rocket sled?

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shim and ravski
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rocket sled?

Post by shim and ravski » Sun Mar 28, 2004 10:09 pm

hi our names are alex ravski and alex shim and we are new to this forum and completley new to vaveless pulsejets. we have some knowlege about spudguns and we also know how pulsejets work from our research.
i have a few general questions about these types of engines..do they provide enough power to pull one person on a skateboard?(we have a long board) and do all of the materials have to be stainless steel? is it neccessary? is aluminum acceptable? we both know how to weld, which is a relief because i have recently saw a thread that if you cannot weld you cant get very far on building an engine. is a blowdryer enough to power the engine? air compressor ? and lastly i have a propane torch and a bottle full of propane..will this be enough to power the engine? (it really does not matter how long out engine will run, just as long as it can run for a few minutes. please help us..sorry if we sound a little awkward
alex shim /alex ravski

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Post by Stephen H » Mon Mar 29, 2004 12:18 am

1) its a jet not a rocket
2) Jets push not pull
3)for LH valveless it will be HEAPS even to much for a skate board of any type.. look at http://www.aardvark.co.nz/pjet/lhkart.shtml
4) SS is prefered because it dosnt rust. normal steal works ok. Pjets get VERY hot and would melt aluminum so much faster then it it would be worth.
5)The air compressor or what ever you use is to start the jet, they keep going without forced air (if made properly)
6) these have the potential to go very fast, skate boards have a high COG. not a good mix! think about a go-kart or something more stable

Stephen

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Post by shim and ravski » Tue Mar 30, 2004 3:44 am

really?
i didnt think that valveless pulsejets had enough power to push the skateboard even 10 miles per hour
I looked at that go kart site but i dont plan on making that big of an engine. would a 100 centimeter engine in size be enough to power a go kart or a skateboard?
alex shim /alex ravski

Stephen H
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Post by Stephen H » Tue Mar 30, 2004 6:38 am

what kind are you thinking of ?.. i wouldnt sugest having a skate board just because of the high COG would be to dangerous. and you might find it hard to find a pulsejet 100cm long that will produce thrust. they need to be properly designed!

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Post by Raymond G » Tue Mar 30, 2004 6:43 am

shim and ravski,
Since I grew up probably not 10 miles from where you are now, I couldn't resist posting. I personally don't know much about Pulse Jets, but can give you another idea on how you can seriously injure yourself with your skateboards. Make a sail. You'll get going plenty fast to get all the road rash you could ever want. We used to wait for the Santana winds to blow us UPHILL so fast we would get speed wobbles, and would inevitably wipe. If sails don't cure your need for road rash, I suppose you will still have to try the PJ thing, but then you can also add burns to your road rash!

Regards,
Raymond

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Post by shim and ravski » Tue Mar 30, 2004 6:46 am

i am thinking of chinese valveless pulsejet, anything that will get that skateboard moving..what are the usual requirements for the pulsejet to produce enough thrust? do i have to make the nozzle small? and how many pounds of thrust are needed to push a skateboard with a person on it? are there any good plans of the chinese vavless pulsejet which will produce thrust? i will get the design as soon as i get enough information
alex shim /alex ravski

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Post by shim and ravski » Tue Mar 30, 2004 6:56 am

we really want to make pulse jets to power anything that rolls and our goal was to understand the concept of the pulse jet. please understand that we are not trying to be reckless and we dont want to hurt ourselves. if you want us to power a go kart for safety then no problem, but we were going to use a skateboard because even a medium sized pulsejet would not get us fast enough or even get a go kart moving. we also plan on using the el toro airfield, someplace like that, not in the middle of civilization.
alex shim /alex ravski

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Post by Raymond G » Tue Mar 30, 2004 7:07 am

I hope you don't think I was being condescending or anything. I was just being a little light, as I havn't seen the words 'Irvine' and 'skateboard' in the same place in a long time. It took me back 25 odd years. El Toro eh? When I lived down there the guards would have shot me if I tried to use their airstrip! Personally I would think that a gokart would be more interesting and safe. I've also seen pix of a guy put an afterburning turbojet on a scooter. Generally when you 'flight test' a propulsion system, you want the 'airframe' to be a non-issue so you can concentrate on learning the engine, not having to control the vehicle. Scooters and gokarts have handles where you can mount your throttle, and you don't have to worry about balancing a go-kart. Just my 2 cents.

Regards,
Raymond

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Post by Raymond G » Tue Mar 30, 2004 7:14 am

we were going to use a skateboard because even a medium sized pulsejet would not get us fast enough or even get a go kart moving
Just a little perspective. It only takes about 6 lbf of thrust to move a racing bicycle 30mph, and at that speed, is equivelant to about .5 HP . You may find that a small engine will get you going pretty fast. Just don't expect huge accelerations from the small engines.

Later,
Raymond

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Post by Mike Everman » Tue Mar 30, 2004 7:21 am

So lengthen the wheel base, or worry about the vehicle style in the fullness of time, when you have long since been consumed by getting the next motor running! ;-) Beleive me, if you make an engine worth pushing you around at any clip, you'll not want to straddle it, or be really close to it for very long, but I admire the desire. My suggestion is a valve type in this size. Check all the plans on the site, much easier to start and I'm told easier to be successful first time around.
Mike
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shim and ravski
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Post by shim and ravski » Tue Mar 30, 2004 7:22 am

thanks for the help raymond
el toro airbase is completly shut down and all it is, is just a large piece of land with no more blue angels :(
ok thanks for the info raymond...
i do have access to a turbocharger but i was not going to use it because it is too complex to build a jet engine..unless i have a plan of some sort..
i chose a pulsejet because it would be much easier to build
im not sure where to start
lol
alex shim /alex ravski

Raymond G
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Post by Raymond G » Tue Mar 30, 2004 7:32 am

And another thing........
I don't know how old you guys are so I really don't know how aware you are of your surrounding, but you are living on the edge of Aerospace Surplus Nerdvana! You asked about materials in an earlier post. In both Orange and LA counties, there are so many aerospace parts and metals support/surplus houses i couldn't even count! (Or at least there used to be) If you can find some 'scrap' stainless (or titatium or inconel :o) ) at one of these places, you should save a lot of money.

Regards,
Raymond

shim and ravski
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Post by shim and ravski » Tue Mar 30, 2004 7:41 am

thats a very good idea
fyi were are both 16 years old
yes, i often see parker and lockheed aerospace near where i live...i guess that makes us kinda lucky
anyways we have both started to design what i think looked like the chinese pulsejet but really is a locky-hiller engine without a u curve..what is that called?
ill post the plans soon
alex shim /alex ravski

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Post by shim and ravski » Tue Apr 06, 2004 6:00 am

we have finished our pulsejet plans.. please give us feedback and if we need any design changes
[/img]
Attachments
jet.jpg
jet.jpg (13.57 KiB) Viewed 11482 times
alex shim /alex ravski

Stephen H
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Post by Stephen H » Tue Apr 06, 2004 9:39 am

did you calculate that or just make them up?... a usual lockwood has 40% of thrust out of the end closest to the CC and 60% from the other end. if im wrong please tell me... but you would have 60% going foward and another 40% pushing it back... there for you are running at only 20% efficiance when on full throttel??

am i right there ?

Stephen

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