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Pulse Jet Go-kart
An Anonymous Coward writes: "For those who liked the jet-engine beer cooler, here's another back-yard inventor from New Zealand who likes playing around with jets - he's not looking at the more common turbojet, but instead seeing how he can improve the long-neglected pulse-jet engine. For some background, see his homepage or just look at the go-kart he built to try out his jet." Pulse jets are an inefficient design that has been entirely superceded by other engines - but wow.
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I think there is a world market for maybe five personal web logs.
Now that would be a go-cart worthy of a GLH designation. GOES LIKE HELL!
More like GBH - Grievous Bodily Harm
Since this is propane powered, he should mount a BBQ grill onboard and do "shrimp on the barbie" as he howls along.....At $3 per minute he needs a sponsor, maybe Food Network would sponsor him. He could start his own TV show, Jet Chef...
It's quite similar to the tale of the Rocket Car.
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PaxTech
All movements for social change begin as missions, evolve into businesses, and end up as rackets.
And apparently you arn't an engineer either, using 'thin' as a synonym for 'small cross section,' a technical misuse of the language that an engineer would never make. When an engineer uses the word thin in reference to tubing he is refering to its wall thickness.
Assuming of course that he is using tubing. For all you know they could be solid bars. Of course as someone who has worked as an automotive engineer and custom builder of bicycle frames, racing suspension components and. . . yes, karts, I know that would be silly.
Givin the nature of his project and his obvious penchant for using common and inexpensive materials where such are appropriate it appears he has used common 1" mild steel square tubing such as can be obtained at any home improvement store.
If you were versed in such matters you would know that square tubing is more rigid in bending than round tubing at that 1" square has about the same bending stiffness as the 1 1/4" round tubing used in the best full bore 100 mph plus racing karts. Indeed, 1" tubing is allowed by the rules and considered quite acceptable for such racing karts, even when using the round stuff.
As it happens I have a stack of 4' lengths of it right here, as it is my prefered material for quick and dirty prototyping. I defy you to bend even a 4' length of it across your knee. In fact you probably couldn't bend it by resting each end on a bit of 4x4 and jumping on it. Oh, it'll flex, but it won't bend. Cut it in half and it won't even flex. He used two tubes, the mechanical equivalent of cutting to half the length. I've built a street luge out of single SIX foot length of such tubing. It hasn't " bent across my knee" or anything.
To give an example that most people might be able to relate to a bit more the top tube of a cheap Huffy bicycle, such as you can by at K-Mart for under $100 American, is made of 1" diameter mild steel ROUND tubing, ( remember, round is easier to 'bend across your knee'), exactly like the kind you can buy at the home improvement store. I don't think are many out there can imagine bending it across their knee. Indeed I use just such a top tube sawn from a discarded frame as a "cheater bar" when I need to exert hundreds of pounds of leverage an a short handled wrench. I've never noticed it flex AT ALL when used as such.
You might be surprised to learn that the frame of the Lotus 8 racing sports car was made from only 21 pounds of 1" diameter * 18 and twenty gauge*, ( thiner than what you get at the home improvement store, much), round mild steel tubing. The car is still in service over 40 years after its construction, the first several of which it spent in serious competitiion.
By the way, your street car is constructed of 18 gauge mild steel sheet, which you CAN easily fold across your knee.
The brake he constructed is admitedly crude, but basically the same as that used on the early racing karts, and essentially the same as that still used on "fun Karts" such as you can buy at Sears today. Quite acceptable for his purpose and in no way indicative of a future as a Darwin Award winner. Easily as effective as a bicyle brake, quite possibly more so, and certainly as effective as that used to stop street luges weighing nearly the same going 80 miles per hour. Those brakes are called " Keds."
As for the likelyhood of the frame supporting the jet engine bending I would like you to perform a little experiment. Take a child's tricycle, ( which is likely made from 1" diameter * electrical conduit*, no, I am NOT making that up, it is actually electrical conduit, and I defy you to bend the tricycle across your knee), and apply 30 lbs of force to it.
Does it bend? Does the seat post, made of even smaller diameter tubing of even more dubious lineage, bend?
No.
Ok, apply 100 lbs of force to it.
Gee, still not bent even though we have applied the maximum amount of thrust his most powerful engine produces.
How about *1000* lbs of force? 10,000 lbs? A million? An *irresistable force?*
Why won't the damn thing bend no matter HOW hard you push on it? Because it isn't an immovable object. It has * wheels.*
The harder you push, the FASTER it goes as the energy of the push is converted into the kinetic energy of the tricycle. The actual force felt by tube pushed upon is actually quite small. This is the same fact of physics that lets a man pull a 10,000 lb box car with his teeth, or for you to apply a 100 lb force to the 18 gauge sheet steel making up the trunk of your car without it "folding across your knee."
