FN5 turrets for Wellington

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Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » October 31st, 2019, 3:35 pm

Many thanks Stewart. My photo's are not the best. For reasons I do not understand when I photograph them in the workshop, they tend to come out unduly yellow without a flash. Just as we were packing-up, Alex (or Alec?) Whiticker <sp?> the RCME photographer found us, and took a load of pictures with a proper camera and tripod, so I'm hoping he's got some shots rather better than what I've managed to date.

The highlight of the day for me was a Polish father and son, the lad being about six, who just beamed at being allowed to operate the elevation and looking through the gunsight. When the lad read the Polish language cautions on the doors, and (I think) the father then explained that these were Polish-crewed, he was completely made-up. It was a real privilege to see this education and enthusiasm from one generation to another, and it is just what I had in mind making them. (My father, an RAF fighter-pilot right at the end of the war, used to take me, at a similar age as this Polish lad, to the Polish Airman's memorial in Northolt http://bbm.org.uk/of-interest/places-of-interest/the-polish-war-memorial/ as we drove to my gran's. He had strong views on how poorly the Polish ex-servicemen were treated, and likewise all Bomber-command aircrew at the end of the war, and to a degree, since. Hence my choice of a Polish Wellington, of which choice, I think, he would have approved.

The Wellington was also his favourite aircraft, as like most putative aircrew, as he awaited a posting overseas for training, he was put to work on Bomber-Command squadrons to help with the daily efforts to ready aircraft for the next raid. As he was something of an amateur engineer and chemist, he really liked the geodetic design of the Wellington. His chemistry was put to nefarious use, when in the Summer of 1940 my then teenage father was contriving home-made bombs in case Jerry invaded. He and my uncle let off a particularly large one on top of the family Anderson, which set off the local sirens, earning them both a class one bollocking and invitations to join-up without delay! His mains operated high voltage wasp-trap still makes my Aunt chuckle 80 years later!
Attachments
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1940
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Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » November 20th, 2019, 6:35 pm

Progress on the turrets has slowed recently, as the workshop is disagreeably cold. However, I conspired with a Airfix type kit master-modelling mate, to do the "weathering and dirtying". We sat down first and examined the internal turret structures and pipe-work, and determined which area would be liable to get a misting of hydraulic fluid, and then subtracted from these areas those which would have been possible to clean well from inside. The remaining areas were then given a heavy slathering with Alclad's "Dirt and Grime" (A lot goes a short way!). Testing on painted super-ceded parts showed that water-based pigments would not migrate over the surfaces of printed nylon at all well. We then experimented, and found that applying the well diluted pigments to wet methylated spirits with a drop of washing-up liquid proved just the job, and more importantly, the meths didn't attack Alclad enamel, or metal effect paints, or indeed the "dirt and grime".

Although my mate had brought a profusion of pastels, powders, and oil-paints, we decided to 'quit whilst we were ahead'. The weathering has visually tied the differently coloured parts of the turret together rather nicely, but it's difficult to photograph)

The main effort at the moment is getting the MDF shapes cut out to make the 1st of two plugs required to eventually vacuum-form the cuplola windows. Pics to follow as that gets under-weigh.

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Steve Perry
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Re: FN5 turrets for Wellington

Postby Steve Perry » November 21st, 2019, 8:37 pm

I took some photos of the inside of the Wellington turret in the conservation hanger at Cosford, I will upload them when I have time to resize them, basically everything inside is mat black.

stuart knowles 1611
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Re: FN5 turrets for Wellington

Postby stuart knowles 1611 » November 21st, 2019, 11:00 pm

This turret is simply a work of art and, sadly, I feel that it has no place on a flying model. It would be such a waste.
It reminds me of the Spitfire and Mustang models on display in Hendon / Cosford and built by David Glen and it deserves an equally auspicious home. Fair pay to you Mr Huff, I think that you are breaking new ground in the modeller's art.

Incidentally, I noticed that the Mustang had moved from its former display space in the entrance hall at Cosford. I hope that it only a temporary move. Anyone know?

Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » November 22nd, 2019, 1:29 am

Steve Perry wrote:I took some photos of the inside of the Wellington turret in the conservation hanger at Cosford, I will upload them when I have time to resize them, basically everything inside is mat black.


You're quite correct that matt-black is by far the predominant scheme, however at least two others existed. As far as I've been able to determine the schemes were:

Initially bare-metal, until towards the end of 1940 as there was a huge demand for turrets and the two main manufacturers struggled to keep pace with demand. Often painting was left to the Squadrons to do. From late '40 to roughly the end of '41 a grey-green scheme was used for a short time, which became an all-black scheme at the end of '41. Often one can come across turrets in different schemes on the same aircraft, which is either a consequence of them being swapped out, or, simply that they used the paint from the previous scheme at Frazer Nash until the paint was exhausted, only then moving to the new colour. (supposition on my part) Additionally there are what appear to be grey painted schemes, so this may be from local paints being used to moderate the reflective qualities of the bare metal turrets, or simply the vagaries of wartime colour film.

I decided to use a mixed scheme of mostly green-grey and some bare metal. The reason is to aid "depth of field" when photographing from within it. The brighter the turret interior, the more likely the turret interior and outside world both, will simultaneously be in focus - which requires a decent depth of field. An all black scheme might therefore have proven difficult.

Regarding the Cosford Wellington, although the turrets are correct in colour for the era of the marque of Wellington - a T10 - iirc, the existance of the turrets is not. The T10 is a very late war or post-war Wellington built as a flying class-room for navigators under training. Neither turrets were fitted, and instead the positions they'd have occupied were faired over. in 1969 or so the decision was taken to remove the fairings to make it resemble a standard wartime Wellington by adding turrets from another aircraft, but the interior remains to the T10 configuration. There are also differences to the construction of the inner-wings to the more numerous Mk III and MK Ic Wellingtons.

Consequently it's a bit of a "sheep in wolves' clothing", so to speak, and one needs to be a little careful in using it as a guide in some respects, although, you're perfectly correct that matt black was far and away the most numerous scheme.
Last edited by Timothy Huff on November 22nd, 2019, 2:08 am, edited 3 times in total.

Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » November 22nd, 2019, 1:38 am

Many thanks for your kind words. I think if it had been scratch-built, rather than 3dprinted, I'd probably have readily agreed with you, but really all the hard work was on the CAD side, and so in theory I could build a further pair turrets in 8 months or so, whereas these two, in effect prototypes, took nearly 4 years to design and build. Indeed I'm seriously considering re-working the design to simplify assembly, to correct 1 or 2 dimensional errors, and to make them printable in any scale between 1:3 and 1:10, so that if anyone wanted to build and fit them, I could make the parts to the required scale. Once that process has been done, I may well design other turrets to a similar design method, if there's a demand for them; commencing with the FN5a, FN50 and FN20/120 turrets (Lancaster front, mid-upper and rear turrets respectively), followed by some of the Boulton Paul turrets. They are, deeply satisfying, to make. I'm aiming to make the revised design to be buildable in a matter or perhaps 4 months for a pair of turrets.

stuart knowles 1611 wrote:This turret is simply a work of art and, sadly, I feel that it has no place on a flying model. It would be such a waste.
It reminds me of the Spitfire and Mustang models on display in Hendon / Cosford and built by David Glen and it deserves an equally auspicious home. Fair pay to you Mr Huff, I think that you are breaking new ground in the modeller's art.

Incidentally, I noticed that the Mustang had moved from its former display space in the entrance hall at Cosford. I hope that it only a temporary move. Anyone know?

Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » January 11th, 2020, 4:37 pm

The last few weeks have been spent on the thorny problem of making moulds for the cupola windows. After a great deal of thought and endless costings, I've decided to only produce the mould for the front area of the turret, as this is the area with the most pronounced compound-curvatures. The "windows" to the side and above of the cupola are only mildly curved, and could I think be achieved with thin flat acrylic sheet, then as they're bolted in place, I'll try and achieve the required curves by gently heating the acrylic with a hair-dryer or similar. The worst thing that can happen is I write off some sheet.

