my tipjet ultralight copter

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Re: my tipjet ultralight copter

Post by Mike Everman » Tue Dec 21, 2004 4:08 pm

Just a note, all those rotor tip jets are subsonic. It's very likely that he could have started it by hand. I have no personal experience, but I'll bet it touches of at less than 100 mph which doesn't represent a lot of rpms on a big rotor.
Mike
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Re: my tipjet ultralight copter

Post by luc » Tue Dec 21, 2004 4:58 pm

Hi Bruno,

Bruno wrote
In a nutshell, now that you have cracked the secret of the pressure jet, what do you think about it?
I the pressure jet is a marvellous engine. It's autonomous, it can be started and re-started without any air suply, it has no moving parts, it is rugged, with a wide throttle range. Its draw back is that it need fuel suply boots, but this can be easelly achieved and it need tuning. But once this is done, you have an engine that provide you with hours of fun without any maintnance and changes.
Obviously, you find it a good engine, or you wouldn't be wasting your effort on it, but just how good?
So good, that after close evaluation of all the other engines types, it was clear to us that this engine has the biggest potential. Putting efforts on other engines would be limited to their own specific limitations (i.e : Pulse jets=valve limitations and no throttle, Lockwood=Start air required ...ect.)
For instance, if someone wanted to power a machine with a jet engine of between 50 and 100 lbs thrust and wanted to build the engine himself, in a moderately well equipped garage or basement workshop, what would your verdict be?
Today, I would tell him to build any thing, except a pressure jet. When Viv and will done with our project, I will tell then to build a pressure jet. Lets put it this way, when we will be done, anyone equipped with a TIG welder, a sheet metal roller and a grinder, will be able to build a pressure jet.

Don't forget one thing do. Most of the peoples here, build engines according to plans they have and as far as thrust is concerne, they take what is written on the plans as figures and sware by it. It seem to much peoples are just happy with the fact that their Gokart move forward or their planes flys. But how many peoples actually have a "LoadCell" test bench to validate what they have built. The Pressure jet need that bench for tuning. Otherwise, you don't know what you have built and it is one of his drawback. But is'nt it the drawback of all jet engines???

Still today, companies like Pratt & Whittney, Roll Royce and GE, bench mark each engine for thrust certifications. So, does'nt this fact trigger questionning in your mind. It sure does in mine.. And beleive me, I know this because I have worked 5 years for CEL Aerospace, which is the main jet engine test cell suplier for those 3 companies. I beleive this is where you seperate the real builders and designers from the hobby one.
Build a Viv/Luc/Gluey pressure jet? A Lockwood? A big Chinese? An Escopette? (Assuming that all the plans were available in correct form.)
The Viv/Luc pressure jet, as you call it, is smaller and more powerfull then the lockwood, it is shorter and more powerfull then a Chinese and an Escopette. And like previously pointed out and compared to all other types, it is autonomous, require nothing else then fuel and a spark to start or re-start and incorporate no mechanical moving parts.

I think a can not be more specific about it. But ask your self one thing; Do you think a guy (Viv) would migrate all the way from UK to Canada, just on pure assumptions ... I personnaly don't think so.

Hope it answers your questions.

Cya,

Luc
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Re: my tipjet ultralight copter

Post by luc » Tue Dec 21, 2004 5:24 pm

Hi again guys
Mike Everman wrote:Just a note, all those rotor tip jets are subsonic. It's very likely that he could have started it by hand. I have no personal experience, but I'll bet it touches of at less than 100 mph which doesn't represent a lot of rpms on a big rotor.
You are probably correct in what your saying Mike. None the less, even if it require a few hand pushed revolutions, as little they have to be, they are still a 3rd action that has to be done.

I, personnaly, prefer the "Ignition ON, Fuel ON" option and I think I have sent this image out ... To many time mayby. No need to argue about it anymore I think.

I am starting to beleive, that at the stage Viv and I are in our project, we need to stand back and just read. Obviuosly, we are not ready to give you guys something more to chew on, But it will come.

But for now and until we can offer something else then plain repetition of what was already said, I think we just need to sit back and enjoy the ride.

We will keep you posted when will have something new.

Sorry if at some point, I was anoying with my perpetuous and continuous same answers.

Regards,

Luc
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Re: my tipjet ultralight copter

Post by Mike Everman » Tue Dec 21, 2004 6:48 pm

Luc, the larger Lockwood style engines need no starting air when fueled with propane.
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Re: my tipjet ultralight copter

Post by larry cottrill » Tue Dec 21, 2004 6:57 pm

Guys, don't forget the main reason ramjets were ever considered for this application: They are the lowest mass engines per unit of available power ever designed.

