HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Mar 12, 2012, 12:05 AM
Pilot, Co-pilot, Navagator
nemoskull's Avatar
United States, AZ, Yuma
Joined Sep 2009
2,766 Posts
Discussion
random idea. micro turboprop engine.

been tossing an idea around in my head for a while. a jet engine with a prop on it, a turbo prop engine. but very small. like a 4 oz plane small. cox .020 scale.
been thinking of a simple paddle wheel turbine with a shaft attached to a simple paddle wheel compressor. a chamber linking the two. output shaft turning brass gears on a 50:1 ratio or so. attach that to a prop.
carb on the intake, run 1/2a fuel for the oil. Ball bearing or perhaps use castor oil like modern turbochargers on cars.
basically a engine that can be made on a lathe, drill press and minimal routing.
i can figure out how to start the thing, tho (in my head).

fuel delivery is a problem as well. the main question is can you make a combustion jet from non pressureize fuel. like use a velocity vs pressure effect and a shaped nozzle to create a jet. i dont know, yet.
well, what u think?
i'll dootle some idea later.
nemoskull is offline Find More Posts by nemoskull
Reply With Quote
Sign up now
to remove ads between posts
Old Mar 12, 2012, 02:11 AM
Registered User
Boomerang1's Avatar
Sydney Australia
Joined Mar 2005
907 Posts
Before tossing the idea too far take a look at what very knowledgeable people have made to run or even better developed to the point where they can offer them for sale.

http://www.lambert-modellturbinen.de/html/english.html

Is the smallest succesful turbine.

http://www.wrenturbines.co.uk/engines/turboprop

Is the smallest succesful turboprop.

The Lambert turbine runs at over 240,000 rpm, these are not things you 'make on a lathe & drill press with minimal routing'.

Jet engines have constant pressure in the combustion chamber known as case pressure, that's why they use a fuel pumps to deliver fuel & control speed.

John.
Boomerang1 is offline Find More Posts by Boomerang1
Reply With Quote
Old Mar 12, 2012, 08:07 AM
Registered User
Joined Oct 2004
1,080 Posts
I was approached by a university student to help fabricate parts for an axial flow jet engine 20mm in diameter.
I politely declined explaining that I didn't think it would work.
Interesting idea, but not practical IMO.
706jim is offline Find More Posts by 706jim
Last edited by 706jim; Mar 12, 2012 at 05:08 PM.
Reply With Quote
Old Mar 12, 2012, 09:09 AM
Complete RC Idiot Savant
The Netherlands
Joined Nov 2009
2,768 Posts
Never say never, 35 years ago a turbine that could fit in a model airplane was considered impossible until some English guys made one.
Later Kurt Schreckling constructed a turbine that could be made with under 100$worth of materials by anybody who could use a lathe and had some sheet metal working skills.

So far, turbines are not yet REALLY small, and for now we do not have the materials to handle RPM and temperatures, and efficiency cannot yet be boosted to a level where such a small turbine would actually be self-sustaining.

Carbs will never work on a turbine, due the incredible temperature rise in the compressor stage (you have to compress an explosive fuel/air mixture in a way that generates probably sufficient heat to make the mixture ignite while still in the compresion stage) so the real problem, even if you could really build a super small turbine, would be the fuel supply and turbine monitoring and control system.

Most likely nothing that cannot be solved in the (maybe near??) future, but for now such solutions would most probably terribly expensive.
And for what? An engine that has by nature of things a horrible fuel efficiciency (needs a tremendous amount of fuel for a very small amount of useable output)....

Brgds, Bert
Brutus1967 is online now Find More Posts by Brutus1967
Reply With Quote
Old Mar 12, 2012, 10:24 AM
Dieselized User
gkamysz's Avatar
Chicagoland
Joined Feb 2000
7,325 Posts
The problem is compressor and turbine efficiency. All of the ideas suggest that there is no knowledge of turbine design behind the concept.

Could a 50 shaft watt turbine be built today and run? Yes, I think so. With paddle wheels and a drill press, no.

Right, Jim. Axial flow presents it's own set of problems. Axial flow is impractical in model sizes, let alone 20mm.

Greg
gkamysz is offline Find More Posts by gkamysz
Reply With Quote
Old Mar 12, 2012, 01:07 PM
"Unnecessary Necessity"
coriolan's Avatar
Canada, BC, Vancouver
Joined Sep 2006
5,759 Posts
Small Japanese turbine

Bigger than 20mm but not by much!
http://homepage2.nifty.com/tachino/engine2.html
I think there is video of it running somewhere on Youtube
http://www.rcgroups.com/forums/showt...8#post19044246
coriolan is offline Find More Posts by coriolan
Reply With Quote
Old Mar 12, 2012, 01:33 PM
Dieselized User
gkamysz's Avatar
Chicagoland
Joined Feb 2000
7,325 Posts
20mm axial flow is not the same as 31mm radial flow. Turbines based on the Borg Warner KP-31 compressor wheel are common (Lambert Kolibri). It was the smallest available turbocharger compressor available a few years back. I'm not sure if it still is.

Greg
gkamysz is offline Find More Posts by gkamysz
Reply With Quote
Old Mar 12, 2012, 06:49 PM
Gas Only
Fokker DII's Avatar
USA So. Cal.
Joined Sep 2010
1,064 Posts
Only $4,995 for a Wren Turboprop from a dealer right here in Cal. And it only burns 6Oz of fuel per minute. I don't want one that bad ....
Fokker DII is offline Find More Posts by Fokker DII
Reply With Quote
Old Mar 15, 2012, 08:18 PM
Pilot, Co-pilot, Navagator
nemoskull's Avatar
United States, AZ, Yuma
Joined Sep 2009
2,766 Posts
Well for now it's a moot point. But fuel delivery is the thing I can't wrap my head around. I could edit the thing with a very small computer but an injector that small is not here yet. And the idea is not to be the best but just usabe
nemoskull is offline Find More Posts by nemoskull
Reply With Quote
Old Mar 15, 2012, 09:57 PM
Dieselized User
gkamysz's Avatar
Chicagoland
Joined Feb 2000
7,325 Posts
Yes of course, the turbines in production today are far better than the first one made by Kurt Schreckling. A fundamental understanding of how a turbine works is needed, however. There is no "injector" in model turbines!

Greg
gkamysz is offline Find More Posts by gkamysz
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Idea random magnetic act servo idea.... nemoskull Scratchbuilt Indoor and Micro Models 7 Oct 27, 2011 01:34 PM
Sold Allison Turboprop Engine Model - $115.00 Shipped GTMAXX Non R/C Items (FS/W) 0 Nov 14, 2010 10:29 AM
Discussion Random airboat idea spacephrawg Dock Talk 6 Dec 16, 2009 06:38 PM
Discussion Need a LARGE TurboPROP engine.... rustie Jet Turbines 10 Nov 17, 2009 04:58 AM
Discussion turboprop rc engine peterpont Engines 3 May 15, 2007 10:13 AM