The Great Ramjet Challenge!!!

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Zippiot
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The Great Ramjet Challenge!!!

Post by Zippiot » Tue Dec 12, 2006 3:55 am

These are the rules thus far:

Jet must have no moving parts.
Jet must sustain Ram operation (no pulsejets that cant sustain ram)
No size limits
No weight limits
No restriction on materials (nickel metal is stronger at 1500F than it is at 70F)
No restrictions of fuels
Any type of safe ignition, including oily rag up the tailpipe or a squirt of gas in the cc


Goal is first ramjet to create a thrust to weight ratio of 5:1 (subject to change if contestants ask so).
Post pictures and progress here along with in your own threads.
Thrust will be measured from the jet only, the blower cannot be attatched to the sled or other measuring device.
Try to post the airspeeds of your blowers, if you know them.

Did I miss anything?

Join in at any time, the more we have competing hopefully the more different types of jets that will appear.

Ask for help if you need it, dont worry I doubt we will steal your idea...
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Irvine.J
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re: The Great Ramjet Challenge!!!

Post by Irvine.J » Tue Dec 12, 2006 5:34 am

Lol this is a great idea and it will be lots of fun, I hope the cheat and Mr burquist will enter their jets also! A thrust to weight ratio of 5:1 will be hard (though hopefully not impossible) for me because my jet atm is about 2.5 kgs! Its a heavy sucker! hahaha. Anyway, this is a great idea, so I will enter the "Millenium Lance" and attempt to bribe you with excessive amounts of booze and chocolate! Hahahah. Should we say your allowed to have 1 entry, and everyone wins a prize... the prize being you don't catch on fire! Anyway we can work that all out as we go.
Goodluck everyone, this will be fun for sure.
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Zippiot
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re: The Great Ramjet Challenge!!!

Post by Zippiot » Tue Dec 12, 2006 5:42 am

Well since it is a first to the 5:1 contest, I'd say you can enter as many as you would like until you hit that mark!

There are so many different things you can put into your design.

Here are a few ideas for anyone on the fence about joining us:

intake cone or no intake cone?
delaval nozzle, plug nozzle or just exhaust cone? All 3?

Flameholders types: conical baffle, cheese grater, holes in a piece of metal, fingers, many design pics can be found on the ramjet page of the main site

So many combos can be put to use, that is what makes this a challenge. Since there is almost no info on subsonic ramjets it is hard to know if anything like a plug nozzle will work at all...guess and check!
Sailing Student- How do I know if my life jacket is tight enough?
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Sailing Student- Yes
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Zippiot
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re: The Great Ramjet Challenge!!!

Post by Zippiot » Tue Dec 12, 2006 9:39 am

Mock up of my first attempt:

I call it the Peregrine1, hope you like my paper molding skills.

Took so long to roll it out of paper...gonna suck to make it from metal...
Attachments
jet1.JPG
13 inches from intake to exhaust
jet1.JPG (27.21 KiB) Viewed 11606 times
jet2.JPG
closeup of convergent-divergent exhaust
jet2.JPG (20.76 KiB) Viewed 11605 times
jet3.JPG
down the exhaust looking at the 4 finger flameholder
jet3.JPG (30.15 KiB) Viewed 11607 times
jet4.JPG
takes up exactly 30% of the cross sectional area of the CC, hard to see pic though sorry.
jet4.JPG (10.58 KiB) Viewed 11606 times
jet5.JPG
cone coming out of the intake
jet5.JPG (25.54 KiB) Viewed 11608 times
jet6.JPG
the whole thing
jet6.JPG (23.58 KiB) Viewed 11613 times
jet7.JPG
disassembled minus flameholder
jet7.JPG (68.74 KiB) Viewed 11615 times
Sailing Student- How do I know if my life jacket is tight enough?
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Sailing Student- Yes
Me- Then its too loose!

Zippiot
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re: The Great Ramjet Challenge!!!

Post by Zippiot » Tue Dec 12, 2006 10:45 am

I stumbled around this site many times but never noticed the pics of the ramjet!

http://www.rocketresearch.org/ramjet.html

Claimed 7 pounds of thrust running at 160 mph. I think our blowers can top that, so it is possible to get good numbers. I once recorded 8 pounds but the jet quickly deformed and melted...no pics of the run or of the jet.

My blower is a 5hp vacume, puts out just over 200 mph. I actually have 2 vacumes, may one day build a wind tunnel with a high flow shop blower, a big reducer to bring it down to size and shoot some 200 mph straight down the middle just to make sure the airspeed is sufficient.
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Irvine.J
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re: The Great Ramjet Challenge!!!

Post by Irvine.J » Tue Dec 12, 2006 11:49 am

Entering the "Millenium Lance" !!!
Lol, zippiot that looks like a sweet jet mate, very nice n compact. Don't worry about rolling paper, I think its harder then rolling metal, seriously I had dramas rolling the paper too hehe. Get a nicko with a thick flat tip, put the paper on your sheetmetal, then trace around it with half the nicko on the paper and half on the metal... if you cut along the nicko line you'll have it to perfect shape. I had to do a bit of grinding as I wasn't quite used to the nibbler so I guess it figures though. My gas lines are installed for the first run tomorrow morning woohoo!
A note about my soda bulb quad line, It would be MUCH easier to drill 4 holes along its side then around it like I did as I've just figured out, my gas lines are all over the place, so i'll make another one later. As long as its under pressure it shouldn't matter that there are 4 inline.

