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Does This Make Any Sense?

06/19/2013 1:25 PM

Please you engineers and thermodynamicists out there comment on the propulsion system used in this new helicopter, shown at the Paris Air Show this year. I cannot believe it makes any sense.

http://www.gizmag.com/sagita-sherpa-helicopter/27962/

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#1

Re: Does This Make Any Sense?

06/19/2013 1:36 PM

I would say its because they need the compressed air to be as hot as possible to take advantage of the expanding air and accelerate the blades. It might not be a efficiency thing but it could be.

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#2

Re: Does This Make Any Sense?

06/19/2013 1:45 PM

Why not. Do we call it a turbo-prop?

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#8
In reply to #2

Re: Does This Make Any Sense?

06/19/2013 4:04 PM

I don't know why you jump to the conclusion that it is turboprop. It doesn't even state what the primary engine is. It doesn't have to be gas turbine: it could be an internal combustion engine.

"That compressor feeds some of its air to the engine to aid combustion, while the rest draws heat from the Sherpa's cooling system before being mixed with engine exhaust fumes to heat the air to 100º C (212º F)."

So it could be a supercharged I.C. engine. In fact, the whole thing sounds like a turbo-compound engine, as used in the final evolution of aircraft piston engines, such as the Wright 3350-DA3 powering the Lockheed Constellation.

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#10
In reply to #8

Re: Does This Make Any Sense?

06/19/2013 4:12 PM

"Do we call it a turbo-prop?" is not jumping to conclusions. It's asking a question.

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#11
In reply to #10

Re: Does This Make Any Sense?

06/19/2013 4:15 PM

Fair enough - it sounded like a rhetorical question.

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#3

Re: Does This Make Any Sense?

06/19/2013 2:57 PM

I don't know if this would add to it.

Back in the 1990's, I always had hobbies. One of them was building something similar.

The design I initially had used ram jets, powered by propane, after worked out most of the issues, Being pressurized, my transfer valving frosted up due the expansion of the propane, after some trail and error of preheating the fuel with limited success I decided to use Alcohol. And coming from the farm, I had a good supply of raw material, (Corn). Problem was the heat capacity of alcohol burned cooler and the energy value was also lower.

( needed to look into this, at a link below, I see they developed a bi-fuel using Alcohol and hydrogen peroxide). If I wasn't so ignorant, I never would have started this, but building the still was fun…….

As I was searching in the library, This guys name Eugene Gluhareff kept coming up. But nothing was really said about him, but it seems that he was pretty instrumental on a lot of this technology. In one of the books, it give an address, I searched and got a phone number and called.

Turns out he was a retired engineer living in California. He had worked for NASA on I believe he said its "Pinwheel project".

Eugene was a nice guy, very informative and would talk for hours. He had developed an engine called a pressure jet.

Unfortunately as I was modifying some events happened, I changed jobs and had to move, and Eugene as well as his wife's health deteriorated. It left me in the lurch and I lost interest. (to my dads relief)

But the biggest issue I had was the fuel transfer on the rotor section, I had solved that with a silcone/carbide sanitary seal from a centrifugal pump.

I see that this is pretty wide spread in kit form but with various power plants, this looks like a pressure jet.

All in all, I felt pretty fortunate to have been able to talk to this pioneer Eugene Gluhareff.

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#4
In reply to #3

Re: Does This Make Any Sense?

06/19/2013 3:13 PM

btw, That is one compact engine.

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#5

Re: Does This Make Any Sense?

06/19/2013 3:15 PM

I don't see this as being more efficient or more reliable.....

Yours for just 34k

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#7
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Re: Does This Make Any Sense?

06/19/2013 3:28 PM

If that's an R-22, I'd be leery of $34K. Must be an old one.

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#9
In reply to #7

Re: Does This Make Any Sense?

06/19/2013 4:04 PM

Price may not be too far out, considering you have to assemble it.

Back in the 90's I had also looked at Revolution Helicopter kits that were about I recall around $25,000.00-$30,000.00.

