As I've discussed before, I wanted to make headlamps that can be quickly
switched from yellow to red when the vehicle reverses, and to run off a
car battery for many hours. So LEDs were the logical choice. But the
final effect has to look like a gas mantle.

The headlamp reflectors are two feet wide and the LEDs have to shine
towards the reflector, so a normal LED bulb is no good.
I decided to have 90 yellow LEDs and 30 red LEDS. Here they are, wound on
a copper heat sink (of course normally only one colour would be on at a
time):

http://i39.tinypic.com/9gbo90.jpg

Here's a finished lamp with a Teflon tube and nylon mesh around it to
diffuse the light:
http://i41.tinypic.com/1zx7hjs.jpg

Here are the copper and brass heatsinks:
http://i43.tinypic.com/2qno2ky.jpg

But the 90 yellow LEDs got a bit hot after 20 minutes, so I put a 12v 1.4
watt computer fan on the back and that cooled the LEDs down to barely
warm:
http://i39.tinypic.com/vynsxs.jpg

Here's the lamp without a diffuser. Looks a bit weird!
http://i43.tinypic.com/w9be6q.jpg

I put some 0.5mm Teflon around to diffuse the light.
http://i41.tinypic.com/2dl0i90.jpg

Here's the headlamp from the front:
http://i43.tinypic.com/so47rl.jpg Yellow

and switched to red:
http://i43.tinypic.com/2v9t8jn.jpg Red

Full steam ahead!

On 05/01/2014 09:30, MattyF wrote:
As I've discussed before, I wanted to make headlamps that can be quickly
switched from yellow to red when the vehicle reverses, and to run off a
car battery for many hours. So LEDs were the logical choice. But the
final effect has to look like a gas mantle.

The headlamp reflectors are two feet wide and the LEDs have to shine
towards the reflector, so a normal LED bulb is no good.
I decided to have 90 yellow LEDs and 30 red LEDS. Here they are, wound on
a copper heat sink (of course normally only one colour would be on at a
time):

http://i39.tinypic.com/9gbo90.jpg

Here's a finished lamp with a Teflon tube and nylon mesh around it to
diffuse the light:
http://i41.tinypic.com/1zx7hjs.jpg

Here are the copper and brass heatsinks:
http://i43.tinypic.com/2qno2ky.jpg

But the 90 yellow LEDs got a bit hot after 20 minutes, so I put a 12v 1.4
watt computer fan on the back and that cooled the LEDs down to barely
warm:
http://i39.tinypic.com/vynsxs.jpg

Here's the lamp without a diffuser. Looks a bit weird!
http://i43.tinypic.com/w9be6q.jpg

I put some 0.5mm Teflon around to diffuse the light.
http://i41.tinypic.com/2dl0i90.jpg

Here's the headlamp from the front:
http://i43.tinypic.com/so47rl.jpg Yellow

and switched to red:
http://i43.tinypic.com/2v9t8jn.jpg Red

Full steam ahead!

Don't want to worry you after all that work... but are you sure gas
mantles are that yellow? ISTR them as surprisingly white - more so than
a standard incandescent lamp. But it's many years since I saw one.

Andy

On 05/01/2014 17:30, Vir Campestris wrote:
On 05/01/2014 09:30, MattyF wrote:
As I've discussed before, I wanted to make headlamps that can be quickly
switched from yellow to red when the vehicle reverses, and to run off a
car battery for many hours. So LEDs were the logical choice. But the
final effect has to look like a gas mantle.

The headlamp reflectors are two feet wide and the LEDs have to shine
towards the reflector, so a normal LED bulb is no good.
I decided to have 90 yellow LEDs and 30 red LEDS. Here they are, wound on
a copper heat sink (of course normally only one colour would be on at a
time):

http://i39.tinypic.com/9gbo90.jpg

Here's a finished lamp with a Teflon tube and nylon mesh around it to
diffuse the light:
http://i41.tinypic.com/1zx7hjs.jpg

Here are the copper and brass heatsinks:
http://i43.tinypic.com/2qno2ky.jpg

But the 90 yellow LEDs got a bit hot after 20 minutes, so I put a 12v 1.4
watt computer fan on the back and that cooled the LEDs down to barely
warm:
http://i39.tinypic.com/vynsxs.jpg

Here's the lamp without a diffuser. Looks a bit weird!
http://i43.tinypic.com/w9be6q.jpg

I put some 0.5mm Teflon around to diffuse the light.
http://i41.tinypic.com/2dl0i90.jpg

Here's the headlamp from the front:
http://i43.tinypic.com/so47rl.jpg Yellow

and switched to red:
http://i43.tinypic.com/2v9t8jn.jpg Red

Full steam ahead!

Don't want to worry you after all that work... but are you sure gas
mantles are that yellow? ISTR them as surprisingly white - more so than
a standard incandescent lamp. But it's many years since I saw one.

Andy

Gas mantles often had a pronounced greenish-tinged light. (They were
still using them on many Southern Region stations back when I was at
school in Surrey.)

--
Rod

On 05/01/2014 17:30, Vir Campestris wrote:
On 05/01/2014 09:30, MattyF wrote:

Full steam ahead!

Don't want to worry you after all that work... but are you sure gas
mantles are that yellow? ISTR them as surprisingly white - more so than
a standard incandescent lamp. But it's many years since I saw one.

Slightly greener than incandescent lights, according to my digital
camera. But it's a while since I used one, and ICBA filling up an
Aladdin lamp to check. I last saw the standby gas lamp in the "useful
junk" drawer in the house kitchen, along with a couple of spare mantles
and gas cartridges.


--
Tciao for Now!

John.

On Sun, 05 Jan 2014 17:30:47 +0000, Vir Campestris wrote:

Don't want to worry you after all that work... but are you sure gas
mantles are that yellow?

I wasn't going to say anything. B-)

ISTR them as surprisingly white - more so than a standard incandescent
lamp.

Agreed, a nice white light with sometimes a hint of green. That
yellow looks more like a wick based oil lamp light source than a gas
(or paraffin) based mantle one.

But it's many years since I saw one.

About a year, the last power cut...

--
Cheers
Dave.

In message o.uk, Dave
Liquorice writes
On Sun, 05 Jan 2014 17:30:47 +0000, Vir Campestris wrote:

Don't want to worry you after all that work... but are you sure gas
mantles are that yellow?

I wasn't going to say anything. B-)

ISTR them as surprisingly white - more so than a standard incandescent
lamp.

Agreed, a nice white light with sometimes a hint of green. That
yellow looks more like a wick based oil lamp light source than a gas
(or paraffin) based mantle one.


Yup, the butane/propane gas lanterns we use when camping give off a
white light.

However, whilst Matty does say gas mantle, I wonder if that is what he
means? If these are to replace the original lights on steam train
surely they would have been paraffin or something, not gas anyway?
--
Chris French

On Sun, 05 Jan 2014 18:08:11 +0000, Dave Liquorice wrote:

Agreed, a nice white light with sometimes a hint of green. That yellow
looks more like a wick based oil lamp light source than a gas (or
paraffin) based mantle one.


The original lamp was very likely to be a wick based oil lamp, and I
wanted a nice cheery yellow colour to match the existing small interior
oil lamps. Besides a pure white light might look a bit much like LEDs,
and I can't have that!

Some early steam engines had arc lights, but other drivers complained
about being blinded by them.
I hope to make a steam powered generator to keep the battery charged.
There will be a lot of lights on the rest of the train, and they need
power.