|
Post by Deleted on Dec 18, 2014 10:49:42 GMT
I believe that the two spools were counter-rotating on the Pegasus to help eliminate torque reaction at low manoeuvring speeds ??
|
|
|
Post by Roger on Dec 18, 2014 11:37:25 GMT
No, it looks like its a single spool
|
|
|
Post by Deleted on Dec 18, 2014 13:22:24 GMT
Yes, yes------Extract from Wikipedia (Also I've seen a similar thing from an American Harrier pilot on his forum recently---)......................... Design[edit]............ en.wikipedia.org/wiki/Rolls-Royce_Pegasus ................ USMC Harrier short-takeoff run on wet deck. The Pegasus vectored-thrust turbofan is a two-shaft design featuring three low pressure (LP) and eight high pressure (HP) compressor stages driven by two LP and two HP turbine stages respectively. Unusually the LP and HP spools rotate in opposite directions to greatly reduce the gyroscopic effects which would otherwise hamper low speed handling. LP and HP fan blading is titanium, the LP fan blades operating in the partly supersonic region, and airflow is 432 lb/s.[6] The engine employs a simple thrust vectoring system that uses four swiveling nozzles, giving the Harrier thrust both for lift and forward propulsion, allowing for STOVL flight. Combustion system is an annular combustor with ASM low-pressure vaporising burners.[6] Engine starting was by a top-mounted packaged combined gas turbine starter/APU.[6]
|
|
|
Post by Deleted on Dec 18, 2014 13:36:38 GMT
Here's a quick tour by Ralph Hooper, one of the designers....This is at the Brooklands Air Museum which is/was inside the Brooklands Race Track......... www.youtube.com/watch?v=D1i4ukSdqjc ...........
|
|
|
Post by Jim Scott on Dec 18, 2014 13:44:46 GMT
Hi Guys You learn something new every day. I certainly wasn't aware that the shafts were contra-rotating until I checked. Same info on www.gracesguide.co.uk/Rolls-Royce_Engines:_Pegasus. The contract R&D company I worked for (later taken over and eventually closed by by Rolls Royce), developed automated TIG welding equipment for closure of the cooling air holes at the tip end of the Pegasus engine blading. This was my first introduction to computer controlled TIG Welding circa early 1990's. Jim S
|
|
|
Post by Roger on Dec 18, 2014 13:59:20 GMT
Well I never, so my memory was right in the first place! It's basically similar to all the TurboJets we know and love. I did wonder how the large fan could possible work at the same speed as the core of the turbine, and there's the answer. Well done Alan!
|
|
|
Post by Deleted on Dec 18, 2014 14:06:37 GMT
------ and so I should be !! Ha-Ha------Now try this BUT, be warned it's HIGHLY NOISY and EXTREME so go to FULL SCREEN and pump up the volume !! ( Music is }--- Kick start my heart by Motley Crue ) >>>>>>>>>>>>>> www.youtube.com/watch?v=ALaxCSqpCGk ..........
|
|
|
Post by GWR 101 on Dec 18, 2014 14:18:49 GMT
Opposite rotation of the stages to improve stability is another reason to not try and adapt an off the shelf model gas turbine. I see for any one interested there is a full size one for sale on the web for £7500 + vat, ( usual disclaimer I have no connection with the seller). I am not sure what the neighbours would think if you ran it up to speed, would certainly be louder than any other machinery or engine noise that we make. Regards Paul
|
|
|
Post by Deleted on Dec 18, 2014 14:36:59 GMT
they'd be "Blown away" !!
|
|
|
Post by Roger on Dec 18, 2014 14:39:18 GMT
Hey, if it's all been done before, that kind of takes away the motivation and the challenge. I think it would need to be a pretty big engine simply from the size required to make it a twin spool engine. I'm not sure that's what I showed in the video a while back, that was a pretty small engine to fit that all into. It's a very tricky engine design to get the proportions right on but I suppose there's some information available from the guys at the GTBA who've built turboprop aircraft and helicopters. My problem is that I wouldn't want to go to all that trouble only to have it smashed up in an accident. I think I'll stick to something less risky.
|
|
|
Post by Deleted on Dec 18, 2014 17:14:26 GMT
Quote..."I think I'll stick to something less risky."... the next round of Bankers and their Toxic Assets might do it ??
|
|
uuu
Elder Statesman
your message here...
