why hasnt this been tried

[Zippiot]

disclaimer: this is all to the best of my knowledge and internet research

from what i have found, the top speed of most turbine rc jets is between 200 and 280. at 200 mph a ramjet can be started, i have a ramjet that is 7 inches long and 4 inches wide, it makes well over 8 pounds of thrust. and it weighs nothing, it can be shelled around a turbine to make the sr-71 type engine.

my question is, why cant i find a ramjet strapped to an rc jet? if anyone was serious about trying to break the speed record of an rc plane they would for sure use a ramjet mounted on a turbine craft.

here is a pic of my ram on startup, running off of bacon grease mixed with gasoline and nitromethane. the jet is running far too rich, but all i gotta do it turn down the fuel and it roars to life. and i mean roar, i have had the police at my house numerous times from the noise made.

[motorbikemike]

Ive seen a few over the years. I ve seen lots on u-line planes and there pretty darn fast. I think they just went by the way side due to the volume of noise they make.

[Hovertime]

May simply be too fast to control is space awailable...

[arrow5]

M/Bmike,I think you are talking about pulse-jets similar to the NZ guy. Ram-jets are different concept . they need speed (therefore fast air passing through ) before lighting up. Next one up is the scram-jet , it is supersonic. NASA or someone has had one up to Mach 6 or 8 in a small RPV.

[downunder]

Yes, ram jet and pulse jet are totally different. If you're running one at home it's a pulse jet unless you've got a 200+ mph weed blower up front :D

There was a helicopter that had small ram jets at the tip of the rotor blades to eliminate torque but it had to be spun up to high speed before the ram jets would light up. The engines in the F111 became a part ram jet but only after Mach 1.7 when the fuel supply to the core engine starts to get cut back.

Scram jets have worked twice so far. The first one was flown by a team of university students here in Australia and cost 2 million dollars. The second one was done by NASA a couple of years later and cost several billion dollars :D :D

[GregG]

If you are indeed speaking about pulse jets it has already been done. There is s flyer in Alaska that came to my home field a few months ago. He brought with him a video tape of his twin engined pulse jet powered RC plane. Pretty impressive, wish that I had a copy of that video.

[George99]

I seen a video of a jet with three pulse jet on top, it flew very fast and loud!! On second attemp the jet took fire.

[R/C Flier268]

Whats the diffrence between a scramjet, and a ramjet?

[trashmanf]

that's explained earlier in this thread, or google it.

george I would like to see THAT video!

[airmcn_3]

disclaimer: this is all to the best of my knowledge and internet research

from what i have found, the top speed of most turbine rc jets is between 200 and 280. at 200 mph a ramjet can be started, i have a ramjet that is 7 inches long and 4 inches wide, it makes well over 8 pounds of thrust. and it weighs nothing, it can be shelled around a turbine to make the sr-71 type engine.

my question is, why cant i find a ramjet strapped to an rc jet? if anyone was serious about trying to break the speed record of an rc plane they would for sure use a ramjet mounted on a turbine craft.

here is a pic of my ram on startup, running off of bacon grease mixed with gasoline and nitromethane. the jet is running far too rich, but all i gotta do it turn down the fuel and it roars to life. and i mean roar, i have had the police at my house numerous times from the noise made.

Go look at what they are doing over in Eourp. There are birds that break the 350mph mark. Just search for RC Jet Speed world records.

[CANNONBOY37]

M/Bmike,I think you are talking about pulse-jets similar to the NZ guy. Ram-jets are different concept . they need speed (therefore fast air passing through ) before lighting up. Next one up is the scram-jet , it is supersonic. NASA or someone has had one up to Mach 6 or 8 in a small RPV.

Well, no, actually. IF you pass compressed air from, oh say a compressor of some kind you can start those things on the ground. :D

[arrow5]

I stand corrected, you are right.

[SJ]

Theyn are too noisy, and therefor banned here in Denmark :-(

Besides...who needs to go faster than this simjet 2300 powered Jet :-)

http://www.youtube.com/watch?v=tErGXfwMI0I

One more vid of it:

http://www.youtube.com/watch?v=rT-DtoKyYS4

[ronmeister]

Hey that's the vid that jurgen heilig shot.

[HELModels]

At the end of the video, not the landing, there seemed to be a serious variation in speed. Is there a speed control on pulse jets?

[Andycap]

At the end of the video, not the landing, there seemed to be a serious variation in speed. Is there a speed control on pulse jets?

If your refering to the video above, thats a Turbine not a pulse jet. And as far a Pulse jets are concerned they are basically on or off.

[HowardSmith]

Whats the diffrence between a scramjet, and a ramjet?


