Avro Shackleton on M25 today. Where from and to?
XS587 Sea Vixen will not be going anywhere, it is a core component of the collection and will in time be restored to running condition. Some work has been carried out in the past couple of years on treating corrosion. We are hoping that our latest planning application is approved. If it is, the Sea Vixen will be housed inside and therefore a lot of the problems caused by being outside will simply not occur.
I was told this week that the Shack will become a gate guard, of course plans change!
pm575
I was told this week that the Shack will become a gate guard, of course plans change!
pm575
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WR963 taxi run and the Sea Vixen at GAM
Great video Richard, thanks for posting link to it-and I've "Liked" and "Favourited" it.
Thread drift: here's a link to the photo I took of the Sea Vixen when I visited GAM in 2011:
https://www.flickr.com/photos/48975048@N06/15371796708/
Thread drift: here's a link to the photo I took of the Sea Vixen when I visited GAM in 2011:
https://www.flickr.com/photos/48975048@N06/15371796708/
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Two of the reasons for the Shackleton/Griffon's contra rotating propellors were that the Shack inherited the Lincoln's wing including its' engine spacing distances, and that while the Reno Racing pilots can handle all that torque from a conventional propellor on take-off the average military pilot, on a bad day, might not.
I'm confused.
But it's the front prop that has the larger overall diameter, is it not ?
you may also notice the rear prop blades were a different profile and longer than the front prop blades
It's worth remembering that the rear propellor of a contra-prop can absorb more power than the front. In simple installations such as the Griffons in the Shackleton I'm not sure how much account is taken of that, but when the two props have separate power sources various schemes have been used.
For ultimate efficiency, a single blade is what you need. There are practical difficulties of course, but always use the fewest blades you can for efficiency, more blades for less noise / less space.
More than two rows? Only in ducts, ie in jet engines!
More than two rows? Only in ducts, ie in jet engines!
Thread Starter
There are practical difficulties of course, but always use the fewest blades you can for efficiency,
It turns out the reason for the single blade is to acheive an automatic variable pitch prop:
http://www.ultraligero.net/Cursos/va...e_una_pala.pdf
Last edited by Mechta; 19th Oct 2014 at 00:36.
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Dave,
I may be mistaken on the prop location, I really only saw them fitted to one of my engines after we cut, a damaged tip set down so as to fit to the engine sitting in my office reception, along side it relative from slightly earlier years the Merlin.
Peter R-B
Lancashire
I may be mistaken on the prop location, I really only saw them fitted to one of my engines after we cut, a damaged tip set down so as to fit to the engine sitting in my office reception, along side it relative from slightly earlier years the Merlin.
Peter R-B
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The Shack: always described to me as 10,000 rivets flying in close formation. But am I now one of the few left that actually saw Shacks and their 'predecessors' the Lincolns in action?
In 1953 I used to watch Lincolns from Changi flying a short circuit over Johore Bahru bombing terrorist camps then in 1966-67 Shacks from Khormaksar doing similar short circuits bombing terrorists in the Radfan. So local that in both cases I could hear the crumps of the bomb bursts.
Were these in fact the only times either aircraft were used in action?
In 1953 I used to watch Lincolns from Changi flying a short circuit over Johore Bahru bombing terrorist camps then in 1966-67 Shacks from Khormaksar doing similar short circuits bombing terrorists in the Radfan. So local that in both cases I could hear the crumps of the bomb bursts.
Were these in fact the only times either aircraft were used in action?
Last edited by Four Wings; 21st Oct 2014 at 21:43. Reason: Spelling
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Alan,
I am puzzled by your comment "Two separate power source's for the Shack Contra Prop"
We took apart a very old Griffon 58(to see how things worked) and the simple answer to the two power sources are a set of differential gears that fed of the front part of the crankshaft, that in turn fed one big power transmission shaft which was the rear prop, with a slightly smaller and longer power transmission shaft running through the larger one to power the front prop, all this superb engineering was what could be called , very accurate but very steam age and bordering on the agricultural in size of gears and huge ball and roller bearings, according to the RR people I spoke with to get detailed drawings for said engine the power division was equal, looking at the gears and shafts it really cant have been anything but equal.
P R-B
I am puzzled by your comment "Two separate power source's for the Shack Contra Prop"
We took apart a very old Griffon 58(to see how things worked) and the simple answer to the two power sources are a set of differential gears that fed of the front part of the crankshaft, that in turn fed one big power transmission shaft which was the rear prop, with a slightly smaller and longer power transmission shaft running through the larger one to power the front prop, all this superb engineering was what could be called , very accurate but very steam age and bordering on the agricultural in size of gears and huge ball and roller bearings, according to the RR people I spoke with to get detailed drawings for said engine the power division was equal, looking at the gears and shafts it really cant have been anything but equal.
