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Author Topic: Pulse Jet Stunt design  (Read 6401 times)

Offline Bud Morrison

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Pulse Jet Stunt design
« on: May 30, 2014, 09:45:36 AM »
Thread continuation from the speed forum thread http://stunthanger.com/smf/index.php?topic=35335.0


Offline John Cralley

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Re: Pulse Jet Stunt design
« Reply #1 on: May 30, 2014, 10:07:55 AM »
Email Kaz Minato (a member of Stunt Hanger) and ask what model he was using for the YouTube that he posted.

Google pulse jet stunter #1 to see it fly.

Also Dan Banjock has pulse jet stunter.
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Online mike londke

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Re: Pulse Jet Stunt design
« Reply #2 on: May 30, 2014, 10:48:33 AM »
From Bud- Actually my bladder plans I am using were from Bruce.                                                                                                                                                                                                                                                                                                                                                                                                                                                    Bud I think that Bruce's bladder system in the bottle will be too bulky for a CL ship.  I am going to build a profile plane with a large foam wing with the bladder tube right down the CG. I am using Phil Cartier's yellow jacket bladder material. It is much smaller than what Bruce uses and can be buried in the wing inside a light bulb tube.  I have run this bladder tubing with the cline valve on my Dynajet several times and it has more than enough pressure to keep the engine running. As I said in the other thread, the cline valve on a bladder is the only way to go for a pulsejet stunter. There is no change in tank pressure no matter what the attitude is. It eliminates so many problems that come with a metal tank. I will post some pics later.  Mike
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Offline Bud Morrison

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Re: Pulse Jet Stunt design
« Reply #3 on: May 30, 2014, 11:14:41 AM »
Email Kaz Minato (a member of Stunt Hanger) and ask what model he was using for the YouTube that he posted.

Google pulse jet stunter #1 to see it fly.

Also Dan Banjock has pulse jet stunter.

Dan and I have discussed this. I am the one who posted the last video of his pulse jet stunter on youtube.
Thanks for the Minato tip.
« Last Edit: May 30, 2014, 11:34:04 AM by Bud Morrison »

Offline Bud Morrison

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Re: Pulse Jet Stunt design
« Reply #4 on: May 30, 2014, 11:30:34 AM »
From Bud- Actually my bladder plans I am using were from Bruce.                                                                                                                                                                                                                                                                                                                                                                                                                                                    Bud I think that Bruce's bladder system in the bottle will be too bulky for a CL ship.  I am going to build a profile plane with a large foam wing with the bladder tube right down the CG. I am using Phil Cartier's yellow jacket bladder material. It is much smaller than what Bruce uses and can be buried in the wing inside a light bulb tube.  I have run this bladder tubing with the cline valve on my Dynajet several times and it has more than enough pressure to keep the engine running. As I said in the other thread, the cline valve on a bladder is the only way to go for a pulsejet stunter. There is no change in tank pressure no matter what the attitude is. It eliminates so many problems that come with a metal tank. I will post some pics later.  Mike

Well barring an electric pump the bladder is the way to go. The turbine guys run electric pumps for the most part. I have looked into that and the weight isn't actually bad. But the cost is another subject. An electric pump setup with a header tank would prolly work well but man its like $300.00. But I have not ruled it out. As far as room that would all be relative to the design of your plane. A strait wing on a jet looking front fuse with a twin boom tail and tricycle gear I'm thinking is going to be my aim at this point. Either way I want the engine on top the plane. And its not going to be a small plane so fuel tank room I don't think will be an issue. I was thinking around 1000sq" of wing area.
I've also thought about converting Bruces shockwave to control line. But don't think it would turn sharp enough :) Then there's the whole bellcrank and leadout issues http://www.btemodels.com/shockwave.html

Offline Bud Morrison

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Re: Pulse Jet Stunt design
« Reply #5 on: May 30, 2014, 11:36:18 AM »
One more design requirement. The design must fly long enough to complete the entire stunt pattern :)

