Jonathan's blog

The result of an idle thought.

Dear Top Gear,

I’m trying to imagine how a car would handle if mounted on bicycle wheels. I wager that some sturdy mountain bike wheels would take the weight of a light car, and that it could probably be driven forward. I bet the spokes would disintegrate as soon as the driver tried to steer at all.

I’ve looked around on the internet for videos of other crazy people who might have tried this, and I found nothing. It would therefore make my day if someone could persuade James May to get his spanners out and fit some 26″ mountain bike wheels to a Renault Clio.

Best,
Jonathan

As I cycled to work this morning, I had a crazy idea. It’s just daydreaming and will probably never happen, but it’s fun to think about. I’ve already posted this idea to the linux-audio-user mailing list in case anyone there has any insights on synthesising/sampling engine sounds.

I want to measure how fast I’m turning the pedals on my bike (the cadence) and synthesize/sample the sound of an internal combustion engine.

As far as I can work out, there are three major parts to this.

1. A sensor that can measure my cadence. A simple magnet switch that triggers once a revolution won’t be enough to measure the cadence with sufficient resolution, since my cadence is usually between 50 and 80 rpm, and I will need to sample more than once a second. I would probably need to mount multiple magnets spaced equally around the chainwheel and have a single sensor on the frame. Then I have to get it to supply this information to my control program.

2. I need a control program that can read in the input from my cadence sensor and convert a cadence reading of “66 rpm” into a frequency that should be sampled/synthesised, e.g. “500 Hz” (I’m making these numbers up). It will also need to be able to somehow smooth out the readings, perhaps by interpolation, so when I accelerate, the sound of the revs climbing doesn’t increase in obvious steps. It could also have other logic, e.g. when my cadence is 0 rpm, the sound of the engine is idling rather than off.

3. I need a synthesiser or sampler that can take an input from my control program and make the sound of an engine (or more likely, a sine wave to start with). I’ve never sampled or synthesised on a computer before but this engine-specific sampling technology already exists in video games, such as torcs.

I have absolutely no idea why I would want such a device – just for the fun of building it, I guess. I would like it to work in realtime (rather than later generating the soundtrack from recorded cadence data). The thought of sitting at the traffic lights with my earphones in and then hearing the mighty roar of a V8 as I pull away would be really satisfying…

Any thoughts – useful, interesting, humorous, or otherwise – are welcome!

You might wonder what there is to discuss about bike lights. But in my several years as an urban commuter cyclist, and with my fascination for toys such as bike lights, I’ve made some observations which might prove useful to other cyclists.

What you need

Before you go out and buy a light, decide what your needs are. Choose a bike light to suit your needs (and budget, of course). If your daily needs cover two or more of these categories, you should consider buying either a light which ticks all of the right boxes, or two lights.

How to mount your lights

When you are riding in traffic and your lights are in flashing mode, I would recommend angling your lights directly forward. Most LED lights are not bright enough to dazzle other drivers, but pointing them forwards will make them appear much brighter, and will cause them to shine into the wingmirrors of cars in front of you.

If in doubt whether your lights are too bright, or inconsiderately aimed, sit in a car and get a friend to ride your bike at you

When riding with very bright lights, it’s plain rude to point them into driver’s eyes. Dip them like every other vehicle.

When riding on an unlit path, don’t use too much light because it dazzles other cyclists. Keep your lights aimed low. Flashing lights aren’t required here to attract attention, and the flashing can make it hard for oncoming cyclists to see.

Branded vs generic

As a student, I was strapped for cash and I would always buy cheap, generic bike lights from eBay. Now I have a job, I always buy Cat Eye.

In my experience, the cheap lights are usually similar in brightness but the beam pattern is never as good as a branded light. Most importantly, the cheap lights have very poor quality brackets which usually snap off long before the light breaks. One such light whose bracket broke has now been turned into a makeshift photography light, which I gave to my brother. I’m so generous!

Nowadays I almost always buy Cat Eye. They are the Coca Cola of the bike accessories world, and I’ve always found them to be consistently high quality in terms of the brackets and the brightness, beam pattern and battery life are excellent. They’re not the cheapest, but I reckon you’ll be pleased if you buy them.

