How To Install Air Horns On Your Truck – Part 1

By Reg Robinson

 I wrote this article because of my interest in having air
horn on my truck and the lack of comprehensive information on such a
project. There are posts wandering about
the Internet on the results of someone's mod with a picture here and there but
nothing that answered the many questions that I had nor anything that
approximated a “how to guide”. Even the
company that supplied my kit offered little useful advice. I do apologize for the pictures since I wrote
the article after the horns were installed so bear with me in the photographic
aesthetics area. 

 Secondly let me state that this installation is about air
horns. Those used in industrial
applications. You know the big boys that
use serious air. Not the plastic
trumpets driven by those Coke can compressors. I have one in my Explorer and it doesn't even compare. If it comes from the local Auto parts store
this article is probably not for you. 

 Further there are many variations of how to do things and I
cannot cover every angle. I will state
what worked for me.

 Let's
begin.

The Cost

  The installation of these horns is
expensive. Plan on spending several
hundred to well over a thousand when all is said and done. There are places costs can be shaved and
places it shouldn't. More on that
later. 

The Parts

Horns:

I installed Nathan Airchime P3 horns on my F 350. These train horns cost a bit over $700. You can find train horns, marine horns, and
such in many places. I have watched
auctions and they all end at $500 to $1000 for a set of train horns. What do the letters and numbers for the horn
mean? The P is the series of horn. Airchime made M, P and K series that I know
about. I am not a serious train buff so
if you want more information “track” down a train enthusiast site. There's a couple in the Yahoo Groups
area. They also sell horns there. The bonus buying there is the knowledge and
expertise from those with a passion for trains. The “3″ means three trumpets or bells. Each is tuned to a different note. Airchime continues to manufacture K series and other horns for
industrial applications such as mining. Those horns have a coverage of up to 6 kilometers and can put out 147 db
at 1 meter.

 The M is an older series, has a mellower sound is rare and
thus more costly. The K series is what
you hear on modern locomotives. It is
about the loudest horn out there putting out a teeth rattling 114 decibels at
100 feet. But volume has its price. They use lots of air. That is why I chose the P series. It was Nathan's most efficient horn for air
usage and is more than loud enough for me. Efficiency is important to us
because we are limited on air supply. 

 I also paid more because I bought from a business that
refurbishes and sells these horns. 

Marine horns are another option. Buy what you like and will work for you. Think about mounting and function in making a
decision.

 That plate
supporting the horns is ½ inch thick
steel. 

 

Air
source:

 Something
has to drive the horns. The choice is
basically tanks or bottles. I'll mention
the two then compare.

Air Tanks:

 The
louder the horn and the longer you blast the more air is required. A small tank just won't maintain the sound
volume for long. A few blasts and your
done. The larger the tank the more time
you have and the longer the sound can be sustained. I strongly recommend 5 to 6 gallons
minimal. I installed twin 6-gallon tanks
on the F 350. Even with the P3's a
short blast drops pressure 5 to 10 psig. I bought my tanks, which came in a kit
from groverairhorns. The price? $500+. But this included all hoses, fittings, pressure switch, inlet filter and
compressor. Most everything is top
shelf. I had problems with the fittings,
which, I will mention later. 

 If you
opt to shop around for a tank ensure it is in good shape, you know its history
and it is pressure tested. Some machine
shops will pressure test the tanks for you. Avoid anything that was picked up from a junkyard or other dubious
origin. These horns operate around the
120-to150-psig range or higher and are going to be mounted on your vehicle
possibly near vital lines. Don't go
cheap here. Try to get tanks with a
drain valve. Water will accumulate in
the tank and this valve will make it much easier to get rid of it.

Compressed gas:

 Compressed air bottles are an option
as a gas source. Bottle sizes vary. I
have never heard of scuba tanks or fire and rescue (SCBA) style being
used. Don't use propane tanks or
anything that held a flammable or toxic gas. Using anything but compressed air is going to be costly and may change
the tone of the horn due to the density difference of the gas. 

 Here's a letter sent to me from
another member on a train horn site:

 Reg,

 “I have
been told to expect to pay between $15 – $25 per bottle in an
exchange system, empty for full. One person uses compressed nitrogen at
2200psi and 142cuf volume. Bottle weight is 76lb empty and 90lb full. Aluminum
bottle types are available and are far less weight than the steel ones. You
will
need a regulator to attach to your bottle in order to control flow to your
horn.
I employ a standard Graham White modulating horn valve and it works excellent.
3/8" ID airline is a minimum requirement. I suggest an output of around
70psi -
100psi for plenty of punch. Blowtime per bottle depends on how much you want to
hear your horn – short toots will prolong a bottle’s life greatly and long, 14L
type blasts will drain a bottle rather rapidly. At a horn honk event, I’ve
emptied 7 full bottles but got LOTS of sound in exchange.

As pointed out, the main goal is finding ‘air’ for the horn. Depending
on how much you blow, the Nitrogen system works great but is the most costly of
the current systems employed by several active group members. If you are
planning on doing a lot of honking, I would recommend a large air tank and a
gas
compressor to get unlimited air. If you are just a casual honker, the Nitrogen
system works well, at least for me. I own 3 N2 bottles and currently exchange
them for around $48.00, all haz-mat, taxes and disposal fees included…they
usually last me a month to 6 weeks until I exchange them for another set of 3
full bottles.

