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Comment by michh | Hacker News Reader

Coincidentally, I bought a 12v car horn yesterday with the intent of wiring it into my ebike's power supply with a little button on my handlebars.

Not because of other cyclists or pedestrians wearing (anc) headphones but because modern cars are so heavily sound-proofed they don't hear a bicycle bell anymore. A recent incident with an inattentive taxi driver in a brand new EV nearly flattening me prompted me to want to pursue this.

I'm still waiting for my cheap AliExpress dc-to-dc step down converter but otherwise I have everything I need and I think it should work. The horn module itself is definitely loud enough: I connected it to a 12v power supply at my desk and jumped out of my chair.

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Be careful with your ears! (And those of others)

A unexpected loud noise recently caused me to get tinnitus and hyperacusis, and trust me, you don't want either of them!

You know a diagnose is bad when Wikipedia lists suicidal thoughts as a common side effect....

https://en.wikipedia.org/wiki/Hyperacusis

May I ask what the loud noise was? And sorry to hear that. Tinnitus and hyperacusis suck.

A small firework rocket that someone launched sideways instead of up exploded within a few meters of me.

I say small but I mean tiny. One of those that are sound only, no visuals.(Why are those even a thing?)

Bottle rockets I assume. I had a lot of fun with them as a kid. Thankfully no one involved with those got hurt.

https://www.nhpyro.com/black-cat-bottle-rockets.html

Yeas ago I motorcycled a lot, all over the world. I escalated to an air horn and hi-viz. But I pretty quickly realized that these made no tangible difference to the behavior of larger vehicle drivers. So I ended up for later vehicles with a stock horn and hi-viz only for heavy rain.

These days our family cycles a lot for commuting. It’s really easy to observe that people in vehicles treat us far better if we look like humans, wearing normal street clothes, rather than wearing high-viz or, far worse, cycling gear.

The bike bell is for polite notice, not alarming. The best alarm system you have is your voice, which is variable volume and tone. For ultimate effect slap the panels of cars, as it is very loud inside the vehicle.

Sadly I had to kick a few cars that thought they could run me off my motorcycle. Worked every time. All of them didn't look out the window or they would have looked right into my face. Yelling and horn did absolutely nothing.

Most of them were extremely apologetic or even shocked (as if I appeared from thin air). None of them were angry for scratching their door. Some people are just lost in thought it seems...

> or even shocked (as if I appeared from thin air)

Motorcyclists are invisible. Never rely on others seeing you, ride as if they're an obstacle you have to navigate.

You can hide a whole truck behind the A-pillar of modern cars, let alone a motorcycle. At certain angles, human eyes have complete blind spots that we're not aware of because our brain filters them out. Motorcycles fit perfectly into those.

Never hover in people's blind spots. Pass quickly or stay back. Do not drive parallel with another vehicle. Goes for cars too.

When approaching another car perpendicularly (like an intersection), remember that humans lose depth perception because their nose covers one of the eyes. A driver literally cannot tell how far you are. Our usual proxy is the distance between headlights. Motorcyles have 1 headlight so this heuristic doesn't work, but we don't realize that it doesn't.

https://www.youtube.com/watch?v=x94PGgYKHQ0

Oh I know. They look at me while turning left cutting me off.

Maybe I need a bigger bike, the 2cyl 400cc is particularly invisible. ;)

Best one was a woman who cut me off doing her left turn. I high-beamed her and honked. She put her hands in front of her face and came to a dead stop in my lane directly in front of me. I was already braking before I honked. Nothing happened. I stopped wondering and just assume everyone is out to kill me.

It's a rule that also applies to bicycles.

> I high-beamed her and honked. She put her hands in front of her face and came to a dead stop in my lane directly in front of me.

Personally I skip the honking and high beams. Just perform evasive action assuming driver will continue on their current path at roughly their current speed. Swerving behind their path of travel usually works great.

Spooked drivers behave erratically. Very dangerous.

So far I've had 0 serious incidents in ~8 years of riding. A couple close calls when I was being an idiot. So I think my approach is working :)

Honking is more for the people behind/around me. I also don't want to be hit by inattentive people following me to closely.

