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supersonicLives Here
Joined: 25 Nov 2005
Posts: 50524
Location: Chapeltown, Sheffield
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 Posted Tue Aug 4, 2009 2:45 pm |
By Dazzza.
With the nights drawing in again, the forum can expect to see an increase in 'what light' threads. Below is some basic info on what is available with a more in depth look at the popular torches.
Intro
Lights have come a long way in recent years, and the technology advances of LEDs have made them the primary choice for a light system as they offer portability, long run times (efficient) and are reasonably cost effective.
You will often hear lumens and candle power [candela] mentioned: The lumen is the SI unit of luminous flux, a measure of the perceived power of light; the candela is defined as the luminous flux divided by the beam angle. So as can be seen, the narrower the beam angle, the higher the candela rating would be (and would be a brighter beam), but the actual amount of light given off is the same if the lumen rating is the same. Think of a laser bean ie very low lumens but that narrow beam concentrates the light and gives a high candela rating.
Typically 250 lumens and a fairly broad beam spread is adequate for modest night riding, but you may want to think about more powerful lamps for faster riding (600 lumens plus), or combining a flood type lamp on the bars with a narrower beam on the helmet. However be aware that beam pattern can vary too ie centre hot spots or a gradual taper to the edges.
When considering a system take into account run times, how they mount, batteries, weight, power and beam spread.
LED torches and systems
Small compact LED torches have become a very popular choice of bike light. Why? Well they are portable, batteries are cheap and easily available, and the torch is quite robust. Popular bike torches are:
MTE SSC [p7]:
http://www.dealextreme.com/details.dx/sku.12623
And for your helmet light something like this c1 [r2].
http://www.dealextreme.com/details.dx/sku.14443
The torch uses what's called a p60 host/drop in module so you can replace leds by dropping in a new one as and when you desire.
As for mounting there are various options, you can use two jubilee clips and a bit of inner tube of you have these, I use the first choice as I find it's tougher and easier to mount.
http://www.dealextreme.com/details.dx/sku.15642
http://www.dealextreme.com/details.dx/sku.792
http://www.dealextreme.com/details.dx/sku.8274
http://www.fenixtorch.co.uk/led_torches/lockblock.html
http://www.fenixtorch.co.uk/led_torches/fenix_mount.html
There are plenty of more expensive light options a good place to start is here:
http://reviews.mtbr.com/blog/category/lights-shootout/
Also check out BikeRadar for many light reviews and reader recommendations.
Personally I like lumicycle led system 3 and nightlighting quad iblaast as both have a good spread of light and runtimes. Plus look at Exposure for well designed, all in one systems that do not use a separate powerpacks and fan favourites such as Hope and Ay Up.
Halogen systems
Many people still use halogen as an alternative as they prefer the colour temperature (warmth). Led is slowly getting there but many still prefer the halogen units. They are not as efficient as LEDs as a lot of the power is wasted to heat, and the more powerful units often require large external powerpacks.
Lumicycle amongst others still make good lights, and with a good sized pack you can see upwards of 3 hours of runtime plus they have an optional tail light.
Here is a typical beamshot; it is brighter in use than the picture suggests.
http://farm4.static.flickr.com/3210/3133478611_642dcba89d.jpg
Most units are MR11 in size and use the same size 12v halogen unit, typically 13 degree for flood and 6 degree for spot.
HID/halide/arc lights
Many of you will have heard about these lights but aren't sure how they work; similar in a way to a halogen lamp except there is no filament. They comprise of two metal points inside a ballast [bulb] with a gas mixture (typically argon and mercury), and an electrical charge is passed between these points to create the light the light. The output is similar in temperature to an led, very white and powerful, but at a price; they take several seconds to start and draw a lot of power when switching on so in such situations where you need them off or you need to save power they aren't an ideal system. However they are still easily available but ballasts are expensive to buy.
With a 10w hid light a 4.4ah 14.8v battery will last for around 5 hours but will be reduced if switched on/off so is usually left on and they are efficient when running.
Here is a beamshot.
http://img519.imageshack.us/i/Halide40W13degree.jpg/
Technical notes and modifications
Many torches and DIY solutions can be upgraded or modded. The runtimes vary with each torch ie for a typical single emitter led such as a q5 or r2 xr-e you would be looking at around 3 hours off a single 18650 lithium battery, on the p7 and mc-e torches they are a 4 die emitter (4 led's in one unit) and typically run for 1 hour again on a 18650 battery.