I had a prolonged look at making the mould in MDF with micro-balloons and resin, but costing this out proved considerably dearer than getting a Chinese 3d printed ABS mould made. I've come across a method of chemically smoothing 3d printed ABS called "Cold Acetone vapour polishing" which I can give a go on some waste ABS bits before working on the mould proper. The only "wrinkle" to solve now is ensuring that heat transfer from the vac-formed Perspex doesn't bugger up the mould! If anyone has experience of coatings that could be applied to ABS to prevent thermal damage I'd be most interested to hear from them!

Attached are pics of the mould. The intention is to fill the hexagons beneath with expanding foam to help prevent it collapsing as it's pulled. Pics to follow when mould arrives and is polished.

1200 MKV PLUG REDUCED 1mm Front for SLA v2.jpg
red denotes area needed
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undersideMKV PLUG REDUCED 1mm Front for SLA v2.jpg
underneath of 2 part mould
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Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » February 12th, 2020, 7:51 pm

Further to the previous post. The ABS pattern (pictured below) has now arrived, and is pretty smooth and much stiffer than I was expecting, so no need for expanding foam or similar. Instead it'll have a skin of fast-cure T28 silicone painted all over the curved surface, with bubbles pricked as they arise. This will be done in 2-3 layers applied at roughly hourly intervals. Then a much thicker layer of T28 mixed with a thixotropic additive to make a stiffer paintable silicone will a slower cure rate that will adhere and not run unduly on steep surfaces. This will go down onto the flat base-board to form a border around the pattern of about an inch and 3/4. (the ABS pattern will be sealed to the baseboard with clay to prevent it running underneath. Some silicones react with plasticine - hence clay)

Once cured, dovetails are cut into this flat layer which will register the silicone mould in a supporting Plaster of Paris/Mod Roc shell. "Feet" will be incorporated into the plaster shell so that when inverted to form the bowl into which resin is cast, it'll sit level and rigid.

Instead of casting the resin/powdered aluminium in one go (which I'm told would likely be too exothermic), it'll be progressively painted on in layers. This should all result in a heat-tolerant accurate form over which to pull the window panels for the front of the turret, as well as teach me some new skills. If you're in the UK, I highly recommend Tiranti Ltd in Thatcham, who have been enormously helpful in teaching me what's required, also Phil from Fighteraces.

Hopefully this'll all work! When to commence is the next issue, as the polyester resin required for the final cast stinks something terrible, so it has to be done in the workshop and that's far too cold at the moment. Also I don't want the silicone mould attracting every bit of fluff, insect etc before the casting is done! Pics etc to follow in due course to account for "Triumphs and Disasters" in the normal fashion. If anyone has experience doing this and has advice or sees an error in "the plan", please sing-out!

It's been fascinating learning how to approach this, and a whole new set of skills are on the cards if I don't make a balls-up of it!

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side elevation of ABS pattern
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underneath
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An example silicone/plaster (in this case 2 part) mould shewing the dovetails/registration.
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Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » February 19th, 2020, 9:42 pm

Lots of progress over the last couple of days. The ABS 3d printed former had been covered with 3 coats of T28 silicone, the first a thin coat, the 2nd with "thixo" added to make it adhere more readily to vertical surfaces without sagging. Silicone is very mucky stuff to work with, I found! Having several missing pots is a good idea, as it's easy to clear cured silicone from within them, but the interval between mixing new batches is shorter than the time required for any given coat to cure. Other than that, it all went tolerably well. I've inspected the inner surface of the mould, and there's neither any air-bubbles nor un-catalyzed silicone, which was a bit of a worry as when I applied the intial coat, although I'd felt I'd mixed the catalyst thoroughly, I saw veins of white uncatalyzed silicone as I poured it on. Luckily it seems to have been catalyzed sufficiently not to present a problem.

This evening I applied the 1st tranche of Plaster of Paris to the exterior of the silicone mould, and then followed that up with a "casing" of "Mod roc" - plaster infused bandage. It's my intention now to allow this all to dry and harden before a 2nd thick coat of Plaster is applied, and then the final casing of mod roc. This should result in a really solid inch and half thick plaster hard casing to keep the silicone mould registered when the pattern is removed.

