How I made a pair of cool looking bicycle lights.

Quest: To have a really good set of bicycle lights without having to spend a whole bucket of money.

Options:

Buying a set of lights: Bicycle lights fall into two categories, the cheap and crap and the good but very expensive. Neither of which are an option as the first is of no help in the dark and the second is financially unobtainable.

Make a set of lights: Cheaper and more fun.

Design points and considerations.

Bulbs

There are basically three technologies to choose from

Light Emitting Diodes: Although these are getting brighter they are difficult to focus to a good beam they still don't compare to a good bulb and reflector. They are however ideal for red rear lamps.

Dichroic: The popular choice for most home made bike lamps and the top end commercial lamps. They are available in small powers of 6 and 10 watts and low voltages of 6 and 12 volts. They are also available with several beam widths suitable for cycle lamps. They are relatively inexpensive and are available in both shops and mail order. However they get hot and I have friends who have tried to use them and they have melted the plastic holder they have made.

Halogen: Although these are efficient they are also only available in higher powers making them power hungry and demand bigger batteries etc etc. They also get very hot making mounting them tricky.

Krypton: Available in smaller powers and have a claimed power output of about 70% over normal bulbs and are available to fit most torches. However their expected life span is short but as they are relatively cheap this is not a problem.

Reflectors

Making a reflector is far beyond the scope of the home builder so converting a torch is really the only answer. My methodology for choosing a torch is to go for a one with a bigger reflector and a clear lens over the front. The idea of using a bigger reflector is that they are usually better made and will hopefully be more efficient. The torches that take the square lantern batteries usually have good lenses because people expect good light from a bigger torch.

Batteries

Lead acid - I find the idea of carrying a lead based battery around on an aluminum framed bicycle somewhat perverse.

NiCad - These have been superceded in both price and capacity by NiMh cells.

NiMH - Now very cheap especially for the common AA cells. I did a price comparison of amp hours vs cost for various sized cells and the AA come up on top as being the best option. There capacity is now similar to that of alkaline cells of the same size. It could be argued that alkaline cells have a slightly higher voltage of 1.5 volts over the 1.2 volts of a NiMh however this is not true at the discharge rates that are to be expected in this application.

Li-Ion - Lithium Ion cells are becoming cheaper and more common in the radio control world then they have ever been but are still not cheap enough to use in a budget solution. They are difficult to charge with out causing damage and can become damaged if the discharge rate / level is ex ceded so a special charger is needed. They are however fantastically light for their capacity.

Non rechargeable cells - Now that is a silly idea.

Dynamo: As I am cycling for health and fitness rather than racing this should be considered, but I wont.

THE FINAL SOLUTION

To use two torch reflectors with 3 W krypton bulbs running from four AA NiMh cells. The torch bodies will be cut up to make them more suited to being mounted on bicycle handlebars and the batteries will be carried in panniers or a special battery pouch. The batterys will be mounted in a cheap battery holder and will connect to the lamps using a suitable power connector. Two or three os these will be made and used on long rides to aid easy battery changeover in the dark and avoid fumbling about with individual cells.

Running time.

Four 2000mAh NiMh cells will run a 3W Krypton light for approx. 3 hours. ( I know that theoretically it works out to be 3.2 hours but you cant rely on the batteries being 100% good.) Two lamps will obviously last half as long so carrying a spare battery pack will be necessary on longer winter rides.

Cost

£1.00 ---- Two torches from a car boot sale at 50p each.

£0.99 ---- Two jubilee hose clamps.

£1.32 ---- Power connectors x 2.

£0.40 ---- Battery holder x 2.

£5.00 ---- New NiMh AA 2000mAh Batteries x 4

Bits from the bits box:

Nuts and bolts.

Inner tube rubber.

Cloth to make battery holder.

Velcro.

Glue.

Wire

Total cost £8.71

Real cost £3.71 (I already have many rechargable AA batteries)

THE BUILD

I'll let the pictures explain how I converted the lamps.

Fig 1. Uni-Lite UK200 Torch, as the manufacturer intended.

Fig 2. Uni-Lite UK200 Torch cut up into bits.

Fig 3. Ready to glue together and start a new life. Note how I'm able to retain the original switch. Apart from being splash proof it will save me the cost of a new switch and the palaver of conveniently mounting it.

Fog 4. Don't they look cool!!.

Fig 5. From the back (More glue needed on the red one.)

Fig 6. Mounting bracket. M6 nut and bolt brazed onto a jubilee hose clamp.

Fig 7. Mounting bracket with inner tube protection rubber. The rubber is also aids the grip of the jubilee hose clamp on the handlebar and keeps then lamp in alignment on rough ground.

--Must take photo--

Fig 8. Battery holder. The wires are soldered to the battery springs on the back of the reflector.

Fig 9. Lights on the bike.

--Must take photo--

Fig 10. In use on an unlit cycle path.

UPDATES

UPDATE  (Sept 2006)

Went out for a 22 mile test ride in the evening, about three quarters of this were in darkness. The lamps held out well and after some small adjustments were lighting my path very well. The batteries had to be changed so I guess I got just over on hour from the first set. Although they are rated at 2000mAh and should have lasted longer they are now over two years old so they will be getting a bit tired and the capacity will have dropped and I also cant be certain they were fully charged to start with.

The lights must be good as a girl chav with hoopy earrings shouted 'Nice lights mate!" as I cycled past. However I was later left wondering whether chavs have the necessary intelligence and whit to be sarcastic.

CONTACT: aarrgghh @ aarrgghh dot co dot uk