Author Topic: 7" Isetta prefocus headlight lamps. 36/42 watt  (Read 2223 times)

AndyL

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7" Isetta prefocus headlight lamps. 36/42 watt
« on: September 27, 2014, 01:52:38 PM »
Does anyone have one or to of these ? they don't have to be working, but the filament should still be visible.

I wanted to get some measurements of the filament spacing. Most of the lamps i see available seem to be for U.S spec lighting.

I do have a halogen lamps, but wouldn't mind seeing how the tungsten lamps compare. This is for my LED refit.
1959 LHD 3-wheel Isetta.

DaveMiller

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Re: 7" Isetta prefocus headlight lamps. 36/42 watt
« Reply #1 on: September 27, 2014, 05:44:50 PM »
I guess that the British Isettas will have used the same size of bulb as most other British cars of the period, and the same shape of reflector.  The wattage will be irrelevant, if you just want to measure the filament position.
The bulbs you need are still readily available at many car shops, or on, for example, eBay.
Look for "BPF" or "British Pre Focus" - £5.80 for two, inc postage, on eBay just now.

AndyL

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Re: 7" Isetta prefocus headlight lamps. 36/42 watt
« Reply #2 on: September 28, 2014, 05:35:54 AM »
The thing is I see two different types.

The first type has two filaments mounted longitudinally one behind the other with the dipped beam filament furthest away and having a small plate mounted undeneath to ensure the light is directed upward towards the reflector. 

The other type has two filaments mounted very closely together, the filaments are wired horiziontally across the bulb but with one slightly offset sideways. There is no plate to direct the light upwards.

Which is correct, or they both correct?
1959 LHD 3-wheel Isetta.

Big Al

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Re: 7" Isetta prefocus headlight lamps. 36/42 watt
« Reply #3 on: September 28, 2014, 07:24:59 AM »
There certainly used to be a halogen conversion kit for these lights. They have been around a long time and I think the bulbs start at 25w/25w, Bonds and chums?, and drift upward in power depending on what they fitted. Once you had the converter you only need swap bulbs if one blew. So that is the part you need. I have a load of NOS Phillips H4 bulbs which were the sort of things put in.
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DaveMiller

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Re: 7" Isetta prefocus headlight lamps. 36/42 watt
« Reply #4 on: September 28, 2014, 10:12:32 AM »
I gather Andy's wanting to try the construction of a small-source LED version.

"Converters" were available (but, I suspect) may have repositioned the filaments ...

You can, however, get BSF bulbs already in halogen.  On my Bond Mk G, I wanted something brighter than the 24/24 W originals, so tried some Indian halogen 35/35 W ones, from eBay, and they were ... well... Hopeless. Worse than the originals as a light beam, as the filaments were - again - not where they were supposed to be.

I then went the paymore route, and got some from http://www.norbsa02.freeuk.com  and when I used those this summer, in the dark depths of the fields surrounding the Dutch Rally site, they were excellent!

(With other, sidelight, etc, bulbs moved over to LEDs, the total load on the Dynastart is back to approximately the original total, and the car runs a slight charge with the 35W headlights on.)
« Last Edit: September 28, 2014, 10:18:40 AM by DaveMiller »

AndyL

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Re: 7" Isetta prefocus headlight lamps. 36/42 watt
« Reply #5 on: September 28, 2014, 01:29:40 PM »
Okay so here is what I have. A Halogen lamp, which i think is probably wrong for my reflectors. I also have a pair of Tiger lamps, these appear to be NOS. I originally thought these may be wrong, but from what has been said here, it seems they are most likely the correct lamps.





1959 LHD 3-wheel Isetta.

DaveMiller

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Re: 7" Isetta prefocus headlight lamps. 36/42 watt
« Reply #6 on: September 28, 2014, 02:06:43 PM »
The 'Tiger' ones look identical (apart from wattage) to the bulbs I took off my Bond - and are in what I'd call "normal" BSF format.  Perhaps the best starting point for trying to position the LEDs?

The halogen ones look similar to the bulbs I finally fitted - not entirely sure, as I'm having to look at 'em through the headlight lens!

I should perhaps mention that my new halogens are excellent on main beam, but cut off the dipped beam very close to the car.

AndyL

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Re: 7" Isetta prefocus headlight lamps. 36/42 watt
« Reply #7 on: September 28, 2014, 02:14:30 PM »
That would make sense. The halogen has the dipped filament staggered further away from the parabola focus.
This might be to cut down any glare.

If I use the positioning of the older lamps, then I'll have to slightly rethink my strategy with regards to the LED's used, and will have to use the smaller cree LED's throughout. The halogen style layout can use a mixture.
1959 LHD 3-wheel Isetta.

DaveMiller

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Re: 7" Isetta prefocus headlight lamps. 36/42 watt
« Reply #8 on: September 28, 2014, 03:06:23 PM »
Sounds about right. Do let us know how you get on.

[Edit: Above, where I twice wrote "BSF", I meant "BPF" of course!]
« Last Edit: September 29, 2014, 05:49:32 AM by DaveMiller »