Cycling UK Forum

A 1W LED though can not compete with car headlights and other sources on steady mode

In what sense, they exceed old halogen dynamo lamps, so seem bright enough to me?
Unless someone is naughtily zooming up in between stationary cars at high speed (as opposed to slowly and with due care as required) I don't see the problem.

Even a 1Watt LED lamp can throw a beam on the ground now (which flashes back at you, as well as rather brightly in front)

When flashing front lights were allowed, I thought this option would just be used for small 3AAA/2AA style be seen style lamps (eg for dynamo users while waiting a junctions), however I keep seeing cyclists with high power flashing front lights that light the road:
these seem a bit annoying to others (and I would have thought annoying to the owner who has a flashing patch of road preceding them), and also if you have a high power lamp why not leave it on steady so as drivers think you might be a big heavy motorcyclist who will dent their car, and not pull out accordingly.

(Like others) I discovered cold white LEDs aren't so good in the rain:

perhaps, some LED dynamo lamps could be offered in warm white for more consistent performance.

By the time high power amber LEDs were available, street lights were usually amber, so it seemed no use for a sole front lamp.

Also, as blue-white lamps cause more discomfort glare, OK for small 1 3 Watt cycle lamps , but surely the LED should have insisted a low allowed level of blue in car lamps so that the hated car xenon lamps and their filament imitators were didn't cause such problems and looked closer to the old warmer coloured halogens.

This led me to look up the (now abandoned) French selective yellow ideas (I think the Germans wanted them to abandon it so that yellow /amber remained only for direcrtion indicators):

it seems they just removed all the blue light component (making lamps only 15% dimmer). Strangely no one seems to have collected any conclusive evidence of whether going to that extreme had any benefits or costs.

Has there ever been a "Drive within range of your headlamps" campaign?

e.g. I saw a roads dept poster for runners to wear reflective material because it gives "drivers 3 seconds more to see them" but I have never seen a campaign aimed at drivers forcefully reminding them when headlamps are their sole illumination they must drive to be able to stop within the range of their headlamps (especially when dipped); i.e. they must be able to stop in the distance they can see to be clear.

Most people seem to exceed the range of Dipped headlamps by a large margin, often helped by cats-eyes
( so could cats-eyes be an overall safety loss? Perhaps they should be used less liberally?)

Now that shimano style free hubs place the right hand (chain side) bearings close to the dropout, but the left probably has spacers if less dish wanted, does that mean the left hand axle has a reasonably long unsupported part, just like on the old screw-on freewheel wheel's right hand side?

531colin wrote:
OK. you've got Cane Creek Aero bars, but what are the little bits the thumbies are mounted on?

They're the Brompton battery lamp mounts (http://www.sjscycles.co.uk/brompton-extension-bracket-for-fitting-batflam-m-type-handlebar-qvbktflambat-prod13669/ )

If no Aero bars are desired (they seemed a good idea at the time...) then a minoura spacegrip might form a simpler basis, or a similar idea to reohn2 's Mon Aug 27, 2012 2:42 pm post on page 10.

Heres mine, I can operate the right (rear mech) shifter from the hoods, but not the left one.

Its the 5 speed index spacing (closer) that I dislike: it makes the hub very sensitive to mis-adjustment/cable stretch, hence I would want compatibility with the 3 speed control...

I have suggested a "AMW" 3 speed to sturmey.....

I like the 27% jumps in a SA 5 speeds inner 3 gears, and the superlow is too inefficient to be useful, and the super high is an unnecessary luxury:

is it possible to convert a 5 speed "sprinter" into a 27% jumps "AMW" 3 speed with 3 speed cable pull (less sensitive to misadjustment) or could its two cable predecessor have its axle strengthened for use in 3 speed only mode?

Perhaps the new Sturmey could be persuaded to manufacture such a 27% stepped "AMW" 3 speed.

but my concern re the power source is that if the generator voltage isn't >6V, you can't run the current doubling mode, so at best you get what you get more or less in terms of current through the LED with some generators.

The switch mode is really a current/voltage conversion circuit, so is not limited to doubling/or not like the voltage doubling rectifiers in http://pilom.com/BicycleElectronics/DynamoCircuits.htm.

You can make a buck-boost switch mode that can cope with input voltage below that of LED (stepup=boost) as well as above (step-down).

However, they could just use a voltage doubling rectifier then a step down switch mode "current source" LED driver circuit.

The switch mode is converting the input voltage /power into the desired LED current, with some added complication that it can't take all the input current because it needs to leave enough voltage and current for a parallel connected rear lamp: hence my idea that it would be better for the front lamp electronics to also power the rear lamp (at the standard 6Volts and <=.1A) and take "total control of the dynamo output". This would also allow a rearlamp failure warning.

Electronics world magazine published a dynamo battery backup which worked by having a voltage doubling rectifier
followed by a step down switching regulator which powered all lamps and the backup charge: it let the dynamo voltage rise to 27V so it got less resistive losses and used the extra 0.5Watt to charge the battery. The output was 6V dc with the battery simply connected via a diode (and parallel charging resistor).

A switch mode current source is not limited to just no doubling / doubling mode:

I would think it hard to beat a high end manufacturer's electrickery and especially their carefully designed optics.

NB the cheaper LED dynamo lamps such as spanninga micro FF LED use 0.5 watt LEDs, so should work at full power from a dyno hub assuming >50% efficiency.

Now that the front high power LED lamp circuitry is probably distorting the voltage and current waveform for a parallel connected rear lamp, I suspect it would be better to start to expect such lamps to provide a 6V output for the rear lamp (which could be monitored, having a associated warning indicator, like the top B&M lux lamp). I suspect this also might allow more efficiency by allowing the dynamo to operate at higher voltage and lower current into a switch mode circuit (but would need a hub dynamo or non-german un zener-ed/unregulated bottle). Testing dynamos with resistors is probably not very realistic anymore.

In the days of filament bulbs, when LEDs were dimmer, I made a 100% efficient rear LED lamp:

by wiring enough paralleled inverse parallel pairs of red LEDs to take 0.5Amp, then wiring in series with the front filament bulb (which acts like a current source ). Delayed lighting of front bulb very slightly but worked.

\Edit current sink changed to current source

Forgot to mention a regulator (reflectalite sell them although two back to back 1.3W/5W zener diodes does the same).

The 5mm maplin leds always seem rated as brighter.

What about a leading shoe only front brake, and relying on rear brake to hold the bike on hills?