As the voltage decreases the speed at which the filament attains full output will be reduced or in most cases will never be attained. So the time that the wire is in it's "low strength" phase will be increased so the chances of the filament failing due to mechanical causes ( vibration) will also be increased


Bike Beesa
Trevor
#271487 - 08/22/09 12:07 pm Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: BSA_WM20]  
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There used to be a big worldwide dealer in Brit parts somewhere in NZ, but I can't remember their name.

Anyway, I actually did run a 12V sealed beam at 6V (alternator) for a while years ago and nothing bad happened. That probably should have been my first comment here!


Amateur Loctite enthusiast.
#271693 - 08/23/09 8:31 pm Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: triton thrasher]  
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Leonc Offline
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New Zealand
In fact it seems the question no longer relevant, as the Legislation that Parliament passed allows for pre 1980 motorcycles to be excluded from the requirement.
All the better for you, as not going to get caught out at night with substandard lighting when you really need it.


Leon
1968 Triton Morgo E/S
1969 Trident Beauty kit
1970 T100C Scrambler special
1971 Rocket 3 Export
#271750 - 08/24/09 1:15 am Re: Bizzar electrical question for the day: 12volt bulbs in 6volt bike. [Re: Leonc]  
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Ignoramus Online content
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Leon
Good one......they havent exactly publicised that!

Thanks for bringing that to my attention...problem solved.

Infact it will give me great pleasure pointing that out to Robocop on a revinue gathering exercise, chances are they wont know.


"There's the way it ought to be and there's the way it is" (Sgt Barnes)

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