Offline Bud Morrison

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Re: Pulse Jet Stunt design
« Reply #6 on: May 30, 2014, 03:17:15 PM »
After more discussion with Bruce while ordering a cline from him I will be getting Shockwave plans with the rib set from the Delta vortex and looking at converting it to control line.   Not sure if I will convert it but if i dont I can always build the RC one :)

Offline Brett Buck

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Re: Pulse Jet Stunt design
« Reply #7 on: May 30, 2014, 06:00:58 PM »
One more design requirement. The design must fly long enough to complete the entire stunt pattern :)

   Prepare to carry A LOT of fuel. I think Danny's plane (in the Kaz video linked above) is around 12 oz, and it's not nearly enough. You need to figure out how to deal with or mitigate the massive CG shift that would be possible.


   Brett

Offline Bud Morrison

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Re: Pulse Jet Stunt design
« Reply #8 on: May 30, 2014, 08:54:54 PM »
   Prepare to carry A LOT of fuel. I think Danny's plane (in the Kaz video linked above) is around 12 oz, and it's not nearly enough. You need to figure out how to deal with or mitigate the massive CG shift that would be possible.


   Brett

Need to put tank on CG

Online mike londke

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Re: Pulse Jet Stunt design
« Reply #9 on: May 30, 2014, 10:06:59 PM »
   Prepare to carry A LOT of fuel. I think Danny's plane (in the Kaz video linked above) is around 12 oz, and it's not nearly enough. You need to figure out how to deal with or mitigate the massive CG shift that would be possible.


   Brett
Brett, I talked to Dan at Huntersville last year and he is actually carrying something like 28ozs of fuel on the nose. CG shift must be big. With the bladder tube running down the length of the wing I can easily put 60ozs or more of fuel in the bladder. This should be more than enough for a 5 min flight. And there would be little to no shift in the CG. On 80/20 methanol and nitro, the fuel rate is 10 or 11ozs a minute. I think Bud is right though on wing area, bigger is better with this propulsion system. It does not need to be fast, just loud and fun. Mike
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Offline Bud Morrison

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Re: Pulse Jet Stunt design
« Reply #10 on: May 30, 2014, 10:49:26 PM »
We figured 36 oz should do the whole stunt pattern if I use a mix similar to what Dan is presently running.

Offline Bud Morrison

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Re: Pulse Jet Stunt design
« Reply #11 on: May 31, 2014, 04:03:14 PM »
This morning I ran across this picture. Sort of the direction I was thinking. Except with around 800sq wing
http://www.rogue-eagles.org/PhotoGallery/VRCS2012/BruceTharpePulseJet-800.jpg
« Last Edit: May 31, 2014, 04:26:29 PM by Bud Morrison »

Offline Dennis Toth

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Re: Pulse Jet Stunt design
« Reply #12 on: May 31, 2014, 08:58:56 PM »
What do you think the thrust to weight ratio needs to be to for a success jet design?

It indicates that they are running methanol and nitro, it seems that running gasoline would greatly reduce the fuel use and still get about 5 lbs of thrust from a Dynajet. Is that enough?

Best,          DennisT

Online mike londke

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Re: Pulse Jet Stunt design
« Reply #13 on: June 01, 2014, 08:52:23 AM »
What do you think the thrust to weight ratio needs to be to for a success jet design?

It indicates that they are running methanol and nitro, it seems that running gasoline would greatly reduce the fuel use and still get about 5 lbs of thrust from a Dynajet. Is that enough?

Best,          DennisT
Dennis, Gasoline would give a much longer run but you cannot use it in a bladder with a cline valve. It will destroy them. The reason for using a bladder and cline valve was to get away from having put in a large metal tank. Bladders will give a more reliable run if you want to stunt.  Mike
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Offline Dennis Toth

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Re: Pulse Jet Stunt design
« Reply #14 on: June 01, 2014, 09:36:40 AM »
Seems you could use a polyethylene bag and either springs or shock cord around two plates to give you pressure (Jim Walker pressure system style) with a regulator. Other fuel mixtures are possible check this web site:  http://www.pulse-jets.com/phpbb3/viewforum.php?f=16&sid=e9d93637030890082527950dac32d5ed they have some great videos also.

