Engine platform for a small aerobatic machin?

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JonArne23
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Engine platform for a small aerobatic machin?

Post by JonArne23 » Mon Mar 01, 2010 7:52 pm

Im looking at 2 pulsejets engines for my aircraft project. I started out wanting 1 or 2 turbines but soon found out that they are WAYYYY over my budget of 30k USD . A freind from the flying club tiped me about using a pulsejet. Im a complet noob at pulsejets but i have someflying and building experience . 1500 hours full IR and ATPL and buildt a Rand-Robiensen KR-2 and helped build a RV-6.
My project is a singel seater aerobatic machine loosly based on the BD-5 microjet . Im following the KISS rule for my plane (Keep It Simple Stupid) , and cheap .... At the same time i want somthing that people have not seen before and i can use as a crowd pleaser. The endurace does not have to be great since i know the Pulse jets are thirsty as hell. compared to a 100++ hp prop engine .
Im looking for somthing in the 150lb + thrust range x2 that is ...my first consern is safty and reliablity of the engines ....my old rutine lasted about 5-7 mins +takeoff , holding time and landing . i need atleast 45 mins total time as a bare minimum. everything over that is good.
i know this engines run on just about any fuel , but i read that some fuels are better then others ? the fuel must be liquid ...no gas since i cant get a reg number for it with "experimental fuel".

I have some basic questions =
-How heavy are they , for the 150-200lb range ? in stainless steel ?
-Fuel consmusion ? 2x (need to make it safer,, safty in numbers and all that)
-Size ? Length , diameter ?
-Throttebillity ? this is a must. I have read alot of articals online and some say no throttle ...others say 15% - 100% range. ?
-Valved or valvless? i know the Valvless are simpler and last longer ?
-TBO time ? (Time Before Overhaul)

thanks for ur help ..

Jon-Arne

PS : My first language is not english so ignore the spelling .

Kool
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Re: Engine platform for a small aerobatic machin?

Post by Kool » Mon Mar 01, 2010 9:07 pm

Well, at first I would say, put a extra S so you get KISSS Keep it stupidly simple and SAFE

However I couldn't you advise very much about the engine's (maybe you should contact Bob Maddox, he builded pulsejet engines from 50 to 700lbs), I could say that you have to look at a very solid construction which would moderate the very large vibration which come of the pulsejets.

I'm looking forward to you progress.

BTW: are we talking about such a plane? http://vimeo.com/2044289
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Viv
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Re: Engine platform for a small aerobatic machin?

Post by Viv » Mon Mar 01, 2010 9:54 pm

The first point I would make is that in all the time pulse jets have been around there are not many accounts written up about successful manned flights, you have to stop and wonder why that is ;-) in fact the last account I read of a good flight was a certain German lady towards the end of world war two in fieseler fi 103, the pilot was Hanna Reitsch see http://en.wikipedia.org/wiki/Fieseler_F ... henberg%29

The next point is about the fundamental problem of Pulse jet power, its "on" or its "off" and it can stop dead in one cycle (no fly wheel) so an engine running at a 100 hertz can stop dead in one hundredth of a second, as a pilot you may find that an issue ;-)

Hope that helps, I would maybe go back and ask that helpful guy exactly what he meant by recommending a pulse jet as a suitable alternative to a turbine?

Viv
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WebPilot
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Re: Engine platform for a small aerobatic machin?

Post by WebPilot » Mon Mar 01, 2010 10:14 pm

Image

Jumping from an airplane is much too tame for Bob Maddox. He needs something a little more extreme. That’s why he plans to strap himself to a four-engine pulse jet rocket, ride it to around 25,000 feet and then jump off.

Strap On 4 Homemade Rockets and Say Your Prayers
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metiz
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Re: Engine platform for a small aerobatic machin?

Post by metiz » Mon Mar 01, 2010 11:51 pm

4 one thousand pound pulse-jet engines surrounding this guy might not be the best idea ever. won't those engine sync up and create such massive vibrations that it will tear him appart from the inside out?
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JonArne23
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Re: Engine platform for a small aerobatic machin?

Post by JonArne23 » Tue Mar 02, 2010 11:10 am

poech prut wrote:Well, at first I would say, put a extra S so you get KISSS Keep it stupidly simple and SAFE

However I couldn't you advise very much about the engine's (maybe you should contact Bob Maddox, he builded pulsejet engines from 50 to 700lbs), I could say that you have to look at a very solid construction which would moderate the very large vibration which come of the pulsejets.

I'm looking forward to you progress.

BTW: are we talking about such a plane? http://vimeo.com/2044289
Yes thats what im using a s a base for my airplane. only im making mine out of carbon fiber and it will be slightly large and longer to make it abit more stability.

JonArne23
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Re: Engine platform for a small aerobatic machin?

Post by JonArne23 » Tue Mar 02, 2010 4:40 pm

the engines would have to be profesional buildt. I did take some welding classes back in school, but that was 15 years ago. From what im reading on this forum and other places the dimensions need to be exact or the engine will run poorly or not at all. I will contact Mr Maddox when the time comes .

As for safty , thats my main consern.. how reliable are the engines ? ......is it just pure chanse if the engine runs or not ? and throttle ? i also read that they are not safe to throttle at all ?

Does anyone knoe the size and how heavy a 150lb jet is ? And the fuel consumtion?

Thanks

Jon Arne
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dynajetjerry
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Re: Engine platform for a small aerobatic machin?

Post by dynajetjerry » Tue Mar 02, 2010 5:26 pm

Jon,
The most efficient p-j of which I am aware was Aeromarine's 205 lb thrust version for a U S Navy target drone. It burned about 400 lbs auto gasoline each hour and could not be significantly throttled. This works out to be about 67 gallons (254 liters,) or 180 kg per hour. Statically, its reed valves lasted about 2 hours and more but could fail at any time, quite suddenly. It is more realistic to figure consumption as 25% more than the above because of the difficulties in attaining truly efficient p-js. Too, many larger p-js employ fuel injectors that are behind the reeds; Dyna-Jet style injectors serve to cool the reeds and extend their useful lives while the former do not. For more exotic fuels, consumption will be considerably greater than the above, perhaps as much as 1.6 X that amount. Of course, such fuels will often provide slightly more static thrust.
In any case, I would advise you to heed the warnings of most of the people on this forum: be very wary of trusting the reliability and power of p-js for manned aircraft. The reference to Hanna and her flights in a V-1 may have been true but such craft were intended for less than 1 hour flight times.
Jerry
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JonArne23
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Re: Engine platform for a small aerobatic machin?

Post by JonArne23 » Tue Mar 02, 2010 7:51 pm

@dynajetjerry

thanks for the info.... like a said i know very little about PJs , I think i will consider other engine options. I building a RC 1/3 scale for proof of consept atm, may put 2 PJs on that for shits and giggles.....

BTW ...has anyone ever tryed to make a mechanical valve system with a step motor or pico actuators ? im guessing the reed valve is the acilise heel of the pulsejet ? if it fails it stops .....and while we on the subject ..... the radient heat problem could be solved with a ceramic liner in the hotsones ? not just ceramic paint but a full tube in the steal casing ?

thanks again for good feedback

JonArne23
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Re: Engine platform for a small aerobatic machin?

Post by JonArne23 » Tue Mar 02, 2010 9:06 pm

Do u guys know the jetbettle turbine jet engine ? i found a guy in Taiwan hwo makes a 150lb thrust turbine engine. or his working on one at least ...his got a few wids on youtube.

http://jetbeetle.com

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