Flamethrowers using junkyard parts!

Dear group;
Recently, there has been some renewed interest in exhaust flamethrowers. I've searched around on the Net and the prices for a flamethrower kit are simply outrageous! By using a bit of ingenuity a person should be able to make pair of flamethrowers for under 20$ and a leisurely afternoon. If anyone is interested, reply to this topic and I will explain the procedure.
Your friend;
LAMAR

Oh, Please explain how you can accomplish this for under $20.00. I'd love to try.

Mr. Fabulous wrote:Oh, Please explain how you can accomplish this for under $20.00. I'd love to try.

Dear Mr. Fabulous;
It shall be as you wish my friend.

First, we will need to collect some stuff. For vehicles with dual exhausts, you will need two old, working coils. The type of coil is immaterial to the project as long as they function normally. A pair of old oil filled tower style coils work nicely and a person should be able to find them just about anywhere.

Next, you will need a pair of old spark plug wires about 18" to 3' long. If you are using the old low capacitive discharge coils then you must use solid copper core plug wires. If you've opted to use the more modern HEI or TFI style coils, then carbon wound wires must be used. Again, this should not pose a problem.

Next, you will need to scrounge up an old electric automobile horn that can be disassembled and reassembled and is also still functioning. The old GM style horns work great, and if memory serves correctly, the horn assembly consists of two halves that are held together around the periphery of the horn body with small screws. This style is the perfect horn to use.

Next, you will need a momentary ON switch of some sort. I prefer to use the spring loaded button style switch that is ON when pressed and OFF when released, but any style of switch can be used.

Next, you will need about 25' of 16 or 18 ga. wire to wire evertything up and some terminal hardware if you wish to have a neat and tidy installation, along with some electrical tape and zip ties.

OK! This is the complete parts list! Not too bad, is it? And now, on to the install!

First, take apart the horn and remove the diaphragm that is inside. The horn diaphragm is the thingy that moves back and forth at a million times a second and makes the sound. Remove all of this, leaving the contactor assembly inside of the horn, undisturbed. The contactor assembly consists of two contacts, one of these being bi-metal. When a current is applied to the bi-metal contact, this causes the bi-metal contact to vibrate at about a million times a second, contacting the other contact, which then permits an electrical current to proceed to the diaphragm coil. The coil is then energized, causing the iron core attached to the diaphragm to move suddenly outwards, then back inwards as the field is being energized and collapsed by the bi-metal contact. The rapid movement of the iron in and out of the coil's resulting magnetic field is what causes the horn to go BEEEEP!

Since we don't want the horn to go BEEEEEP, we therefore remove the diaphragm guts from the horn casing, leaving behind only the contactor assembly.

After gutting the horn, check to ensure the contactor is still functioning properly by rigging up a 12V stop light bulb in series with the horn. The horn assembly should have either one or other terminal contacts. If the horn has a single contact, it is grounded through the horn mounting stud. If it has two contacts then the horn is grounded via a ground wire.

Either way, with the horn case still apart, contact a 12V load, such as the stop light bulb, in series with the now gutted and forlorn looking horn. next, energize the horn by jumping a wire from the horn contact (if it's a two terminal style horn, then the + side of the horn is the bi-metal contact) to the + side of a fully charged 12V battery.

If the horn is a single contact design, the light bulb should illuminate and the contactor assembly should be buzzing merrily away. If the horn i a two terminal design and if the light bulb does not illuminate, reverse the terminal wires going to the battery. Again, the contactor inside of the horn should be buzzing like an angry bee.

If this is so, carefully reassemble the horn halves, then re-test the horn as above to ensure that you didn't screw something up whilst reassembling the horn halves.

This is no longer called a horn, rather it is now known as the *exciter* because it is going to excite an electrical field for us.

Putting our exciter aside for a moment, we now slither under the rear of the vehicle (if the exhausts exit beyond the rear bumper). We now mark a spot on the exhaust pipes 3" to 6" from the end of the exhaust pipes that will be convenient to drill a hole into. You shouldn't drill the hole at a 6 o'clock position in relation to the exhaust pipe, as this could cause the soon to be mounted spark plug to contact road debris. Instead, the hole should be drilled to where the spark plug will be up and out of the way of the undercarriage's slipstream, but not within 2" of the body or chassis. This is to ensure that the spark from the coil will reach the spark plug instead of being re-routed to the vehicle chassis or body. This is known as arcing and it needs to be avoided in order for the flamethrowers to function properly and also as a preventive measure to keep someone from inadvertently getting chit shocked out of them.

Start by drilling a hole in each exhaust pipe, using a 1/8" (or a #30) drill bit. Remember, 3" to 6" from the end of the exhaust pipe ONLY! If you install the spark plug too far away from the end of the exhaust pipe, there will not be enough oxygen from the atmosphere to ignite the unburned gases that are exiting the exhaust and if you drill the hole too close to the end of the exhaust pipe, the exhaust gases will not have enough time to ignite before reaching the end of the exhaust. About 4" from the end of the exhaust is usually pretty close to ideal.