May I ask where you are riding? I am currently in Bavaria. The danger level is usually higher after the winter. Drivers need to re-accustom themselves to sharing the road with two wheeled riders.

Evasive action could be even more dangerous in cities. In my experience being able to come to a stop without hitting anything is even better.

Lot's of dead people had the right of way. Ride safe, I agree. I also had 0 accidents so far in 30 years. But you still experience new things you hadn't thought would be an issue.

> May I ask where you are riding?

San Francisco Bay Area. I never got into motorcycling back in Europe although the roads are lovely, the short riding season felt like a deterrent. Also the extremely long process to get a license.

Here in CA it was almost scary easy to get M certified.

Must be cool to have bike weather all year round. ;)

Yeah, snow and scooter/motorcycle is not a great mix here. But touring the Alps down to Lake Garda was amazing. Can recommend.

Yup. If you don't have armor around you the only real defense is to assume you are invisible unless you know they've seen you or can't help but see you (for example, going in the traffic direction in front of a stopped car that's waiting to go--they're looking at the cars, they'll see anything else coming along.) Doesn't matter if you have wheels or feet under you, you still are invisible.

Slapping panels in the US will occasionally get people trying to fight you, as I've had happen. Not really sure what a good solution to that looks like short of cultural changes.

As a pedestrian I slapped a panel of a slow car that failed to yield to me at a crossing. The driver glared at me and looked ready to reverse into me. I never slapped any panel any more.

Second the fact that it's only useful for polite notice. Emergency, someone's already not paying attention and it's probably the car.

Car horns are useful warnings because speeds are higher and thus stopping time is longer--more opportunity for someone to hear and react.

I want to see a bike with a train horn. Cars do it all the time. [1][2][3][4] illegal and highly satisfying

People have used drills+pumps to drive similar hand-held horns at football games so it is doable.

[1] - https://www.youtube.com/watch?v=NOKgg5iCw_c

[2] - https://www.youtube.com/watch?v=enF0m6J7g2w [Tiny car with train horn]

[3] - https://www.youtube.com/watch?v=w31s5NsoOyg

[4] - https://www.youtube.com/watch?v=jLfD1AFsb1I

Oh yeah... the good old 3 or 4 tone "train" honrs from Cadillacs

https://www.tacomaworld.com/threads/are-you-tired-of-your-wi...

When I was commuting 60k/day on my bike in shitty suburban conditions, I used one of these instead - you get limited use per trip, but you can always fill it up with a CO2 cylinder/bike pump:

https://www.hpvelotechnik.com/en/recumbent-trikes-bikes/acce...

It is loud.

That’s a crappy pressure vessel holding 350ml of 80psi air, for about 100J of stored energy. I’m not entirely sure I’d be comfortable with that, especially anywhere with my face in the line of fire it it fails.

Good point, but I abused it pretty well and it seemed to do OK - was also in a water bottle holder so closer to the legs than anything.

> That’s a crappy pressure vessel

That's a huge assumption, and likely incorrect.

Your bike already has two crappy 80psi pressure vessels, why not three?

Those two pressure vessels are highly engineered and are wrapped with materials with pretty good tensile strength. Also, they’re made out of materials (fabric and rubber) that absorb a decent amount of energy when they tear and that don’t fragment. And the whole assembly usually depressurizes slowly.

Having personally blown up beverage bottles by overpressurizing them (be very very careful doing this!), when they go, they go violently.

I've blown up beverage bottles for fun. Hooking an air compressor to a 2L bottle and exploding it makes a satisfyingly loud boom.

*We had a valve on the air line so we could be at a safe distance when pressurizing. Be very careful. It's unpredictable exactly at which point they'll blow. Sometimes they hold full pressure for a couple seconds and then go.*

i like to use dry ice for pressure, make sure you have a gun to shoot it if it doesn't go off

When we did it, it always went off on its own. It's been a long time since I did it, but I think the longest it took would've been on the order of 30 seconds. Really makes a person jump when it finally goes.

If this is a modern bike, 80psi is way too high. 50psi is sufficient and will give you a more comfortable ride as well as higher efficiency on real-world surfaces.

