Large Model Association Forum

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.

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.

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.

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:






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.

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

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.

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!



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.

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.

This week has gone rather better. The last lot of 3d-printed parts arrived, and ever since I've been steadily drilling and tapping holes, and building such assemblies as can be made prior to painting. The handgrips are done, with detailing screws, and the gun-cradles assembled for both front and rear turrets. Each cradle consists of 7 parts and is entirely screwed together, no glue, in case it has to come apart later on.

Since then the workshop has got rather chilly, so I'm back at the drawing board - in the warm! Also this week the tiny 12V "grain of rice" light-bulbs arrived, in amber and white, which will illuminate the Bendix signalling lamps (used in case of intercom failure), the (dim) amber service lamp, which could be used over enemy territory without attracting unwanted attention, and the internal spot-light used when first getting into the turret. The amber light will also, I hope, illuminate the reticule onto a slanted piece of glass within the gunsight. Silly... but fun to make!

So the box of "ready to be painted" parts is gradually filling, and the "to be drilled/tapped" one emptying. By the way, I've drawn a blank with both Cosford and Hendon, trying to discover the colours - if any - of the Bendix lights, which are usually fitted as a pair or trio, on the port stanchion. If anyone has information on these I'd be most grateful to hear from you.

Since I last posted, I've been busy building components for the FN5 and FN5a turrets, chiefly the seats, the console and D section piece which anchors the lower end of the two 'hydraulic' rams, the spent cases chutes, and the hand-crank for traversing the turret in the event of an hydraulics failure.

Lately I've been finalising the last nest of parts for the printers, in which I've added a lot of detail to the chordal braces - the two arms on each turret which support the axle about which the gun-cradle revolves. I had to reprint these as I discovered an error on the ones I'd previously done that wasn't recoverable. Still, it's all been good experience, both in terms of drawing, and error-checking previously drawn objects.

This week I finalised the lenses for the reflector-sight, which, with a little luck, should cast a tiny but bright 'pipper' on the refecting "glass" within the sight. "It says here"! Silly, but enormous fun to make. All the other lights have been made, and I've finally found someone who can tell me the colours and sequence of the 3 Bendix signalling lamps (used in the event of intercom failure, or in emergency). Apparently they're blue (top), amber (middle) and red (bottom) with increasing brightness top to bottom. Visible PVC wiring will be swapped for dyed cotton-covered wire - with different paths for cabling! - at a later stage, similarly all non-functioning transformers, rheostats etc will have cosmetic cotton-covered wiring by way of detail.

Still waiting for some parts before I can start painting, so have been figuring out how exactly to model the belted ammunition in the boxes and feed-chutes, and the build sequence as the main parts of the turrets go together. Hence using little or no glue in the construction, I can back-track if needbe.

One area I'd really appreciate some help with is the mechanism used to guide spent cases and links from the inboard edge of each gun down into the gun-cradle, before they're subsequently caught by the chutes beneath the cradle. There must have been some form of guide chute, which could have been pressed metal, or woven asbestos. These chutes, or whatever they were, are always missing in photographs, or out of shot, and museum turrets always seem to lack them too. (Hence my suspicion they may have been asbestos). If anyone has, or can direct me to, a picture or example of the chute, I'd be most grateful. Attached is a picture of the shape I surmise must have been fitted..... Advice most welcome!





As the eventual aim is to put an FPV camera in the turrets, 'depth of field' is a problem. To try and increase depth of field, there will be illumination within the turrets - out of shot - and the scheme will be the early-war natural aluminium rather than the soot-black of mid-war turrets.

Absolutely fantastic!
Every now and then a project is posted that is a true work of art.
Terrific,
Steve

Kind of you to say so, I must say I'm similarly, and perhaps more so, in awe of the builders here who produce flying models in balsa, something I'd never manage. Each to his own I guess! I've certainly learned a lot about CAD and 3d-printing over the course of this project. Nothing but nothing ,imho, will teach you to draw in CAD more efficiently than attempting to replicate an FN5's feed-chutes! Those really 'gave me the horrors' as the Aussies say.