Posts: 2,809
|
Post by uuu on Dec 18, 2014 17:47:55 GMT
And the tubine is there ONLY to drive the compressor, just the same as the turbo on a car. If you're going to start nitpicking, you could argue that the turbo on a car does not have a compressor - it's an impeller. As with many miniature gas turbines and with the Rover unit that's used as an auxiliary on a...Vulcan bomber. Wilf
|
|
|
Post by goldstar31 on Dec 18, 2014 18:10:50 GMT
Of course- or OFF course,there was the ShmittArgus( sp?)Doodle bug V1 and a frequent visitor to our shores in Days of Yore or correctly Days of Me.
I recall making one to a Corporal Henwood's Design in Aeromodeller. Quite exciting stuff. I had my Fireman's badge in the Scouts, so there was nothing to fear.
And dammit, I ended up at RAF Hendon in my defence of the realm or whatever it was, and was pushed in a pre-war barrack block that had been 'doodle bugged' earlier.
Ah well
Norman
|
|
|
Post by vulcanbomber on Dec 18, 2014 21:42:56 GMT
Well I never, so my memory was right in the first place! It's basically similar to all the TurboJets we know and love. I did wonder how the large fan could possible work at the same speed as the core of the turbine, and there's the answer. Well done Alan! My anoraks about to get a telling off.
|
|
|
Post by Deleted on Dec 18, 2014 22:01:40 GMT
Of course- or OFF course,there was the ShmittArgus( sp?)Doodle bug V1 and a frequent visitor to our shores in Days of Yore or correctly Days of Me. I recall making one to a Corporal Henwood's Design in Aeromodeller. Quite exciting stuff. I had my Fireman's badge in the Scouts, so there was nothing to fear. And dammit, I ended up at RAF Hendon in my defence of the realm or whatever it was, and was pushed in a pre-war barrack block that had been 'doodle bugged' earlier. Ah well Norman For me it was the JETEX motor--light the blue touch paper and RUN !!---------------------
|
|
pault
Elder Statesman
Posts: 1,496
|
Post by pault on Dec 18, 2014 22:47:04 GMT
Roger your right about the front nozzles blowing relatively cool air the rear ones are hot with the jet exhaust. As you get near the ground the hot gasses are deflected horizontally and sucked up into the intakes
|
|
pault
Elder Statesman
Posts: 1,496
|
Post by pault on Dec 18, 2014 22:49:24 GMT
During development they used hover pits so that hot gasses and turbulence/ground effects were not an issue
|
|
|
Post by Deleted on Dec 18, 2014 22:52:44 GMT
It's all explained in that video I posted, including the heat deflectors to the rear of the rear nozzles, and that the rear half of the plane is made from Titanium as it handles the higher temps. better...........Yep, Military hardware does not come cheap--- and the aero department is dearer still !!
|
|
|
Post by Roger on Dec 18, 2014 22:57:51 GMT
We've got so used to seeing the fully developed Harrier that it's easy to underestimate what an achievement it was. I saw three in a row doing their thing at an air show, nodding to the crowd etc, amazing stuff. I found this video that shows just what a knife edge those early flights rested on.
|
|
|
Post by vulcanbomber on Dec 18, 2014 23:04:26 GMT
And the tubine is there ONLY to drive the compressor, just the same as the turbo on a car. If you're going to start nitpicking, you could argue that the turbo on a car does not have a compressor - it's an impeller. As with many miniature gas turbines and with the Rover unit that's used as an auxiliary on a...Vulcan bomber. Wilf But like I said, the turbine is there ONLY to drive the compressor or if you like the compressing part of the engine, the turbine is a drain on power... I used a car turbo to explain it from a different/more friendly angle not to nit pick.
|
|