Part 1 Part 2

9th May 2007

Nearly Finished!

She's all welded together now, and I've attached a spark plug. The general consesus is that it's not worth welding a bolt to the combustion chamber, but to instead weld the plug in place. The mild steel will expire long before the plug. I'm pretty happy with how ithe engine turned out, but there are several imperfections that I'm not so keen on. Firstly, the fitting of the various parts wasn't perfect, so some welded areas have to bridge a small gap, which made the internal weld somewhat rough. Secondly, again due to less than perfect fitting, there's a couple of degrees difference between the intake and exhaust tubes which irritates me!
I've already started work on a 'chinese' style focused wave engine of a slightly smaller size (though because it is linear, will be about 7.5 feet tall!). This engine I have ensured is millimeter perfect so far and is looking great, though not having a pinch roller at home means I've had to form the cones and tubes by hand. Not so hard with mild steel, but may be tricky when I come to use stainless.

Anyway, here are some pictures of the finished product. I'm going to build some basic mounts (it is essential to consider that the engine will expand as it gets hot, so requires mounts with movement) so I can give it a test run:

14th May 2007

Pop! bang! Kerbang!

First tests look fairly promising!
I bought some propane gas from the local garage (;£25 tank deposit + £25 gas fill), and with my trusty companions Joe and Pete, we gave the engine a quick whirl in his garden. At first the day seemed doomed to failure: the car battery I was hoping to borrow was flat, and the I had no confidence in the ignition circuit I had thrown together. Sparks seemed to be weak and somewhat irregular.
We first tried an alternate method of shoving lit rags into the combustion chamber before turning on the gas, but this was very unsuccessful. I was talking of packing up and trying again when I had a battery when Ivan volunteered his old car to provide charge to the starter circuit. It was very 'Heath Robinson', but we tried, and lo an behold, the old girl fired up a bit. Damn these things are loud. We hadn't had any luck for over an hour and weren't expecting my circuit to work, so that first bang you see was a real shocker!
As you can see from the video, we got a few raspy pops that really looked like the engine would eventually start. In hindsight, I started giving it way too much air towards the end of the test, hence the billowing flames out the exhaust. Best results seemed to be when holding the blower at a distance, and giving little blasts of air. I suppose these are the things you learn when testing! I've also learnt that it's goign to have to be held down a lot tighter next time; you can see it lurching forward, even after the big granite block was added to the weights holding it in place!

Overall, I'm happy with how it went, though seeing it sustain would have been ideal. I'm not so happy with the fuel rail still: the brass fittings clearly leak (needs PTFE tape, and the copper piping needs supporting), and the internal supports I believe restrict air flow too much. When I get some time, I'll redisgn the whole thing before the next test. I'm also going to give the next rail more holes and try to spread the fuel slightly better.
Finally, since Joe's mum stated that she nearly wet herself, I'm going to have to find some other place to test the engine. This is going to be tricky, as I don't want to be near to livestock, etc. Perhaps somewhere near the airport where people expect a lot of noise...



20th May 2007

Not so successful test

Well, I reegineered the fuelling system to something that I believe would be far less restrictive for air flow and would make forbetter mixinf og the gas with the air. We set the rig up, now with a properly built sliding test rail to allor for expansion, but unfortuately the ignition system really let us down. The spark provided is both weak an irregular. I belive the problem lies both with the coil that has drained all of it's oil when i over-polished it, and the car indicator flasher unit which I belive doesn't make the contact quick enough (when the switch if first flipped, there's a much stronger spark than the following sparks produced by the flasher unit). Unfortunately, I dropped my camera and thoroughly busted it, so I can't provide decent photos of the changes I have made. All I have right now is a video of the couple of times the ignition did actually work, thought he whole engine seemed to be filled with gas, so it's a pretty big pop. I'm going to pick up a decent relay from somewhere, and maybe build a proper electronic circuit that I believe will create a few sparks per second. I've read that a system using an electric drill and magneto from an old lawnmower or something can also be effective.
Here's the video:


27th May 2007

She runs!