Carrying spares

I think it is crucially important to carry either multiple lights or multiple sets of batteries with you while commuting. Especially with LEDs, it’s not always obvious when the batteries are running out so it’s easy to be caught short. If your lights run from AA/AAA batteries then it’s no problem to keep a spare set in the bottom of your bag all the time.

If you’re lucky enough to own a set of lights with a rechargeable battery pack, it’s not always practical or possible to carry a spare set with you. In this case you’d be wise to keep a spare LED light with you. Doesn’t matter if it’s a cheap one

Multiple lights

As well as keep a “spare” set with you, you might want to mount two or more lights on your handlebars.

I find that having two lights on the handlebars, both flashing, is a great way to attract attention. They never quite flash in perfect time and this effect is rather eye-catching.

It also means you can put out twice as much light when running in constant mode, which is great news if your commute takes you on unlit roads or paths.

I have 5 headlights on my bike. I have a pair of RSP Asteri 2 LED headlights which I use in flashing mode in the city and dim constant mode on the Bristol-Bath bike path. I have an extremely bright pair of Cat Eye ABS-35 halogens to be used on the unlit sections of the path when there are no oncoming cyclists. They have a thumb switch to turn them off quickly if anyone comes into view. And I also have a head-mounted flasher, a Cat Eye HL-EL400.

Head-mounted lights

Head-mounted bike lights are a controversial topic among cyclists and motorists.

I use a helmet-mounted front and rear light because they can be seen over the tops of cars in heavy traffic. It used to make me nervous that if I was currently being overtaken, the car behind the overtaking car might not be able to see my rear lights mounted in the usual place, below the saddle.

I also think it’s very versatile because you can choose to direct light wherever you turn your head. Part of my journey takes me along a stretch of road that has two lanes. Drivers frequently change lanes without looking sideways, where I often am. If I have a head-mounted flashing light, I can look into the car window, directly at the driver, and then they usually notice my presence.

However, one of my colleagues who drives (and also cycles) says he dislikes head-mounted bike lights because it is impossible to see a cyclist’s eyes and therefore the driver can’t always tell if the cyclist has seen the car.

If you read my blog, you’ll have seen my recent review of my RSP Asteri 2 bike lights. I talked about making a bottle battery, and now I have.

Unfortunately I forgot to take photos after the first couple of steps but never mind.

What you’ll need

I used the following parts, but you can use whatever you like.

A note on batteries

• It doesn’t matter what kind of rechargeable batteries you use – NiCd, NiMH and Li-Ion are all fine.
• It doesn’t matter what size of batteries you use. If you wanted to make a smaller “pouch” of batteries you could use C type.
• You must have precisely 4 batteries in each series loop, but there’s nothing to stop you using 8 batteries and having two series loops in parallel.
• The capacity (measured in mAh) is an indicator of how long the batteries might last.
  • The batteries that come with the RSP Asteri 2 are AA NiMH batteries; 1600 mAh each. The manufacturer reckons you can get 1-2 hours on full power and 6 hours on flashing.
  • Inexpensive D type batteries might give you around 3000 mAh, which immediately doubles your battery life.
  • My D type batteries give a claimed 8000mAh. Scaling up the manufacturer’s estimate, I might be able to get 5-10 hours on full power, or 30 hours flashing. This basically gives me the ability to do a week’s commuting on full power without recharging until the weekend.

Building it

I cable-tied the battery holders back-to-back as they happened to have holes in the right place. A pair of D batteries just about fitted through the neck of the bottle if I squeezed the bottle. I attached the batteries in two pairs so they could sit on top of each other.

I soldered the battery holders together in series using the single-core wire. I used fairly long stretches of wire (about 8″) between the upper and lower pairs of batteries, to make it easier to feed the batteries into the bottle.

Wiring diagram

I taped up the exposed solder with insulating tape so there was no chance it could make a short circuit if the batteries moved around once in the bottle. I packed the batteries into place with bubble wrap so they wouldn’t rattle and risk damaging the solder.

