MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - Information on Lucas headlamps?

Does anyone know where I can find information relating to Lucas 700 headlamps?

I have been trying to understand which headlights are correct for my cars. In Clausagers book he shows a picture of the "European" headlamps. I have a very nice original pair of these, but, are they correct for UK cars?

Also I have seen a lot of variations of the F700 lamps (with "700 headlamp" under the Lucas emblem.) Some lamps appear to have this etched, others moulded, into the glass. Some units have markings to the lower left of the Lucas emblem, some with ˇ°right hand driveˇ± or a small triangle at the top etc, etc.

Do these variations indicate production years or just the accuracy of the reproduction?

Are there big variations in the quality of lense and reflector as with the P700 (tripods ¨C that I intend to replace).

Also, during the production sealed beams were introduced. Does anyone know if this was standard or option and which sealed beams...?

Any help would be much appreciated.

Neil
Neil McGurk

Neil-
I have the Lucas listings for OE fitting, but it'll take a bit of looking.
"European" lights would not be correct for UK fitting, as they are right dipping for LHD drive. They might look very similar, though there may (frequently) be visible asymmetries in the lenses.
Moldings in the glass are either design variants or required markings for different jurisdictions.
Repros are probably second order take offs of OE moldings, so there will be nothing new about them except inaccuracy. That is subject to how the moldings were done, and many other factors involving the casting or pressing of glass into molds, and also the assembly with well or poorly produced other parts - reflectors and bulbholders/bulbs.
In my experience, sealed beams were primarily a US developed and required thing, deriving from laws regarding the deterioration of old time reflectors. It is the summary of the US attitude of make the object responsible for (bad lights), and absolve the driver/operator of all responsibility or choice. They may have been used or specified in other places.
For precise fitting, send me exactly what cars you have, and where they were or are used, and I'll try to look it up. It's sort of a waste of time though, since lights were optionally fitted based on all the above and more. The "correct" light would be any that is right for the jurisdiction and era.
FRM
FR Millmore

Thanks FRM,

I have a 1959 1600 and a 1962 MKII, both UK cars.

What I am really after is the way to tell visually if the lamps are of the correct type and period. I have quite a selection of good used BPF and sealed beam units. The P700 tripods are either very old repros or original Lucas units as they have been on the car for almost 30 years. The silvering is begining to look a bit tired and I want to change to an original type unit as the car is otherwise pretty much concours.

Neil
Neil McGurk

Neil

If you are talking about the reflectors... "silvering is begining to look a bit tired"... have you thought of having them replated? Or are these sealed beam units? I remember having the reflectors replated quite successfully on my PA 4-seater that I rebuilt 14 years ago.

Steve
Steve Gyles

This thread reminded me of a question I have meant to ask and only now am getting around to. I have several of the 576 fog and driving lamps. A few have reflector rot (corrosion). How can the reflector be separated from the glass lens without damage to either? Also, any recommendations to vendors that re-silver the reflectors?

Thanks,
Steve
Steve Brandt

Steve

If you fail to find anyone who can refurbish them, replacement glasses and reflectors are available new. I got a set from: http://www.holden.co.uk/

Type 576 into the keyword search.

