Interior/Exterior Air Horn - an exercise in taking a mod to the extreme!
#1
03-26-2008, 08:21 PM
Air Horn - an exercise in taking a mod to the extreme!
Several times I joked about how much fun it would be to have a real air horn in a MINI. Not some plastic bits powered by an immediate on-off air compressor, but an honest to goodness airhorn... something worthy to be put on a train or a semi. A few years ago I was surfing around on ebay and thought "Hey! I can do this!"
It has taken me almost 2 years to assemble all of the parts and find the right design that would accomplish my goals.
1. Very Loud
2. Nice sound - at least 2 tones, maybe more
3. High pressure horn for the right power
4. No solenoid valves... I wanted true control to bleed into notes
5. Stealth - no visible signs of the horns
6. Safety (of course)
I originally bought a pair of air horns from a 2-ton military truck and refurbished them. There were several tablespoons of sand in 'em. Unfortunately, I recently discovered that the diaphrams were shot and I couldn't "voice" them properly... the would either leak too much gas or seal completely... no vibration to make the noise. I did a lot of searching, but I couldn't get replacement parts for 'em. I had to break down and get a new set off of eBay, but at least I got a nice, compact 4 horn setup.
To get the controls right, I had to buy from an aircraft supply house. It's a bowden cable setup with a t-handle that I've mounted right next to the handbrake. It lets you pull quickly for a sharp, full blast or eeek your way into a note. It also looks pretty slick, IMHO.
The cable runs back to a good old fashioned air valve made for a semi. If I could have figured out how to run a pull cable up over the driver's door, I would have done it for the classic trucker 'honk' motion, but it just wasn't practical as the horns weren't going to be mounted on the roof.
Where to hide the horns? Well, I just installed a single muffler exhaust in December (Alta Sportone 2.5"), so the major components are tucked into the space where the missing muffler used to be... back left corner of the car. The Bowden cable runs down the exhaust channel to this location.
Power? Well, I didn't like the idea of having an air compressor on-board... too noisy when it kicks on, which (given the size of air tank that could be installed on a MINI) would be almost every time you honked the horn. It just wasn't the aesthetic I was looking for... I had to keep looking. I started thinking about CO2. It's readily available at sporting goods shops (paintball canisters) and the bottles are fairly rugged and inexpensive. Kobalt (tools made for Lowes Hardware) just started making a CO2 regulator for these sized bottles to power air nailers, so I hit the jackpot. A few hours of wandering hardware stores later to find a suitable way to protect the regulator and CO2 bottle, I was in business! The nice thing about CO2 is that it is stored as a liquid instead of a gas. If I can remember my college chemistry well, that means that you get 22-28 times the volume of CO2 compressed into the same size container as you could store compressed air (stored as a gas at normal temps and pressures).
The CO2 bottle and regulator is mounted inside a thick PVC electrical conduit box that I painted flat black to blend in nicely under the car. It's easy to get at with 4 screws and 2 thumb-screws clamping it in place. The box keeps stones and other misc. debris from harming the CO2 tank. Everything is vented and stored outside of the car so if the CO2 tank gets overpressurized due to heat, a safety valve will blow and vent all the CO2 safely on the outside of the car.
Here are pics and links to video:
Video 1: http://video.google.com/videoplay?do...60924064999400
Video 2: http://video.google.com/videoplay?do...86540893594282
Video 3: http://video.google.com/videoplay?do...33359737900479
It has taken me almost 2 years to assemble all of the parts and find the right design that would accomplish my goals.
1. Very Loud
2. Nice sound - at least 2 tones, maybe more
3. High pressure horn for the right power
4. No solenoid valves... I wanted true control to bleed into notes
5. Stealth - no visible signs of the horns
6. Safety (of course)
I originally bought a pair of air horns from a 2-ton military truck and refurbished them. There were several tablespoons of sand in 'em. Unfortunately, I recently discovered that the diaphrams were shot and I couldn't "voice" them properly... the would either leak too much gas or seal completely... no vibration to make the noise. I did a lot of searching, but I couldn't get replacement parts for 'em. I had to break down and get a new set off of eBay, but at least I got a nice, compact 4 horn setup.
To get the controls right, I had to buy from an aircraft supply house. It's a bowden cable setup with a t-handle that I've mounted right next to the handbrake. It lets you pull quickly for a sharp, full blast or eeek your way into a note. It also looks pretty slick, IMHO.
The cable runs back to a good old fashioned air valve made for a semi. If I could have figured out how to run a pull cable up over the driver's door, I would have done it for the classic trucker 'honk' motion, but it just wasn't practical as the horns weren't going to be mounted on the roof.
Where to hide the horns? Well, I just installed a single muffler exhaust in December (Alta Sportone 2.5"), so the major components are tucked into the space where the missing muffler used to be... back left corner of the car. The Bowden cable runs down the exhaust channel to this location.