At the neck of the bottle, I terminated the two single cored with a terminal block and connected the twin-core cable to the other side. I threaded it through the spout of the bottle and screwed the cap on. The terminal block also allows you to easily reverse the polarity of the circuit if you accidentally wire it back to front for your LEDs.

I measured the trailing cable to make sure I had the right length, before trimming it and soldering the DC power connector on the end.

The screw cap seemed tight and waterproof so I left it alone, but I plugged the gap around the cable through the spout with hot-melt glue gun.

The batteries I bought claim to come fully charged so I was able to test it immediately. Which brings us on to our next section.

Recharging

Obviously it’s going to be a bit of a pain to remove the batteries to recharge them, so we will charge them through the neck cable. Buy a female DC socket to match the plug you bought for the bottle battery. Also buy a female connector to match the RSP charger’s plug. Solder them together and ta-da! You have an adapter cable to connect your battery to the charger. Watch the polarity here, or you might set fire to your house.

If you don’t want to take the risk of breaking your original RSP charger, any DC power supply capable of supplying 7.5V with at least 300mA should do the trick.

Considerations

The original RSP battery had a warning LED for low battery. You don’t, so be careful you don’t over-discharge the bottle battery or you might damage the NiMH cells. As soon as the LEDs start to go dim, switch them off. You would, of course, be wise to keep a regular battery light in your bag in case of emergencies. I keep a Cat Eye HL-EL510 for situations like these.

The original RSP battery had automatic charging shutoff when it was full. You don’t, so be careful not to overcharge the batteries. Probably 12-18 hours will be enough. Check the instructions that came with your batteries.

You can get around both of these considerations if you pilfer or copy the PCB in the top of the original RSP battery pack. Again, depends if you are willing to sacrifice your original battery pack, and if you can be bothered with the effort.

Today my new bike lights arrived – a pair of RSP Asteri 2 LED lights.

The manufacturer’s website has hardly any details and reviews of these lights are scarce, so it is practically my duty to write this review, for the benefit of anyone else who is considering buying them. Also note that the pictures on the manufacturer’s website are wrong. Both the battery pack and the lights are different!

What you get

In the box, there are two lights, each with one 1W LED. There is a battery pack which actually contains 4xAA NiMH rechargable batteries. There is a Y-adapter to attach both lights to the shared battery pack, and there are two velcro straps to attach the battery pack.

The box

Build quality

Build quality is not actually as good as I might have hoped.

The lights themselves seem sturdy. The silver ring around the front is metal and feels solid. But the attaching mechanism is made entirely from rubber. I don’t know how supple this will be after a couple of years. Other rubber cycling products I’ve seen have perished after a few years and no longer stretch, eventually causing them to crack.

One of the lights

The battery pack is flimsy in my opinion. It has a belt clip which can be used to attach it in a number of ways, but it looks brittle and would expect it to snap off before too long. The lid of the battery pack is held on by a single screw, which could be damaged by over-tightening. Be careful! There is also no rubber seal between the lid and the body of the battery pack, so I don’t know how it will fare in rain. However, the box does claim that the set is waterproof, so we will see.

The battery pack

The battery pack

The cables are thick and appear suitably strong. Their connectors are all standard push connectors, but they have a “click” to keep them in place. The strength of that “click” seems to vary across the connectors and some are not as strong as I would like. I don’t plan to unplug mine very often so I will probably tape them up with insulating tape.

Mounting

The mounting facilities are not as good as other sets of lights I have used. The headlight units attach to the handlebars with a rubber strap with holes, and a plastic peg that pushes into the hole. There is no way to set the tightness to a setting between holes (e.g. the way that other lights have a screw).

Mounting of the battery pack doesn’t seem great either. The pack itself simply has a belt clip. There is a velcro strap in the box, presumably to attach the unit to part of the frame. However you’d have to figure it out yourself, and loop the velcro under the belt clip. Luckily I have some other rubberised velcro strips from other cycling products I’ve bought over the years.

Bear in mind that you will probably have to remove the battery pack in order to charge it (unless you leave your bike within reach of a mains socket overnight).

