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Using a mini thrower as a bike light

I want to start off by saying I am by no means an expert in this field, this is just based on my own experiences. For context, my background of knowledge comes from orienteering, night hiking and cycling.

I am someone who loves to hunt down a bargain but also appreciate good, well made stuff. I’m not against buying branded stuff, as long as I am buying quality. What pisses me off is when you end up paying brand tax on something that is quite honestly a bit naff.

I am certainly not casting shade on any companies here, there’s plenty of reasons why my cons for certain types of lights might not be an issue for you.

This all started when I was looking to do more night riding and taking lights on multi day trips. I love night riding and it can be the best time to ride as you get places all to yourself. It’s great for pushing yourself or just clearing your head.

I have plenty of commuter lights but these are to be seen — not to see with. They usually emit around 10 - 800 lumens. Something I’ll come back to shortly… So to see where you’re going at night you’re going to need something a bit more powerful.

The problems with bike lights

After shopping around for a “proper” headlight this is what I found. I’ve broken them down to categories with their pros and cons.

Pros:

  • Small & Lightweight
  • Affordable
  • Tend to be detachable so handy for if you need to get off the bike / fix something etc.

Cons:

  • Tend to max out at around 800lm or start to get really pricey.
  • USB Rechargeable —Great for commuting, not ideal when on a long trip.
  • Burn time can be limited.

Pros:

  • Never run out of light… in theory.

Cons:

  • Requires a dynamo — great if you’re touring and on road. Not so good if you’re off road where you’re going to struggle to have a decent output for light.
  • Once it’s mounted it’s mounted.
  • Not actually that bright, falls more into the be seen than actually see stuff category.
  • Can be expensive to set up.

Pros:

  • Good sizes / Compact
  • Great light emitting capabilities

Cons:

  • Mostly USB Rechargeable — not ideal when on a long trip. Or battery pack (see below).
  • Once it’s mounted it’s mounted (the majority of time).
  • Burn times are usually pretty wank. Great for mountain biking when you’re riding for may be an hour or two, not ideal when on a long night ride.
  • Really fucking expensive.

Pros:

  • Long burn time (easy to change to your preference with more power)
  • Great light emitting capabilities

Cons:

  • Once it’s mounted it’s mounted.
  • Weight — I’m not a weight weenie, but some of these packs can be pretty damn weighty.
  • Ugly AF mate. I’m all for bike bags but they just always seem to look a bit naff, and I’ve not keen on having more wires on my bike.
  • Again, these can get super fucking pricey.

What am I looking for then?

So to summarise, this is what I was after.

  • Something fairly compact, can be mounted easily in various positions.
  • Detachable so it can be used off the bike.
  • Decent burn time — we’re talking over 4 hours.
  • Good setting variations — “Full beam” isn’t needed all the time.
  • Replaceable power source. For long rides / multi day without access to re-charge so it’s easy to keep the light running.
  • Not too heavy.
  • Under £50 seems reasonable.

For me, with a background in going outdoors at night, why not use a torch? This isn’t a new idea. But with LED and battery technology progressing so much in the last few years there are sure to be some great stuff out there. Like with bike lights, there’s lots of different lights for different applications.

A limiting factor with size is down to the battery cell size. All self powered lights have battery cells inside.

I started looking into retro-fitting some lights to make the light I wanted, but I knew something must exist. So I started digging into the tech a bit more.

Roar like a Li-ion

One of the biggest progressions in battery technology recently has been with Lithium-Ion, specifically 18650 cells. This is what you’ll find in a laptop and also what powers Tesla and almost all other electric cars… just a whole fucking load of them! Unlike the popular AA and AAA batteries from yesteryear, these have much higher charge rates, capacity, output and last much longer. When you’re buying something that is USB rechargeable where you can’t change the battery it probably has some of these inside.

The next generation to the 18650 is the 21700. This actually what Tesla has been developing for its next generation of batteries and today you can more commonly find them in Vapes due their even higher output. They are slightly bigger which contributes to the larger capacity.

5:20 Vape.

The thing that I clocked when looking into battery cells was their size. A single 21700 battery is quite similar in size to lot of commuter lights. I imagine a lot of them probably have 18650 cells in. I’ve had a couple of FWE and similar size commuter lights over the years and have a draw full of mounts (go pro, handle bars, helmet etc).

