Running Pulsejets - Setting up and running pulsejets SAFELY

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Eric
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Running Pulsejets - Setting up and running pulsejets SAFELY

Post by Eric » Mon Sep 08, 2008 2:26 am

Maybe this could be expanded on and set as a sticky thread. Lately I have had a lot of email questions about setting up and running the pulsejets safely, stemming from a lack of accessible information for those who do not have a copy of my pulsejet CD, and those who see other people doing things improperly and think its ok to do the same.

There is a lot of common sense things that most people know to do or not to do, but there are also a number of things that often go over looked.

Setting up your new engine:


Once you build or receive your shinny new pulsejet, there are a few things you can do to ensure that you will have a healthy life long pulsejet addiction .

If the engine is small it can usually be mounted with one mounting point, though it is a good idea to have a support bracket to support the tail pipe length so it does not sag from heat. You want the bracket to allow the tail to slide back and forth from thermal expansion.

Large engines typically need several support points. For a large U or J shape engine it is best to have a rigid mounting point that will hold the engine down, slightly past the combustion chamber section. At least one tail support bracket is needed, also its a good idea to have the bracket set up so that the tail can not move upwards as well as sagging down. With very large engines the thrust produced can cause the tail to rock up and down, keeping this from happening will prolong the engines life considerably.

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When making your engine you should set aside a portion of your budget for making the test stand. A good test stand makes your project look better as well as allowing you to safely run the engine and keeping the engine from damaging itself.

Radiant heat is another issue that you need to take into consideration. Mild steel will radiate much more heat than stainless steel. Using stainless will result in a more efficient engine, and one that wont cook you from several feet away. Either way you want to make sure to use a reflective metal shield to block any heat from objects that will burn or melt. Aluminum works great as a heat reflector, polished aluminum is able to reflect around 97% of radiant heat. Reflective shields are very important if you are putting a jet on a vehicle.

Starting Systems


There are a number of ways to start a pulsejet, including throwing sparklers into the combustion chamber. The main thing is you want the engine to start quickly and reliably. A spark plug and spark ignition source is the most effective way to start and run engines, its a little more expensive but it also works a lot better.

Model T ignition coils are superior to making an ignition system out of a car ignition coil and making a relay circuit. After all the parts, work, and replacement parts for a relay system, a model T ignition coil system is also usually much cheaper. The model T coils make a lot of sparks per second, and while shocks can be painful, they are probably not deadly. I've been shocked a dozen times or so, sometimes by accident, sometimes to demonstrate that bumping the spark plug wire wont kill you.

You have to figure that some way or another you are going to get shocked by your ignition source, either you forget to turn it off when the engine is running, or whatever. Its extremely important to never use ignition systems that would result in a lethal shock. NEVER USE NEON SIGN OR HIGH VOLTAGE TRANSFORMERS. Any high voltage appliance transformer will kill you dead, TV's, microwaves, neon lights, and quite a few others can instantly kill you if you get shocked.

Other things that work are small motor magnetos powered by electric drills, and torch / grill piezo electric ignition units.

Usually most engines need some kind of forced air provided to start the engine, this can come from air compressors, leaf blowers, or even hair dryers. The number one thing you want to look out for is if leaf blowers are required, their size and shape usually require you to be standing behind the engine, in an area where there will be large flames produced from starting. J shape engines give you a little more room to work, and better fuel injector design can allow you to start stubborn engines with smaller air sources.

The classical lockwood pulsejet is notorious for being stubborn to start, usually requiring leaf blowers to get them going. With an advanced infinijector style fuel injector almost any large engine can be started with a small blast of compressed air, or even set up to self start.

Safety Gear

The most immediate safety need when running pulsejets is hearing protection. Once you run the engine you will know exactly why you need hearing protection, if you think you are a baddass and can just walk around the engine and act tough without hearing protection, you will go deaf. Any close exposure will damage your hearing, the more exposure you get the worse your hearing will be.

Small engines you can typically get away with just ear plugs or high quality shooting ear muffs, though it is a good idea to wear both ear plugs and ear muffs. Ear muffs and plugs may not block certain frequencies effectively, and wearing both will ensure the highest level of protection. When running big engines its absolutely necessary. I wear ear plugs and Swiss artillery gunner ear muffs, you can get similar military surplus muffs for reasonable prices at a number of catalogs and websites.

Eye protection. Its always a good idea to protect your eyes no matter what you are doing, ESPECIALLY if you are going to be around running jet engines. Never go behind the engine without eye protection, little bits of metal, welding flux, and sparks can shoot out at 600+ mph. When you get hit with these little sparks and sand grain size bits, it stings, getting hit in the eye would be very very bad.

Leather gloves are also a good idea, when starting theres usually some big flames or flames coming out the intake that you want to protect your hands from, also if the engine is difficult to start you will want the protection from infra red while the engine warms up.