80+psi is for old-style road bikes with narrow 23mm tires. Modern bikes (even road bikes for racing) don't use these any more; 28mm is the minimum these days.

… I have a modern bike (a Specialized). The tires' rated range is 75psi to 100psi. I usually pump it to around 80–85psi. The tires are 33mm.

You're overinflating your tires. A lower pressure will increase your speed and efficiency unless you're riding in a velodrome. Here's a video about this:

https://www.youtube.com/watch?v=7r8f3w89XeM

(watch out, there's a lot of extra stuff in this video about the machine they use to measure efficiency)

(Well, they should tell the manufacturers…)

The video's result for both tires they tested was peak efficiency at 5 bar. They had a really coarse sampling of a whole bar, so that works out to a pressure of 65–80 psi.

>(Well, they should tell the manufacturers…)

The manufacturer rating is likely a max allowable pressure rating.

Not to be pendantic (but to be pendantic) 80psi is the correct pressure for 28mm tires ridden briskly on good roads. At least according to ye olde Silca tire pressure calculator. Back in the day when folks ran 23mm tires they would typically run above 100psi (though that may not have been optimal...).

That calculator is wrong. Cycling people have been overinflating their tires for ages (as well as using too-narrow tires), with the assumption that the ground is perfectly smooth. Lower pressures yield higher efficiency (and better comfort) on rougher surfaces.

Surface quality is an input in that calculator.

Because the danger posed by a fairly low energy pressure vessel is highly related to it's failure mode. That's why OSHA has rules about what compressed air pipes can be made of--it's not about the pressure resistance, it's about what will happen if one fails.

It's likewise why most military boom is mostly not actually boom. With artillery you obviously need a very tough case, but standard aircraft-dropped iron bombs are mostly that: iron. They don't need that kind of strength except specialized bunker-busters, they're built that way because for a given weight of bomb you'll do more damage by throwing bits of bomb casing from a smaller charge than from a bigger charge without the fragments.

It's a soda bottle - it fits in your water bottle holder, and you can replace it for a couple of bucks if it fails. 80 psi is pretty low pressure (typical narrow tires are 100-120) and the bottle itself is very low mass, so the fabric around the bottle should ensure safety if it bursts.

IIRC these came out in the early-mid 90s; a bike messenger trick at the time was to fasten the horn to your handlebars with velcro, so you could take it off and hold it near a car window when triggering it.

If it fails by blowing the end off toward your face what damage will it do?

I suppose I should maybe not worry about 80 psi so much. An ordinary bottle of soda on a moderately warm day is around 80psi. The energy is 1/2 * pressure * head space (roughly), and head space is minimal. But you can chill it in the fridge, then open it and quickly pour out half, then close it and let it warm up, and you may still be near 80 psi, and I’ve never heard of anyone getting maimed by an exploding soda bottle.

> When I was commuting 60k/day on my bike in shitty suburban conditions

Here I thought my 4.5 mile (7.25 km) bike commute was a bit long...

An hour and a bit each way, took about as much time as public transit and better than a coffee for waking up. A good road bike goes a long way, and the suburbs suck for road sharing but are great for not having to stop at many lights.

The winters were rough though.

I used to bike ~20 mi / day … back when there were offices. Just as fast as public transit.

Aside from idiots with cars, it's relaxing. Only some of my route was on the road, though.

Like the other poster says … The winters were rough though. I just didn't bike, though my coworker kept trying to get me to.

Yeah I had something like this for several years. Works really well for cars

I wonder if one of those recently-emerging Chinese electric blowers that sub for canned air would generate enough air volume to sound the horn usefully. Possibly not quickly enough.

Can confirm, AirZound is great!

I did that, but I used battery - couldn't figure out how to hook up to the e-bike's 50v electrical system (plus the DC-DC converter with high enough current...)

So I am using LiPo 3S, 2200mAh. Works like a charm. I keep it at its storage voltage (3.7-3.8v per cell), and it hardly drained the battery (there is no paracitic drain). Whole thing was like $20.

I pondered doing that but thought it would agitate other road users so decided against.

