Re: Electrical Puzzles - proper answers

[Glenn Merrell <gmerrel@domain.elided>]

Hello Peter and John,
	No, your question was quite clear, I suppose I went into a bit more detail than
was needed, and did not address your specific question correctly, so lets look
again at your questions:

PGAHOWELLS@domain.elided wrote:
> 
> What I am asking is why is it 25 amp fuses for each 55 watt headlamp bulb, and
> 10 amp fuses for each 55 watt dip lamp bulb. They are the same bulbs GLB448.
> They all have dedicated wire. Why the difference in fuses?
> Peter H
> 
and;

>  PGAHOWELLS@domain.elided wrote:
>  >
>  > Hi all
>  > Puzzle 1
>  > Why is there a 25 Amp fuse for each headlamp and a 10 amp fuse for each dip
>  > lamp.
>  > In UK they are all the same bulbs, 55watt. divide 55 by 12 Volts =  4.58
> Amps.
>  > Thus 10 amps should be enough for both main and dip.

Answer.
	The fuse size has nothing to do with the headlamp current, except when it is
initially switched on or short circuits.  The fuse size has to do with
protecting the wire to the headlamp only in the event the headlamp short
circuits.  This is so the wire does not burn up.  

So your questions are:
	Why is there a 25 amp fuse for the main beams when there is a 10 amp fuse that
seems large enough for the Dip beam having the same wattage size as the Main
Beam?  

	To analyze this problem, the question arises that if the bulbs are the same
size in the UK market for Main inner/outer beams, is the wire in the harness
large enough to safely supply a 55 watt bulb for the Main beam, or visa versa?  
Your calculation from your previous post question is basically correct, 55 watts
/ 12 volts = 4.58 amps  But car electrical systems have to take into account a
voltage range of 10.5 Volts Direct Current to 14.5 Volts Direct Current, that is
dying battery vs a fully functional charging system. Then something must be
amiss here?  Why a larger 25 amp fuse for a lamp that is the same wattage on
both circuits?

	In order to properly answer this question, we will need to take a look at ALL
the market bulb combinations, shall we?  In the ROM section 86.70.00 sheet #2 as
a bulb reference for all markets.  There are two combination of Stags that have
the ability for BOTH filaments in the Main Beam, with the  UNIPART GLB410 (a
dual element bulb) and USA Sealed Main Beam, to be ON at the same time (see
schematic on ROM Sections 86.00.07-08-09-10).  This gives the total wattage of
this bulb in the Main Beam position the total wattage of 85 watts and 87.5 watts
USA spec.  That is just how things are wired.  Now from your equation  P/E=I,
that is Power in Watts divided by the Voltage = Current, 85 watts(or 87.5 USA
Spec) / 12 volts= 7.08 amps (7.29 amps USA spec).  Now, add the ability of both
elements to be switched ON from OFF, the current surge could easily exceed 10
amps, popping the 10 amp fuse.  In fact, if you would put a current meter on the
circuit and switch on the main beams, you would see an instantaneous current
surge of over 20 amps with the engine off and an absolutely cold bulb. 
Electrons flow faster when cold, slower when hot.  Flashing or dipping the beams
also causes current surges that could pop a smaller fuse.

	And that, Peter and John, is why the Triumph engineers placed a 25 amp fuse in
the Main Beam Positions, to protect the wire, but not let a 10 amp fuse pop on
other market applications with larger bulbs!!

To see if your wire is properly sized for a larger load, check out the Vintage
Triumph Site about Triumph Wiring at
http://www.vtr.org/maintain/wiring-harnesses.html written by our own hobbyist
Dan Masters, one absolutely great article produced by a VTR member.

As to why 
>>Puzzle 2
>>On the cover of the fuse box we see Headlights Main Beam 1
>>then Headlights Main Beam 2
>>then Headlight Dip Beam RH
>>Headlamp Dip Beam LH
>>Why use a 1 and 2 convention in naming the main beams, and a RH LH convention
>>to name the dip beams?

I'll defer to John Clayton to answer that one.  BTSOOM!  I do recall an
explanation some time ago about Main 1/2 vs RH/LH, but the reasoning escapes me
now.   

Please excuse that my previous post was not specifically to the point of your
fuse size question, and provided an over complicated answer.

In my Humble Opinion, Yours for Speculation......

Regards,
Glenn  Merrell
Triumph Stag Register USA VP

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