Sealed Beam?

[fido]

I recently got a copy of the 1948 BSA motorcycles brochure. It looks like my A7 was the top of the range model at the time as the Star Twin is not listed. In the spec. it describes the headlamp as "sealed beam". Did this have a different meaning in 1948 or do they mean the type of headlamp where the whole reflector and lens is part of the bulb? The parts book does not include electrics.

[groily]

The sealed beam headlamp was introduced in the US in about 1940, and was adopted pretty well universally I think over there for cars, usually in 4 light set-ups, usually, I think, at about 6" diameter. That certainly lasted through to the late 60s minimum, as I have a US-export UK car with just such an arrangement of 4 sealed beam lights. I'm sure US-based members here will be able to add to that.
So the technology was there and I have never heard 'sealed beam' mean anything other than what we think it means Fido. At the same time, I've never knowingly seen a sealed beam unit on a bike, but then i have never even thought about it till now!

[G/F DAVE]

Fido. The sealed beam lamp refers to the actual glass & reflector as one unit unlike earlier LUCAS lamps like DU & MU models having a seperate glass &  reflector with a cork gasket as a seal. With this type of lamp you can change the bulb mostly BPF type unlike the sealed beam units as used on cars that have a one piece glass moulding that houses a filament that can,t be renewed once blown. G/F Dave

[goldstar 39]

Hello came across this head lamp today it has LUCAS SSU700P MADE IN ENGLAND stamped on the headlight shell  and it has SEALED BEAM  GE MADE IN USA on the glass at the front   and it has three pins on the back of the unit with three wires .Is this a head lamp someone has thrown together or is it supposed to be like this.? it all fits together nicely and worked when i put it on a 6 volt battery .    were these fitted to A10s ?
Richard

[iansoady]

The sealed beam unit is essentially a huge bulb which cannot be dismantled and AFAIK was only made in 12 volt versions (although it will light up on 6 volts it won't be very bright). The code SSU700P  refers to the shell itself - both sealed beam and normal pre-focus (separate bulb) units will fit it. Lots of later 1960s / 70s British bikes were fitted with the sealed beam.

[trevinoz]

Ian,
           Are you sure that late 60s and 70s bikes had sealed beams?
I have not seen an original fitment sealed beam but have seen owners fit them.
The problem with fitting a sealed beam is that motorcycle headlights do not dip to one side but car headlights do.
I can't imagine the industry making sealed beams for such a small market.
I am pretty sure that later bikes had halogen lights but they were a special unit made to take the halogen globe and were not "sealed"
Another point about motorcycle headlights, the bulb is different to the car type even though they are interchangeable.
The filament construction is the difference. The dip beam filament is in the same plane as the high beam on the motorcycle but to one side on the car.
  Trev.

[BSA_54A10]

1) 6V sealed beam lamps were made but to the best of my knowledge never fitted to a motorcycle.
Most that I have seen were single element so would have been used on vehicles with twin headlamps.
2) 12 V sealed beams were not usually fitted to motorcycles
3) Sealed beam referred to glass & reflector as one unit as previously mentioned. A quick glance at the relevant parts book would have verified this as the "sealed beam" models all list a headlamp bulb.

[iansoady]

Ian,
           Are you sure that late 60s and 70s bikes had sealed beams?
I have not seen an original fitment sealed beam but have seen owners fit them.

You could well be right as my bikes have always had several previous owners, but both my Commandos had sealed beams when they came to me.

[lawnmowerman]

Interesting topic. I have a Lucas 700 headlamp and it has "Right hand drive" moulded in the glass at the top. When I took the bike for an MOT last month I got an advisory for dip beam dipping to the right (I am in the UK so drive on the left). The MOT guy stuck a piece of tape over the glass to mask out the light going to the right so I got a pass.
The bike passed OK last year and the only thing I have done since is to fit a new high power 12V bulb which I got from Paul Goff at a bike jumble.
My question is:
Have I always had a problem even with the old bulb and the MOT guy was not as diligent last year?
Should I have a headlamp glass with "Left hand drive" embossed on the front for the UK so the prisms mask off light going to the right on dip?
Have I been sold a car bulb which is causing the dip to the right instead of straight down?

Sorry to hijack your thread Fido

Jim

[fido]

That's confusing as we call normal UK cars "Right Hand Drive" so if it was intended for a car you would expect it to be the correct, left hand dip version. 

[goldstar 39]

thought you may be interested in this headlight its sealed beam  says general electric company on the back of the glass unit and 6-8 v
does this mean 6 to 8 volts the shell is a ssu700p  it lights up nicely on a 6 volt battery
Richard

[trevinoz]

Jim,
         Your "right hand drive" unit is correct for you Pommys and for some of us Colonials who use the correct side of the road to drive on.
However, you should have a light with "motorcycle" embossed on it for a bike. It has a different diffuser pattern.
Also you should have the correct motorcycle globe, as I mentioned earlier, which doesn't dip to one side.
I think that your tester may be a little confused or you have a right hand dip globe as your light unit would have been on millions of motor vehicles!
Having said all that, I have only one serviceable "motorcycle" unit in my possession and many "right hand drive".
You use what you can get.

  Trev.

[lawnmowerman]

Yeah that confused me too Fido - unless it means that it is designed for vehicles which drive along the right hand side of the road, rather than those which have the steering wheel on the right. I think I may try the old bulb and see if it dips straight down as it may be the filament layout in the halogen bulb mentioned earlier by Trev which is causing the problem.

Jim

[lawnmowerman]

Thanks Trev - you beat me to it. Looks like my halogen bulb is for all those countries which drive on the "wrong side of the road" 

Jim