Duxford museum (and a question to any engineers)
Discussion
Today I went to the Aircraft museum at Duxford.
Bloody brilliant! An amazing display of aircraft, well laid out, with two restoration hangers (axel stands 5 feet high!!!). My favourite was a section of the Iraqi Supergun, made in Halesowen.
And the 3,000 mph SR-71.
And the Vulcan.
And the....
Well worth a visit. No doubt they would entertain a Pistonheads meeting there- a good displeay of cars. That would be a very enjoyable day. (They would'nt let us use the runway, though...)
Ok, now for the question. There's an aircraft there called the Fairly Gannet. It has two engines, side by side in the fuselage. It also has two propellors spinning from the same hub (one behind the other, contra-rotating).
My question is this: What is the coupling for this mechanism?? One engine drives each propellor, but the drive for one propellor must go through the drive for the other one. And they turn the opposite way. It must be horrifically intricate, and I (not being an engineer) cannot picture how this mechanism would work.
Can anyone explain this to me please??
many thanks
Bloody brilliant! An amazing display of aircraft, well laid out, with two restoration hangers (axel stands 5 feet high!!!). My favourite was a section of the Iraqi Supergun, made in Halesowen.
And the 3,000 mph SR-71.
And the Vulcan.
And the....
Well worth a visit. No doubt they would entertain a Pistonheads meeting there- a good displeay of cars. That would be a very enjoyable day. (They would'nt let us use the runway, though...)
Ok, now for the question. There's an aircraft there called the Fairly Gannet. It has two engines, side by side in the fuselage. It also has two propellors spinning from the same hub (one behind the other, contra-rotating).
My question is this: What is the coupling for this mechanism?? One engine drives each propellor, but the drive for one propellor must go through the drive for the other one. And they turn the opposite way. It must be horrifically intricate, and I (not being an engineer) cannot picture how this mechanism would work.
Can anyone explain this to me please??
many thanks
Well worth a visit. No doubt they would entertain a Pistonheads meeting there- a good displeay of cars. That would be a very enjoyable day. (They would'nt let us use the runway, though...)
Willimp
Last year's Mania was held at Duxford and the runway was opened up in the late afternoon for the sprinters to have a go. More than 500 TVRs went along. You can see a review of it here:
http://web.ukonline.co.uk/cambs-tvrcc/duxford-mania.html
AF
Not being an engineer myself, the intricaies as to how these coupled engine systems work is not altogether apparent. Mosr propellors are driven through a gearbox (known as the reduction gearing) and I think the two driveshafts were somehow coupled within this gearing thereby having one final drive to each propellor. I would assume that one shaft was hollow. Contra-rotating props, both single and twin engined, became popular in the 1940s as designers struggled to extract as much efficiency from both piston and turboprop engines. Examples of twin coupled ebgines include the Bristol Brabazon airliner and the SARO Princess flying boat. The necessity for such complicated arrangements was obviated by the arrival of the jet engine.
EricMc got the basics right, but not being an engineer I cant really go into too many details. But it is a single engine with a reduction gearbox that drives the second propeller on the same spindle. Anyway, the reason is that the engine is so powerful they need to do something to reduce the effects of yaw.... cant explain it any better than the following link:
www.aerospaceweb.org/question/dynamics/q0015a.shtml
Aint the web great....
Dont forget that Spitfires at the start of the WWII had something like 400-500BHP engines. At the end they were pulling 800+. The Seafire was then upto 1000+. Modern warbird racers in the USA get even higher with 1200+ common....
Cheers,
Paul
www.aerospaceweb.org/question/dynamics/q0015a.shtml
Aint the web great....
Dont forget that Spitfires at the start of the WWII had something like 400-500BHP engines. At the end they were pulling 800+. The Seafire was then upto 1000+. Modern warbird racers in the USA get even higher with 1200+ common....
Cheers,
Paul
Today I went to the Aircraft museum at Duxford.
Bloody brilliant! An amazing display of aircraft, well laid out, with two restoration hangers (axel stands 5 feet high!!!). My favourite was a section of the Iraqi Supergun, made in Halesowen.
And the 3,000 mph SR-71.
And the Vulcan.
And the....
Well worth a visit. No doubt they would entertain a Pistonheads meeting there- a good displeay of cars. That would be a very enjoyable day. (They would'nt let us use the runway, though...)
Ok, now for the question. There's an aircraft there called the Fairly Gannet. It has two engines, side by side in the fuselage. It also has two propellors spinning from the same hub (one behind the other, contra-rotating).
My question is this: What is the coupling for this mechanism?? One engine drives each propellor, but the drive for one propellor must go through the drive for the other one. And they turn the opposite way. It must be horrifically intricate, and I (not being an engineer) cannot picture how this mechanism would work.
Can anyone explain this to me please??
many thanks
About the SR71. It's top speed was mach 3 which is about 2100mph ish. 3000mph is just over mach4.