So I knew the sort of size light I wanted. It needed to have a diameter of about 25mm for it to fit into a the standard light mount.

This is where I hit a bit of a wall. There are plenty of lights and torches out there of this size, but they are usually limited to a single LED which means that they usually max out at about 800–1000lm. This is actually plenty but with a single light you don’t get much flood. Or they’re chunky bastards and then they’re going to need a custom mount made. I don’t have a 3D printer and I’m far too lazy to make something when I already have plenty of mounts that already do a job well.

How bright does a bike light actually need to be?

Cameras love to tell you how many megapixels they have. This is meaningless if it has a shit lens. Most people won’t need even a fraction of what they are capable of. You’re a fool if this is what you’re chasing when buying a camera.

Why am I talking about cameras? Well the same goes for lights. I know I have mentioned lumens a lot (and will continue to do so), but this is what manufactures love to sell to you on. The reality is you’re probably being oversold.

To give you some context. Let’s talk cars. Sorry, I’ll get back to bikes I promise. It the law now for cars to have 3 primary light modes — this should be the same for cyclists. Why it isn’t is beyond me, it’s mostly likely due to lack of legislation for cyclists… Hopefully this gets some traction and this will become the norm as manufacturers standardise things and people just become more informed. Back to cars and the 3 modes…

Always on — These tend to be 400–700lm

What you use from dusk til dawn and at night with lit roads — Industry standard is around 700lm

When it’s pitch black or poor light — Industry standard is around 1200lm

The one I’m not covering here is fog lights… Mainly as they aren’t technically “headlights” and I’m going to go into this in another article soon where I talk more about selective yellow lighting.

But overall, those numbers seem pretty reasonable. If cars traveling at speeds over 80kph can cope with 700–1200lm then I can assure you, when you’re pootling along at night, this will be more than enough for you too.

It’s not all about the brightness…

So the important factor missed out here is how the light is actually spread. Like a decent lens in a camera — the reflect in a torch plays a huge part in its performance.

The light emitted directly from the source (LED in this case) is the flood (or spill). If you imagine a bulb without a lampshade, this is full flood.

Torches have a reflector which allow the light to be controlled in a beam which is called the throw. How far and direct the light is.

There are 3 main types of reflectors in a torch (flashlight if you must American folk).

Source Wikipedia

The more surface on the reflector, the more the light can spill out and create a flood of light. A smooth reflector will create a much more focused light beam. The most common type is a textured like surface, as this gives a uniform light beam whilst also giving a decent amount of flood.

For cycling you want focused light near by, 5–10m in front of where you are riding (dependent on speed) so you can see obstacles clearly in front. When you are in more technical situations where things are narrow you want a good flood of light so that you can have good view of what’s either side of you and ahead. In most riding scenarios us common folk will rarely need full beam for long periods of time. May be a super fast technical descent will be the longest you need it on for. General rule is faster you travel the more throw (range) you need from the light.

So ideally a combination of both of these would be ideal. Focused light ahead, with good flooding capabilities when needed.

The other important factor is your eyes. If you have spent any time out at night for long periods, you’ll know that you want your eyes to adapt/adjust to the darkness. This means that actually, in most situations you’ll want a low light, rather than something super bright.

The best light for low light night vision is actually red light, however as this is reserved for your arse end, this is no good for a headlight. I’ll go into into more detail about this in my selective yellow light post. But for long periods of time, super bright white light isn’t actually very useful in a lot of night riding situations for prolonged periods.

Mini Throwers

As I explained above — there are 2 main patterns for how light is given off, throw and flood.

After lots of digging through forums I came across some mini thrower lights. These are lights that have a really long range but are much smaller than a traditional thrower light. Because they are capable of throwing light a long distance they have a high lumen output too.

I’m not going to bore you with which light is best — you can do your own research. I’ll just cut to the chase with a run down of the light I chose and why I found it to be best for the job.

Sofirn C8F 3500 Lumen

Off / On — Battery Status light only visible when selecting mode. Does not come with selective yellow filter.

So this is the unicorn light that I’ve found. You can do a Google to get more info or read some more detailed reviews (it’s highly regarded for its price), but here are all the reasons I chose it for this specific purpose.

