Drawings of a small pulse jet

Discussion in 'Off Topic' started by oldsalt, Nov 7, 2011.

  1. oldsalt

    oldsalt New Member

    I have drawings of a small pulse jet. They are VERY loud. Control Line Speed planes [with 72 foot lines] go better than 200 MPH. If it were put in an RC a guy would quickly loose the plane. But if he followed the fire engines he would be able to again locate it.
     

  2. loquin

    loquin Active Member

    200 MPH at the end of a 72 foot line means that the operator would be spinning at almost 39 RPM... (less than 2 seconds per rotation.) That would get you dizzy in no time. Plus, you would have to be fairly nimble on your feet ;-)

    The other problem with a 200 MPH pulsejet at the end of a 72 foot line is the centrifugal force: if the plane/engine weighed only 10 pounds, the the centrifugal force would be more than 370 pounds! Better anchor the 'pilot' to a car axle, set on end, in concrete!
     

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  3. oldsalt

    oldsalt New Member

    logim

    How crass! Especially the :) you felt necessary to add. And from a dude that has "Administrator" under his avatar! Every word I posted was true. Looks like you were so anxious to be a smartass and show up some dummy that you left your *** hanging out a mile. For a number of years I was into control line speed planes. I have on many occasions witnessed jet class planes clock at better than 200 MPH. In fact a 'C' class piston engine plane [.60 engine of the ABC type] run about that speed also...believe it or not.

    You at least have the RPM around the pilots pylon correct. At an official AMA sanctioned contest there is a stake driven in the ground [blacktop] that has a bearinged yoke at the top which the flyer must keep his wrist positioned on so that his flight circle is 72 feet. Most often young people are used to do the flying and have to practice spinning in circles to acclimate themselves to the task. The airplane must fly no higher than 6 feet as that would shorten the distance of a lap. Seven laps are necessary to be timed to get an official speed. You don't get all that dizzy in a total of, say, 12 laps and several of those are with the model getting up to speed. The 72 foot wire is called a 'Mono Line' in as much as there is only one wire. If you wish to PM me I will be happy to explain the mechanism that makes the single wire able to control the tiny elevator tab. But you probably won't because you obviously know everything already. The motor is started with a compressed air bottle and the plane is set on the track. The plane does not have any landing gear; it takes off with a light wheeled dolly that drops off the plane when it is airborne and skitters off the course.

    A 10 pound plane!!! The plane is typically equipped with a thin aluminum 'belly pan' to which the wings an horz. stabilizer is attached [no rudder]. The fuel cell is faired into it and is under pressure to supply the fuel. As I never competed in the control line jet class, only the internal combustion speed classes, it will be necessary for me to give you my best guess as to all up weight. The Dyna-Jet engine [that is a brand name of a commonly used motor] and all other components would not weigh more, and again my good friend, this is only a best guess, 2 or so pounds.

    Really sir; you should learn to hold your piece, even when your lack of experience allows you to believe you can make a splash at someone else's expense, until you have thought it over and did a little research.

    The attached pic is of what I compete with currently, the control line speed planes were a 70s thing I messed with.
     

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  4. loquin

    loquin Active Member

    oldsalt;

    I've taken this portion of the pulsejet engine thread offline, so we can talk about it privately.

    I'm really not sure just why you've got the burr under your saddle? I was not out to put you down, or to make a point at your expense.

    I don't understand why you think my response was "crass." I was making a point that a 200 mph plane tethered to the end of a 72 ft. line would be spinning around pretty quickly. I know that I would get dizzy! I also stated that you would have to be nimble on your feet. You reinforced this when you said that the pilots have to practice quite a bit to get to the point where they can 'pirouette' with the plane, and still keep the plane under control.

    Really, the only thing I posted that was incorrect, was an assumption of a plane that could be up to 10 pounds. I've done some RC model plane flying, and there are some very large RC planes today; I've seen RC models with wingspans of 8 feet, with flying weights in the 20 pound range, so that assumption wasn't that far out of the realm of possibility...

    The centrifugal force calc indicates that you have a 37:1 centrifugal force to plane weight for those speeds and circle radius. So, your 2 pound plane would have a lateral force of over 70 pounds. Still not easy to hold and control!. But, if you DID have a 10 pound plane, you would have to be rigged like a sport fisherman!

    In the future, if you see a response like I made, please don't assume that someone is trying to shoot you down - why not point out that the physics of the situation meant that the plane weight had to be kept low?
     
    Last edited: Nov 8, 2011
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