Power? Well, I didn't like the idea of having an air compressor on-board... too noisy when it kicks on, which (given the size of air tank that could be installed on a MINI) would be almost every time you honked the horn. It just wasn't the aesthetic I was looking for... I had to keep looking. I started thinking about CO2. It's readily available at sporting goods shops (paintball canisters) and the bottles are fairly rugged and inexpensive. Kobalt (tools made for Lowes Hardware) just started making a CO2 regulator for these sized bottles to power air nailers, so I hit the jackpot. A few hours of wandering hardware stores later to find a suitable way to protect the regulator and CO2 bottle, I was in business! The nice thing about CO2 is that it is stored as a liquid instead of a gas. If I can remember my college chemistry well, that means that you get 22-28 times the volume of CO2 compressed into the same size container as you could store compressed air (stored as a gas at normal temps and pressures).
The CO2 bottle and regulator is mounted inside a thick PVC electrical conduit box that I painted flat black to blend in nicely under the car. It's easy to get at with 4 screws and 2 thumb-screws clamping it in place. The box keeps stones and other misc. debris from harming the CO2 tank. Everything is vented and stored outside of the car so if the CO2 tank gets overpressurized due to heat, a safety valve will blow and vent all the CO2 safely on the outside of the car.
Here are pics and links to video:
Video 1: http://video.google.com/videoplay?do...60924064999400
Video 2: http://video.google.com/videoplay?do...86540893594282
Video 3: http://video.google.com/videoplay?do...33359737900479
Last edited by agranger; 03-27-2008 at 07:18 AM.
#3
03-26-2008, 08:41 PM
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03-26-2008, 09:51 PM
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#8
03-27-2008, 07:17 AM
This is not a mod for the feint of heart... I probably spent 5-6 hours just on the fabrication and install, not including the time spent in design, research and wandering the hardware stores looking for parts to make it all work.
Come on by and have a listen at the MINI show at MOTD 2008... I'll be there!
PS: Thanks for the kind comments on my overall MINI design. It was a long time in the planning and I'm very happy with the way it all came out.
Come on by and have a listen at the MINI show at MOTD 2008... I'll be there!
PS: Thanks for the kind comments on my overall MINI design. It was a long time in the planning and I'm very happy with the way it all came out.
#10
03-27-2008, 08:40 AM
I'm running 9oz tanks because they fit nicely into the space and I could find a box that would fit the regulator and tank. Once you mount the horns, there isn't a bunch of room for the tank and I really wanted to keep the tank on the outside of the car for safety reasons.
I've been working on this mod for over 2 years, but I can add up at least $200 in parts just off the top of my head.
I've been working on this mod for over 2 years, but I can add up at least $200 in parts just off the top of my head.
#11
03-27-2008, 09:35 AM
I'm running 9oz tanks because they fit nicely into the space and I could find a box that would fit the regulator and tank. Once you mount the horns, there isn't a bunch of room for the tank and I really wanted to keep the tank on the outside of the car for safety reasons.
I've been working on this mod for over 2 years, but I can add up at least $200 in parts just off the top of my head.
I've been working on this mod for over 2 years, but I can add up at least $200 in parts just off the top of my head.
#12
03-27-2008, 09:44 AM
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#13
03-27-2008, 10:41 AM
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I'm running 9oz tanks because they fit nicely into the space and I could find a box that would fit the regulator and tank. Once you mount the horns, there isn't a bunch of room for the tank and I really wanted to keep the tank on the outside of the car for safety reasons.
I've been working on this mod for over 2 years, but I can add up at least $200 in parts just off the top of my head.
I've been working on this mod for over 2 years, but I can add up at least $200 in parts just off the top of my head.
So with the 9oz tanks (two of them, I assume), how long can the horn blow without recharging them? Also, is there a significant drop-off in sound as the tanks depresurize? Finally, if you don't mind me asking, how much is it to recharge the tanks?
I really like the idea of using CO2 or possibly N2, so any tips you could provide would be appreciated.
Thanks.
Last edited by iblack; 03-27-2008 at 11:35 AM.
#14
03-27-2008, 11:42 AM
CO2 is stored as a liquid, so you can't use a pressure gauge to tell how full the tank is. It's basically full (pressure-wise) until it goes empty. When they fill the bottles, they have to do it by weight for this very reason. When they mount NO2 bottles inside, they have to have the blow-off safety valve plumbed to the outside of the car. The quick release of even 9oz of CO2 would cause a massive sudden pressure increase inside the car and I didn't wanna be in there when it happened. The TX summers are HOT and I was worried about a CO2 canister being inside the car when the interior temp hits 150 degrees.
As soon as I know how long it will last, I'll let you know. I've had the whole system assembled and pressurized for 2 days now... probably 10-15 good long test and/or filming blasts with no change in tone or volume.
The cool thing is that I'm only running at 80 psi... The horns will go even louder with more pressure, so I may dial it up a bit the next time I change out a tank. I was worried about leakage of the tank at all the fittings... if a bit of air leaks out, the compressor can just come on and top off the tank. CO2 will just bleed out until it's gone and I have to replace the tank. I couldn't find anyone that was using tank CO2 to power an air horn of this size, so I'm kinda on the bleeding edge here... learning as I go. A few ships use large CO2 tanks to power their very high pressure horns, so I was just guessing that it would work and I'm really happy with the results.