SCramjet = Supersonic Combustion - the airflow remains supersonic through the engine.

[treehog]

Re: Zippiot

from what i have found, the top speed of most turbine rc jets is between 200 and 280. at 200 mph a ramjet can be started,....


naw the brazilians have a speed competion and one of thier delta things got 420mph in a dive with standard turbine way to go....

if your ram jet can add more speedyyyyy to that count me in

what details for your ram jet

Ralf

[Zippiot]

I am finishing my newest ramjet today. Its a design I'm playing around with and was kinda shottily put together, but if the deisgn proves itself I'll make an attempt at a flightmotor.

So far I have a jet that weighs 5.1 ounces and makes 8 pounds of thrust at 180 mph winds, 12 pounds at 200 mph winds! My new jet weighs more b/c its made of sheet steel I bought at the hardware store. If it works I'll make one out of 347 stainless (I think thats right) with many carbon fiber parts. This jet should kick out 10 pounds of thrust at 180.

But any flight wouldn't last long, these things eat about a liter every 45 seconds. The fuel efficiency improves with speed, around 400 mph they would only use 1/10th that for the same thrust.

[treehog]

For this type of project I would consider it best to make a delta jet that uses a propeler and glow motor to get airborne and and that would use not to much fuel as you climb high as possible

then enter a dive light up motor and realy get the speed going for a few seconds

Another posssible solution would be to tether the same delta on a round the pole system similar to U/Line or C/L but still RC for elevator and motor controls and when speed from glow motor gets to say 100mph light up the motor and go for it

The biggest problem will be to have a inflight light up system
possible make a small sugar candy rocket to burn up inside as a starter system
and hopefully the neighbours can handle the DB
what DB you expect???
or are you in stickville silcon valley

Alternitivly a ejectable cheapo sugar candy rocket launch system booster made from plastic pipes and sugar candy for fuel to try to get speeds up to 300mph from take off in a few seconds will mean the the RAM motor if it can then get you to 400mph plus will result in much longer flights but trying that combo on first flight without lots of previos flight testing is less likly to pan out so well

Hopefully your project works and you can put some plans for motor up on the net

Still monerting the thread

Ralf

[Zippiot]

I thought I posted a reply, oh well...

So pretty much at 200 mph this jet will consume 37 gallons of fuel per hour at 12 pounds of thust. Thats about .6 gallons per minute :)

Now at 400 mph its a very different story. It'll use about 20 gallons per hour for the same thrust. So 1/3 gallon a minute at 400 mph...fuel consumption continues to drop until mach 2.7ish

Now I seriosuly doubt my ability to control something going 200 mph, 400 is insane and anything beyond that I will end up in prison for the casualties it causes...

A rocket is a good idea but it'll take one huge motor to propel a delta to 200 mph, anything over 125 grams cant be transported without a big permit and FAA's permission.


These jets will weigh a fraction of their turbine counterparts, so this allows some freedom on a plan to get them up to speed. If I make one super-booster slingshot launchpad with a rocket assist...

A subsonic ramjet being the sole flight motor is starting to look like a handheld railgun. Maybe fitting one to a turbine craft to give some extra thrust, a properly designed ramjet could easily take a well designed model near mach but the problem of controling it

[Zippiot]

paper mock up of my next jet:

[Zippiot]

Scrapped, too big and heavy. Making a new, smaller one should be working next week. Pics of both soon...

[Balsa Bender]

Hi, I am glad to find somebody that seems to even know what these are. I have come accross a few vague references to ram jets, an i am now curios. What are they? What level of skill do they require? And how do you aquire them? (I have googled it and ebayed it, and yahoo'd it, etc. I can find nothing.)

[Zippiot]

They are super simple yet vastly complex :)

I am building this jet along with a few people from pulse-jets.com forums, we are having "the great ramjet challenge!!". The goal is to be the first person to make a subsonic ramjet with a power to weight ratio of 5:1

This is very hard, as at subsonic speeds ramjets can't get very much pressure gains in their diffusers. Basically, the air going in is slowed and expanded (bernoulli's principal). As the air enters it is slowed it expands, and contraty to common sense it actually GAINS pressure as it expands. Subsonically the pressure gain is very little, but ramjets have been flown at 200mph. So the air is expanded heated pressurized and slowed down, combustion speed is onyl a few meters per second. After the air has been sufficiently expanded it enters the combustion chamber [CC], where it meets the next essential part of the ramjet. The Flameholder slows the air even more and creates little turbulence pockets. The flame is sustained behind the flameholder (in a perfect world...) and shoots out the exhaust. Only a convergent nozzle is used in subsonic ramjets, no divergent section required as it actually decreases performance.
They can run any fuel, but the length of the CC should vary with desired fuel. Kerosine has a longer CC, propane a short one. I use gasoline as it is readily available, cheap and lights quite easily.