Tomorrow I'm off to Alchemie to purchase some Epoxy resin, infused with alloy powder, which will - Insh'Allah - result in a highly polishable "metal" former for the vac-forming process. If this all goes as I hope, the end-result will be correctly curved windows for the cupola with optically clear panels - important if good footage is to be achieved from the turrets in flight.

https://www.youtube.com/watch?v=L-pR2LEO8iM Preparation

https://www.youtube.com/watch?v=rwQ2c7wgrs8 Applying the silicone

https://www.youtube.com/watch?v=E_3ixlcwwJ0 Applying the initial plaster and mod-roc to form the mould casing

Tomorrow I'm off to Kineton to procure the EP426 resin and what-not for the resin side of things.

Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » March 10th, 2020, 1:13 am

A slight side-project has begun. I was very kindly given what looks to be a lifetime's turret research recently - some 15 GB of pictures, films, photos and .obj "mesh" drawings. So while I wait to get my beans in row to pour the resin, I've started drawing the FN4 in CAD, using the .obj file given to me as the basis of dimensions and positions. It's sufficiently different from the FN5 to be a welcome change, and thus far, the Brownings, gun-sight and sighting bar are drawn. Eventually I hope to offer this, and the FN5 as kits, in their own right, which can be optimised according to three variables, cost, weight and mechanical complexity - ie does stuff "move"/light-up. I'm also optimising the drawings and build method so that the customer (I can dream!) can specify the required scale.

fn4inprog.jpg
The FN4 - rather less advanced than this picture would seem to suggest!
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The new CAD drawing of the gunsight
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Last edited by Timothy Huff on March 12th, 2020, 1:24 am, edited 1 time in total.

Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » March 12th, 2020, 1:23 am

..and the Fn25, still an .obj, so weeks of work before it's anything like ready to start making parts, and much geometry to check to get a "working" model. This was not a successful turret, as the poor visibility therefrom made tracking fast targets extremely difficult, and the weight, and drag of it when deployed was performance sapping right at the instant when best possible speed was needed. It did however, serve well as the housing the anti-u-boat searchlight "leigh light", when installed as a steerable searchlight used in combination with ASV radar in the Wellington.

FN25 wireframe.jpg
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Re: FN5 turrets for Wellington

Postby Timothy Huff » March 16th, 2020, 3:27 am

Been a busy couple of days. After thinking through the resin pour, it was obvious that managing the movement and position of the male and female moulds, the latter both unwieldy and very top heavy, was going to be difficult, and if I ballsed it up, I was liable to have a great deal of expensive resin covering:

A: The workbench
B: My feet
C: Any tools in the area
D: The floor

This would have been an event not calculated to brighten my day.

So I devised a wooden box and sort of adjustable-gantry arrangement to put all of the above out of contention, and to be able to control the depth vertically of the male mould in the resin, and to control and fix it's position so I didn't end up with a cast with lop-sided wall-thicknesses. No idea if this was all necessary, but as this is all new to me it seemed a sensible precaution to spend a day hammering my thumb and getting splinters in my fingers (I am utterly hopeless at woodwork, in the manner that some people cannot parallel-park), to forestall any forseeable foul-ups once the thing is full of resin, which would not be a good time to try and devise solutions for problems!

Film of the box design and whatnot at https://www.youtube.com/watch?v=29dsCVFI0HM

And a few stills:

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Looking slightly down between M and F moulds
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view from other end
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The sticks on top tension ABS M mould to gantry via twisting the wires
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From above. Top of gantry about waist heigh
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Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » March 18th, 2020, 6:32 pm

Did the pour yesterday. Film here:

https://www.youtube.com/watch?v=NUdkm9IOzCc&t=475s

Not easy, for reasons stated in the film, with a few things catching me by surprise. With a little luck it'll be ok, as I fear there are bubbles in it. On uploading the film yesterday started to feel a bit grim, went to bed at 6pm and awoke 1pm, decidedly under-par. (We've been self-isolating since my daughter copped for a high temperature a couple of days ago). Fortunately I can tinker in the workshop or work on CAD, and not go "stir-crazy" as some will no doubt do! Amazon delivered loads of wet-and-dry in various grades today, so assuming the demould goes well, I can start sanding the resin to within an inch of its life over the next few days, and then polish it. There's also the heat-treat and cool-down to do, but I'm going to take some advise on that, as it's possible it'll cause bubbles in the resin to expand and damage it.