Not much progress in the last couple of weeks, mostly endless painting with primer, and the occasional bit of hand-painting. I did manage to get the gunsight for the FN5 working as I wished. The reflector-plate has since been lacquered and is much clearer. I'm also experimenting with microscope "cover-slips" and etching them with hydrofluoric acid to see if I can etch a more strongly reflective "pipper" on clearer-glass. The sight stands about an inch tall btw. The two supporting arms need some sanding.

I've just about finished the priming now, next is two coats of gloss-black prior to alclad alloy colours. Printed out various aspect wireframe picture to start plotting out what bit gets painted what colour, so I can start bundling parts into groups by colour.

Work on these two turrets continues, and most of the components are now painted and where necessary lacquered. I had occasion to "dry-fit" the larger parts the other day, of the rear-turret, and took a few shots. No "weathering" has been done, other than the suggestion of paint being rubbed away above the ammunition bins, where the gunner's arms would rest. Before it's complete it'll be sprayed with a suitable paint to tone down the appearance of the aluminium parts, and will have had various powder pigments applied to the same end. Missing in these shots are all the small detail parts - switches, fuses, transformers gun-handles etc, all of the wiring, both working and cosmetic, the chordal-brace stiffeners and a lot more besides.


Next task, once the lacquering is finished is to finalise the electronics/servos for raising and lowering the gun-cradle, with the servo concealed within the "hydraulic" ram, and then make/print any final bits and pieces.

Looking very nice but what does it weigh. My Wellington was built as light as I could at the back end and still needed quite a lot of weight in the nose to balance ?

John

Less than you might think, it's a veritable swiss-cheese under the visible parts, and I took great care to make every component as light as possible. The only metal parts are the base-plate, and ball-bearings for the traversing side of things. All the rest is 3d printed or sheet plastic, generally well under 1mm thickness, with a few parts made in ABS plastic for strength - the "arch" and fixed and moving rings about which the turret traverses.

As the geodetics are intended to be made from extruded alloy channel, of 0.8mm wall-thickness, with rectangular dimensions of 12.3 by 6mm (iirc). It remains to be seen what the all-up aircraft weight will be. Although I've done a lot of calculations, I'll have a better idea when I've made - and weighed - some test-pieces next year. I did successfully make some similarly sized carbon-fibre geodetic channel, using flexible silicone moulds, which came out at 33mm to the gramme, but it had a failure rate that would have meant an astronomic cost for the overall airframe. I'll see if I can dig out a picture of those, as it was a fun problem to solve. The idea of course was to pin the silicone mould over the required curve, leave it under vacuum, and then de-mould it once it was hard. It worked - sometimes!



I confess I'm surprised that you had to put ballast forward, the Wellington usually carried ballast weights just forward of the tail-wheel. At least in the case of the 1C. Of course the absence of "crew" weight probably plays some part in that? The intention is to use at least one of the hollow ammunition cans, either in the tail or nose turret, as required, to carry lead-shot for ballast purposes, the other may house some electronics and fuses. Incidentally, I must apologise for getting your name wrong up-thread, your Wellington was first brought to my attention as the "Greenwood" Wellington, and I fear I must have unthinkingly repeated the error!


I had what promises to be an interesting idea yesterday: using sheet PTFE (very thin, order of 0.15mm) as a low friction packing between 3d printed parts that are moving in relation to each other. I'm hoping these will help reduce friction in the mechanism that mechanically links the movement of the sighting-bar in relation to the elevation of the guns, so the gun-sight remains parallel regardless of elevation. If anyone has found a lubricant suitable for 3d printed parts that doesn't cause swelling, I'd be most interested to hear of it.

Well the hydraulic ram innards are all squared away from the design point of view, and the motor and gear-box ordered. Lead-time 5-8 weeks - ouch! I've found a lovely old boy in the village with a watch-maker's lathe who can turn the necessary connecting collar 'twixt gearbox and lead-screw. With a little luck, this'll just need the one ram "operating" and I'll be spared the fun and games of trying to balance two motors. So the ram is on the back-burner for the foreseeable.