A p7 led runs around 3.6-3.7v and draws around 2.8a at 10w so you will find most are directly driven from the battery with no kind of driver board[regulator]. The q5/r2 however is different, the led again is 3.6-3.7v but because of it's small size most are a p60 drop in unit such as this.
http://www.dealextreme.com/details.dx/sku.11836
As you can see it can handle greater voltages, that is because a driver board it built inside to regulate the voltage, on some torches you can run two cr123a batteries which doubles the voltage but halves the run times, you get more light for it so it's a popular thing to do.
You MUST make sure that if you do this your torch or host unit is capable of doing so otherwise you risk damaging it.
With these torches most aren't put off by run times as batteries are cheap and you take as many as you need with you.
Both above lights compliment each other very well as you get flood from the p7 and throw from the c1 on the helmet or the bars. Always use protected 18650 li-ion cells in these torches and a good charger for safeties sake: this is what I use:
http://www.dealextreme.com/details.dx/sku.1251
http://www.dealextreme.com/details.dx/sku.26247
There are several choices of led the most common being made by cree and seoul semiconductor[ssc]
Cree xr-e [r2] 250 lumen http://www.photofreek.com/images/371_PC250005.jpg
Cree mc-e [k-wc] 600/700 lumen http://media.photobucket.com/image/cree%20mc-e%20beamshot/amticoman/10stem2.jpg
Ssc p7 [c/d] 600/700 lumen http://img88.imageshack.us/i/ufc2sscp7kravinuc6.jpg/
Those leds are what you see in the majority of lights both bike or torches. The BIN number you see (r2 for instance) are alphabetical and refers to the quality of the led, so the higher the bin number the brighter but more power your led will consume.
I hope this help explain the differences in types of lighting, and the popularity of the torch route.
Dazzza.
Zaskar LE 1996
Zaskar Carbon Team
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nicklouseLives Here
Joined: 20 Mar 2003
Posts: 50632
Location: A Yorkshire man in Sweden
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Posted Tue Dec 8, 2009 10:27 pm |
| Trailradar wrote: | There is a sizeable range of off-road MTB lights on the market, covering an equally large spectrum of prices, and much has already been written about both (See Mountain Biking Product Reviews - MTBR.com). Our aim here is to guide you through some of the technologies available, and as such, this is not so much a review of what's out there as a discussion to help you make your choices.
Night Riding: why bother?
For many folk, it is the simple answer to the shortened winter days, and the conflicting demands of work, social life and biking time. Other people see it as almost a separate biking discipline, with its own equipment, strategies and challenges. Anticipation-time and reaction-time are cut down to the beam-dimensions of your lights, and together with the added navigational demands, the whole experience is a much more intense affair. Even your usual mtb trails take on a most unfamiliar and challenging air, and it can be difficult to maintain the required level of concentration for much more than a couple of hours.
The process of acquiring off-road mountain bike lights
Psychological studies have revealed that the would-be night rider passes through several recognisable stages on their way to enlightenment.
i) Denial: "They want how much?!?", "There is no way on earth I'm going to pay that!" etc. etc.
ii) Improvisation: Riders at the improvisation stage may be spotted with "that nice powerful mag-lite that lives in the car" duck-taped to their helmet. It ultimately depends on neck muscle strength, but this stage rarely lasts for more than a couple of rides.
iii) Self reliance: During this stage, statements like "I could make one of those for a quarter of the price" are common. Depending on individual abilities, some riders never get beyond this phase, and there are complete news-groups dedicated to the subject.
iv) Acceptance: Out comes the credit card.
Handlebar or Helmet mounted systems?
For road use, UK law stipulates that bicycle lights need to be attached to the actual bike, but for off-road our money says a head mounted lamp is definitely the way forward, used either alone or along with a handlebar mounted one. If lamps are mounted too low, the merest bump in the trail can create a large pool of shadow that could be concealing anything. What's more, on twisty singletrack, the handlebars are not always pointing in the direction that you want to look in. Helmet mounted lights get around these problems, and are also a great boon when trailside repairs are required. As an added bonus, because they attach to you, rather than your bike, there is great scope for cross-over usage, be that adventure racing or crawling under the floorboards looking to fix that draught. The only downside with head-mounted lights comes when it is foggy or snowing; in these conditions the light scatters off particles close to the eyes, and it can be difficult to see the ground ahead. In these conditions, a back-up handlebar lamp can be very useful.
Batteries
There are essentially 4 different battery formats used in bike lighting systems. Starting with the oldest (and heaviest and cheapest) technology first, these are Lead-Acid, Ni-Cad (Nickel-Cadmium), NiMH (Nickel metal hydride) and Lithium Ion.