A 9oz CO2 fill costs $1.50 to $2. I've got 4 of 'em, so I don't think I'll have to go in for fills very often.
Now that Lowes is selling full CO2 canisters, you could buy it from them if you have one handy. They sell for $21 when new but you can trade in the empty bottles for something like a $18 credit (I think), so a 9oz refill costs you only $3 or so.
As soon as I know how long it will last, I'll let you know. I've had the whole system assembled and pressurized for 2 days now... probably 10-15 good long test and/or filming blasts with no change in tone or volume.
The cool thing is that I'm only running at 80 psi... The horns will go even louder with more pressure, so I may dial it up a bit the next time I change out a tank. I was worried about leakage of the tank at all the fittings... if a bit of air leaks out, the compressor can just come on and top off the tank. CO2 will just bleed out until it's gone and I have to replace the tank. I couldn't find anyone that was using tank CO2 to power an air horn of this size, so I'm kinda on the bleeding edge here... learning as I go. A few ships use large CO2 tanks to power their very high pressure horns, so I was just guessing that it would work and I'm really happy with the results.
A 9oz CO2 fill costs $1.50 to $2. I've got 4 of 'em, so I don't think I'll have to go in for fills very often.
Now that Lowes is selling full CO2 canisters, you could buy it from them if you have one handy. They sell for $21 when new but you can trade in the empty bottles for something like a $18 credit (I think), so a 9oz refill costs you only $3 or so.
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03-27-2008, 12:06 PM
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03-28-2008, 03:11 AM
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03-28-2008, 04:29 AM
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03-28-2008, 07:15 AM
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CO2 is stored as a liquid, so you can't use a pressure gauge to tell how full the tank is. It's basically full (pressure-wise) until it goes empty. When they fill the bottles, they have to do it by weight for this very reason. When they mount NO2 bottles inside, they have to have the blow-off safety valve plumbed to the outside of the car. The quick release of even 9oz of CO2 would cause a massive sudden pressure increase inside the car and I didn't wanna be in there when it happened. The TX summers are HOT and I was worried about a CO2 canister being inside the car when the interior temp hits 150 degrees.
As soon as I know how long it will last, I'll let you know. I've had the whole system assembled and pressurized for 2 days now... probably 10-15 good long test and/or filming blasts with no change in tone or volume.
The cool thing is that I'm only running at 80 psi... The horns will go even louder with more pressure, so I may dial it up a bit the next time I change out a tank. I was worried about leakage of the tank at all the fittings... if a bit of air leaks out, the compressor can just come on and top off the tank. CO2 will just bleed out until it's gone and I have to replace the tank. I couldn't find anyone that was using tank CO2 to power an air horn of this size, so I'm kinda on the bleeding edge here... learning as I go. A few ships use large CO2 tanks to power their very high pressure horns, so I was just guessing that it would work and I'm really happy with the results.
A 9oz CO2 fill costs $1.50 to $2. I've got 4 of 'em, so I don't think I'll have to go in for fills very often.
Now that Lowes is selling full CO2 canisters, you could buy it from them if you have one handy. They sell for $21 when new but you can trade in the empty bottles for something like a $18 credit (I think), so a 9oz refill costs you only $3 or so.
As soon as I know how long it will last, I'll let you know. I've had the whole system assembled and pressurized for 2 days now... probably 10-15 good long test and/or filming blasts with no change in tone or volume.
The cool thing is that I'm only running at 80 psi... The horns will go even louder with more pressure, so I may dial it up a bit the next time I change out a tank. I was worried about leakage of the tank at all the fittings... if a bit of air leaks out, the compressor can just come on and top off the tank. CO2 will just bleed out until it's gone and I have to replace the tank. I couldn't find anyone that was using tank CO2 to power an air horn of this size, so I'm kinda on the bleeding edge here... learning as I go. A few ships use large CO2 tanks to power their very high pressure horns, so I was just guessing that it would work and I'm really happy with the results.
A 9oz CO2 fill costs $1.50 to $2. I've got 4 of 'em, so I don't think I'll have to go in for fills very often.
Now that Lowes is selling full CO2 canisters, you could buy it from them if you have one handy. They sell for $21 when new but you can trade in the empty bottles for something like a $18 credit (I think), so a 9oz refill costs you only $3 or so.
Where are you located? I'm a bit curious because I know that CO2 cools as it converts to a gas and I've heard about some issues with freezing in colder temperatures when CO2 is relied upon heavily by paintballers. Have you heard/read/learned anything about that? My guess is it isn't a big deal since you're not going to use the horn often, but I'm curious if you've worked through that at all.
On the regulator, which Kobalt one are you using? Does it have the ability to vary the psi output? I've noticed that the paintball regulators seem to have standardized on either 800/850 or 300 psi output. You said yours is running at around 80psi, and many air horns max out around 200psi, so I was curious how flexible the regulator your found is.
Thanks again.