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Given the valuable information from A G Wood I’m not surprised that your light output is poor. The 1139 is rated at 18 watts - I use these as brake or indicator lamps. A 36 watt bulb gives an adequate output but I would question the silvering of your reflectors plus that glass does seem too ‘stippled’ for good light output.
Stuart
Stuart, I'm no expert on pre-war lighting on American cars, and I welcome any input from one, but I feel the #1129 globe may be original spec, even though its output is <18W.
Looking at the bulbtown data it also has '21MSCP' which I believe is the rating of the #1129 in candle-power
(as you most likely know there is no direct conversion from W to c.p.).
Based on D W Moore's report at deepblue.lib.umich.edu. which I acknowledge as the source of my data:
21 c.p. globes would fit in well with pre-1940 US automotive lighting practice where there was a plethora of different systems and the only attempt at a standard was the requirement to fit only 8-5/32, 8-1/2, 9 and 9-1/2 inch headlamps with 21-candle-power globes. The two-beam system wasn't developed until ~1924/5, and by 1940/41 lighting was standardised as 2 x 7 inch 'sealed beams'.
I would also suspect that OPs headlamps have no dipping mechanism either, as according to Moore, 'anti-dazzle' measures were a secondary concern in the US at that time, and some allowance (if an inspection was called for by local legislation) was even made to allow the beam to rise above the horizontal.
Anorak discussion aside, I do agree that 36W globes would do the job, and I know from my own experience with my own pre-war car that re-silvering makes a biiig difference. I believe that in the States reflectors can be aluminized as well which is more durable.
Regards
AGW
Given the valuable information from A G Wood I’m not surprised that your light output is poor. The 1139 is rated at 18 watts - I use these as brake or indicator lamps. A 36 watt bulb gives an adequate output but I would question the silvering of your reflectors plus that glass does seem too ‘stippled’ for good light output.
Stuart
Stuart, I'm no expert on pre-war lighting on American cars, and I welcome any input from one, but I feel the #1129 globe may be original spec, even though its output is <18W.
Looking at the bulbtown data it also has '21MSCP' which I believe is the rating of the #1129 in candle-power
(as you most likely know there is no direct conversion from W to c.p.).
Based on D W Moore's report at deepblue.lib.umich.edu. which I acknowledge as the source of my data:
21 c.p. globes would fit in well with pre-1940 US automotive lighting practice where there was a plethora of different systems and the only attempt at a standard was the requirement to fit only 8-5/32, 8-1/2, 9 and 9-1/2 inch headlamps with 21-candle-power globes. The two-beam system wasn't developed until ~1924/5, and by 1940/41 lighting was standardised as 2 x 7 inch 'sealed beams'.
I would also suspect that OPs headlamps have no dipping mechanism either, as according to Moore, 'anti-dazzle' measures were a secondary concern in the US at that time, and some allowance (if an inspection was called for by local legislation) was even made to allow the beam to rise above the horizontal.
Anorak discussion aside, I do agree that 36W globes would do the job, and I know from my own experience with my own pre-war car that re-silvering makes a biiig difference. I believe that in the States reflectors can be aluminized as well which is more durable.
Regards
AGW