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Re: FN5 turrets for Wellington

Postby Timothy Huff » March 26th, 2020, 12:26 pm

Well, the demould is done. In the words of Lady Macbeth "if it were done, best it were done quickly". It took 2 days to get the blighter out. The reason was an error of judgement earlier in the process, when I used the maximum amount of 'thixo' for the last two coats of silicone. This lead to a very "knobbly" exterior to the mould, so that putting the plaster bandage straight onto it would have been problematical. Instead I covered it with a sufficiency of plaster, and then once that was smooth-faced, followed it up with mod-roc.

This created two new problems. The first was that as the plaster dried and cracked a little - as it's won't to do - one or two little pieces migrated down between the silicone and the hard plaster, altering the shape of the casting when poured. I was very fortunate in that this only occurred in one place, and is easily dealt with. The second problem was that later on, I couldn't detach the casting and the silicone easily from the plaster/mod-roc casing, so had to demould the resin from the intact plaster/silicone mould. As the resin alone weighs some 15-20 kg, this was not easy. Had I been able to remove the cured resin cast and silicone from the plaster easily, then peeling the silicone from the resin cast would have taken seconds, not 2 days.

The silicone also had an air-tight seal on the resin. I tried injecting air with syringes - no joy. In the end I inserted 100 old lolly-sticks between the silicone and resin, and eventually reduced the area the silicone was in contact with the cured resin just enough to move one slightly in relation to the other. All the sticks were then removed, and reinserted at one end, and finally I got the bugger out. It was one of those jobs you have to keep walking away from, as you feel the frustration building, as it would have been folly to go in with harder tools and break or score the resin.

The next job is the post-cure heat treat, but I have to make a set of supports for it, as it will only fit in the oven at a peculiar angle. A temperature probe and a good book will make the hours fly by as I babysit this thing in the oven - the temperatures are far below what my oven thermostat can achieve, so it'll have to be turned on and off using the hand-held probe as a guide.

https://www.youtube.com/watch?v=o9gEYqm3L6A, more or less covering the above.

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Re: FN5 turrets for Wellington

Postby Timothy Huff » April 1st, 2020, 8:33 pm

The post-cure heat-treat has been done, without causing any warpage of the resin vac-forming tool, or issues with trapped air in the resin breaking it. It took four hours, in my kitchen oven turning it off and on to maintain 40C degrees for one hour, then 60C, 80C, 100C before an overnight slow cool-down.

It did make my "chips" taste a bit peculiar for a couple of days afterwards! :lol:

Since then, I've been sanding the resin tool with more and more fine grades of wet-and-dry, filling-in any low-spots with car-body epoxy-filler and then re-sanding it. I'm now down to 1200 grit, and it's starting to look pretty smooth and blemish free. As I can't get the pull done until this blessed Cv19 falls over, I intend to give it a gentle sand or two each day with 1200 grit until such time as it gets pulled. I've some polishing wheels (woolen) coming, so can polish the acrylic post-pull as well, using a Proxxon. Anyone have a recommendation as to the best polish they've used on acrylic?