Lead-Acid batteries
These batteries, essentially the same as the ones in your car, still feature in cheaper systems. They are heavy compared to other formats, present environmental concerns over their disposal, require a smart charger to get the best performance, and are damaged by being completely discharged. Sealed units are relatively cheap and easily available from electronics suppliers like Maplins, and correspondingly this format retains a following with the DIY crowd.
Nickel-Cadmium (Ni-Cad) batteries
Ni-Cad batteries are smaller and lighter than the corresponding Lead Acid version, and need to be fully discharged before recharging to avoid "memory effects" impacting performance. For many years, Ni-Cad was the only suitable rechargeable battery for portable electronic devices. However, they are highly toxic to the environment and will be banned in the European Union in the near future.
Nickel Metal Hydride (NiMH) batteries
These batteries are smaller and lighter than the corresponding Ni-Cad version. They are less prone to memory effect than Ni-Cads and do not benefit from full discharge, but they do self-discharge during storage so need intermittent attention.. As there is no Cadmium these units are less environmentally damaging than Ni-Cads.
Lithium Ion rechargeable batteries
These batteries are smaller and lighter than the corresponding NiMH version, and currently feature in lap-tops and mobile phones. There is no memory effect, self-discharge is less than half that of nickel-based batteries, and they are more environmentally friendly than NiMH. The format is not fully mature, and as with most cutting-edge technology, there is a considerable price tag attached.
Lamp units
A good bulb should change electricity into light without too many losses, often in the form of heat. Output is measured in Lumens per Watt (amount of visible light per unit of electricity) and the higher the value the more efficient the bulb. Another important factor is the light quality or "Colour Temperature". This is measured in Kelvin (K), and the higher the number, the closer to pure white light.
There are currently 3 main types of bulbs used in high-power off-road lighting systems: Halogen, Metal Halide and Light Emitting Diodes (LEDs).
Halogen Lamps
By far the most established light-source in the off-road lights market, halogen lamps belong to the incandescent family, in that the light is produced by passing an electric current through a filament. The resistance to the electrical current causes the filament to heat up to such an extent that it emits light. This process is contained within a chamber filled with various inert gases which enhance the performance of the filament and prevent it from burning out by reacting with oxygen.
Some manufacturers gain even higher performance from their bulbs by a process known as over-volting. By attaching for example a bulb designed to run at 12 volts to a battery producing 13.5 volts rather than 12 volts, the bulb will produce a comparative increase in both brightness and colour temperature. This improvement comes at the price of a shortened bulb life, but the benefits are generally considered to outweigh this.
Metal Halide Lamps
Halide lamps are arc types in that the discharge of an electrical arc between two electrodes produces light. Performance is increased by the addition of metal halide vapours into the chamber or discharge tube surrounding the electrodes. Because the vapours in the discharge tube are under high pressure, these lamps are also sometimes called High Intensity Discharge (HID) lamps. These lamps represent the pinnacle of bulb technology, and similar systems are to be found in soccer stadium flood-lights. They produce a characteristic hard white light (high colour temperature) and have a longer life span than Halogen lamps.
With so many positive attributes one might wonder why anyone would still bother with halogen bulbs, but of course there are some draw-backs too. As with emerging battery technology, the forefront of bulb research and development comes with a hefty price tag, and you can currently buy an entry-level bike for less than some of the lighting systems using these bulbs. Because the circuitry employed to initially create the arc takes time to reset itself, these lights cannot be switched on and off at will, and the life-span of the lamp is affected by the number of ignition cycles.
Light Emitting Diode (LED)
Not so much a bulb as a piece of electronic circuitry, LEDs are an attractive proposition for bike lighting because of their extreme energy efficiency. The units themselves are nothing new, and started appearing in bike rear lights in the 1980's. Because of the lack of suitable "white" units, early front LED lights used fairly ineffective yellow or green LEDs. More recently, higher output white LEDs have become available/affordable, and there are many who predict that the future of off-road lighting lies down this path. The technology is still developing, so it is pricey and there remains scope for improving the brightnes.
Some benefits of LED lights are:
• Instant-on/off (unlike HID)
• Flicker-free(unlike HID)
• High Colour Temperature (much like HID)
• Power efficient
• Affordable
• Long bulb life
Another bonus is that LEDs will run with whatever power is available and so dim slowly as battery power ebbs. By comparison, HID bulbs will cut out when there is not enough power. |
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