IT WORKS

Only a week off schedule I had a go at running the pulsejet.
I wasn't particularly optimistic as people have said it's difficult to start in the first place and I was worrying that the fuel rod may not be able to deliver enough fuel fast enough.
However I was wrong.
It started ridiculously easily using compressor-different to the usual use of a leaf blower.

I was also worried the it would just melt out due to thickness of mild steel but fortunatly we didn't run it long enough to see that happen. It did start burning the wooden pallet and glowed red hot though.

My Dad was controlling the gas flow with the cylinder regulator from a distance whilst I started it (typical). The gas regulator acted as a throttle replacing the need for valves like other models I have seen use.

It was quite loud (although not as loud/deafening as I'd expected-ear protection wasn't really needed). It also shook the ground and I even saw a neighbour across the road open a window to find out what the noise was. This would've been made worse if we'd have run it up to full throttle-we only went up to about half in this run.

The steps from here that I would like to take are:
To test the thrust produced
Run it at full throttle and possibly at night to see it glowing red hot
Attatch to a go-cart for a laugh.

Make a 'turbocharger' jet engine or another pulsejet-possibly valved?

FINISHED WEDLING

Finished welding all of the pieces together and fitted the fuel rod. I also made a stand for it using some steel angle to avoid it scorching the ground-I was careful not to restrict the engine too much as Bruce Simpson mentions how one of his Pulse-jets crumpled because he had rigidly mounted it and not allowed for the thermal expansion of the metal.

Just need to connect the gas bottle and get some decent weather to test it in.

FUEL ROD BUILD

I drilled the holes in the fuel rod and welded the end up. I decided not to use the ball valve to regulate the gas flow as we can just use the gas cylinder regulator.

TACKED TOGETHER

I grinded a few parts of the straight seems down and re-welded them slightly better. I intended to get all the circumferences welded today completing the main body of the Pulsejet ready for filling the fuel rod to and setting up.
However, the weather was terrible.. I've said in my risk assessments that any substantial amounts of welding I intended to do should be done outside to minimise fire risk and improve ventilation. Wind also makes welding more difficult because it blows away the shield gas making the welds of worser quality. This meant I couldn't do much more than tack the pieces together. This has made me miss the deadline date set for completion of my artefact. However, I intend to get it finished next weekend and in evenings instead. This shouldn't postpone the project and EPQ by too much and I therefore believe this isn't a huge problem.

These are the pieces tacked together:

FUEL ROD DESIGN 2

I've sourced a piece of hydraulic tubing that would be better suited as a fuel rod having a smaller diameter and thickness therefore impeding the gas flow less.

Here is the original design and the updated one:

STRAIGHT SEAM WELDS

I got all of the straight seams welded today (still on schedule). There are a few strips where the welds could be better so I'm thinking about whether it's worth grinding them down and redoing.

From reading that the surface of the metal has a large effect on weld quality, I looked at different ways of cleaning the metal in preparation for welding:
Sand-paper

Brush

Disk Grinder

I chose to use disk grinder as it cleaned the metal quickly and well:

I also found that parts where the metal joint had a gap didn't weld as well as when they were butted up tight.

FINISHED CONES

Managed to get all the cone rolling done today today just about on schedule.


To cut the inside radius for the combustion chamber flare 2, it was difficult to cut such a tight radius neatly using an angle grinder so I tried cutting it out using a hole saw on the advice of my dad but this wouldn't cut through the metal so ended up cutting a rough radius slightly smaller than the desired one and I can just flatten the top of the cone once rolled with a belt sander or something to give the desired diameter.




On the longer pieces such as the combustion chamber and tailpipes which I had my worries about being able to roll into a cone, to twist the metal in the rollers to ensure a cone is rolled, we slackened the rollers, twisted them, re-tightened them, and then rolled a bit more.
A fair amount of brute force was needed to marry the edges up.

All of the pieces are now tacked in shape; they just need the seams welding up and then all welding together and it'll be ready for fitting the fuel rod to.

CONE TRIAL 2

I looked at the option of adding a bracket guide to the metal roller but there seemed nowhere to mount it so that idea needs more thought. The man in the video also tightens one side of the top roller more than the other to achieve a tighter radius at one end of the metal.
I tried rolling the intake tube-the convergence on this cone isn't very great and it's very close to a standard tube-This was fortunate because of the length of the metal, there was a large amount in contact with the rollers making it very hard to twist straight to form the cone in the rollers. This wasn't too much of a problem because the difference could be corrected using brute strength and tacking the cone closed before putting it in the roller again to neaten it out.
This has worried me for rolling the exhaust pieces though as they are the longest pieces and have a greater convergence so will be difficult to make into a cone.
 The guide idea may need revisiting to help with this.

   

This piece also married up well to the intake flare (first test piece) which is positive sign. 

CONE TRIAL

I cut out the intake flare from the mild steel using an angle grinder; this seemed to work well enough even though it has a relatively tight inside radius. I also tried with tin snips but found this distorted the metal too much and was hard work. To roll the metal I put it in the roller and whilst rolling had my dad to keep the metal perpendicular to the roller.

The cone's dimensions are close enough to the desired measurements to make it feasible. The cone is slightly off-round in parts but with the metal being thin this can be altered by hand and welded in place. This cone looks reasonable enough to use on the actual pulsejet so i'm going to keep it; if the preceding cones are a similar sort of quality then I can use this, if they are better I can re-make it. 

When it was almost fully rolled I welded the come up so the edges met up well and put it back in the roller to improve it's shape. 

   

Also, if any of the cones have a tighter radius to cut, I can cut it roughly and once the cone is rolled sand down the top horizontally. 