P R-B
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Peter, as I read it, Alan was referring to an engine/prop arrangement such as the SARO Princess rather than the Shack's Griffon:
From Wikipedia.
I think the Brabazon had a similar arrangement driven by Centauruses?
Any others?
The Princess was powered by ten Bristol Proteus turboprop engines, powering six propellers. The four inner propellers were double, contra-rotating propellers driven by a twin version of the Proteus, the Bristol Coupled Proteus; each engine drove one of the propellers. The two outer propellers were single and powered by single engines
I think the Brabazon had a similar arrangement driven by Centauruses?
Any others?
Quote
Alan,
I am puzzled by your comment "Two separate power source's for the Shack Contra Prop"
You would do well to be puzzled, had I written that. To save you scrolling back I wrote:
In simple installations such as the Griffons in the Shackleton I'm not sure how much account is taken of that, but when the two props have separate power sources various schemes have been used.
If that is not clear enough I cannot and will not help it, but it seemed clear enough when I wrote it that I was contrasting the Griffon/Shackleton props with those driven by separate power sources (e.g. Macchi MC72, Fairey Gannet, Brabazon and SARO Princess, etc.).
Alan,
I am puzzled by your comment "Two separate power source's for the Shack Contra Prop"
You would do well to be puzzled, had I written that. To save you scrolling back I wrote:
In simple installations such as the Griffons in the Shackleton I'm not sure how much account is taken of that, but when the two props have separate power sources various schemes have been used.
If that is not clear enough I cannot and will not help it, but it seemed clear enough when I wrote it that I was contrasting the Griffon/Shackleton props with those driven by separate power sources (e.g. Macchi MC72, Fairey Gannet, Brabazon and SARO Princess, etc.).
Thread Starter
Although the RPM will be equal on the Griffon's differential gear driven contra prop, it should be possible in theory at least, to have different pitches on the two propellers so the rear one could absorb more power.
I can believe that on push/pull aircraft like the Cessna Skymaster and Dornier 335 the rear prop would be in the slipstream of the front one and would thus need higher pitch anyway. Can anyone say if this is this also the case when the two sets of blades are right next to each other as on a contraprop?
I can believe that on push/pull aircraft like the Cessna Skymaster and Dornier 335 the rear prop would be in the slipstream of the front one and would thus need higher pitch anyway. Can anyone say if this is this also the case when the two sets of blades are right next to each other as on a contraprop?
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XS587 Sea Vixen will not be going anywhere, it is a core component of the collection and will in time be restored to running condition.
Delighted to hear it! It's a unique and fascinating aeroplane. I had grave fears that it would be sold-off and some numpty would paint it grey and white! I wish you well with your efforts to preserve it.
I hope the Shackleton that has gone to Bruntingthorpe will eventually move under its own power. The prospect of seeing (and hearing) four Griffons and two Vipers at full power is an exciting one. I can almost see the tail fins waggling already
Delighted to hear it! It's a unique and fascinating aeroplane. I had grave fears that it would be sold-off and some numpty would paint it grey and white! I wish you well with your efforts to preserve it.
I hope the Shackleton that has gone to Bruntingthorpe will eventually move under its own power. The prospect of seeing (and hearing) four Griffons and two Vipers at full power is an exciting one. I can almost see the tail fins waggling already
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Mechta,
From my simple "agricultural" eye of engineering , when we ( my mechanics and I ) started to dismantle the front end(prop end) of the Griffon 58 we removed all the streamlining then started on the hydraulic feathering pot , this in turn was connected to the front prop, which was connected to the two way thrust bearing(this had a rotary oil tank and I cannot remember its name) this in turn was connected to the rear prop, all these Prop to bearing connections were highly engineered straight bars with gear teeth cut into the diameter of the pull/push bars, when any command from the cockpit to alter the pitch of the props was made the props worked in unison, it seems it was unable to offer alternate pitch degrees to the twin set of blades, unless some initial offset was put in at the final assembly of the prop sets. the hydraulic was fed by an internal oil tube coming from the front of the gear casing thru the center of the prop shaft set, and the rotary oil tank pitch change bearing it seemed had a service life of 100hours but all the record cards I ever saw suggested that these were changed almost weekly, when the Shacks were in service, it was the failure of these parts that caused the loss of Pelican 16 into the Southern Sahara desert whilst it was on its way to the UK for a refurb
Perhaps a more enlightened aero engineer could make my explanation easier to grasp!