The Gannet was originally designed as a carrier borne anti submarine aircraft. The fuselage mounted twin engines were designed to eliminate the excessive torque effect which can be disastrous in the event of an engine failure on a conventional twin, especially on take off.
The Gannets served on the Royal Naval carriers from the mid 1950s right up to the withdrawl of HMS Ark Royal in 1978. The final versions of the Gannet were very different to the original ones, These last types were known as Ganner AEWs and provided early warning radar cover for the fleet. Ironically, it was the lack of any airborne early warning radar during the Falklands campaign that led to the loss of so many ships. Gannets were unable to operate off the new, smaller, Through Deck Cruiser type carriers.Following the Falklans, some Sea King helicopters were converted to carry out the AEW role - pity they hadn't thought of that before 1982.
The Gannets served on the Royal Naval carriers from the mid 1950s right up to the withdrawl of HMS Ark Royal in 1978. The final versions of the Gannet were very different to the original ones, These last types were known as Ganner AEWs and provided early warning radar cover for the fleet. Ironically, it was the lack of any airborne early warning radar during the Falklands campaign that led to the loss of so many ships. Gannets were unable to operate off the new, smaller, Through Deck Cruiser type carriers.Following the Falklans, some Sea King helicopters were converted to carry out the AEW role - pity they hadn't thought of that before 1982.
pbrettle said: EricMc got the basics right, but not being an engineer I cant really go into too many details. But it is a single engine with a reduction gearbox that drives the second propeller on the same spindle. Anyway, the reason is that the engine is so powerful they need to do something to reduce the effects of yaw.... cant explain it any better than the following link:
www.aerospaceweb.org/question/dynamics/q0015a.shtml
Aint the web great....
Dont forget that Spitfires at the start of the WWII had something like 400-500BHP engines. At the end they were pulling 800+. The Seafire was then upto 1000+. Modern warbird racers in the USA get even higher with 1200+ common....
Cheers,
Paul
Actually the Mk II Spitfire, introduced just before the Battle of Britain, was rated at 1,030hp. By the time the Mk IX came along in early 1943, and the first to feature direct supercharging, this figure had gone up to an officially quoted 1,700hp. Amazing to think that these were often flown in combat by 20 year olds with less than 20 hours on type. Heroes.
And don't forget that the final version of the Spitfire, the Mk24 with its Rolls Royce Griffon was producing 2,500 hp.
I am equally impressed by the heavy bomber pilots. Those lads were invariably aged between 20 and 22, most of them didn't even posess drivers licences. The entire welfare of the crew was in their hands as none of the RAF heavies (Lancaster, Halifax and Stirling) had a co-pilot (unlike the American B-17 and B-24). If the pilot was killed or injured, the aircraft was in big trouble. Many pilots gave basic handling lessons to their flight engineers so that they could at least hold the 'plane straight and level in order that the crew could bale out.
I am equally impressed by the heavy bomber pilots. Those lads were invariably aged between 20 and 22, most of them didn't even posess drivers licences. The entire welfare of the crew was in their hands as none of the RAF heavies (Lancaster, Halifax and Stirling) had a co-pilot (unlike the American B-17 and B-24). If the pilot was killed or injured, the aircraft was in big trouble. Many pilots gave basic handling lessons to their flight engineers so that they could at least hold the 'plane straight and level in order that the crew could bale out.
In answer to the original question, each turboprop engine in the Gannet drives its own prop through a reduction gearbox. The solution is pretty simple - the output shaft from one gearbox is hollow, with the other passing inside it.
This idea of hollow shafts isn't as uncommon as you might think nowadays. All modern airliners use turbofan engines with multiple stages of compressors and turbines. Each stage (or spool) runs at a different speed, and hence has a separate driveshaft. A RR Trent has three spools, so three concentric shafts.
Another great advantage of the Gannet design is that it eliminates the torque effect of a single prop, from both the engine's rotation, but more importantly from the propwash flowing over the fuselage. Counter rotating props act much more like a jet in simple terms. Even some of the later Griffon engined Spitfires ran counter rotating props from a single engine, in a bid to control this.
A final oddity is the wartime DeHavilland Mosquito. A conventional twin engined design, each of its Merlin engines rotated in a different direction to counter the torque effect on such a light but powerful aircraft. Not down to different gearboxes, but the engines themselves fired in oposite directions!
Right, enough waffle from me!
Pete
(AMRAeS, frustrated ex-aero engineer)
This idea of hollow shafts isn't as uncommon as you might think nowadays. All modern airliners use turbofan engines with multiple stages of compressors and turbines. Each stage (or spool) runs at a different speed, and hence has a separate driveshaft. A RR Trent has three spools, so three concentric shafts.
