I would like to build my own LED bicycle headlight ...

[IanB]

My suggestion was to think outside the box and not look at bike lights, but look at regular "tactical" flashlights combined with a mounting bracket.

Bike lights (well mine, anyway) have a trapeziodal light pattern, so they have a more consistent illumination pattern when angled downwards. Plus side lobes to illuminate the kerb or verge.

I guessed that might be the case.

In the old days before LEDs, bike lights were dim and couldn't light up the road at all. Now, they could be almost as bright as car headlights. So it makes sense to have a beam pattern to avoid dazzling oncoming vehicles, as well as putting more of the light where it's wanted.

But a small LED light with the sole purpose of being seen might not need much in the way of a beam pattern, perhaps?

[mendip_discovery]

Just buy one of these,

not road legal in the uk,all bike lights are supposed to be fixed to the bike

What does legal stuff have to do with cycling? Its not like they can be told off or anything. Even these electric motorcycles are free for be used by everyone, the police are too busy to do anything about it.

[deadlylover]

Yeah I'd figure out a flashlight mount and just change the lens.

Buy something like a Convoy S21E and get an elliptical lens (they call it striped).

I like the Nichia 519A emitters, relatively neutral (though sometimes a bit above the BBL) with good CRI. Make sure you get the version with the Anduril driver, you'll be able to flash the version to Anduril 2, though I'm pretty sure Anduril 1 has a bike flasher strobe as well.