Peter R-B
From my simple "agricultural" eye of engineering , when we ( my mechanics and I ) started to dismantle the front end(prop end) of the Griffon 58 we removed all the streamlining then started on the hydraulic feathering pot , this in turn was connected to the front prop, which was connected to the two way thrust bearing(this had a rotary oil tank and I cannot remember its name) this in turn was connected to the rear prop, all these Prop to bearing connections were highly engineered straight bars with gear teeth cut into the diameter of the pull/push bars, when any command from the cockpit to alter the pitch of the props was made the props worked in unison, it seems it was unable to offer alternate pitch degrees to the twin set of blades, unless some initial offset was put in at the final assembly of the prop sets. the hydraulic was fed by an internal oil tube coming from the front of the gear casing thru the center of the prop shaft set, and the rotary oil tank pitch change bearing it seemed had a service life of 100hours but all the record cards I ever saw suggested that these were changed almost weekly, when the Shacks were in service, it was the failure of these parts that caused the loss of Pelican 16 into the Southern Sahara desert whilst it was on its way to the UK for a refurb
Perhaps a more enlightened aero engineer could make my explanation easier to grasp!
Peter R-B
The two way thrust bearing was called the translation unit. If it failed, although you could feather the front prop, the rear prop was uncontrolled, and the dynamics of props are such that it would go fully fine. You would get, not a full blown overspeed, but a fast windmill producing a lot of drag.
Had one catch fire and fail on a Mk 3 in '66. We were heavy and could barely maintain height. Started the Vipers, but at that time they were only able to be run at idle or 100% (that was later changed), and they could not be run at 100 for long. Ended up jettisoning fuel with the Vipers running, which had not been cleared. Geoff Grimsdale was the captain.
The oil line to operate the pitch change came through drillings in the sump of the engine. If a piston failed, the con rod was then likely to chop through the sump, so that both props went fully fine and oversped. Don't know about Pelican 16, but this was I believe the cause of the Culloden Moor crash landing (Pop Gladstone) and the Indian Ocean ditching (Hugh Blake)
The straight bars with teeth were called rack bolts. It was possible for one to fail, in which case the front prop and two blades of the rear prop could be feathered, but the one blade would go fully fine. A slow windmill, but lots of vibration.
To get oil from the rotary oil tank to the rack bolts there were spring operated pistons in cylinders attached to the oil tank. Every 5 hours in flight it was necessary to lubricate the T.U.s. This involved increasing the RPM to 2600, then reducing down to the feathering gate, doing one engine at a time. At high revs the centrifugal force pushed oil into cylinders, at low revs the springs pushed the oil out to the rack bolts.
All this from memory. Now, what did I have for breakfast? Damn, I think I forget to have breakfast.
P.S. As regards prop pitch settings, Joe Ashworth's book quotes Front prop fine pitch 23 degrees, feathered 90degrees, Rear prop 24 fine, 91 feathered.
Had one catch fire and fail on a Mk 3 in '66. We were heavy and could barely maintain height. Started the Vipers, but at that time they were only able to be run at idle or 100% (that was later changed), and they could not be run at 100 for long. Ended up jettisoning fuel with the Vipers running, which had not been cleared. Geoff Grimsdale was the captain.
The oil line to operate the pitch change came through drillings in the sump of the engine. If a piston failed, the con rod was then likely to chop through the sump, so that both props went fully fine and oversped. Don't know about Pelican 16, but this was I believe the cause of the Culloden Moor crash landing (Pop Gladstone) and the Indian Ocean ditching (Hugh Blake)
The straight bars with teeth were called rack bolts. It was possible for one to fail, in which case the front prop and two blades of the rear prop could be feathered, but the one blade would go fully fine. A slow windmill, but lots of vibration.
To get oil from the rotary oil tank to the rack bolts there were spring operated pistons in cylinders attached to the oil tank. Every 5 hours in flight it was necessary to lubricate the T.U.s. This involved increasing the RPM to 2600, then reducing down to the feathering gate, doing one engine at a time. At high revs the centrifugal force pushed oil into cylinders, at low revs the springs pushed the oil out to the rack bolts.
All this from memory. Now, what did I have for breakfast? Damn, I think I forget to have breakfast.
P.S. As regards prop pitch settings, Joe Ashworth's book quotes Front prop fine pitch 23 degrees, feathered 90degrees, Rear prop 24 fine, 91 feathered.