Steve
Steve Gyles

Neil and all-
Tripods that old are certainly original Lucas, as there were no repros then, but there was old stock fairly easily available until mid 70s. The BPF system was supplanted by QH bulbs by then, and all newly designed lamp units were to suit H4 and the like.
There may be a semantic issue with "sealed beam": That is usually correctly used for the US style hermetically sealed unit with glass reflector and lens welded together in production (molten glass). I have seen the term used for the "semi sealed" lamp units like the 576 or the tripod/PL units. These have glass lenses glued to metal reflectors, and actually aren't sealed at all, since bulb removal gives open access to the lamp cavity for grubby fingers and dirt/humisery to eat the reflectors. Most UK and European lights are like this.
The previous (by default not sealed) method of lamp assembly was to have separate lens, reflector, lamp housing, bulb, and a number of gaskets, etc, all put together by your local drunk with dirt and fingerprints everywhere. This was why the US required true sealed beams.
The lamp specs for the cars are frequently spec'ed as "not including light unit", especially for export apps.
Light units are variously Right dip, vertical dip, left dip; special for Sweden, France, US or other jurisdictions. For instance there is "for North America, not US"
Usually the problem with lamp units is that they come apart by they little selves, but not when you want them to. You have to figure out what combination of heat or solvents will do the job. I have a number of really good Cibie and others that fell apart in storage, so humidity is one factor, if there is no pressure on the joint as there is when they are mounted. I can't figure out what the glue is, it looks like an early RTV silicon, but those don't usually dissolve in water vapor.
It is critical to remember that the reflector is a precision optical device and must not be distorted, so no prying. And the assembly and orientation of the lens to reflector is also just like a telescope. Resilvering is the creation of a first surface mirror, so it is more in the realm of an optical shop than a normal metal plater. Astronomy groups may have sources, since they would need the service to make reflector scopes.
The lens is also a true lens, like your glasses or a telescope. It is a non-symmetric fresnel lens in fact, and if it looks like a bottle bottom it is not going to work well. That's what's wrong with most US lights; look at the difference between a Cibie lens and any US sealed beam and it's real obvious. This is also about the only way you can tell a repro from a real one - quality of glass, unless you set up to do optical tests. Don't get me started on plastic lenses!!
Neil, if you can post somewhere, or send me, good photos of the lenses of your lights, I may be able to tell you what they are, since I have clear pictures of many Lucas units.
FRM
FR Millmore

Even Moss UK now sells the 576 glass/reflector assembly repro these days - much cheaper than on ebay...
dominic clancy

I realize I have written so much of the matter of illuminatory devices, that I may as well finish it, with regard to the silvering of reflectors, so brace yourself!
The first mirrors were polished metal. It is difficult and expensive to create a stable and regular surface, so they were small and expensive, and very subject to damage. Anybody who has tried to get an extreme polish on metal knows that after all that work, it tarnishes or gets scratched.
Glass turned out to be a good and relatively cheap and stable material, amenable to working to desired shapes, so it became the basis of mirrors. These were first surface ones, with silver as the reflector, still prone to oxidation from su;phur, and easily scratched. Then it was found that silver could be applied to the back side, and protected with lacquer, forming a durable second surface device. Fine for flat mirrors, but the glass between the 1st and 2nd surfaces acts as a lens on curved units,; not good for optical instruments.
Light reflectors were first made of metal, with first surface silvering using real silver - they tarnish badly and the required polishing destroys the factory polish, since field polishing procedures are not up to the job. These were in use through the 1940s.The US solution was the sealed beam, with the delicate reflector permanently sealed inside the glass bulb. A very good solution, had the bulb and lens/reflector package been well designed and carefully manufactured. That is too difficult and expensive, so we got lights that always worked reliably at a low but constant level of acceptability.
The rest of the world continued to use metal reflectors and openable lights, but used the much more durable aluminum metallized reflector, and put the responsibilty for maintaining the lights on the operator. The result was lights that could range from good to horrid, depending on design, manufacture, and maintenance.
The early reflectors were electroplated with silver, as in any electroplating process. Metallized reflectors are made by preparing the substrate to the correct shape and high polish, and then applying a thin layer of aluminum in a vacuum chamber. The piece is connected to a voltage source to creat a potential between it and the source of vaporized aluminum, and the vapor is drawn onto the substrate. The final surface is exactly the shape of the original, but with a thin coating of aluminum. It is in effect electroplating through space, rather than through an electrolyte solution. This surface is very durable, since it is soon oxidised to aluminum oxide, one of the hardest and most chemical resistant substances going. Deterioration is virtually always a result of things affecting the substrate, not the surface.
Reflectors can be resilvered by metallizing, but I don't know where, the telescope making community will know. The process is commonly used for such as "chrome" plastic parts, and as partial mirrors in window films. As an aside, metallization can be used with other metals; gold is used for reflectors to block intense visible and IR light, as in welding glasses or NASA helmets. In any case, the condition of the substrate is paramount in the performance of the light after resilvering.
FRM
FR Millmore

Do you want to drive your car at night? If so, the original bulbs are 45/40 watts, from memory, so not adequate for today's roads, speeds, and traffic.
Replacement 7" sealed beams are easy to fit, just change the wiring connectors. These are 75/60 watts or thereabouts, so the improvement in light output is significant. But not for concours cars, I guess.
Peter.
P. Tilbury

This thread was discussed on 22/03/2007

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.