It has a 25mm(ish) diameter shaft so fits into FWE (other brands available) bike mounts. The grip is… super grippy! Which means it stays in the mounts really tight (more so than the actual lights for the mount). It’s certainly not going to fall out when mounted under your bars.

Shaft is the practically the same size as the smallest FWE light I have (25 x 60mm).

It’s also a torch, so as you might expect, it works really fucking well as a torch off the bike. Great for camping and proper overnight adventures.

I actually keep it on me most the time if I have a bag.

Most convenient location, but due to the size it’s also mountable to my GPS mount (most stable), crown mount and my helmet mount.

It comes with an (optional) 21700 battery but also comes with a 18650 Adapter shoe, if you have existing batteries for fallbacks (which are currently more commonly available). You can buy it stand alone or as a bundle with a 21700 battery and charger if you don’t already have these. The advantage of li-ion cell batteries is they aren’t heavy so you can carry spares with you if you are planning a big adventure. The optional charger is also small and USB for when you’re around a power source, however be warned; it’s not the quickest of chargers. But you are getting the best of both worlds.

21700 batteries are only going to get better (and cheaper) so this is a solid investment.

One of the sells for this specific torch was all the different modes. There are 3 different group modes you can set it to with 8 different lumen settings, including a 4th mode allows you to ramp up and down should you prefer that style (personally it’s not for me). It ranges from 1lm to 3500lm! 3500lm is unnecessary and will only work with a super juiced up battery — but the high 1800lm setting is more than capable of anything you’ll need.

On the highest setting (3500lm) it will run for 45m — as mentioned above you won’t ever need this. The run times on this vary depending on the brightness setting (obviously). If you use it on the lowest setting (1lm) it will run for 550 hours, oh the extremes... Obviously you also wont be using this while riding (it’s designed for map reading). So here’s the chart of modes with the lumen outputs and burn times.

So lets talk real world. I currently run the light in Group 2. What isn’t clear here is Moonlight mode (1lm), Turbo (3500lm) and Strobe are actually outside of the single click cycle. So they can be accessed at any point with multiple clicks or holding down the selector button down for a certain amount of time.

Have you worked it out yet? This means Group 2 has 3 light settings — perfect.

Be seen mode. This is actually fine for most riding situations where its not pitch black, your eyes can actually adjust to this really well for a lot of riding.

Low Beam. This is for riding in real darkness or when you want a bit more visibility on a sketchy road and need to be seen a bit further ahead.

Full beam. Shits more than bright enough, you’ll rarely need this. Remember most car headlights on full beam are only 1200lm. If you’re riding something super technical and fast this is probably the only time you’ll need this.

So the reality is you’ll mostly be jumping between 100 >700lm. So if you’re smart you’ll easily get over 6 hours of burn time.

This is a mini thrower, meaning it is designed for long distance (300m on the 3500lm setting). One of the reasons I chose this specific model is obviously the size of shaft in combination with the reflector. A lot of lights this size use a single LED — but this has 3. This means thats not only does it have a really good throw, but when you ramp it up to the higher settings it actually has an incredible flood too. Which is perfect for cycling.

1800lm Mode — Trees ahead are well over 100m away here. This is over a little valley too, plenty of throw & flood!

I you were to find a flaw, some might say this it it. The body is metal and construction is super solid. This obviously means weight, that said without the battery it’s only 200g. I honestly don’t care about this sort of shit, but some people might. For the size of it, it’s solid and well built. It could be plastic which might be lighter and there are plastic options out there… they’re just a bit shit. The metal also acts really well as a heat sink when in the higher lumen modes — not that I’ve really noticed it getting hot.

One thing I really like is that there are 2 buttons. There is an on/off switch on the tail which means when it’s off, it’s physically off. There is also a mode selection button just behind the reflector. This is much easier to use when riding and it also has a battery indicator light on it.

This where click buy now happens. £30 torch > £50 w/ the charger & a battery. You can find some deals around where you can actually get the bundle for as little as £30 but you can easily find it for £50 which is just incredible value.

What you get in the bundle. Torch, 21700 Battery, 18650 Shoe, Charger & USB cable, lanyard & some spare rubber seals.

I don’t have any affiliate links or plugs here, you know how to use Google if you’re interested.

For a budget torch it has been fantastic, for a budget bike headlight its fucking incredible and I couldn’t recommend it any more highly!

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