FN5 turrets for Wellington

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Timothy Huff
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Joined: January 23rd, 2018, 4:12 pm
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FN5 turrets for Wellington

Postby Timothy Huff » January 23rd, 2018, 9:34 pm

Hi all,

I'm working on (roughly) 1/4 scale Vickers Wellington, and have started with the turrets, having taught myself CAD over the last year. Early drawings were with sharp pencils!

The FN5 was a twin gun turret, used front and rear on the Mk IC Wellington, with a slightly different cupola (Perspex bit) on the rear turret. Later the rear turret was up-graded to 4 guns, which was common on MkIII's onwards.

The turret, even at 1/4 scale presents some challenges both in drawing and building. I set myself the aim of making as a near a copy as I could, with concealed servos for traverse and elevation, and to have the gun-sight remain parallel to the guns in elevation as they are raised and lowered. The in intention, eventually, is to fit an FPV camera in the back of the turret - hence going a bit OCD with the design. Some drawings were donated from a very talented mate who shall have to remain nameless.

There were a number of parts that exceeded my skill to make, even using 3d printing, so a lot of redesign had to happen to replace rivets with bolts/machine-screws. There are two limit-switches hidden within the chordal braces (main support for the gun-cradle), either of which will kill current to the elevation motors as the cradle reaches +60 degrees/-45 degrees. The linear motors are again concealed within the hydraulic rams. The traversing step motor will operate underneath at the rear, and again has little pylons to engage with limit motors to prevent over-running the +/-110 degrees for the front turret.

I recently completed the 4 10" long "Brownings", and reacquainted myself with using an Airbrush after 30 odd years hiatus. Since this photo I've added the painted Armourers numbers and "L" and "R" to each gun. If anyone can tell me the words typically stencilled to the top of the guns at the rear I'd be much obliged!

Early FN5's were essentially bare aluminium internally, which is the scheme I'll adopt, rather than the soot-black later adopted.

If anyone spots any egregious errors, I'd love to hear about them.
LMAFn5wireframe.jpg
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LMAbitsFn5.jpg
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LMAFN51ocC.jpg
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lmabrownings.jpg
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LMAFn5nc.jpg
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ian redshaw
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Re: FN5 turrets for Wellington

Postby ian redshaw » January 25th, 2018, 11:44 am

Hi Timothy, a very interesting project for sure. In the ceiling space of my workshop I have the ex Ghost Squadron Wellington which (when I get round to restoring it) I planned to do the very same thing with. This is just under 1/4 scale so I'd be interested if you would be able to supply any turret parts etc as the ones on this one have disintegrated a bit and have no internal details. Yours look superbly detailed which is the way I'd want it to be for the potential 'aircrew viewers'. How is the airframe on yours, planned, built or work in progress? In in no rush as I have so much other non model aeroplane stuff going on at the moment. We also have a brace of 1/4 scale Defiants which need detailed turrets, I made a start on some of the basic parts for the Boulton Paul turrets using the design packages we have at school (Pro Engineer) Any more pics you can share, the quality looks superb!

Cheers, Ian.

Timothy Huff
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Joined: January 23rd, 2018, 4:12 pm
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Re: FN5 turrets for Wellington

Postby Timothy Huff » January 25th, 2018, 1:29 pm

I'd be happy to help, however, using predominantly 3d printed parts is a very very expensive route, and if you're aiming for "stuff to move" using the linkages of the full-size turret, then there's a great deal to fit into a small space. The drawings for this turret took a year, with several hundred distinct parts and over 600 revisions. This would have been less but I was forced to change the scale halfway through, and of course I was "learning" CAD during the course of it, The ammunition chutes alone were drawn over 40 times until I was happy with them - and learned to do 'compound curves'.

Were I doing a turret from scratch now, with some decent technical drawings to go from, I could probably draw it in 4 months or so, and produce the parts in a few weeks. The problem, is price, you need a lot of very accurate prints if everything is to move correctly - around £800 per turret from a commercial printer. If it's non-moving, then my suggestion would be to buy a Dremel 3d printer, and to print the parts yourself. The other difficulty with the DIY printing is the relatively small "maximum part size". That route would probably bring the price down to £800 and leave you in possession of a useful tool as well as the turret...

My parts have a profusion of 0.8mm and 1.4mm holes to tap out at M1 and M1.6 respectively so they'll take a year to build on current estimates.