If you are going to be running engines for a long time, or really big engines, you might experience pulsejet sickness. Its basically your bodys reaction from being vibrated back and forth 100 or so times a second by the extremely intense sound. You can get dizzy, nausea, accelerated bowel movements....... and many other unpleasant effects, including extreme energy loss, and feeling like you need to sleep immediately. When you run engines for long periods of times or big engines, its best to just get as far away from them as you can, or be behind a wall to keep the sound energy from hitting you.

If you are going to have people watching the engine run, make sure they stay away from the engine, and never let people go behind the engine while its running.

It also would be a good idea to have some means of putting out a fire should you accidentally start one.

Running the engine



Once you have the engine set up in a proper test stand, with all the starting gear and safety gear, running the engine is pretty straight forward. This section wont tell you how to run the engine (there are plenty of those around) but will focus on things you should not do.

Never run pulsejets indoors. Some people might run them in the doorways of industrial buildings with fire proofing such as welding shops, but the engines should not be fully inside, or inside of normal building structures. The sound they produce, if not given a place to escape can build to such a level that glass objects can shatter, things fall off of shelves etc, along with the very very high fire hazard, and explosion hazard of having fuel vapor build up inside, not to mention any fumes produced from the exhaust.

Dont pour water on the engine to cool it down unless you have to in case of a fire, rapid cooling of the high temperature components puts a lot of stress on the metal and welds and can result in cracking. Engines can be run in the rain, though rain is not the same as instantly dumping a bucket of water on a red hot engine.

Dont run the engine with the tail pointing into the wind. If you have trouble starting it, any flames or fuel clouds will blow back towards you.

Keep in mind that a lot of engines dont like when things move behind them when they are running, and that they can be unstable at high throttle levels and spontaneously flame out.

Either walking behind or sticking something behind the engine could very well cause it to flame out, producing a big fireball in your face.

Be aware of any neighbors you might have and try not to point the engine at their houses, they dont usually like that..... In the absolute best case scenario they might "move to a nice quiet house in the city".

Jet powered Vehicles

If you plan to put the engine on a vehicle, there are a large number of other safety concerns.

1) The vehicle needs to be safe, it needs to be able to hold together at high speed, take any shocks from hitting bumps and turning, as well as being able to brake at high speeds. Jet bikes are fun but bikes are not made for going significantly faster than people can pedal downhill. Putting a 50-100 lb thrust engine on a bike is asking to have a very bad accident.

2) The engine should be mounted in a safe way, if you do have an accident you dont want to land or be sandwiched against glowing orange hot pieces of metal. Also special considerations need to be made to keep the engine from bouncing around when you hit bumps. Shock absorbers in the suspension and engine mounting system should be considered.

3) The engine should not be mounted off to the side of the vehicle. A number of people have asked about putting jets on the side of bikes because of a certain self proclaimed worlds leading pulsejet designer put a valved engine on the side of a bike and says that it doesnt affect the control. ANY imbalance of thrust relative to the center of the vehicles mass, and wheels, is going to result in control problems. If you notice in the videos he has to lean off to the side to keep the bike balanced, as you would expect from having 20 or so pounds of metal hanging off to the side of the bike, if you have to worry about leaning to the side while going 50+ mph on a bike, your ability to control it is not going to be anywhere near what an inline engine will allow. You not only would have to lean, but also correct for the force of the engine pushing you forward off axis, and if the engine suddenly stops, instantly correct your balance and steering. Honestly I am surprised it has not resulted in an accident already.

Hopefully this helps, I will try to get some more pictures hosted to insert and add more info to it now and then.

Eric
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Talking like a pirate does not qualify as experience, this should be common sense, as pirates have little real life experience in anything other than smelling bad, and contracting venereal diseases

zueg
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Re: Running Pulsejets - Setting up and running pulsejets SAFELY

Post by zueg » Mon Sep 08, 2008 2:45 am

Nice set of rules. Might want add something about the fuel system, making sure all connections are tight, fuel tank far enough
from the heat, and possibly an emergency shut-off valve. just a few things that popped into my head.
ZUEG K.I.S.S. Keep it simple stupid

Sebastian LFT
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Re: Running Pulsejets - Setting up and running pulsejets SAFELY

Post by Sebastian LFT » Mon Sep 08, 2008 5:30 am

"accelerated bowel movements....." The Myth Busters should 'o used a big 'ol pulse jet to work out their brown note myth.

Seriously though, good set of common sence safety rules. How about those internet junkies with a jam jar pulse jet, crude hybrid rocket motors, home made solid rocket motors, or whatever with fire right in front of their pc monitor next to a pile of papers upstairs in a bedroom in their pj (jamies)....... Makes one wonder :|
You'll never know 'till you try it.

Eric
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Re: Running Pulsejets - Setting up and running pulsejets SAFELY

Post by Eric » Mon Sep 07, 2009 11:43 pm

Finally managed to convert one of my valveless animations into a flash animation, gives a good view of the basic internal workings of a pulsejet.

http://www.beck-technologies.com/info.html
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Talking like a pirate does not qualify as experience, this should be common sense, as pirates have little real life experience in anything other than smelling bad, and contracting venereal diseases

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