Like I said, it all depends on how much you plan to honk your horns. Carrying
compressed gas cylinders is always considered hazardous and not recommended for
the general public. I’ve been learned on how to use these cylinders but only do
so during horn testing/recording or at a major horn honk event.

Pros: Quick, Convenient, Powerful & Easy to Use
Cons: Heavy, Bulky, Costly & Potentially Dangerous”

EM

Comparison:

Compressed air bottles work fine but, if you are like me you
will have to have the tanks professionally refilled as mentioned in the
letter. Basically once you run out
you're out of the game until you can repressurized the tanks. Also if something
happens and you develop a leak there goes the entire tank until the shop
reopens. The larger horns gulp air down
and a single compressed gas bottle with its regulator may or may not be able to
keep up. Mine quickly outpaced the shop
compressor, which puts out 6.3 SCFM at 90 psig. But it's a matter of how long you want to maintain the sound.

There are usage and transportation restrictions on
compressed gas bottles that need consideration. Further I don't like the idea of 2500 psig of energy tucked beneath or
behind me, especially in an accident scenario. I associate with a professional Firefighters and, provided a life is not
in danger, none are willing to approach a vehicle in trouble if it has
high-pressure gas on board. Also if you
decide on compressed gas and use anything but air then do not route any
pressurize lines inside the cab. A leak
could be fatal.

Along with Mr. Marks comments the upside of using compressed
bottles is a simpler installation as you do away with some hoses, compressor
mounting and wiring, pressure switches and such.

My suggestion? I'd go
with an onboard tank or tanks and a compressor. Why? As long as the atmosphere
exists and you have battery power you have an unlimited energy source for the
horn. Some setups can even run tools.

 This article focuses on a compressor setup. If you opt to use a compressed gas bottle and
don't require a tank then the discharge of the regulator will attach to the SOV
or manual valve.

 Here are my
tanks. You can just see the second at the far
end of the skid.

The
Compressor:

 If you're
not going the compressed bottle route then you have to put back in what you
take out. For an occasional horn blaster
like me the Viar compressor that came with the kits does fine. The horns can easily out run its low output,
which is why I installed two 6-gallon tanks. However sounded horns like these is impressive. You only have to do it once. Trust me you won't want to do it a lot. There are much higher SCFM compressors out
there made by manufactures such as Oasis. These things can operate air tools and could drive the horns directly
but probably not at their recommended pressure. Also plan to fork out $1000+ for one of these. If you don't plan to run tools off the truck
or have no need for such a beast the money can be better spent elsewhere. Like other modifications. The cost of the Viar? About $250.

 The intake for the compressor must be routed away from
water. Mine is piped into the cab to
take advantaged of dry air-conditioned air in Virginia's wet and humid weather.

 If you plan to install the compressor outside of the cab
ensure it is spray and drip tight.

 Here's are
pictures of the Viar. It is designed for
exterior use. Tubing protection was later added to the black equalizing line in
the photo on the right.

Pressure
switch:

 Unless you want to manually turn the compressor on and off
while staring at a gauge then you need one of these. In conjunction with a relay it cycles the
compressor to maintain proper tank pressure. 

 This part
is critical to safe operation of the system. The setpoint for the switch should not only be based on the horn's
operation pressure but also should complement the compressor's output. That is, the switch should not be rated
outside of the compressors range or safe operating pressure for the tanks. Mine cycles from 115 psig to 140.

 The brown
material on the leads is electrical liquid tape.

Note the
clear tubing protecting the gage line.

This is the
front of the forward tank.

 

Hoses:

 Get the
best quality you can buy. Buy new if
possible. These lines are exposed to weather and often run beneath the vehicle
subjecting them to various road hazards as well as vibration and rubbing. Ensure all are rated for the pressure.

The
Valve:

 You need a way to sound the horn. Train engineers use a manual valve. The most common goes by the name of Graham White but that is for the purist. A manual valve simplifies the installation,
provides a positive means to isolate the horn and allows variation of
tone. It also means you have to find a
way to run lines in and out of the vehicle as well finding a way to mount this
valve. They aren't small or cheap. The prices I have seen are 100 to $150 for
new or near new. I don't see why any
plumbing ball valve wouldn't work. It
won't be pretty but $5.00 vs. $150? Seems
an easy decision for me.

 I use a
fast acting SOV wired to a switch mounted on the cover below the steering wheel. The upside is a much easier time running
wires vice hoses, it's cheaper at about $40 for the SOV and the sound is
instantaneous. The down side is more
electrical connections, water entrainment from the tanks and that all such
valves have temperature limits. Mine is
a GC 12 SOV. I contacted the company and
they stated that although the valve is rated for freezing temperatures it could
flow liquid O2 but that not recommended. I operate hundreds of these style valves at work and although I can't
remember any failing due to temperature but it can happen. Having a valve supplying a horn stick open
would be ugly. It is recommended that
these valves be installed in the engine compartment for the heat.

 In Virginia
the winters are often mild so mine is installed beneath the bed on the frame
rail. 

 Extra
wiring allows moving the valve w/o bleeding
the system. The valve is angled to promote
drainage.

The
gauge:

< style="text-align: justify;"p> You need
to know what is going on so install a gauge. For convenience I ran a line inside the cab and have the gauge sitting
below the dash and above the transmission hump. Protect this line wherever it enters the truck from rubbing. If this thing ruptures I hope your seats are
vinyl because you will be cleaning them when you get back home.

Click here for part 2.

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