Some locales are downright itching for a reason to road rage so I don’t blame you. One thing I have to say about being a motorcyclist is that our residents in California are so considerate and have never once mistreated me for beeping, lane splitting/filtering, stalling my bike at a green light, etc.

mm, if i can't get it to work with the dc-dc converter i'll definitely go that route, good idea

If diy doesn’t work I’ve been using loud bicycle horn and it works great.

https://loudbicycle.com/

Gah! mini usb instead of USB C. Love the concept but it is remarkable how long bike accessories have been holding out on USBC.

At least they’re forward about it - I’ve lost count of how many bike accessories claimed to be USB C, but they only charge when connected to their specialized cable that converts from USB A to C.

Double-sided USB-C connections require a handshake before sending voltage. USB-A ports can have the 5v line active at all times. Cheap USB C gadgets often don't make the handshake, they just use it as a 5V input, necessitating an A to C cable.

Interesting. Does UsBC spec/licensing require any sort of notation for products that don’t implement handshake?

There is no handshake, all that's needed are two 5.1 kΩ pulldown resistors. By omitting them the manufacturer saved all of about 0.1c and made their device incompatible with compliant usb-c chargers.

More info: https://hackaday.com/2023/02/07/all-about-usb-c-manufacturer...

Such products shouldn’t exist by spec, they’re just not compliant.

If you add 5.1kΩ pulldown resistors on the CC lines for USB-C, you can get the standard 5V without a handshake although current may be limited by some chargers without negotiation.

One of the many deficiencies of usb-c (who knows what power your cable supports, charger supports, if you accessory will charge, of it will connect at all)

I think you're overstating this. The "handshake" is purely 2 simple resistors correctly installed. The problem is a lot of folks do it wrong for various reasons, most likely never testing with anything more than type a to type c cables.

https://people.kernel.org/bleung/how-to-design-a-proper-usb-...

I'm still waiting on full-size usb-c instead of current mini-usb-c

I’ve got one of these fwiw, and it’s outstanding.

> because modern cars are so heavily sound-proofed they don't hear a bicycle bell anymore

Agreed. I had a supercharged V8 Jaguar that I could barely hear.

And my Audi has a system that actually pumps engine noise into the cabin, so you can hear that, but not the outside world.

The Fire Department I was at was looking at "thumpers" - augmentations to sirens that make cars in front of them vibrate (a la those people playing too much bass too loud).

Not just sound proofing, but inattentiveness. I've been behind people on semi-rural quiet roads with my 40,000lb fire engine behind them, lights, sirens, and airhorns, and they've driven for a mile or two completely oblivious.

if you ever want an upgrade look into nautilus air horns. I had one on my 250cc Vespa that would clear an intersection.

Needs like 18 amps if that tells you anything.

> I bought a 12v car horn yesterday with the intent of wiring it into my ebike's power supply

Putting an aerosol fog horn (available from boating supply shops) in the bikes water bottle holder is much simpler, louder and more effective.

And where does your water bottle go then?

Courtesy forbids me from suggesting where it could go.

for your safety, when people hear a car horn, they’re going to be looking for a car.

It should make a ring-ring sound but at 120 decibels?

Ooh, the telephones in the 80s! You should get one of those!

A motorcycle horn might be a better choice

on the rare occasions where I need to loudly indicate my presence to a motor vehicle I wouldn't really want to be moving my hands - if I have time to move a hand to a horn I probably have time to brake/manouvre instead.

Generally in those situations I shout really loudly at the driver, and in general they seem to hear me

Aside: folks living near bike paths where this happens are going to suffer. I don't know what the solution is, but increasing volume to defeat increasing sound-proofing seems like a recipe for noise pollution.

I had a digital bell from aliexpress on my winter commuter because pogies on the bars prevented a typical dinger. It was very annoying and very effective; my wife referred to it as "the friend maker".

Seconding the point to please not use this on anyone not in a soundproofed car.

Squeeze horns are usually loud enough to be heard by cars in my experience.

LOL. I put the loudest 12V train/air horn I could buy on my 60 mph escooter with a 72V to 12V buck converter and a motorcycle handlebar button. It was pretty easy to install. (I added a fuse too.) Stupid motorized vehicle drivers get the horn of doom.

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