Finally, I got the engine running today!! It was only a quick run as we upset Fab's neighbour and we soon ran out of gas, but I can say that she does run! We only cranked it up to maybe 50% power output, and I gave Joe the wrong hand gesture, so he shut it off instead of cranking up the power. We have a new bottle of gas, and I'm going to make some kind of rig to measure thrust in the near future. Enjoy the video:



28th May 2007

Monkeying around with the power

With the fuel rail in the perfect position, the engine starts and runs fantastically. Today we gave it several sustained successful runs which was great to see. I did screw up, however, by leaning blocks on the engine which dented the u-pipes when it was running and hot. This in turn led to a weak spot which failed when we flipped over the tank and ran the engine on liquid propane. I believe the fuelling needs to be heavily re-worked to be able to run from liquid fuel. I also need to replace the U-pipe, annoyingly. I may well reinforce the whole engine while I'm at it before I get into running it at max chat.
Enjoy the video:



11th june 2007

Upgrades and repairs

Luckily, I only needed to replace one of the elbows for the U-bend, which saved much welding. I ground it out and remounted it as neatly as possible, though there may be a slight angle difference since it all had to be mounted in situ. The other annoyance is that the MIG gas ran out just after I had finished the weld, so I'm not a little concerned that the weld might not be perfect. Time will tell!

I've put together a basic rig to try and control liquid fuel. As you saw in the fourth test, we were starting the engine on gas, then manually tuning the tank over to fuel it with liquid. If this is to be mounted to some vehicle, it needs to be able to be started from cold on liquid fuel.
As you'll see in the video, the gas low is split in two.On the left is a Wade valve, which allows for very precise control of the flow of gas, and the flow is very restricted, even when fully open. This valve will act as the idle setting. I'll need to basically open up the valve to a level that allows the engine to run whilst producing minimal thrust. On the right is a small ball valve that will be used to throttle the engine up and down. This valve provides less control, but can be opened and closed very quickly. I'm still awaiting a third valve that will be used as the engine shut-off.

I have some safety concerns with using liquid propane: people could be squirted with the liquid that would could imbed itself in clothing and burn, which would be nasty. Also, the pipes get very cold, so I don't want any cold burns coming from this. We'll have to be careful with the runing gear. I'm also not positive the gas fittings will be able to take the pressure of the tank, so this will be one to keep an eye on.

From the picture, you can see that I've wrapped the fuel line around the engine to pre-heat the fuel a little prior to it entering the engine. This will help it vaporise much easier, so will provide better running.
I have no photos as yet, but I have produced a very crude thrust-measuring rig that basically uses a skateboard and some spring scales to measure the thrust produced by the engine. If everything holds out, I'll hopefully be able to get some values and compare them to the theoretical 33Kg of thrust that the engine should be able to produce.
I also added a third center support mount as there was a slight sag at the other mounting point where the weight of the engine had distorted things a bit when the engine was hot. I'm adding some thin strips to act as heat sinks and strengtheners to hopefully make the engine last that bit longer!
Finally, I have attached a short video of the new ignition system that will hopefully make starting the engine that much easier. The circuit was kindly created for me, and works an absolute treat.





22nd December 2007

Full power ahead!

Further to the updates above, I made the neccessary repairs along with several new features, most notably being the thrust augmentor. This piece of kit adds aignificant thrust to the engine by drawing in cool air as the hot exhaust gasses flow through it. What would have been wasted heat increases the temperature of the fresh air which in turn expands and provides more thrust. There is a small weight gain for this luxury, and augmentors become a hinderance if the vehicle they are attached to travels at high speed as the extra thrust they produce is negated by the increased drag. This isn't an issue for this engine, however.
It looks like the valves work just fine, and it was fantastic to see the engine running at max power. Unfortunately, a section of cone imploded whilst we were running the engine at full power, which in turn damaged one of the elbows, so I will have to rebuild it and reinforce it all. This is one of the problems of using mild steel to create a pulsejet.
I'm really happy with the way this engine has turned out, so I'm begining to think about buying a sheet of stainless to produce an identical engine that will be tougher and long-lasting. For now, I think I'll repair this engine, and see where this takes me.



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