My entry, the Millenium Lance.
Attachments
a.JPG
My entry.
a.JPG (36.42 KiB) Viewed 11590 times

thecheat
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re: The Great Ramjet Challenge!!!

Post by thecheat » Tue Dec 12, 2006 1:13 pm

I challenge thee! I'm working on my design at the moment.... but I hope to have something soon!

PS: I really like your jet James... It's pretty even without being red hot! However, I think you need to implement some proper carrying procedures... and stick a warning on it that says "sharp object, puncture wounds in jugular veins are known to be lethal in the state of California."
Lasers, jets, and helicopters HURAH!

larry cottrill
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Re: re: The Great Ramjet Challenge!!!

Post by larry cottrill » Tue Dec 12, 2006 1:35 pm

Zippiot wrote:Here are a few ideas for anyone on the fence about joining us:

intake cone or no intake cone?
delaval nozzle, plug nozzle or just exhaust cone? All 3?
Zip -

Forgiveness requested - I chuckled a bit when I saw this, because it sounds like no one could possibly know what will work and what won't. This is not the case. A deLaval nozzle (or an equivalent plugged nozzle) will only work as a deLaval nozzle if certain conditions are reached. Essentially, you need sufficient chamber pressure to achieve Mach speed (under the local gas condition) at the throat.

This is important, because a nozzle that you THINK is a deLaval nozzle works against you if the critical pressure is not achieved - that is, it will act as a venturi with low pressure in the throat, and the tail cone acting as a diffuser, slowing down the exhaust gases. Even on a deLaval nozzle that is fully pressurized, you can get into trouble if the tail cone is too long! The only meaningful use for the deLaval nozzle on jet motors is on engines that are meant to work at about sonic speeds.

As a rule of thumb, any engine that develops only moderate chamber pressures should use a conventional convergent nozzle. An engine with high chamber pressure will benefit from a deLaval nozzle. An engine with very high chamber pressure can use a straight pipe the diameter of the chamber (no "nozzle" at all)! And an engine with REALLY high pressure can use the deLaval tail cone alone, with no convergent "nozzle" leading into it !!!

It is a virtual certainty that with the limited blowers we have available, there will be nothing resembling "high" pressure in our combustion chambers. An exception might be something I have suggested before: A VERY small supersonic ramjet, driven by compressed air. It would be very hard to separate the engine thrust from the air drive thrust in such a beast, though, so results might be arguable at best. It would be fun to see a string of Mach diamonds out behind an amateur engine, though! Ha!

L Cottrill

thecheat
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re: The Great Ramjet Challenge!!!

Post by thecheat » Tue Dec 12, 2006 2:59 pm

Oh, I've come up with a design for my jet.... I'm adding a plug nozzle (I loved that aerospike rocket so much I had to incorperate that into my design!) The best part is: I've made it so I can adjust the "constriction" of the plug by moving it further into the jet or farther out. picture when I get a sketch up...
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jthompso
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re: The Great Ramjet Challenge!!!

Post by jthompso » Tue Dec 12, 2006 3:29 pm

Zip--you said there's no restriction on fuels but does that include solid fuel ramjets too?

thecheat
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re: The Great Ramjet Challenge!!!

Post by thecheat » Tue Dec 12, 2006 4:12 pm

don't think so... that'd be a rocket. :D
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heada
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re: The Great Ramjet Challenge!!!

Post by heada » Tue Dec 12, 2006 5:17 pm

Actually, there is such a thing as a solid fuel ramjet. The fuel is just that, a fuel. The oxidizer still comes from the compressed (rammed) air. Normally, we use gas fuel (propane) or liquid fuel (kerosene) but you can also use low oxidizer AP (ammonium perchlorate) AN (ammonium nitrate) KN (potassium nitrate) or even parafin wax.

http://www.missilesandfirecontrol.com/o ... 2_SFRJ.htm

Personally, I think it would be above most of our abilities, but still allowable.

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Zippiot
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re: The Great Ramjet Challenge!!!

Post by Zippiot » Tue Dec 12, 2006 5:43 pm

Solid fuels are allowed! But no rocket fuel, by solid fuels I mean tar, charcoal or a big wad of melted sugar (they actually work!).

Larry: thank you I would have for sure screwed myself with that one. I wanted to make a plug nozzle but lack the welding skills to have a smoothe finish and dont have access to a lathe to do it otherwise.

Might try to make a plug out of refractory, see if it'll last at all.

For solid fuel you can light it with a bit of rocket fuel, but the thrust generated by the rocket doesnt count (without a nozzle I doubt you would have gotten any thrust from the rocket parts).
Sailing Student- How do I know if my life jacket is tight enough?
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Sailing Student- Yes
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Zippiot
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re: The Great Ramjet Challenge!!!

Post by Zippiot » Tue Dec 12, 2006 8:48 pm

tip-jet helicopter.
Attachments
helicopter ramjet.JPG
(95.14 KiB) Downloaded 1476 times
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Eric
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re: The Great Ramjet Challenge!!!

Post by Eric » Wed Dec 13, 2006 5:49 pm

What do you mean by "self sustaining" ? That typically involves a dangerous high speed vehicle to put it on.

If you need a blower to get it running for thrust measurements, why not use a pulsejet since its basically a noisey blower?

Getting one to run well behind a pulsejet is 100 times harder than with a blower.

If it were allowed I would have one to enter :)

Eric
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Talking like a pirate does not qualify as experience, this should be common sense, as pirates have little real life experience in anything other than smelling bad, and contracting venereal diseases

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