Also, as long as the basic principles are observed, they can be nearly any shape. I have seen cylinders, squares/rectangles, semi-circles and ovals all are known to work.

At subsonic speeds they are fuel dumps, more efficient than any rocket with an isp of (at the lowest) around 500. Above mach they increase exponentionally to mach 2.7 where they pass turbines in fuel efficiency. They lose all efficiency around mach 4ish...but no turbine can run near that. Some ramjets have been run above mach 6, but are highly protected secrets so little info on them is avaiable. Scramjets are ramejts where the air is combusted supersonically (SupersonicCombustionRAMJET=SCRAMJET).

Many different ways to "personalize" your supersonic ramjet have been proven, but subsonics dont seem to be positively effected enough by intake spikes or plug nozzles to make enough difference to counteract weight.

My final wish is to have a ramjet r/c plane...It WILL happen one day but there are many obstacles to conquer. Such as minimum speed...and me controllign one of the [possibly] fastest r/c jets of all when I struggle with my 40 mph flying wing!!! Maybe I'll strap it to a rocket instead, less likely to kill me and others around me if its going straight up right?

There are some videos of ramjets running on pulse-jets.com forums, none of mine yet but the videos are of proper ramjet operation. Little or no thrust was probably acheived, it is hard to find the correct ballance of size weight and power, our 200 mph airsources are leafblowers and vacume cleaners. Make a jet too big and it is starved for air, too small and combusting the fuel is tricky...its all trial and error at the moment as, like you said, little to no info on subsonic rams is available!


I am sure I got something wrong, there is always someone out there who knwos better please correct me if you are watching!!

[Zippiot]

If you want to do the most fun you will ever have with fire, visit this site and build the jet. It costs less than 20 dollars to make and the only power tool it requires is a blower of sorts (shop vac or leafblowers work fine!). I made one myself but mine was a bit different, It is sitting enxt to the computer right now but is all melted. Turns out a 50/50 mix of whitegas and bacon grease melts steel...

If you want to make one before getting parts contact me in this thread, I will help you save money by getting the correct parts depending on needs! It doesn't make any thrust, but IS LOUD ENOUGH FOR THE NEIGHBORS TO CALL THE POLICE!!!!!!!!!!!!!! It easily makes all background noise go away, the vacume stereo and circular saws could be on you wouldn' know!

I ran mine on liquid fuels and that proved to be easy and a cheap set-up, no propane conenctors or anything required just a waterbottle and some silicone tubing.

here is the link:

http://cottrillcyclodyne.com/Maggie_Muggs/Maggie.html

[Balsa Bender]

[QUOTE=Zippiot]

If you want to make one before getting parts contact me in this thread, I will help you save money by getting the correct parts depending on needs!

Okay, I am posting! if you can help me, this looks kinda cool. Are you using yours in a model? Is it safe to do so? if it is, I am a crazy sob, an I will do it!! Now I know what to do with my spare electronics!!

[Zippiot]

Calm down this ramjet doesn't make enough thrust to be used in a model...sorry bout that. It is a real working jet engine though, and from the experience learned in making this jet you could easily build one that makes useable thrust...well I shouldn't say easily.


First thing you want to do is find 2 Stainless steel cups, like those in the article. You can save a lot of pain if you get two with mouths about the same size, I actually heated one up and pounded it into the other. Together forever!! Dont get 2 of the same cups, one should be smoothe and gradual the other should have a shap curve in it near the mouth. Next you need a steel drain thing (forgot what its called...) with a bunch of holes in it, make sure its diameter is bigger than that of the cups. If you have a welder weld the strainer in place, if not wedge the crap outta it and hope it stays!

There is another type of jet that can be used in an r/c plane, its called a pulsejet. We are very close to getting a valveless pj to fly, but not yet. Check out this build log:
http://www.pulse-jets.com/phpbb2/viewtopic.php?t=3401
These jets are throttleable but are prettymuch on or off...somewhere in the 150-250mph range. A pulsejet can be built for about 5 dollars worth of steel but you need a welder. There are no weld pj's but they are heavy and lack performance.

[Balsa Bender]

cups and drain thingy, what about the other parts? the instructions don't really give a list, I will fo start building hi tommorrow, but I would prefer to make only one trip to ace. What about using it for, say, a rocket or a car?

[Zippiot]

It needs high speed air moving into it for ram operation to work, so a car wont work. A rocket might, if I get my jet working well I plan on sticking it on a rocket.

