With the aim of reducing virus transmission due to gatherings during the pandemic, the Dutch government have banned fireworks. The people of the Netherlands like their noisy things so we’re told that the ban has been widely flouted, but [Build Comics] are a law-abiding group of workshop tool heroes. For their lockdown noise, they created an entirely-legal pulsejet. The interesting part is that it was made entirely using fairly basic tools on a minimalist budget, with TIG and MIG eschewed in favour of a mundane stick welder.
The form of the pulse jet will probably be familiar as it has been taken from other published designs. A long tube is bent back upon itself with a combustion chamber placed in one of its arms such that the jet forms a resonant chamber that produces continuous pulses of exhaust gas. This one is made from stainless steel tube, and the exhaustive documentation should be worth a look for anyone tempted to make their own. Welding thin sheet with a stick welder requires quite a bit of skill, and in a few places they manage to burn a hole or two. One requires a patch, but the time-honoured technique of running a bead around the edge manages to successfully close another.
Their first attempt to fire it up using a leaf blower with a 3D-printed adapter fails, but following the construction of a more resilient part and a more efficient gas injector the engine starts. It’s then taken out on a farm for some serious noise without too many angry neighbours, as you can see in the video below the break.
The hero tools of Build Comics have appeared here before, most recently with an analogue meter clock.
21 thoughts on “A 136 Euro Pulse Jet For Some No-Firework Lockdown Fun”
For the record, the reason for a fireworks ban was not the reduced transmission, but rather the alleviation of hospital workers. Typically, a new years eve results in a lot of firework accidents in the Netherlands. This year, that number was greatly reduced, giving the hospital workers that have been under high pressure due to the corona crisis a slight ‘break’.
Note, ~80 victims less than last year. Normally around 380/450 people get injured while celebrating the new year, small number compared to the 17 million living here. Biggest drop in numbers was around 2014/2015 with ~130 less victims.
Still, rather have them getting hurt by fireworks than having them get hurt by a pulse-jet gone wrong. Best is to never get hurt at all.
The simplest technique I have seen for making a pulse-jet was when Colin Furze hydroformed one. He cut two sheets of aluminium in the right shape, welded them round the edges, inserted a valve, and pumped water in from a pressure-washer. It worked.
Since it got glowing red hot it can’t be aluminum.
That said, hotwired (or with defective pressure regulator) pressure washers can produce INSANE amount of pressure, so I wouldn’t be surprised he made it out if 1 or 2mm metal sheets.
That one was made of stainless steel as well. It seems simple, but still required a TIG welder and creating the template I’m sure must have taken a dozen interations. But having said that, it was an awesome job to create a pulse jet this way. I sure wanna try hydro forming one day if I get the chance.
Violation of noise pollution regulations is a crime in most of EU countries. No wonder they covered their faces.
So let’s test fire it, and point it at the house!
Shows some balls.
That’s definitely not legal in the Netherlands. It far exceeds the dB limit.
How many dB does it go to if you actually want to make a lot of noise? (Think of the car audio competitions where the only objective is to get the most dB.)
Why is it not called a rocket engine?
Good question. I suspect that it is because people typically refer to jet engines that carry their own oxidizer supply as “rockets” and jet engines that obtain their oxidizer from the atmosphere as “jets”. There are other criteria, of course, but no need to dig into the fine details here.
I won’t comment on how useful this is or not, but i wonder how much chance you have that this thing will explode and make metall parts fly everwhere.
I wanna say you get higher peak pressures in your gas powered lawn mower.
Doesn’t look to be making much thrust.
It’s coupled to the ground… just last week, there was an announcement that the earth’s spin had sped up, coincidence?
Beat me to it ++
“and the exhaustive documentation should be worth a look for anyone tempted to make their own. ”
I see what you did there!
Coulda gone for… “exhaustive documentation should pump fuel into the fires of anyone impulsive enough to blow through a build…”
I don’t think there are nearly as many V1 RC-models in the world as there could be…
I remember when Lennox made a furnace that had one of these inside.
The fireworks ban is mostly just ignored by rude people who strive to be obnoxious to their neighbors, like this guy…. Wonder why we are talking about that ban 15 days after the new years though? unless the point being made was that we dont allow fireworks besides at certain dates?
Also this is very much grey area (in super short we are only allowed model rockets that are bought at stores, and thats about it, officially we have very few rules about building your own rocket/pulsejet engine, but most Dutch rocket forum users agree that you should not do this unless you want to (A) annoy somebody and then (B) get a visit from the cops) wich is why he blurred his face..
Long story short, in part due to the introduction in this article, this mostly comes across as a rather sad cry for attention thats long been surpassed by better youtubers, who live in area’s where they’re allowed to make actually trust-producing pulsejets.
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