My advice, would be to give a small list of parts that are going to be highly visible, such as the guns and perhaps main mounts to someone like me to draw, and then to print the parts yourself, building as much of the rest of the turret as possible from balsa etc to keep costs down. Resin machine-guns of various types are available on the web, and can usually be re-scaled as required by the seller. If it's .303 Brownings you want, I can price-up them up. If they can be made at "my" scale, I'd do that for free, other than the cost of printing. If they need rescaling there'd be a bit of redrawing to do as hole-sizes for machine-screws and the brass barrels diameter need to be corrected.

The cocking levers and working-parts on my Brownings draw rearwards against spring-pressure, and the guns are correctly "handed" ie both guns have the cocking levers and fire/safe switches on the inboard face.

My intention is to build my Wellington in extruded aluminium channel at 1/4.5 scale, using redesigned "shear" and "wishbone" fittings of the original, amended to allow for what are effectively oversize rivets/machine-screws. Turrets first though! I've built the jig for the fuselage last year, which allows for it to rotate about the longitudinal axis at waist-height and be locked off, so that as the fuselage is built, I can work on all sides equally easily. Important in a small workshop.

I attach a picture of the redesigned geodetics fittings, (the profile of the channel has changed since) and a clearer drawing of the Brownings I did in case they're of use to you or anyone else. Mine are 10" long.

If you want help with drawings or to have parts made, let me know. Some elements of mine are not mine to give - as they were done by someone else.

LMAbrowning v61.jpg
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lmajig.jpg
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LMAgeodetics assembly with 2.0v6 shear fittings v42.jpg
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Timothy Huff
Posts: 6
Joined: January 23rd, 2018, 4:12 pm
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Re: FN5 turrets for Wellington

Postby Timothy Huff » January 25th, 2018, 9:12 pm

You may also be interested in the ammunition-belts I'm currently working on. They're designed to resemble linked .303 rounds, but also to behave as linked rounds do, IE be slightly flexible about three axes relative to the neighbouring round. I did this by making the "link" entirely cosmetic, and by actually linking each pair of rounds from underneath, each round engaging with the next via tapered shaft and larger, differently tapered cavity in each adjoining round. These will be 3d printed and painted.

For clarity, I've made some pictures "false colour" so you can see how it works:

rounds over false colour.jpg
What's going on viewed from "good" side
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rounds under false colour.jpg
What's going on underneath
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rounds closed.jpg
How they appear assembled
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rounds opened.jpg
How they're constructed
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I'm having a look at the Defiant turret - the Boulton Paul turret would be several months work, as it's not an FN5, but making parts for your Wellington should be possible, at least for two-gun FN5's. If it's a Mark III onwards it should have an FN20 4 gun turret, which would again require a great deal of additional work. Looking at the Ghost Sqn site, it suggests your Wellington is 1/6th scale. What might be a sensible thing to do, therefore, would be to make a 3d printed-turret using my designs, but only capable of traversing. I could then leave-out a lot of invisible components and effectively fuse-together the principle parts of the structure giving you something that resembles mine without generating work rescaling lots of smaller components. You'd need to make the cupola yourself, as I've not yet produced patterns for making that. Mine will have the shaped straps of metal on the outside of the turret done via chemically-etched alloy, most likely.

John Greenfield
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Re: FN5 turrets for Wellington

Postby John Greenfield » January 26th, 2018, 9:18 am

Ian / Tim
I can confirm that my Wellington was built to a scale of 1:4.5.

http://www.ghostsquadron.co.uk/wellington.html

Would be great to see it out flying again Ian.
There is also Andrews Wellington on the GS website which was built to a smaller scale and which we are still flying.

John
Ghost Squadron

Timothy Huff
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Re: FN5 turrets for Wellington

Postby Timothy Huff » January 26th, 2018, 3:31 pm

Ah, must have been the other one I saw. I've always known yours as "The Greenwood Wellington" rather than "the Ghost Sqn one", I didn't realise they were one and the same. May I say what a truly beautiful model that is.