You do NOT want concentrated mass at the tip of a rotating blade! At least, not any more than you need for reliable operation.

From the standpoint of the rotating mass having reasonable moment of inertia, it would be better to have the heavy part of your engines inboard as far as possible, and route the gases out to [or near] the tips for discharge. On an engine like a pulsejet, where you need physical length and where the mass is somewhat higher, that would be the way to go. Sort of a superheated lawn sprinkler. Well-designed ramjets are so light and compact that such extreme measures should be unnecessary.

L Cottrill

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Re: my tipjet ultralight copter

Post by hinote » Tue Dec 21, 2004 7:14 pm

Mike Everman wrote:Luc, the larger Lockwood style engines need no starting air when fueled with propane.
IMHO it should be possible to create a starting system for any valveless type using only propane, and no supplemental air.

A properly designed fuel probe, placed correctly in the intake tube (and possibly with a tiny eductor at the tip) should induce airflow along with the fuel--and possibly even the required turbulence to stimulate resonance.

I was able to autostart the QD on occasion, even with its low-velocity fuel injectors.

Bill H.
Acoustic Propulsion Concepts

".......some day soon we'll be flying airplanes powered by pulsejets."

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Re: my tipjet ultralight copter

Post by Mike Everman » Tue Dec 21, 2004 7:17 pm

Let's also not forget the two main detractors, IMO, that is the drag at the tips stops the autorotation on power-off. The mass is second order to this. They're also major gas hogs. I think you'd be much better off with a couple of hobby turbojets not all the way out on the rotor, so as not to over-tax the jets bearings(?)
Mike
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Re: my tipjet ultralight copter

Post by Chris McDonald » Tue Dec 21, 2004 9:09 pm

Guys,
i guess i really stirred the soup and got you all talking since my tipjet heli showed up. this is good for us all. don't worry about me flying this heli that's a long way off. it is an excellent test bed for engines so far. if i got some lift and light on the skids that would make me happy. if i need to fly i have friends with "normal" aircraft. i will look at more prints and read over your thoughts. talk to you soon.
chris

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Re: my tipjet ultralight copter

Post by Mr. Yuk » Wed Dec 22, 2004 12:36 am

That is very impressive Chris. I would love to see that thing run. I'm currently working on a G8-2-20, it would be fun to build another and stick them on a heli, even if it didn't fly, it would be worth it just to build.

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Re: my tipjet ultralight copter

Post by Chris McDonald » Wed Dec 22, 2004 2:11 am

mr. Yuk,
i had just unrolled my G8-2-20 prints on the living room floor engouraged by Luc and Viv to re-explore them.
i never built them because of all the compound curves to work up and i heard from many that there was a bug in the plans that lent low thrust.
now i see the nice job you have done! you shall become Sir Yuk in the knighthood of pressure jet folk soon. please share with us the metal flaring and forming of all those curves someday.
i have to respond to all that are wondering how my old engines ran with just hand tossing over the rotor blades, hope you are all reading. no my engines did not fill the job or i'd still have em but they brought the rotors up to a good speed. as i remember it was like over 150 rpm. with full drag attack (there's one problem). some possible explaination of this might help.
my first engines ran on propane. there was of course 100psi available and i used a heat expansion coil in each to bump up and vaporize a'la Ghluey. missing was a fuel regulator to keep every thing from backing up (problem two).
the fuel nozzle and inlet diffuser were somewhat aerodynamically tuned so the the fuel spray pulled in the air right from the get go. might be part of my success? there was no flame lock device in the plans (problem three) that long pulsejet type tail was not needed because it was more of a ram jet (problem four) so we cut them off. worked just as well.
them suckers did get real hot but somehow did not harm my spruce core composit blades. who knew? i have a good plan for heat isolation next time anyway.
Yuk, keep talking to everybody and we will make that G-8 work.
all the best to everyone and keep up the joined effort,
chris

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Re: my tipjet ultralight copter

Post by Chris McDonald » Wed Dec 22, 2004 2:37 am

Yuk said:
"even if it didn't fly, it would be worth it just to build".

this is the spirit we need to succeed!
chris

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Re: my tipjet ultralight copter

Post by Chris McDonald » Wed Dec 22, 2004 2:53 am

Luc & Viv,
catch up with this guy, Sir Yuk. he is near finis with this G8-2-20. yeah he might have to back up, chop and reweld but here is a chance for you to make an improvement. you could work together. my only thoughts right now are a telescoping tail pipe to tune it and a NACA teardrop high speed intake. there is no better thing than an engineering education than some good engineer friends.
chris

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