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Fidd88

Frazer Nash FN5 gun-turrets

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Love a bit of James May. His life size Lego house was also very good, as was the Meccano motorbike which (eventually) managed a lap of the Isle of Man TT course.

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bloody hell....

 

I thought this thread was a question about turrets in the wrong bit of the forum...

 

what I stumbled on is absolutely exquisite - you do what I try and do which is replicate every single bit, bob and doodad in an aeroplane structure, only you do actually do it!

 

bravo

 

...(oh and please don't ever put it in a model that actually leaves the ground...)

 

Peter

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Kind of you to say so Peter, I don't think we're comparable in that respect. All your work is highly skilled and careful - proper modelling and scratch-building really - whereas mine is simply creating shapes on the PC and printing them. It's time consuming and looks good, but it really isn't in the same league as what you've done with the P51. My approach is limited by the few materials I use, whereas you move heaven and earth to recreate a "whatyamacallit" in breath-taking detail - and then hide it! (the very definition of a 1st class modeller?)

Hehe.

For me, it's the engineering of the Wellington that is my primary interest, it's just such an elegant piece of design. I got into it when I realised that the issues which killed this technology stone dead in 1945, namely speed of jet aircraft being higher than the necessarily flexible fabric covering could withstand, and, a better understanding of metal fatigue, which didn't affect Wellingtons as most were struck-off-charge or lost in combat inside 2 months; but which certainly would have affected airliners in longer service. Lastly, it really wasn't possible to pressurise, which put the tin-lid on this technology.

I realised a while back that this technology would be ideal for cargo drones, as it confers a great weight-saving over stressed-skin, is easier to assemble and provides around 30% more "usable space" within the airframe. It's also very tolerant of failures within the structure, and "fails soft" as we might say now, rather than breaking up.

Looking at that problem led me to the Wellington. My father was an RAF fighter pilot at the end of the war, but like many would be aircrew waiting to be sent overseas to train (he went to 1BFTS in Terrel, Tx) he was sent to bomber-stations to assist with the marathon daily efforts to re-arm, re-bomb, service, repair and air-test aircraft for the next mission. He was put with a Wellington squadron, and it was far and away his favourite aircraft, because like me, he was something of an inventor/tinkerer/amateur-engineer

In fact the whole reason he ended up in the RAF was because in 1940, as a teenager he, aided by his brother, had built a home-made bomb, in case the Germans invaded. He didn't forsee that detonating it would set off most of the local sirens, after-which he and his brother were given a 1st class bollocking and invited to join up without delay!

It's certainly my intention  to fly the turrets, within what is in effect, a miniature Wellington, with the geodetics similar to the original but at scale. I admit I shall be rather relieved when the aircraft has a few flights under its belt, and it's quite likely that I'll do early flights with the turret positions fared over and ballasted. Just in case! Because fixings- rivets and bolts - have different properties at scale from a metallurgical point of view, and they cannot be miniaturised to the same degree as the rest of the structure, I've had to accept using what are in effect over-size rivets,  and that impelled a lot of changes to the geodetics sheer and gusset fittings so as not to introduce weaknesses through over-size rivets being set too close together.

To the untutored eye, however, it should look pretty close. One day! For now I've just enjoyed researching, fabricating the turrets. I attach an early test of the infamous "bomb". Sadly no footage or still of the one that caused all the trouble exists. I gathered from my uncle that it "weighed several pounds" and took out several windows. It did, however prove that the Anderson Shelter was "fit for purpose" as they detonated it on top with them inside! The logic of which you probably have to be male,  17 and at war, to follow!

have you seen the films on youtube Peter?

bw1.jpg

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fascinating :)

 

so you do intend on building an entire Wellington and not only that, following the geodetic design principle, and after doing that, commiting it to actual flight?

 

..and I thought I needed a check-up from the neck up...

 

can't wait to see more :)

 

Peter

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Just so. There's obviously a ton of "show-stoppers" that if I can't find solutions for will render it incapable of safe flight. The first is if I can accurately curve extruded alloy channel without great deformation of the cross-sectional shape. I have some ideas for that, but it remains to be seen if that can be achieved. The intention, once the turrets are finished is to attempt to make a geodetic "football" circa 2 feet in dimeter, and then test it to destruction with vibration and shock-loads to see roughly how robust - or otherwise - the structure is. If it's still a go at that point, then the next issue is calculating the wing-loading/weight, and if that comes in ok, calculation of the likely C of G. If all that elicits positive answers, then building the fuselage will commence. In the meantime, I have the turrets done. I started with those as it gave me more time to think about the rather more tricky aspects of wrangling the geodetics.

But as Voltaire said "no problem can withstand the assault of sustained thinking".

My wife says of this project "it's not the destination, it's the journey", meaning that the endless technical problems to solve are fascinating in their own right. She says other things when  I float the idea of hanging the completed fuselage from the sitting room ceiling! :banned:

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5 hours ago, Fidd88 said:

My wife says of this project "it's not the destination, it's the journey", meaning that the endless technical problems to solve are fascinating in their own right. She says other things when  I float the idea of hanging the completed fuselage from the sitting room ceiling! :banned:

I think she’s been taking to my SO - it’s a conspiracy! 

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Truly. Today I started assembling the "cosmetic" ie non-functioning hydraulic pipes. In order to save money by being able to make the "nests" of parts more efficiently packed with parts, I had omitted all straight sections. These were very accurately made from 1/16" K & S metals brass tube which could be glued onto very fine lugs on the ends of 3d printed plastic parts. For now these will be painted and salted away for later fitting. This is because fitting the windows is liable to involve a lot of test-fitting of the cupola, and I don't want to damage the hydraulic lines by fitting them too early.

Film:

and the preceding one of the working pneumatically driven mechanism for raising and lowering the guns:

 

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I just watched both videos and am once again in utter awe at the scope of this work

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