Still wondering about thrust to weight for stunt. I assume that some cut and try is needed to get a ship with the right amount of drag to get a reasonable lap time. There was a ship that the Martin Dynajet company offered as a kit for the Dynajet called the Martin Thunderhawk. It was offered around 1948 - 49. I saw one at the 1998 Nats, one of the speed guys had it but I never got to talk to him. Would love to get plans if someone has them.

OS use to have a smaller jet that had 2 ish lbs of thrust, maybe that would be a better size for stunt?

Best,          DennisT

Offline Brett Buck

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Re: Pulse Jet Stunt design
« Reply #15 on: June 01, 2014, 09:55:44 AM »
Still wondering about thrust to weight for stunt. I assume that some cut and try is needed to get a ship with the right amount of drag to get a reasonable lap time.

    Thrust to weight is the least of your problems! The 36 oz of fuel (which will weigh, say, around 36 ounces) is a minor problem. But if you are going to evaluate it for a stunt system seriously, the biggest problem BY FAR is the fact that the thrust is just about constant, or even climbs slightly, with forward velocity. Any propellor-driven system that doesn't involve a runaway has thrust that drops dramatically with forward velocity. You might have 5 lbs of thrust, static, but in normal level flight it's around 2-2.5 lbs, and at normal level flight +20 fps, you might have zero, or negative, thrust. With the jet, it's going to be about 4 lbs no matter what. First maneuver and it will slow down drastically and take a long time to recover, unload it and it will take off.

    Brett

Offline Bud Morrison

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Re: Pulse Jet Stunt design
« Reply #16 on: June 01, 2014, 10:22:25 AM »
    Thrust to weight is the least of your problems! The 36 oz of fuel (which will weigh, say, around 36 ounces) is a minor problem. But if you are going to evaluate it for a stunt system seriously, the biggest problem BY FAR is the fact that the thrust is just about constant, or even climbs slightly, with forward velocity. Any propellor-driven system that doesn't involve a runaway has thrust that drops dramatically with forward velocity. You might have 5 lbs of thrust, static, but in normal level flight it's around 2-2.5 lbs, and at normal level flight +20 fps, you might have zero, or negative, thrust. With the jet, it's going to be about 4 lbs no matter what. First maneuver and it will slow down drastically and take a long time to recover, unload it and it will take off.

    Brett

Actually the speed recovery issue is not as bad as you think. Watch this video.   The biggest problem Dan has with his is how very nose heavy it is till it burns off fuel as his tank is in front of the engine. That is why we all want to get the fuel on the CG

Online mike londke

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Re: Pulse Jet Stunt design
« Reply #17 on: June 01, 2014, 12:02:29 PM »
Here is what I believe to be a good set up for a pulsejet stunt plane. Light bulb tube bladder compartment, latex bladder material,and a cline valve. 80/20 fuel mix. Tank pictured is 16ozs for test runs. It can be made much larger for flying. My thought is to run it right down the CG inside the wing like a combat plane. This set up runs no matter where the bladder is. The engine does not care. I believe this to be an advantage over a metal tank. It is simple and it works, I've run it. I am close to having a  test plane ready for further evaluation by summers end. Mike
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Offline Bud Morrison

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Re: Pulse Jet Stunt design
« Reply #18 on: June 01, 2014, 01:19:28 PM »
I am close to having a  test plane ready for further evaluation by summers end. Mike

I'm going to work on mine over the winter as I have 2 electric stunt conversions I need to get done like asap. For now I will continue to accumulate parts and work on design then I will solid model it before building.

Offline Brett Buck

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Re: Pulse Jet Stunt design
« Reply #19 on: June 01, 2014, 01:50:41 PM »
Actually the speed recovery issue is not as bad as you think. Watch this video.


   I have seen it fly in real life. Being tolerable and having the right characteristics for a competitive stunt plane are twi wildly different things.

    Brett


 

Offline Bud Morrison

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Re: Pulse Jet Stunt design
« Reply #20 on: June 01, 2014, 03:13:05 PM »

   I have seen it fly in real life. Being tolerable and having the right characteristics for a competitive stunt plane are twi wildly different things.