After the pilot holes have been drilled into each exhaust pipe, step up the holes until the spark plugs can be threaded into the exhaust pipes until they are seated snugly. A uni-bit and cordless drill work great for this. Install the spark plugs into the holes and proceed to the next step.

For the next step, I will describe the wiring procedure starting from the power source and working backwards. THis is much easier to understand than by working from back to front.

Locate a switched 12V power source and tap into it with the 16 ga. wire. Terminate this wire to one pole of the momentary ON switch. Connect the remaining wire to the other end of the switch and route this towards the rear of the vehicle.

Once you've routed the wire to the vicinity of the exhaust pipe mounted spark plugs, STOP! Using a circuit light or voltmeter, check the install at this point to ensure that there are 12 volts running through the ON switch and out to the end of the routed wire. By doing this, you are saving yourself a lot of hassle later on, should something fail to work.

Next, you will need to mount each coil in close proximity to each of the 2 spark plugs. Wherever you decide to mount the coils, make sure that they will not come into contact with the rear axle, shocks, etc. Also, ensure that the spark plug wires will be long enough to extend from the spark plugs to the coils.

Once the coils have been mounted, it's now time to mount the exciter. I've always mounted the exciter inside of the vehicle, such as in the trunk compartment in order to keep the exciter out of the elements. The contacts are subject to corrosion, therefore the exciter needs to be mounted in a spot where rain and snow cannot enter the assembly.

Once the exciter has been mounted, it's now time to finish wiring the project. Take the wire which has been routed to the end of the vehicle and cut it at the exciter. Then, terminate the end of the wire from the ON switch to the + side of the exciter. Next, connect the remaining wire (that is running to the rear of the vehicle) to the - side of the exciter.

Next, connect the end of the wire that comes from the - side of the exciter to each of the two coils + terminals. Next, ground each coil to a good chassis or body ground by connecting a wire from the - side of the coils to the chassis or body.

And that's it! And this is how it works:

When a current is directed through the momentary ON switch, the exciter contacts become energized, thus opening and closing rapidly. This is turns causes the fields within the two coils to energize and then collapse rapidly. This in turn allows the coils to build extremely high voltages and every time the fields collapse within the coils, the resulting high voltage is routed from the coils high tension outputs, through the spark plug wires and into the spark plugs, thus causing a spark to jump across the electrodes of the plugs. The energizing/collapsing effect is so rapid that it should look as if the arcs from the spark plugs are continuous.

Rev up the engine and as soon as it return to idle, hit the momentary ON switch for some truly spectacular effects.
It's REALLY cool if you are at a drive-in such as Sonic and you can catch a car hop walking behind your ride. Hit the button when she gets really close to your ride and watch the food and drinks FLY! You said you wanted that burger to GO? Well, it's GONE!

Just be prudent about using flamethrowers. Even though I know of no law that specifically makes flamethrowers illegal, whenever a cop sees them being used on the street, they just HAVE to think of something to write you a ticket for.

Also, before installing your junkyard flamethrowers on your pride & joy, mock everything up on the work bench. You can do a 100% functional test of the entire system all at the same time, to include a 12V car battery, the exciter assembly, coils and spark plugs. Just be sure and ground the spark plugs to a good ground source and then you can test the entire system for functionability and reliability before you ever touch your ride.

And that's how we do it in the trailer park!

Good luck and have fun!
Your evil minded friend;
LAMAR

Lamar wrote:
Next, you will need to scrounge up

HaHa!

Good write up!

Dear Cratethis;
Thank you my friend. Honestly, most hot rodders should already have everything they need stashed in their garage or storage shed somewhere.

If someone doesn't wish to go the *horn* route, the same setup can be built, only substituting the horn exciter with the engine's own ignition system.

By tapping into the low tension lead between the distributor housing and the coil and then routing the resulting wire to one side of the momentary ON switch, this effectively replaces the exciter.

Because the exhaust mounted spark plugs will then fire 8 times (on an 8 cylinder engine) for every 360 rotation of the engine, the resulting sparks from the two exhaust mounted spark plugs is substantial.

Also, by tapping into the lead between the coil and distributor, no damage to the ignition system will result, as the amperage provided from the distributor is more than adequate to energize two additional coils.
Your friend;
LAMAR

Unless you have a 2 stroke, a V-8 only fires 4 cylinders every 360 degrees- but who cares, when you can put on a show like that!

Well done and thank you. Previously, the best description I could get about one of these rigs was 'it uses a spark plug to burn gas'. Much appreciated.

Dear Newbie Nate;
It's pleasure my friend! Also, if you have a manual choke, pull it out to fatten up (enrichen) the air/fuel mixture for about 2 seconds prior to hitting the switch. Leaving the choke out, hit the switch and enjoy. Instant flames! Just remember that the shock from those coils can be substantial, so be careful when wiring everything up.
Your friend;
LAMAR