Now that design is finalised, I've compiled the two nests of parts for 3d printing, which takes care of all outstanding reprints. Dull, but most necessary.


The last 3 days I've been working on the "arch", at the top of which is the rotating mount connected back to the terminal ring of the fuselage. I wanted to add "cosmetic" wiring looms, and dyed cotton covered wire several correct colours, twisted same into a loom, and added several cosmetic wires to the left-hand arch. The right hand arch is "still to do" in this respect. The "looms" will go down either side of the arch down the visible cable-runs, but are purely for decoration. Cables carrying current will be routed out of sight with camouflaged pvc insulated cable, excepting the gun-sight lamp, but as this draws only 0.1A, and the cable are routed through different paths, should not cause any issues. I hope! After taking advice, the likelihood is that all services to the turret will be at 5V.

Incidentally, I now have a fairly extensive pile of unusable - for my purposes - parts for an FN5 at 1:4.5. They may not be much good for a "moving" turret, but could be used to detail a stationary one, if anyone is interested..

A few pics attached as it comes together.

Another busy day yesterday. I learned a good lesson too. My drawings usually omit fixings: nuts, machine-screw, washers etc, and when I came to assembling the three threaded brass rods and brackets that help space the spent cases chutes, and hold the hydraulic accumulator to the front of the turret, I discovered that each turret required around 50 washers, 25 or so nuts, and a further 25 half-thickness nuts. All had to be fitted in the correct sequence as the rods were passed through the brackets, and every one was dropped about 8 times before I could get it started on the thread. It drove me, er, "nuts"! If ever I produce a kit of these, that bit will be redesigned with extreme prejudice! The brass rods will be painted duller colour once it's all correctly spaced and tightened-up.

By way of a much needed change, I did the cosmetic wiring on the RH arch sections, with the wires going underneath and then back into the front face again. The looms were also prepared for the LH arch sections. Still work in progress.

Assembly of the turrets came to a grinding halt 6 weeks ago, when I discovered that the ABS plastic I'd used for the moving ring, to which the turret baseplate is attached, and to which all the superstructure will be screwed, wouldn't take a tapped thread in the same ease with which nylon 3d printed parts did. The ABS just turns to powder - not helpful! (ABS was used as it has a much better dimensional accuracy than nylon, so it was in that respect a good choice)

Eventually I ran down a company in China that produces tiny brass nuts with a knurled perimeter designed to be cold-pressed into fractionally undersized holes in PCB's or plastic phine components etc. These proved just the job, and were quick and easy to fit, so the assembly is now back on.


Whilst waiting for their delivery (via emphasemic three-legged donkey, I surmise), I did a ton of work on the CAD side of things, preparing the drawings for the superstructure that holds the Perspex cupolas for front and rear turrets,(similar but not identical) and the former shapes for drawing hot acrylic over to form the desired shapes. The 3d printed supporting structure will be printed in nylon (to tap threads for machine screws into the nylon) and clad in thin brass for strength. So it's full-speed ahead again.


In the pictures below the blue shape is the former, which when covered in 0.5mm thick acrylic should result in the nearby cupola shape. In practice the blue former will be broken down into small panels for ease of demoulding.

Other progress has been making the platted 3-wire leads for the intercom leads, which my daughter made!

Lots of progress over the last couple of days, with most of the major components of the rear FN5 turret screwed together, hopefully for good. I've sent off for the last nest of 3d printed parts, including the beefed--up "chordal-brace stiffeners" - the pressed metal structure with 3 large holes, which goes between the top of the chordal braces and the arch. The previous ones looked fine, but conferred no rigidity to the structure. My teenage daughter kindly platted some brown copper-coloured wire, which now serves as the intercom leads. These plug together and stay fixed together by the simple expedient of putting a small ball of "blutak" in the female jack!


I've also assembled the Brownings into the gun-cradle, with the spacers that determine the lateral position of the guns. This will need to be redone when the new baffles arrive. Once the wiring for the micro-switches is done, and the internal axle foe the gun-cradle is installed, most of the remainder of the assembly can be done; followed by the bearing races.