Another way to make them is from aerosol cans. They already have the intake part formed, all you need to do is think up a nozzle. They are also super lightweight. I made a 4 pound thrust ramjet from an aerosol can, but it only lasted about 10 minutes runtime before it melted away...These thigns get HOT if you dont have enough airflow around them to cool it off. An aerosol can would make a better jet than coffe cups, and is usually cheaper (everyone has an empty can of dust off somewhere) but they dont last as long. Find a drain strainer that fits and fit a nozzle and fuel line, you got a ramjet!

[Balsa Bender]

Zippiot, didn't notice your reply there, must have been editing when you submitted. Now let's get this straight. When it comes to jets, I am a hillbilly.lol.
But, I am now,as the icon suggests. sold on this idea. I will find some use for, whether it be amazing my best friend, or scaring away the neighbors pesky cat!

[Zippiot]

The cat will hate you for this...

They do amaze, loudest thing you have built easily!!!

You will need something of a blower for ground testing, a shop vac or leaf blower will do well.

Remember this:
As long as it sustains ram operation it is a ramjet!! Don't be depressed if it doesnt slide the brick you strapped it to (my 8 pound thrust jet tipped over a cinderblock!).

They require minimal tools to make, I think a hacksaw and a drill are about it for basic ramjets.

You can form a nozzle out of pressed ground kitty litter, but cement or rock hard water putty work too.

I recomend you find an aerosol can, any will do. Make sure its empty, once it is drill out a small hole in the top and cut off the bottom. A basic rule of thumb is the exhaust should be 1.4 times the size of the intake, so if you drill a 1/2 inch hole in the intake how big is the exhaust? All you need them is a flameholder and to squirt some gasoline in there and you are set.
A simple fuel injection is to use copper tubing, 1/4 inch works fine. Stick it in the jet and bend it facing the exhaust. Make it go a least 1 foot away from the ramjets shell (not the injection side) and stick some 1/4 inch silicone tubing over it. Stick the other end of the silicone tubing through the cap of a flexible water bottle and epoxy or glue it in place. You want to find a bottle you can crush the most with one hand, crystal geyser works fine.

Now you have a way of getting fuel to the jet, you have a nozzle intake and flameholder (find a way to stick a drain strainer right near the fuel injection), you have a jet!

Give it a little squirt of fuel and throw a match in there, it shoud make a little fire. This next part takes some finess but gets easier with practice. You need to turn on the airsource and squeeze the fuel bottle at the same time. If you shoot gasoline out the back and a huge orange flame follows it is running rich, move the air closer to the intake until a nice cone forms. You know its working when all you can hear is the roar of the jet!

I would recomend that the intake be about 1/2 the area of the combustion chamber. SO if you use a 2 inch accross can, drill a 1 inch hole. The exhaust should be 1.4 times the 1 inch, so form a 1.4 inch nozzle for the exhaust.


A dremel does a good job of widening a hole if you dont have a 1 inch bit...

And lastly, use some safety!!! I wouldnt say you need safety goggles, but wear clothing that protects you from the heat yet wont melt and stick to your skin. Wear a oven mit on the hand holding the air supply, or you will regret it!!!!!!! HOOOOOTTT

[Balsa Bender]

what about using a a fuel tank of glow fuel? that crap is VERY flammable!

[Zippiot]

That will work fine also. Even bacon grease works as a fuel as long as the jet is up to temp, be careful as the more energetic the fuel the faster it will degrade the steel.
I have seen these things dissolve from a 50/50 mix of white gas and bacon grease.

[Balsa Bender]

All right, the next time I post, it will be after I fire it up.

[Zippiot]

I finished the steel work on my newest jet, it is still made of crappy 22 gauge mild but if the dimensions prove themselves I'll invest in some 347 24gauge stainles...

This jet is much much smaller than the others, I hope it works!!!

I lost the flameholder, bet its in the garage I'll look more tomorrow it is 330 am here.

Its all duct taped together to make sure the fit is ture, still need to do 5 minute of grinding on the intake...

Well here are some dimensions:
intake is 1 inch entrance 2 inch exit at a 15 degree angle for 2 inches.
CC is 2 inch diameter for 3.5 inches
exhaust is 1.4 inch exit and 2 inch entrance, 1.5 inches long at a 10 degree angle

Now that the jet is much smaller I can nozzle the blower for better jet performance, this gauge steel should last indefinitely on gasoline but is heavy. 24 would need much airflow around it and 28 would be flight motor only as it will melt in less than 30 seconds.