The literature I receive looked to be a very simply design, but there was quite a bit of assembly.

And you had to personally assemble over 50% of it.

Did a little research, they were in business for quite some time, (7 years????) but………..due to quality problems they went out of business in 1999, (that was close……..)

Helicopters have pretty complicated mechanism……

I believe that going out of business is the path to allot of kit manufacturers, including this one from the OP.

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#12
In reply to #7

Re: Does This Make Any Sense?

06/19/2013 5:06 PM

Yes I would expect to spend at least twice that for something decent....but if you're the adventurous type(which I'm sure you'd have to be to fly a new design), I'm sure even cheaper can be had.....

Here's an unfinished complete kit with 0 hrs for $11k...

http://rotorfx.com/C/Lonestar_Sport_Helicopter_20080810.htm

more...

http://www.lightsportaircraftpilot.com/EAA_airventure_2005/mosquito-helicopter.html

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#13
In reply to #12

Re: Does This Make Any Sense?

06/19/2013 6:55 PM

I'd want to spend a lot more than that, before I got in the left seat.

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#20
In reply to #13

Re: Does This Make Any Sense?

06/20/2013 9:14 PM

Most copters are flown from right seat. Now why the difference between fixed and rotor, only Igor knows.

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#6

Re: Does This Make Any Sense?

06/19/2013 3:17 PM

The 1:1 scale Sherpa on show in Paris is just a model, and at this stage the helicopter's performance is theoretical

and

Though a full-scale working prototype is yet to be built, Sagita claims to have proven the concept (albeit with an electric motor) with a one-fifth scale model.

It's different, but I think I will wait for the actual prototype with real engine to be built.

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#14

Re: Does This Make Any Sense?

06/20/2013 8:50 AM

I'd say there's not near enough details presented to make even a half-arsed guess at whether this makes sense or not. Tail rotor-less contra rotating blade helicopters are nothing new.

As an un-manned vehicle it joins the ranks of dozens of other designs competing for limited available money.

If we read about a full scale operational prototype in two years I'd be more interested in the details.

Hooker

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#15

Re: Does This Make Any Sense?

06/20/2013 9:21 AM

I do believe what is being presented is in fact a gas turbine with a waste heat power turbine. the "engine" is apparently internal combustion (small one) that only drives the compressor and cockpit auxilliaries (AC, radio, instruments, etc.), and the waste heat is recovered into the compressed air to allow more power in the expansion turbine that drives the rotors. This sort of reminds me of the Italian army air force's attempt at a jet plane. They used an IC engine to drive the compressor, and the thing was so complicated and heavy there was no speed advantage attained.

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#16

Re: Does This Make Any Sense?

06/20/2013 11:45 AM

Apparently this is the type of drive used for the counter-rotating blades:

http://www.secretprojects.co.uk/forum/index.php?topic=19748.0

From this earlier article:

"...its exhaust gas propulsion system is called Turbine Direct Driven Rotor or the acronym REDT.

REDT uses a centrifugal compressor that feeds air to two piston engines and directly to the turbines that turn the co-axial rotors.

The direct bypass air is fed at 1.31 bar and 120° celsius while the piston engines, which also drive the compressor, also direct their exhaust gases to the rotors' turbines..." Mystery solved.

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#17
In reply to #16

Re: Does This Make Any Sense?

06/20/2013 12:12 PM

Thanks! Good answer and now all revealed.

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#18

Re: Does This Make Any Sense?

06/20/2013 12:16 PM

I would question the 85% efficiency, especially since a full scale prototype has yet to be built. Otherwise, it makes perfect sense.

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#19

Re: Does This Make Any Sense?

06/20/2013 5:10 PM

No, it does not make sense. Nor does your 2 sources do any.

Simply for a starter, a counterrotating rotor of that configuration will beat itself to pulp in no time flat. As the blades undergo large amount of flapping going back and forward.

Nice model otherwise.

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#21

Re: Does This Make Any Sense?

06/21/2013 1:55 PM

it makes sense to me on that scale

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