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1932 Austin Seven RN Box Saloon |
The Charge of the Night Brigade!
Who would have expected that fitting LED bulbs to my 1932 Austin Seven to improve night driving safety would produce the undesirable by-product of nearly gassing the occupants of the car? Certainly not me.
I was
prompted into converting to LEDs after a touring holiday in Spain. The car ferry
disgorged us at Portsmouth late one dark and very wet evening and it rained
stair rods for the whole 25 mile journey home. After a few miles the headlamps
grew dim and the single wiper stopped altogether as the dynamo struggled to
keep the 6 volt battery topped up. With a little thought I could have foreseen that.
The dynamo on these 1930s Austin Sevens is of the 3rd brush variety with a summer/ winter charge switch. The position of the 3rd brush on the commutator alters the field current, and hence the output, which should be set to give a maximum of 8 amps in the summer position. This is the most the dynamo can stand without cooking itself. With the switch in the winter setting, the charge is halved to about 4 amps. The sophistication in this set up begins and ends with an electro-mechanical cut out to prevent the battery flattening itself trying to motor the dynamo when it is at rest. This arrangement is typical of most early cars up to about 1935.
The dynamo on these 1930s Austin Sevens is of the 3rd brush variety with a summer/ winter charge switch. The position of the 3rd brush on the commutator alters the field current, and hence the output, which should be set to give a maximum of 8 amps in the summer position. This is the most the dynamo can stand without cooking itself. With the switch in the winter setting, the charge is halved to about 4 amps. The sophistication in this set up begins and ends with an electro-mechanical cut out to prevent the battery flattening itself trying to motor the dynamo when it is at rest. This arrangement is typical of most early cars up to about 1935.
The little
thought that I mentioned above relates to the amount of power
required to run a pair of 36 watt headlamps, two 5 watt side lamps, two 5 watt
tail lamps plus the wiper motor. There is a simple formula that every schoolboy
knows that says W = V x A. Thus, if one
adds up the power required to drive the lights alone, it totals 92 watts.
Applying this to our formula we get 92W
= 6V x A, and so by dividing 92 by 6 we
discover that 15 amps are required to keep the lights alive, whereas the weedy
little dynamo can only punch out 8 amps at best.
So it should
not have come as a surprise that we ended up inching our way home behind what
seemed like a couple of candle lamps. What is
somewhat of a surprise is that we managed to get home at all.
Undaunted, I
started to research solutions to this problem.
The Austin Seven world is a full of clever bods who have been tinkering
and modifying their little cars since time immemorial, or at least since they
were invented in 1922. Some people have
gone down the route of changing to 12 volts. Others have adopted a novel new
alternator with built in regulation that looks just like the original dynamo
right down to the distributor mounted on the end.
The Facts and the Law
LED (light emitting diode) bulbs for cars have been around for a while now, but only comparatively recently have they found their way into older vehicles. The reasons are obvious – far brighter lights for far less current consumption make them ideal for vehicles with charging systems and lamps designed for a by-gone age.
The actual wattage (current
consumption) of LEDs is far lower than tungsten bulbs. LED car bulbs for older
cars don’t seem to be wattage-rated; rather they are sold by application.
However, consider that you would buy a 5 watt LED bulb to replace a 40 watt
tungsten bulb for your home and you get the idea.
Unfortunately the law has not caught up
with this and, technically at least, owners could fall foul of it. This is because the actual letter of the law
states minimum wattages for each type of light in order that they should be
adequately bright. This was clearly a good idea in the time of tungsten bulbs,
but today the wording prevents the legal fitting of LEDs in certain lamps
whilst allowing them in others.The Current Regulations (sorry for the pun!)
*Side Lamps
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First registered before 1.1.72 : LEDs in original lamps OK
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*Tail Lamps
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First registered before 1.1.74 : LEDs in original lamps OK
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*Number Plate Lamps
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First registered before 1.4.86 :LEDs in original lamps OK
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*Stop Lamps
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First registered before 1.1.71 ; LEDs in original lamps OK but non-compliant if first registered after this date, so begs the question why modern cars comply.
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Flashing Direction Indicators
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LEDs in original lamps non-compliant, no date specified, so begs the question why modern cars comply.
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*Headlamps
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LEDs in original lamps non-compliant unless of legal wattage and do not cause dazzle
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The Road Vehicle
Lighting Regulations also allow the use of optional lamps in addition to the obligatory
lamps marked * in the table. Oddly,
there are no wattage requirements for optional lamps, so there is nothing to
prevent LEDs being used in them.
Therefore, if I understand it correctly, you
can stay legal by keeping the correct tungsten bulbs in your original lamps and
fit additional LED lamps as well.
Watts vs Lumens
If the law were changed so that LED bulbs
are rated in light output (lumens) rather than power requirement (watts), the
problem would largely be solved.
Beware
of Dazzle
However, we must not overlook the important issue of dazzle which can arise when LEDs are fitted to some older headlamps, but not all. The optical design of a headlamp reflector and lens requires the light source (bulb) to be in certain position and orientation. In some cases LEDs are sufficiently different from tungsten bulbs not to focus correctly and, even though they throw out a great deal of light, they might also cause dazzle. Think of those pesky cyclists who dazzle all and sundry. No old car driver wishes to be like that.
Shining the headlamps against a wall and then down a (quiet) road with a helper standing in front can show if there is a problem – as will other drivers, who are never backwards in coming forwards with their own headlamp flashers! If necessary, repositioning the LED within the lamp, moving the bulb holder to correct the focus and so on, may cure the problem. But this might not be straightforward and may only be a job for the most hands-on fettlers amongst you.
Of course, dazzle is not confined to
the wrong bulbs in old cars. How often
have you come across an approaching vehicle with one headlamp dazzling you, due
to the owner not understanding the correct way to fit a new bulb to replace one
that has blown? Incidentally, LEDs have
a far greater life expectancy than traditional bulbs and theoretically will pay
back, to some extent, the significant cost of buying them.
Safety gains
There is such a significant
improvement in light output when LEDs are installed which is clearly a huge safety
feature when compared with the originals. Therefore it is hard to imagine
anyone being prosecuted unless you are dazzling other road users. This, of
course, is my own view and none of this is to be taken as authoritative.
Tell them in Westminster
That excellent organisation, the Federation of British Historic Vehicle Clubs (FBHVC), is pursuing this matter with the relevant authorities. But in the meantime, letters to the Secretary of State for Transport, Chris Grayling, and your MP can’t do any harm.In the next Issue
- So, how did I come to expose the unfortunate occupants of my Austin Seven to the risk of being gassed?
- What did I do about it?
- And how I fitted LEDs in a sympathetic and effective way to my Austin Seven.
All will be revealed in the next edition of Vintage and Classic Car Gazette.
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