    Brett

Oh hah we are just trying to get one to fly the whole pattern........we don't really care how pretty it does so at this point :)

Offline Dennis Toth

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Re: Pulse Jet Stunt design
« Reply #21 on: June 02, 2014, 05:48:17 PM »
Mike,
What is the cline valve? Who makes them? Also what is the material and source for the blatter? I like the idea of a pressure system. Seems that way back in 1948 the then manufacture of the Dynajet the Martin Jet company had some kind of fuel system that they offered with the aerobatic ship the called the "Martin Thunderhawk" it was later offered by World Engines with the OS jet.  Does anyone have plans or numbers for this ship?

Best,       DennisT

Online mike londke

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Re: Pulse Jet Stunt design
« Reply #22 on: June 02, 2014, 06:44:07 PM »
Dennis, I really did not use right terminology for the Cline system. As it was designed by Jim Cline he called it a PCFS controller. Proportional Control Fuel System. Jim Cline died a few years ago so he no longer makes them. I got mine from Bruce Tharpe. He has been flying pulsjets with bladders on RC planes for many years. I don't know if he bought all the existing stock or is currently producing them, but he does have them. Here is his link.  http://www.btemodels.com/  Here is a link to an article Bruce wrote on using bladders with pulsejets.  http://jetzilla.com/Vol01Num01/jetZilla.html#Article_2   Note that Bruce's bladder tank is very large latex in an Aquafina bottle. Probably ok for a large RC plane but not for CL. That is why I am using the same dia. latex that I run on my combat planes. Smaller OD than Bruce's and will fit nicely in a light bulb tube. It is yellow jacket tubing available from Phil Cartier on his Corehouse website. He is listed in the vendors section. I don't know about the Thunderhawk other than a few references to it on the web. All I could find was a few ads and pictures for it.  Mike
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Offline Bud Morrison

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Re: Pulse Jet Stunt design
« Reply #23 on: June 02, 2014, 06:50:21 PM »
I'm gonna use the aquafina bottle or 2 smaller bottles and twin bladders :)

Offline Dennis Toth

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Re: Pulse Jet Stunt design
« Reply #24 on: June 04, 2014, 12:10:02 PM »
Bud,
It seems that if you use ethanol you should get 40% more run time for the same fuel load. Don't know were you can get 100% ethanol (basically pure moon shine) but I understand that denatured alcohol is a mix of ethanol and methanol ( the methanol is added so you can't drink it). That you can get at Home Depot, might be worth a try.

Best,        DennisT

Offline Bud Morrison

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Re: Pulse Jet Stunt design
« Reply #25 on: June 04, 2014, 03:23:52 PM »
Bud,
It seems that if you use ethanol you should get 40% more run time for the same fuel load. Don't know were you can get 100% ethanol (basically pure moon shine) but I understand that denatured alcohol is a mix of ethanol and methanol ( the methanol is added so you can't drink it). That you can get at Home Depot, might be worth a try.

Best,        DennisT

Shine not a problem....... pure shine another subject :) Pure 200 proof ethanol lab quality is $134.00 for 4 gallons.
I know you can use denatured in camp stoves so it may be worth a try. 
I did get bladder material today per Bruces instructions I got some of  natural and some of the black in case one is better than the other.

Offline Avaiojet

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Re: Pulse Jet Stunt design
« Reply #26 on: June 05, 2014, 03:13:20 PM »
Ad in Air Trails, 1949.

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Offline phil c

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Re: Pulse Jet Stunt design
« Reply #27 on: June 16, 2014, 12:52:43 PM »
For contest use the biggest problem would seem to be handling 36oz. of fuel.  No matter where it is the flight characteristics will change dramatically from the start to finish of a flight.  Imagine a Nobler that goes from 50oz. to 34 oz. during a flight.  Besides being quiet, that is a big advantage for electric.  The plane flies the same all the time.
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Online mike londke

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Re: Pulse Jet Stunt design
« Reply #28 on: July 12, 2014, 10:19:29 PM »
If you have a FB acct. check out this link. Very cool old PJ Stunter. https://www.facebook.com/groups/34580977383/
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Offline Dennis Moritz

