Beyond The Sprues
Modelling => Ideas & Inspiration => Aero-space => Topic started by: ysi_maniac on November 14, 2013, 11:25:38 PM
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What is maximum in blade diameter ever design?
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AFAIK the largest ever props weren't on an aircraft at all.
The SRN4 hovercraft had four x 21 ft diameter 4 bladers to shift its 320 tons about.
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Thanks!
I have read that SRN4 was powered by Proteus turbines about 3500 hp. I am thinking about T57 turboprop (15000 hp) and whose blade diameter was 6.1 meters. Would it be possible to reach 7 meters? I mean in an aircraft.
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That's about right, the two Mk IIIs had the engines uprated to 3800 hp or so but that's just peanuts compared to your planned 15000 hp!
For sure you'd need some BIG props to dissipate that amount of power but the limiting factor would be the tip speed. As the prop gets larger the tip speed goes up and when it reaches M 1.0 all hell breaks loose. Read the reports on the XF-85H Thunderscreech and see what I mean.
If you run them slower you won't use up all the power so that'd indicate wide paddle blades, but maybe the best solution would be a big contra-prop? The Kuztnetsov NK-12 used on the Tu-95 Bear produces 14795 hp and claims to be '...the most powerful turbo-prop ever produced...' but they're in error if P&W ever actually got the T-57 to run. The NK-12 uses a 20 ft dia contra-prop to absorb its power so that looks the way to go maybe.
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A400M props are 17'-0" diameter powered by 11,000 shp, Hughes HK-1 are 18'-0" powered by 3500 hp
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LOTS of BIG blades on the A400M props though.
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Linke-Hoffman R.II, propeller diameter 6.9 m (22 ft. 7.5 in.), driven by four coupled
Mercedes engines.
(http://www.wwiaviation.com/drawings/Linke-Hoffmann_RII-600px.png)
http://en.wikipedia.org/wiki/Linke-Hofmann_R.II (http://en.wikipedia.org/wiki/Linke-Hofmann_R.II)
The SRN4 MK.1 and Mk.2 had 19' diameter props, when the rebuilds were done
to stretch the body and create the Mk.3, the props were increased to the 21'
diameter.
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Blade length is determined by rotational speed; you really don't want the tips going supersonic under normal operational conditions. For the T57, check out what size propellers were intended for the XC-132 since it used four of that engine. Alternatively, use a contraprop set-up similar to the Tu-95's since the engines are of comparable power.
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what effect does the wash from the front prop have on the 1 right behind it on a contraprop?
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The SRN4 MK.1 and Mk.2 had 19' diameter props, when the rebuilds were done
to stretch the body and create the Mk.3, the props were increased to the 21'
diameter.
AFAIK they increased the diameter on at least one of the Mk IIs before they stretched them. When I was doing oil samples for Seaspeed aboard a Mk II in 1974 it had the big props fitted then.
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what effect does the wash from the front prop have on the 1 right behind it on a contraprop?
With proper design, none; it's a similar situation to modern turbine engines where alternate compressor stages rotate opposite each other and there are no stators for the stages.
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I believe the C-160 Transall's props are 18' in diameter, a fairly big size in relation to the overall aircraft dimensions.
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what effect does the wash from the front prop have on the 1 right behind it on a contraprop?
With proper design, none; it's a similar situation to modern turbine engines where alternate compressor stages rotate opposite each other and there are no stators for the stages.
does the rear prop produce less thrust due to the effectivley increased airspeed?
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Love this
http://www.angelfire.com/wa2/c133bcargomaster/c133bdevelopment.html (http://www.angelfire.com/wa2/c133bcargomaster/c133bdevelopment.html)
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So why did the USAF can the C-132?
It looks as if they'd have the airlift capability of the C-5 some 10 years ahead of time.
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I studied the program a few years ago, Kit. While I'm going purely off memory here, I think it was a combination of cost, trouble with the new high-performance turboprop (never the US's strong suit), and a preference for jet-powered transports.
Cheers,
Logan
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what effect does the wash from the front prop have on the 1 right behind it on a contraprop?
With proper design, none; it's a similar situation to modern turbine engines where alternate compressor stages rotate opposite each other and there are no stators for the stages.
does the rear prop produce less thrust due to the effectivley increased airspeed?
Not if you adjust pitch accordingly; it's all part and parcel of careful propellor design and specification.
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If it had been built I think this might have been the winner for the biggest prop...
(http://davidszondy.com/future/Flight/atomic_airship01.jpg)
(http://davidszondy.com/future/Flight/atomic_aiship02b.jpg)
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^^^^^
Really tasty!! :)