Air horn

[paulg22]

As a long time lurker on this forum thought I'd pop my head above the parapet. Getting a bit fed up of close passes and people pulling out on me on the commute and thinking about some sort of air horn solution. I've had one on my motorbike for years and, whilst used very sparingly I've found it very effective. I know there's been a couple of threads here on the past, but not seen any solutions bar the thing that uses air pressure or a canister.

I've got one a Stebel Nautilus on my motorbike and thought that this step down transformer connected to a 36v feed from my bike battery would do the trick. The horn draws 18 amps at 12v, so reckon the 20a transformer should do it. Would just need a push switch on the bars and then an on off switch between battery and transformer - I ride the bike without electric assist quite a lot so would like the the horn available when power to the bike's off.

It's a Whoosh XF08A kit - any suggestions on the best place to take a feed from, or any other thoughts?

 

[Andy-Mat]

As a long time lurker on this forum thought I'd pop my head above the parapet. Getting a bit fed up of close passes and people pulling out on me on the commute and thinking about some sort of air horn solution. I've had one on my motorbike for years and, whilst used very sparingly I've found it very effective. I know there's been a couple of threads here on the past, but not seen any solutions bar the thing that uses air pressure or a canister.

I've got one a Stebel Nautilus on my motorbike and thought that this step down transformer connected to a 36v feed from my bike battery would do the trick. The horn draws 18 amps at 12v, so reckon the 20a transformer should do it. Would just need a push switch on the bars and then an on off switch between battery and transformer - I ride the bike without electric assist quite a lot so would like the the horn available when power to the bike's off.

It's a Whoosh XF08A kit - any suggestions on the best place to take a feed from, or any other thoughts?

Unless you have an AC Bike(?), a transformer will not work.
You need some sort of DC to DC converter, but a cheaper alternative will be to measure the actual amps drawn, using your 12 volt car battery, (it could be more or less than the stated current, and you need to know accurately!), then work out the value of resistance to drop the voltage of your bike battery to about 15-12 volts (still fully acceptable for anything that runs on a car's 12 volt system) using Ohm's Law R= Voltage/Current. (/ = Divide)
You will need a heavy duty resistor, that could easily be made of several high wattage resisistors in series and parallel. Air cooling would also be good, or in a metal oil bath, to soak up the possible heat over the short term.
You may find this helpful:-

Ohm's Law | Formula, Calculation & Examples - Video & Lesson Transcript | Study.com

Learn about Ohm's law, the power equation & Kirchhoff's rules. Learn how to use them to approach & untangle a complicated circuit problem.

study.com

Any questions, just ask.
Andy
PS A true DC to DC converter would probably be quite expensive for the current that you need. I could not find one for the current you need under €100, this one is just for 5 amps, far too low, but an example for what you need, in a beefier version..

Spannungswandler 24V/ 36V/ 48V DC auf 12V DC 5A 60W Stepdown Konverter CL | eBay

Entdecken Sie Spannungswandler 24V/ 36V/ 48V DC auf 12V DC 5A 60W Stepdown Konverter CL in der großen Auswahl bei eBay. Kostenlose Lieferung für viele Artikel!

www.ebay.de

This MIGHT be better, but I have not had time to read full details, but its expensive for a horn!

12V 20A DC zu DC Batterie Ladegerät

Das 12V Batterieladegerät Lädt Die Aufbaubatterie Während der Fahrt Über Die Lichtmaschine. 3-Phasen-Aufladung, Intelligente Schutzfunktionen. Mit mehreren Batterietypen Kompatibel: AGM, Flooded, Gel und Lithium Deep Cycle Batterien. 10 Jahre Solar Erfahrung. Versand Aus DE.

de.renogy.com

 

[paulg22]

Sorry Andy, poor choice of language on my part - the item I linked to in my original post is a DC-DC step down converter on Amazon - 20a for thirty quid. Would assume that would work?

https://www.amazon.co.uk/XWST-Step-Down-Converter-Voltage-Transformer/dp/B09CTNBBDC?th=1

 

[sjpt]

Or get a 36v air horn

36 or 48 Volt Electric Horn

Flat, round, metal, water resistant golf cart horn made specifically for 36 or 48 volt electric golf carts and utility vehicles. It is approximately 4" wide and rated at 120dB. Plenty of 'honk' here. Note for gas vehicles: This horn is designed for electric golf carts or utility vehicles. If you...

www.golfcarcatalog.com

(they must be available in UK too?)

 

[matthewslack]

How many 12v amps do you need?

I use something like this for my 3A 5V needs, much cheaper than £30, potted so pretty weather proof.

But for such a low percentage use time, I would go really basic, and use either a suitable series resistor to waste the excess volts, or put two 12V or one 24V lamp of the same current needs in series.

Or trickle charge a small 12V battery from the 36V...

Pardon our interruption...

 

[AndyBike]

Maybe ok on a motorized vehicle, but on something like a bike(E or normal) its likely to cause fisticuffs.

 

[guerney]

Hornit 140db - there are two tones, I use the horn-like option because the other one sounds avian, not vehicular. Two AAA batteries last ages, mine have yet to deplete after a year's beeping at drivers and pedestrians. Hmmm... price has increased and it now has a "Garmin style mount".

dB140 | The World's Loudest Bike Horn | Hornit

The upgraded dB140 is the loudest bicycle horn on the market, putting you in control of your safety by letting people know you’re there. It’s small, sleek and enables you to alert distracted drivers and pedestrians to your presence.

hornit.com

 

[paulg22]

Hornit 140db - there are two tones, I use the horn-like option because the other one sounds avian, not vehicular. Two AAA batteries last ages, mine have yet to deplete after a year's beeping at drivers and pedestrians. Hmmm... price has increased and it now has a "Garmin style mount".

dB140 | The World's Loudest Bike Horn | Hornit

The upgraded dB140 is the loudest bicycle horn on the market, putting you in control of your safety by letting people know you’re there. It’s small, sleek and enables you to alert distracted drivers and pedestrians to your presence.

hornit.com

Do you find it effective? It's reasonably cheap, I was looking at the Loud Cycle horn as well that's a couple of car horns in a box with a a battery, but $179! and not sure if they ship to the UK.