I spent a lot of time forming the cones on this jet, that is why the whole things fits together so nicely :)
Sheet metal work is a B****!!!!!!!!!!!!!!

Should finish the fuel injection and welding by wed, I will make a pressurized fuel tank asap so the jet can be run hands free.

I am trying very basic stuff for this jet, no fancy nozzles spikes or plugs. There is another great jet (my biggest competition) here, check it out some great computer generated designs also.
http://www.pulse-jets.com/phpbb2/viewtopic.php?t=3764&postdays=0&postorder=asc&start=30

I will have pics of it pre and post welding tomorrow so you all can make fun of my inability to mig weld.

[Zippiot]

Got some pre-and psot initial weld pics:

[trashmanf]

looks good! haha got to love the duct tape - what temp is that good to??? :eek: :)

[Zippiot]

I just came into the possesion of a cross sectional picture of a messerschmitt engine from the 1960's. It is a combined ramjet/valveless pulsejet! Works as a pj at low speeds, so it produces thrust at 0 forward speed. Once it gets moving faster and faster, it pulses more and more until around 150mph it becomes totally a ramjet. It will continue to produce net-thrust until nearly mach 1.2!!!

If I can recreate this engine, that would salve all porblems of getting the craft up to speed. Problem is the picture leaves a lot to the imagination...much experimentation is to be done.

The engine is very long and requires a shell around it, so it will be possibly heavy...any plane it is strapped to should be long and have much lift as I fear getting the beast airborne isn't so easy; maybe a U-2 style plane would work.
I'll draw up a picture of it soon and show everyone.

[Zippiot]

Oh the duct tape should hold it until red heat :)

[Balsa Bender]

Well, I fired her upn under these conditions. I strapped seven (that's correct, seven) of the biggest rocket engines I could find to the sripped down frame of an rc car that had stopped workin. I then put the ramjet in the middle, and by some miracle me and 5 other guys got the rockets going at the same time. (I put the fuel tank I fashioned about where the reciever used to be, and he wheels were g;ued straight using some glue I got the home depot. GOOD STUFF!!) About half way through the burn of the rocket engines the ramjet got going good. THAT THING HAULED ASS!!!! :eek: that is until my mixture of glow fuel, lighter flued, oil, and grease went KABOOM!!! Unfortunately Iwas to impatient to get ahold of a camcorder, but take my word, the neighbors cat now runs when I approach!!!

[Zippiot]

Can you take a picture of the wreckage?

So it did roar to life, good stuff...next time take a video!

Oh, and be safe and all that stuff I am suppsoed to believe in

[Balsa Bender]

well, i will try. One of my friends only helped me on one condition. (we all somehow knew it was a doomed little contraption) That he got to keep the wreckage. He lives a few towns away, I most likely won't be able to get it til after Christmas, But I definately will post.

[Zippiot]

Got a little work done on the jet today, but everyone is visiting for the holidays and they distracted me (the bastards I need to work!!!) so very little was done today and yesterday... :/

I ground down my CC and intake welds to find I suck at welding but improve as the day goes on...
My intake welds were junk, need to be totally redone but my CC welds are near perfect!!

So tomorrow I weld in the flameholder, then weld the exhaust onto the CC. Soon to follow with my fuel lines and then finally the intake will be welded on to close the jet up. I expect this jet to make 3-7 pounds of thrust, most likely 3...
This is the smallest jet I ever made also, if it was a flight jet it would be made of much thinner metal but for ground testing my 22 gauge should do.

Made a paper mock up of my combined valvless pulsejet and ramjet combo!! I cant think of a name...it is long and has a pointy cone in the intake if someone wants to help me name it.
Hopefully it can both sustain ram and pulse, if it can make enough thrust to get airborne then it will only get more powerful as it increases speed. It comes built in with heat shielding, but I doubt its enough...how do they heat shield turbine models? Hey if it works well enough I'll sell it to the military for drone use!!

[Zippiot]

Fuel system is done and 80% of welding is done, just have to get the intake welded on and grind it down a bit (lets face it, my welding sucks) and the mini-ramjet is done!

Videos of it running soon along with the build up of my next jet, a ramjet that makes thrust at 0 forward speed!!

[infopimp]

naw the brazilians have a speed competion and one of thier delta things got 420mph in a dive with standard turbine way to go....

Quick question: How did they measure the speed?

[Zippiot]

Probably doppler, I know many laptops that can analyze how fast something is going [in a pass] from a stationary videocamera or microphone.

Gotta get me some of that!

[Zippiot]

All done, it could use some polish but it is good enough for me :)

gonna test it soon

[ThunderboltV12]

Or they might have been using one of those data recording systems with GPS.