The frame itself is constructed from a handcart, itself constructed from 1" ROUND, (easier to bend across your knee than square), mild steel tubing. Hey, go bend a handcart across your knee.
Now we know, because * we actually read the article* that the thrust produced by the engine was either 30 or 100 lbs. This happens to be in the range of force producable by a 5'2" 100 lb woman of indifferent athletic ablility. This means that if he were worried that he might run into an immovable object while the engine was running and the the frame might then fold over on him he could take the simple empirical step of placing the front wheels against his garage wall and * pushing on it.* You can simulate this experiment yourself by taking a handcart putting the load bed under something immoveable and pushing on it. Gee, you're looking a little blue around the gills now and the handcart hasn't bent at all. In fact the sheet steel of the load bed will bend before the tubing of the handle will and I defy you to bend even THAT across your knee.
Look, I'm not averse to smartass comments, as this post itself is ample evidence, and I'm sorry if this post is a bit derisive, but you set the tone by deriding a man, who is clearly an excentric, as most of us geeks here are, ( by the way, computer or software " engineer" =! engineer), but just as clearly has a pretty good idea of what he's doing and the accepted practices of empirical engineering for accomplishing it. Your smartass comment only served to show that it is you that is =! engineer.
No one likes a Cliff Clavin.
KFG
I don't work in the aviation industry, but at least I read his site. He knows full well that pulse jets in many ways can't compete with turbine jets. He's researching pulse jets because everyone else dropped them in the 1950's and he thinks there's still interesting work to be done with them.
If you read his full site, you'll note that he's also built turbine jets and attached them to the go-kart as well. He even re-engineered the casing of the turbocharger his turbine jet was made from so that it could drive a gearshaft and drive the kart directly instead of via thrust. Just as you describe, except that he built the thrust shaft himself.
But he's really working on pulse jets, and has already made big advances on them. Pulse jets normally require very long tubes; he's cut the minimum length in half. He's designed a new type of valve that lasts much longer than previous pulsejet valves... etc. The list goes on. His work has even won him some large research grants and corporate sponsorship, fairly impressive for a backyard engineer.
Yes, I'm sure you could build a more powerful go-kart than his, but that's not what his work's about.
I stole this sig from someone cleverer than me.
I work in the aviation industry, and I can think of a better type of Jet engine to use.
Just from memory, the Allison 250 comes to mind. It is small enough to fit behind the seat of a go-cart, prolific enough to find used parts and engines cheap enough. It's also used in helicopters, so all you would have to do is hook up some time of gearing system to the rear axle, since it already has a power output shaft. Not to mention one or two people could easily lift it and move it about. I think it weighs around a hundred pounds or so. And it generates over 400 shaft horsepower!
Now that would be a go-cart worthy of a GLH designation. GOES LIKE HELL!
I always thought that the Star Trek Enterprise would have a similar problem.
-vax computer, vi, lynx. 'nuf said
Since when do sheep run that fast that New Zealand men need jet powered go-karts?
Hmm... This has all the makings of another Darwin Award winner ;^)
Cat-girls are the driving force behind my VR research.
GeekNights!
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I highly recommend checking out some of the homebrew jet websites these guys have. Its wild to see the different approaches they take to reach the goal of self-sufficiency. One guy used plain old cast iron pipe you could buy at Home Depot and got it working. Another is working on an engine that uses a turbocharger from an M-60 tank! He's also got one that has an afterburner on it with some REALLY cool pictures.
This is quite the hobby. On guy built a really sweet engine that used a PLC to help start the engine which is a multi step process. His worked so well he sometimes had trouble keeping his cart braked. Interesting to see how folks also try various fuels from K-1 to LP gas to Diesel.
I honestly was blown away by the time and effort folks put into one of these just to have it run - but it really was a blast browsing all these sites all day - careful!! You might get hooked! :) Geeks with jet engines is a scary prospect!
Top Most Bizarre/Disturbing Error Messages
Anyone seen that show "Jackass" on MTV? Sounds like an accident waiting to happen.
"You'll shoot you're eye out!"
The guy sells them in kit form. But since there is only one moving part I imagine the kits are pretty easy to assemble. They range in price from $120 to $390, depending on thrust. He also sells them assembled for slightly higher prices.
Scroll to the bottom of this page for more info.
--MM
By including this sig, the copyright holders of this work or collection unreservedly place it in the public domain.
It's been far too long since a new gadget was added to shoes. In the halcyon days of footwear (that was the early and mid '80s for you youngins) we had a radically new pedal contraption every couple of weeks! Shoes with no laces?! That's a loafer! Shox? We've had spring loaded tennies for like a decade.
No. What we need is power.
I want to be the first kid on my block with pulse jet game!
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