I'd not really anticipate fisticuffs - it's much more about cars not seeing me - cycled to the chip shop yesterday evening and on the way back nearly got battered by a car turning right across my path and another pulling out on me...

 

[guerney]

Do you find it effective? It's reasonably cheap, I was looking at the Loud Cycle horn as well that's a couple of car horns in a box with a a battery, but $179! and not sure if they ship to the UK.

I'd not really anticipate fisticuffs - it's much more about cars not seeing me - cycled to the chip shop yesterday evening and on the way back nearly got battered by a car turning right across my path and another pulling out on me...

I too considered a 12V horn and DC converter... but I thought I'd try the Hornit first - it's horn sound works very well. Loud enough for drivers to hear inside their vehicles, pedestrians jump out of the way. If you use the 120db horn sound instead of the 140db weird bird-like shriek setting, it's recognisable as a vehicle horn - otherwise people don't have a clue as to what on earth they are hearing, and may even look skywards. My only issue is occasionally the jack plug
(2.5mm audio jack plug connector for the switch) very easily unplugs, so I test it before every ride - this hasn't been a problem often enough for me to glue it on, or otherwise make sure it doesn't get accidentally disconnected.

 

[guerney]

I'd not really anticipate fisticuffs

It's better than suffering in silence.

it's much more about cars not seeing me - cycled to the chip shop yesterday evening and on the way back nearly got battered by a car turning right across my path and another pulling out on me...

Exactly. The switch is right under my left index finger on the handlebar grip - I beep anyone who I don't think has seen me, any vehicle which gets too close, obstacular and potentially obstaculatory pedestrians, and pretty girls. I've conditioned myself to brake first, then give them a beeping good beeping.

 

[Andy-Mat]

Sorry Andy, poor choice of language on my part - the item I linked to in my original post is a DC-DC step down converter on Amazon - 20a for thirty quid. Would assume that would work?

https://www.amazon.co.uk/XWST-Step-Down-Converter-Voltage-Transformer/dp/B09CTNBBDC?th=1

Yes it would, but be sensitive to possible moisture.
Wheras about a dozen high wattage resistors, correctly connected, would still do the job, but for around 10 pounds or less, and resistant also to moisture ingress!
If you managed to measure the exact current drawn, I would make up a suitable connection system for the watts and voltage and where to order as well.....
But 100% your choice.
Thanks for the correction also.
regards
Andy

 

[rogher]

surely, 18A @ 12V is equivalent to only 6A @36v ?

 

[Andy-Mat]

surely, 18A @ 12V is equivalent to only 6A @36v ?

You are partially correct power wise, but in an incorrect and totally impractical manner.
The problem is as follows:-
Connecting the horn to 12 volts needs an 18A draw, we are told.
Using Ohm's law, this equates to an internal resistance of the Horn to be around R = V/I which is 0.67 Ohms. (I is used to demote Amps.)
Therefore, connecting this unit to 36 Volts results in the following I = V/R which gives a current of 53.7 Amps.
Which would result in severe overheating and possible serious damage.
There has to be something in between the 36 volts and the horn, to keep the current at 18A and no more!
A DC to DC converter is the usual way, which is though more expensive and the unit needs to be kept free of water!
The simplest way is to make up a suitable resistance block, with heavy duty ceramic resistors. We need to drop off 24 volts, so the simple Ohm's Law calculation is:-
24/18 = 1.34 Ohms.
Power in Watts is calculated by I x V = 432 Watts. 8 x 10 Ohm woudl give 1.3 Ohms. Using 40 Watt Ceramics, would allow for 320 watts, but in an oil cooler and used only in short bursts, that would probably work fine!!
Probably there are 24 volt horns for trucks, that make the calculation even easier, with less voltage to drop.
Or even buy 2 or 3 12 volt horns, with a lower current requirement, and mount them in series. As even 12 volt horns are usually fully OK with even 16 volts for short periods....but 3 horns in series would be fine.
I found 50 watt resistors on ebay if needed here:-

0,1-470 Ohm, 5%, 10/25/50 Watt, Hochlast Widerstand, Lastwiderstand, Lötfahne DE | eBay

Widerstand: 0,1 Ohm / 0,22 Ohm / 0,47 Ohm / 1 Ohm / 10 Ohm / 100 Ohm / 2,2 Ohm / 22 Ohm / 3,3 Ohm / 4,7 Ohm / 47 Ohm / 470 Ohm / 6,8 Ohm / 6,8 Ohm (wie ausgewählt). Breite: 23 mm (10 W), 27 mm (25 W), 27 mm (50 W).

www.ebay.de

I even found this:-

Elektrofahrrad Horn - 36 Volt 105 db Elektroroller Horn HRN-36 | eBay

Entdecken Sie Elektrofahrrad Horn - 36 Volt 105 db Elektroroller Horn HRN-36 in der großen Auswahl bei eBay. Kostenlose Lieferung für viele Artikel!

www.ebay.de

Problem solved and is very cheap, with NO extra work!!Best wishes to all.
Andy

 

[jimriley]

Another happy Hornit customer here.