The whole 2 person rolling job seemed quite a task so I looked on YouTube for tutorials and found one person who uses a guide clamped to the roller to turn the metal; I'm going to try this on the next cone. 

FUEL ROD DESIGN

I've found some steel tubing in my dad's shed which I will be able to use for the fuel rod-This has a 16mm diameter and is 2mm thick.
I've decided i'm going to mount this at the end of the intake tube. This is for two reasons; the tube isn't stainless steel and taking Bruce Simpson's advice that this position is much cooler compared to nearer the combustion chamber-with this not being stainless steel this will help avoid it melting; and also as it will be easier to fit in this position-not working with a slanted face.
I'm going to drill 3mm holes along the tube.

I have also got a ball valve and gas tube adapter ready to build the fuel system and a gas cylinder regulator that allows the gas pressure leaving the cylinder to be increased from the standard 300 millibars to 4 bars; this flow will be necessary for proper functioning. I'm going to consult my dad about what fittings will be suitable and available for connecting this all together as his experience holds valuable information.

My worries at this stage is that the fuel rod being the size/thickness it is, it may impede the air flow in the intake sufficiently to prevent the Pulsejet from functioning properly. I'm going to have a look around to see if I can find something more suitable but if not will just try with the current fuel rod. The only way to find out if this has an effect is through testing. With the way I a planning on fitting the fuel rod though, it will be relatively easy to remove and replace with a different one if it causes a problem.

PAPER MOCKUP

I found when trying to print the templates that they were bigger than A3 which is the limit of my printer; I tried finding a way of tiling together A3 sheets to make a larger template but AutoCAD makes this very difficult to do. Instead I took the files to Staples in PDF form for them to print to scale on A1 for like £2 a sheet.
I thought that just to verify my templates and give me an idea of what sort of size the engine will be, I made a paper mock-up of the using the actual templates:

This confirms the templates fit together; I will need to do a test run on the actual sheet metal to ensure they still work including the thickness of the metal; if not I will need to remake some suitable templates and re-test them; this is shown on yellow on the schedule. 

SAFETY

From a safety point of view with me being 17 and this being a school project, I was advised by my supervisor to conduct a risk assessment. It basically outlines my dad supervising me throughout construction etc. and using the necessary PPE like welding masks, gloves ETC.

In terms of whilst actually running the Pulsejet, I'm going to have ear protection to hand as with the jet being an acoustic resonator, it can be very loud. I fire extinguisher will also be close to hand just in case.
Bruce Simpson has said that the engine actually has more chance imploding/crumpling more than exploding so a shield won't be needed. I will keep the area facing the exhaust clear in case any hot metal particles are spat out. I will also keep the control board for the fuel and the gas canister as far away from the engine as possible so once it is started everyone can retreat and control it from a 'safe' distance. If I feel extra precaution is needed I could possibly approach the science department in school and borrow a perspex shield I've seen used to protect students during experiments/demonstrations but I don't feel this will be necessary.

FUEL ROD

From looking at the dates I'm surrounding my schedule on, I have found that I have paid little attention to how I will make the fuel rod; due to the timings of when school closes for half term, if I want to use any of the schools resources (ie. pillar drill) I will need to have it made by the 13th of Feb; I need to decide this imminently.
From a quick look at what other people have done the fuel rod is basically metal pipe with holes drilled in to disperse the fuel-Bruce Simpson tells to use a steel tube with roughly 8mm diameter with 1.5-2mm holes drilled in along it facing the walls of the tube (1.12). He suggests two places to mount it: the end of the intake tube or the cone connecting the intake to the combustion chamber. Colin Furze uses this system; a 15mm diameter tube with 3mm holes punched in along which he mounts at the beginning of the combustion chamber.

SCHEDULE

Having been given a deadline to aim for to complete my artefact by (24th February), I have realised how pushed for time I am and see it fit to create the schedule I mentioned to try and aim for: an ambitious one at that.

Up until now I have had limited progress due to other commitments and a reluctance on my behalf to progress without a proper direction from school in fear of not fulfilling the EPQ requirements.
Looking at what days I can allocate to this project every week I have picked these dates to get certain parts finished by. I am assuming I can complete all the logging of the project and the paperwork in my spare time whilst at school and in the evenings; I won't plan for this time as I hope to just complete it as and when it needs doing.

This is the schedule I'm going to try and follow for February when basically the whole thing will have to be built. 

I am currently restricted to being able to weld on Sundays due to the time involved with setting up the welder/equipment, being supervised, the evenings going dark relatively early and working on Saturdays-this shouldn't be such an issue in the half term.

THEORY

Although I have decided not to pursue the true designing of my pulsejet, I have studied the relevant fluid dynamics and thermodynamics to further my own personal understanding and knowledge of how they function. This will also allow me to possibly verify the design I'm using against some of the simple mathematics and rules of thumb that have been developed.

The further reading I have undertook include 'Heat Engines' F.Metcalfe and various online information about the ideal gas law, Avagrado's hypothesis etc.

This will also hopefully be useful for the EPQ presentation to help me provide me a better basic scientific grounding of their functioning to explain.

Here's some compiled notes from The Enthusiasts Guide (1) showing how some of the dimensions are related and why they need to be:

WELDING PRACTICE 2

I've looked at some youtube welding tutorials and found how important the welder settings are so i'm going to have an experiment with different wire feeds.

After another welding practise, welding seems to already be adequate so I don't think there will be any issues there.

There and no beads that need grinding down like last time  to eliminate the thermal expansion problem and the inside of the weld has much better penetration so it stronger and smoother (roughness would create turbulence and reduce performance). They are good enough for the purpose of this.

Note to self:
Metal gets hot after welding so WEAR GLOVES-thumb is v. sore rn