Timothy Huff
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Joined: January 23rd, 2018, 4:12 pm
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Re: FN5 turrets for Wellington

Postby Timothy Huff » February 6th, 2018, 11:56 pm

Ian,

I tried emailing you but it didn't work. I'm happy to have a crack at a simple version of the Boulton-Paul Mk IId turret suitable for your "Defiants", but need some information from you, see attached image. I'm now waiting for parts here, so if you were able to give me these dimensions, and the desired scale of your Defiant(s) I can draw something up. The turret will likely be free to rotate in elevation, but not motorised or similar to do so, and of course you can figure out traverse. It will probably cease at the same level as the lower cupola - chest high for the gunner. You can then decide if you want the basic drawing of the turret and get it printed yourself. I estimate that if you did the printing commercially, the costs would likely be north of £300. The guns I'd print for you, as I'm now hoping to produce kits eventually for the FN5, FN5a, FN50 and FN20 turrets, so obviously am not comfortable with circulating files of stuff that I hope to sell in due course. However, as a one-off, I'm happy to help with your Defiants in this way.

Regarding FN5's, I have some 1:4.5 scale parts that are surplus here, most of the spent-cases chutes, including the V profile lower section, suitable for a tail-turret FN5, and two hydraulic accumulators (only 1 needed per FN5), the top of the gun-sight and a few other odds and sods. You're welcome to these if you can use them, free and gratis. I've yet to build my FN5's, so would rather not be producing parts for these yet other than for my own use, until I'm more certain everything assembles properly, however, if you wanted, for example a pair of Brownings made at 1:4.5, then we could come to terms on that.

Which brings me onto my next point. I designed mine, initially, really just for my own use and as an exercise to see if I could. I think most people, if they'd want them at all, will likely only want particular components 3d-printed, to whit, those shapes that would be under some scrutiny, and which are otherwise very difficult to make. In the case of the FN5, this would mean the Brownings, the entirety of the cradle that carries the guns, the chordal stiffeners, and the ammunition chutes and the hand-grips, plus the "stack" of hydraulic valves atop the central console, between the gunner's knees. Provided that the turret was not being motorised in the manner mine will be - I hope! - these parts would really be all you need, the rest can largely be made from sheet materials, be it balsa, plastic etc. That will likely strike a more reasonable balance between cost and effect, if you see what I mean.

If it helps, here's how I went about drawing the FN5. I found illustrations of the turret from overhead, and from one side, ported these into the CAD package as "canvases", then gradually worked out how it all fitted together referencing photographs, using these illustrations as initial plots for relative dimensions and positions. Hence the huge number of revisions! It's a very long job though.

I won't do anything on the BP turret unless I hear from you, let me know if you'd like the spare FN5 bits, or if you'd like Brownings or other FN5 bits made, likewise, being mindful that I'm yet to assemble mine. I shan't be in the last offended if you elect to draw it yourself!

Type a measurements.jpg
Dimensions (and your Defiant scale) that I'd need.
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canvases.jpg
How I went about the intial drawing
canvases.jpg (170.28 KiB) Viewed 178 times

PS, the "type A" B-P turret is pretty similar, to the Mk IID, if there are differences, I can't spot them. This was the best picture I could find to use.

Timothy Huff
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Joined: January 23rd, 2018, 4:12 pm
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Re: FN5 turrets for Wellington

Postby Timothy Huff » February 15th, 2018, 8:17 pm

Yesterday was a disaster. After previous days tapping M1.0 threads in the 3d printed parts without difficulty, I managed to break all 3 of my M1.0 taps in the space of quarter of an hour. Most aggravating. Looked at it carefully today and figured out what was happening:

When I'd previously been tapping, it was in quite thin material, so the holes had been drilled with a pin-vice/M0.75 drill, prior to tapping them M1.0, again using the pin-vice. Faced yesterday with much longer holes, I'd used my Proxxon, and I believe what was happing was that the extra heat from friction was creating a molten plug of plastic in the hole. As I withdrew the drill from the hole it "felt" correctly drilled, as the drill could move up and down freely in the molten plastic, but after it cooled it was effectively sealing the hole again, adding the torque required enough to break the taps.

This afternoon I did a whole slew of deeper holes, with the Proxxon, then again with the same bit now in the pin-vice, and finally followed up with the M1.0 tap. Result: 50+ lovely threaded holes and no broken taps! Loud cheers.

Felt a bit of a "duffer" naturally, but if anyone else if tapping 3mm deep plus holes in 3d printed parts, this "confession" may save you from similar grief.


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