Another great advantage of the Gannet design is that it eliminates the torque effect of a single prop, from both the engine's rotation, but more importantly from the propwash flowing over the fuselage. Counter rotating props act much more like a jet in simple terms. Even some of the later Griffon engined Spitfires ran counter rotating props from a single engine, in a bid to control this.
A final oddity is the wartime DeHavilland Mosquito. A conventional twin engined design, each of its Merlin engines rotated in a different direction to counter the torque effect on such a light but powerful aircraft. Not down to different gearboxes, but the engines themselves fired in oposite directions!
Right, enough waffle from me!
Pete
(AMRAeS, frustrated ex-aero engineer)
the best time to be there is the few days leading up to the airshows, then you can see the spits/hurricanes/P51 and corsairs chasing each other around the sky practising for the show.
The sound of the airplanes, at full tilt down the runway at 50 feet, rrroooooaaaaaaahhhhrrrrrrr ..damn it makes me fuzzy all over mmmmmmm..
ref SR71, the top speed is still classified, over mach 3 is the official topspeed
The sound of the airplanes, at full tilt down the runway at 50 feet, rrroooooaaaaaaahhhhrrrrrrr ..damn it makes me fuzzy all over mmmmmmm..
ref SR71, the top speed is still classified, over mach 3 is the official topspeed
An official speed record of 2193.167mph was set in 1976, whether it has gone faster has not been released.
Re. the Mosquito, the pictures I have seen of them, both the props are in the same pitch.
If they rotated in different directions, wouldn't one prop be pushing and the other one pulling??
Or am I missing the point here.
Re. the Mosquito, the pictures I have seen of them, both the props are in the same pitch.
If they rotated in different directions, wouldn't one prop be pushing and the other one pulling??
Or am I missing the point here.
The capabilities of the SR-71 being still classified is a bit pointless as there are none in service anymore. I know NASA kept one airworthy up 'til a short while ago but even that's been grounded now. The SR-71 still holds the Trans-Atlantic record with a New York-London time of 1 hour 55 minutes. This record was set in September 1974 when an SR-71 visited the Farnborough Airshow that year.
The SR-71 was retired, and a couple put in storage.
They were reactivated for a short time, (6 months)?? in the 90's then retired again.
Rumour had it that it had been replaced by the Aurora, a Mach 5 replacement.
The reason for retiring the SR71 was strange aswell, as Satellites had many disadvantages, such as predictability.
On the subject of Spyplanes I hear a U2 has gone down in Korea.
They were reactivated for a short time, (6 months)?? in the 90's then retired again.
Rumour had it that it had been replaced by the Aurora, a Mach 5 replacement.
The reason for retiring the SR71 was strange aswell, as Satellites had many disadvantages, such as predictability.
On the subject of Spyplanes I hear a U2 has gone down in Korea.
SUPRAMAN said:Re. the Mosquito, the pictures I have seen of them, both the props are in the same pitch.
If they rotated in different directions, wouldn't one prop be pushing and the other one pulling??
Yes, you're exactly right. The Mossie was definitely designed to use handed engines, but it looks like most early aircraft were built with both engines rotating the same direction. Later models reverted to handed engines, as did the dH Hornet.
I stand corrected
Pete
Re the SR-71. Check out www.blackbirds.net/sr71/sr_reactivation/react.html for the story on how a couple of SR-71s were brought out of retirement in the mid 90s.
I'd also recommend anyone interested in engineering or aviation to read "Skunk Works", the memoirs of Ben Rich. It's a fascinating story of how Lockheed built the U2, the SR-71, and the stealth fighter programme.
Pete
I'd also recommend anyone interested in engineering or aviation to read "Skunk Works", the memoirs of Ben Rich. It's a fascinating story of how Lockheed built the U2, the SR-71, and the stealth fighter programme.
Pete
chris.mapey said: Proud Head on & puff out chest...
My Dad's uniform & medals are on display @ Duxford - in the new Cambridgeshire Reg't section (Far Eastern Prisoners of War - Burma - Thailand railway)
Even apart from family bias, Duxford is a grand day out.
Wow!! Amazing stuff. I saw that exhibition as well, (My Grandad was out in Burma with the Royal Artillery).
On another (not quite so special point), the meseum has two chipmonks. Looking at my old flying log book, I felw in one of them (WB 569) three times (based at manston in Kent). Happy days.
The SR-71 itself was derived from a high speed interceptor called the YF-12. Unfortunately, the YF-12 was cancelled by the Kennedy administration and Lockheed had to think up an alternative role for the aircraft quickly. A number of YF-12s actually flew and I'm sure they still survive tucked away at various establishments in the US. Although it was not revealed for over 30 years, the special shape of the YF-12/SR-71 fuselage was built with stealth in mind.
Another extremely impressive aircraft of the early 1960s was the North American XB-70 Valkyrie.
Another extremely impressive aircraft of the early 1960s was the North American XB-70 Valkyrie.
Gassing Station | General Gassing [Archive] | Top of Page | What's New | My Stuff