Rear light alignment

[GrumpyGregry]

I've tried searching but couldn't craft a good enough search string to find anything worth finding....

Back lights. Super duper bright ones. In this instance a seatstay mounted Smart 7 LED Polaris and a Smart 1/2 Watt Lunar, one atop the other, but that is not important.

Any methods/science/geometry for aliginging them for maximimum effect/visibility to car drivers? I'm thinking along the lines of

"measure 1m off the floor against a wall, mark a vertical line and horizontal line atop it like a T, with your bike lamp 5m from the said wall and perpendicular to it you want the body of the lamp light to hit that the intersection of the T."

I want to be visible aways off, especially in daylight, but I don't want to end up "under the radar" closer up.


Over to you.....

Edit: changed chainstay to seatstay. my bads.

 

[GrasB]

For anything much above 1W I'd be aiming down so a pool of light is made centred about 5-10m behind the bike. For things like the lights you'd mention I'd be aiming the beam more or less vertically, if they're on the seat stay (I assume you mean seat stay as the chain stay runs between the bottom bracket & the rear dropouts) I'd make sure they're aimed slightly up rather than slightly down.

 

[Wobblers]

My Smart 1/2 Watt Superflash is quite low down on the seatstay and aimed slightly up from horizontal, and a Smart Polaris 7 (great minds think alike, eh?) pointing horizontally on the saddle bag. Seems to work (famous last words!). The best way to check the visual impact of your lights is to get someone to ride your bike and drive past them.

 

[TheBoyBilly]

Isn't there a Hi-Viz version of your rather fetching headwear Greg?

Bill

 

[peelywally]

in my experience it wouldnt matter if you had street light strapped to your back cars would still claim they couldnt see you ,

angles would change from bike to bike i imagine then again from car to car , a 4x4 high on the road might be different from a lotus and same for lorry drivers higher up still .

best to try and get a wide spread beam and mount it sideways or up and down to cover field of vision from all drivers ?

 

[zacklaws]

Pointing a tad slightly upright from horizontal would probably be the most universal, I would have thought it would be the angle that would catch a drivers eye, drivers in 4x4's would get the direct beam further away than some one in a low down sports car who would see it later

 

[Norm]

IME, two things will catch the driver's eye. One is movement (either flashing light or wobbling around on a rucksack or a tail pack) and the other is eye-level, so rucksack or head-mounted.

 

[GrumpyGregry]

helmet lights do high and wobbly. a win-win.

 

[Davidc]

I use the Smart 1/2w super flash, and now also have one of the 1w replacements. (note that these are the absolute maximum spec for the LEDs NOT the power they actually run at!)

Smart publish data for those lights and they have quite a narrow beam angle, the newer ones are better. I don't have the information any more but did work out that if in pitch darkness you put the back of your bike about 10 metres from a wall and adjust so that the bottom of the bright part of the beam touches the ground, then the light will give any driver behind, in your lane, a pain in the eye (assuming it's open and not being used to read a text message at the time).

I use 2 of them, one on flash and one steady, and at night a dynamo LED light as well.

helmet lights do high and wobbly. a win-win.

My observation, as a driver, is that helmet lights are just as effective switched off as switched on. They are at the wrong height, not where you're looking for lights.The words totally and invisible come to mind. As an aid to seeing rather han being seen - no problem but the ones at handlebar and seat height are the ones to be seen by.

 

[GrasB]

My observation, as a driver, is that helmet lights are just as effective switched off as switched on. They are at the wrong height, not where you're looking for lights.The words totally and invisible come to mind. As an aid to seeing rather han being seen - no problem but the ones at handlebar and seat height are the ones to be seen by.

+1 I start trying to look for the traffic lights at first THEN realise it's a cyclist.

 

[Norm]

My observation, as a driver, is that helmet lights are just as effective switched off as switched on. They are at the wrong height, not where you're looking for lights.The words totally and invisible come to mind. As an aid to seeing rather han being seen - no problem but the ones at handlebar and seat height are the ones to be seen by.

+1 I start trying to look for the traffic lights at first THEN realise it's a cyclist.

There are no traffic lights on my commute but you play it your way and I'll play it mine.