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Re: Pulse Jet Stunt design
« Reply #29 on: July 25, 2014, 06:36:30 PM »
Dan's tank is 18.5 ounces. Plane flies around 85 miles an hour  About 3.5 minutes a flight. He rips off most of the pattern. 90 degree or so squares. Plane is a bear. Slow it down with a bigger plane and you'll consume more fuel. A pulse jet gone wild could be lethal. The tube glows red. A Molotov cocktail with an instant igniter. Crash the bird and chances are you will be modeling a napalm burst. You guys are worrying me. I'll tap out more about this later.
« Last Edit: July 26, 2014, 05:18:06 AM by Dennis Moritz »

Offline Dennis Moritz

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Re: Pulse Jet Stunt design
« Reply #30 on: July 25, 2014, 10:32:15 PM »
30 ounces of fuel buried in the wing along fore/aft cg is a bad idea. As the fuel is consumed a lateral imbalance will be created. If the fuel is bladder pressed inboard the reduction in tip weight would soon have the plane flying outboard tip high, upright and inverted. Which means the Molotov will be on course towards the apex of the circle where lurks a wide eyed victim. If the bladder is pushing the fuel outboard the the outboard tip will be hanging down further and further. Flapping the elevator should get interesting.

Pulse Jets are cantankerous beasts. Ultra sensitive to air density, fuel, temperature and WHAT NOT. The reeds are short lived. Sources of reeds unreliable. Reeds differ. Some need final finishing to work. Temper of the steel variable. Dan worked with his MiG OS Jet for years to get some consistency. Early on it was often twenty minutes or more at the pump. Changing jets. Figuring out fuel mixture. The Dynojet Stunter is more reliable mostly because Dan has gone through an extensive learning curve AND he is exceptionally skilled at trouble shooting the idiosyncrasies. Engine runs a burst. Dan says this fuel jet or that fuel jet. So on.

Pulse Jets and Turbines, entirely different mechanisms. The methodology of creating thrust far far different. Pulse jets are simple almost simplistic mechanisms. Turbines are complicated held to close tolerances, made of expensive alloys. Pulse Jets cost $150. Turbines $3000.  

Dan runs a chicken hopper tank up front. It feeds amazingly well. He was told over and over that the engine would need pressure and a regulator and... He kept it simple. Went inverted first flight. Second flight inside and outside loops. Big ones. Squares. Big. Yeah. I think there was once a cloverleaf. Top loops done behind the head.

This is a novelty fly. A fab spectacle. Especially at sunset almost dark. Very hard to make work. A serious stunter. lolololololo



« Last Edit: July 26, 2014, 03:55:46 AM by Dennis Moritz »

Offline Dennis Moritz

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Re: Pulse Jet Stunt design
« Reply #31 on: July 26, 2014, 03:56:40 AM »
The academic speculations on this thread are a hoot.

Online dennis lipsett

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Re: Pulse Jet Stunt design
« Reply #32 on: July 26, 2014, 06:26:44 AM »
Bud,
I think that Dan has 3 places he can fly his jet. Our field, Brodak's and the nats.  Even so you can wear out your welcome with a steady onset of pulse jet noise. A jet may be novel for a flight or two,after that it's just really loud noise and can make you about as welcome as a bad cold. Dan averages about 4 flights a year at our field, Brodak and the nats a few. I don't think that either John Brodak or the Flying Dutchmen field could withstand an onslaught of pulse jet noise and escape any form of criticism from surrounding neighbors.
All of the other concerns raised are valid and it just reinforces why your not seeing them used except in one event in speed or experimentally and flown at remote sites like the Arizona desert. Having seen Dan's jet fly from the first flight I can say that while it is an impressive achievement I wouldn't exactly say that it is any challenge to the average stunt flyer at any contest. You don't see jets at any serious aerobatic events in the world, Humm, I wonder why. What! you mean that it can't do a snap roll?
What I'm saying Bud is that there are more rewarding projects to undertake than a Dyna jet stunter that no one really needs or has no place to fulfill it's function.
So when are you going to make it back up to the hill and get some handle time?

Dennis


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