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Re: FN5 turrets for Wellington

Postby Timothy Huff » May 13th, 2020, 11:09 pm

Hi all,

The vac-forming over the resin tool has now been done in 1mm polycarbonate, and a lifetime's supply of 1mm of the same as sheet material has also arrived, which will eventually be used to glaze the extensive fuselage windows of the Wellington 1c. Some will require further moulds making, eg the bombardiers windows in the lower nose, and of course the astrodome. So now the careful business starts of cutting these pulls up, for bolting to the cupola structure and external brass-strapping. Any surplus window panels will be salted away as spares in case of "hangar-rash" or other degradation.

https://www.youtube.com/watch?v=howM3vCfF8Q

Edit: Addendum: Pictures taken earlier today, after trimming and fitting the front and front quarter panes to the front turret cupola. It looks like each cupola will take 4-5 days to do all the fitting and final assembly.
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Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » May 18th, 2020, 7:42 pm

After a marathon effort today, the front turret cupola is finished, bar for the ventilators in the quarter right and left window panels, the position of which I need to research. In the cup2.jpg note the 3 M1 machine screws and nuts per attachment. Each nut was started with my cocktail-stick with a blob of blutak, and has to be placed on the thread end, then very gently teased with the stick until the nut starts on the thread, whereafter I can go on in with nut-spinner and jeweller's screw-driver to finish it. Once the cupola is complete, I'll put a little locktite on the exposed threads to prevent the nuts unwinding with vibration. Once the cupolas are completed I'll post some pictures with them on the turrets. The front of each cupola engages with "feet" on the turret assembly, and then is held down at the back by two screws which go down through the cupola and through the alloy plate on which most of the turret mechanism is built.

cup1.jpg
External view cupola with straps bolted
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cup2.jpg
View within cupola shewing profusion of nuts
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cup3.jpg
gunner's eye view.
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Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » May 23rd, 2020, 11:05 pm

Well, I'm on the home-straight now, and anticipate completing both turrets within 2-3 weeks. Both cupolas are now more or less done, with 3 more window-panels to do on the rear-turret. After they're done, I need to re-tighten all the M1 machine-screws/nuts on the cupolas (roughly 100 of each per turret), and then Loctite them with SF7400 which can be applied to the excess thread to prevent nuts from vibrating and backing off.

The turrets inner gubbins then needs similar treatment for the same reason, as well as a little residual wiring and fault-finding. (one of the collimating gunsights seems to have packed up).

Many thanks to Helimadken who most generously printed the two (different) tubs for the turrets, and who has just despatched the one for the front turret, the fitting of which looks like being the final job. The turrets will then be salted away for eventual fitting to the airframe, and you'll be glad to hear that that'll be an end to posts on the subject! Without his help these large features would have been too expensive to warrant printing commercially. So a HUGE thankyou!

In unrelated news, I've figured out how to convert .obj (mesh) files to .step (3d solid object) files, which means with a little luck I'll be able to convert the drawings of the FN4 and FN25 sent to me by James-in-Newcastle, before amending the designs so as to be able to actually make working turrets/kits.

At the end of the year, when the weather evicts me from the workshop again, I hope to make further progress converting the FN5, FN4 and FN25 turrets into drawings for assemblies that can be glued together rather than bolted, and either printable to a desired scale, or produced as an injection moulded kit in a specific scale, likely circa 1/5th or 1/6th.

Anyway, here's the latest film, shewing the nearly complete turrets and some audio explanation of stills taken during the latest portion of the build.

https://www.youtube.com/watch?v=ppVC-NaSqBM

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Re: FN5 turrets for Wellington

Postby Steve Mansell » May 24th, 2020, 5:33 pm

Stunning!

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Re: FN5 turrets for Wellington

Postby Timothy Huff » May 26th, 2020, 2:56 pm

Cheers Steve

Over the last day or two I've assembled the cupola for the rear-turret and married these to the internal mechanism. I decided to rework the clips which hold the perpex panels in place with the addition of 3d printed scale "penny washers", painted to a brass colour. These make putting the nuts on easier, as the screws can't fall out when trying to start the nut on the thread, and look much better from the inside. So when they've arrived and been painted, I need to refit most of the clips.

Also still to come is the "tub" for the front turret, qv. I'm probably also going to make stands for them, similar to those used at the central-gunnery school, where gunner's under training could operate turrets powered hydraulically by a nearby lorry-borne generator. It'll be ages before I'm in a position to mount them in the fuselage. At some point I'll open the doors and try and photograph them from the view I hope to eventually obtain from the "gunner's eye" FPV cameras.

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