The cables are not curly, so if they’re too long then you’ll have to put up with them being saggy, or tie them up. You’ll need to be careful running the cable between the handlebars and the frame, in case it gets pulled taut when you steer. Nothing is provided in the box to attach the cables to your frame. I plan to use regular cable ties.

The lights have short (5cm) cables and the Y-splitter is perhaps 15cm long. The battery has the longest piece of cable and this is rather annoying. To remove the battery, you also have to remove the cable from the frame, so there’s not much choice to fix it permanently.

The system boasts a low battery warning so you don’t over-discharge the batteries and break them. Unfortunately you are unlikely to be able to see it as it’s on the battery pack, which will probably be on your luggage rack, on your frame or in your back pocket! Never mind.

Both the lights and the batteries are very light.

Performance

Despite my grumbles so far, these lights are really bright. Much brighter than any other so-called “1W” lights I’ve come across. The beam is fairly narrow, such that no light is wasted but it’s by no means a narrow beam. It can be seen from all angles.

Lights running

Each light has its own button, so you can use one light or both. The button cycles through 3 modes – dim, bright and flashing. The separate buttons means you can have one flashing and one on constant. Nice and versatile. Other twin lights I’ve seen have a central button on the handlebars. I guess each system has its pros and cons.

The battery pack contains 4 x AA batteries as opposed to simply being a proprietary NiMH battery pack. The intention is to keep the pack sealed and simply plug the charger into the battery pack to charge it, but of course you can remove the batteries to charge them in a conventional battery charger if you wish. See Modding for other ideas.

Modding

The system is quite simply put together, so it should also be nice and simple to take apart!

As I mentioned above, the battery pack takes 4 x AA batteries, and a set of 1600 mAh batteries are provided. This immediately gives you options – you can replace them with more expensive rechargeables (such as the 2500 mAh ones I use in my camera) or simply use regular alkaline batteries.

Using the included batteries, the manufacturer quotes 1-2 hours runtime at full power, and up to 6 hours flashing. Swapping these for 2500 mAh batteries immediately adds 50% to those figures for not much outlay.

Using AA batteries also has a huge bonus in that you can always keep some spare alkaline batteries in your rucksack so you’ll never be caught out if your rechargeable batteries go flat on you. This is often a problem with rechargeable light sets that use proprietary battery systems.

The battery pack has a standard power connector that you can buy from any good electronics shop. Maybe even a bad electronics shop, too. You can create your own battery pack so long as you use the same connector, and you won’t have to alter (and risk breaking) your light set.

The power connector

I plan to build a bottle battery with D batteries, for long runtime. Naturally I will post about it here when I get round to it.

Verdict

As far as lights go, this is a good, versatile, powerful set. Shame about the build quality. If you buy these, expect to have to do some DIY when you install them. You will probably need cable ties and insulation tape – the kit isn’t even in the same league as a CatEye set. However, it is a fraction of the price!

Some simple oversights exist in the system, such as the battery back not being detachable from its cable. It would cost pennies to rectify the design, but you’ll just have to make those changes yourself, or work around them.

Overall, I would recommend this light set to a fellow cyclist, on the condition that they weren’t expecting miracles, and that they were prepared to do a little work to install it.

My installation

Here are some photos of how I’ve got my lights set up. The other headlights are a pair of CatEye ABS-35 halogen headlights. They’ve long since been discontinued but are still going strong. There’s a 20W spot and 15W flood, with individual handlebar-mounted switches. With both lights burning, you get around 45 minutes runtime…

The new RSPs are mounted below the handlebars, and the CatEyes are mounted above.

Front view

Side view

You can barely see the RSPs hiding below the handlebar in this one. Each light has a switch on its top (so underneath, in my case) which can be a bit fiddly to press while riding. The CatEye lights have the yellow/grey switch to control them.

Cyclist's eye view

I’ve fixed the battery pack to my luggage rack with a rubberised velcro strap.

The battery pack

Another shot showing the CatEye batteries under the bottle cage, and the loose cable for the RSP lights along the top tube. It’s held in place only with velcro straps as I need to remove the cable every time I want to remove the battery for charging.

The cabling

After I’ve used the lights for real, I will post more pictures of them working outdoors at night.