Cromwell Mk 4 1:16 scratch build Ludwig kit

[43rdRecceReg]

Norway Max ( great guy, and purveyor of tasty chocolate.) supplied me with the Clark servo recoil unit along with the Clark Tk 60 that's destined for the Cromwell.
This is what the package looks like, and some of the tools I'm using to get it ready for the turret:

Clark Universal servo recoil and Elevation kit

The first step is to sand the slider- cum-charging handle arrangement that shifts the barrel. This component is actually quite similar to the bolt/charging handle you'd find on an AR15, and needs to slide easily; but not sloppily, in the frame of the gun.

Sanding the slider..

Once the movement's free of sticking points, the gear/ratchet part is attached:

Recoil gear

Then the servo:

In order to get the servo drive wheel in the correct position I connected the assembly to a functioning TK22 setup, and the motor automatically went to 'return' position, before pushing gear wheel onto the spindle.
Then I fitted the elevation gear wheel/ ratchet

Elevation gear in place

As with the Asiatam unit, it's now essential to find the optimum position of the Clark unit in the Turret. It became clear to me, the Ludwig Mantlet would have to be modified, and the kit's mantlet pivots set aside.

[43rdRecceReg]

My broadband is populated by gremlins at the moment . I spent twenty minutes adding to this thread, only for it to unravel in an electronic instant
I began measuring the spaces around the gun when in place. I used spare bits of sprue to establish the gap needed between the mantlet and the front turret plate. 3mm was about right to allow for sufficient elevation.
Meanwhile, I had the Clark unit resting on 6mm of sprue the bring the cannon up to the right height, whilst providing sufficient headroom for elevation, and giving me an idea where the fulcrum for the mantlet pivots should be located

Nice slimline fit compared to the bloated Asiatam unit.

Finding the gap between mantlet and turret front plate

Now for the distance of the pivots from the front plate.. and essential measurement for the pivot fulcrum supports I shall have to make:

Finding optimum position for pivots

I've had to chop the Ludwig mantlet up, and am in the process of bonding bits to it, so that it can mate with the Clark unit (but not in some smutty fashion )
While the glue's drying, I'm going to get on with finishing the external detailing on the tank. The front is pretty well complete, but the rear engine deck looks a tad bare: too bare to pass muster.
I'm going to use this blueprint for the general layout of this '"D" type chassis:

Blueprint for engine deck features

I'll start with the oil and petrol caps..since nobody else makes them.
On the real tank they look something like this:
On a well made 1/35 interpretation from Britmodeller, they were rendered like this:

Location of Fuel caps on small scale model

Right, well I'll just submit this now in case the Broadband gremlins reappear and all my work vanishes in the ether.. Back in a mo... or, if not, I'll be treating my ISP to some unprintable language

[PainlessWolf]

43rdR&R,
You are the man for this job. I've no doubt it will be an engineering triumph once you have the turret working in all axis'
regards,
Painless

[43rdRecceReg]

Ok, some ISP call centre person has been spared a torrent of abuse...for now. The unprintable language wouldd have been Kligon, anyway
In order to get the scale right, on various components, I moved the slider on MacOS 'Preview' feature so that the image of the Blueprint was almost exactly the same length on my iMac screen as the model is. So, in order to find the size of the Caps, I just measured the screen blueprint with a plastic ruler.
Incidentally, I've discovered the importance of scale with this scratch building lark. I found this site useful, but doubtless there are many more out there..probably better too.
http://www.ipmsstockholm.org/magazine/2 ... awings.htm

I began cutting some wee discs out..

Fuel and oil caps- cutting out

Then, not yet owning a lathe (homestead is already bulging with used and unused tools..so ), I improvised by drilling and mounting the discs on a mandrel. My trusty Dremel would then pretend to be a centre lather. Shaving bits off the discs was a doddle with a chisel from the set of five sculpting chisels I bought off Ebay- for the project. They're sharp, cheap, and value for money.

D-I-Y lathe

Getting the right size..

Added some 1mm styrene beading to tiny precut channels at 90 deg intervals...(-ish!)

Progress

Fuel caps fitted and sanded along with some fake hinges

By the way, I'm sure I'm not the only one who's irritated by the way 'auto-complete' changes words here. Time after time, it guesses what I'm about to write- like some sort of fairground mystic- and inserts sometimes really inappropriate words. Or, one might appear to be writing gibberish. Ok, I can do that too; but I'd like to have the choice

Grab handles finally fitted

Finally got a round to drilling some minute holes, and filling then with 9mm staples- doubling as grab handles.
This just about completes the engine deck Apart from sanding and painting properly, the Upper Hull is as it should be.

[43rdRecceReg]

43rdR&R,
You are the man for this job. I've no doubt it will be an engineering triumph once you have the turret working in all axis'
regards,
Painless

Thanks, Maestro (he writes with genuine humility..). I'm trying to include as much as I can about the pitfalls of scratch building; the highs, the frustrations, the tools needed, the patience needed- the hair implants for those ripped out by intractable problems.. and the joy of going back to 'school: to re-learn geometry, basic electronics, and how to avoid getting into a frenzied state!
I'll admit that when this is done, it'll be a while before i get the urge to bring a Comet Tank live-birth into this crazy world Besides..
I have the Tamiya waiting with a full set of instructions, and parts I don't have to invent.

[HERMAN BIX]

I will hand it to you Mr 43'rd like an Academy Award..................best actor for hinges, fuel caps and general pissing about to get a superb result
I agree those Asiatam/Taigen recoil units are a bit "how-ya-doing" as far as plug & play goes.
I love the work gone it to this, huge array of skills & patient execution.
Well done that man

[Raminator]

I'm trying to include as much as I can about the pitfalls of scratch building; the highs, the frustrations, the tools needed, the patience needed- the hair implants for those ripped out by intractable problems.. and the joy of going back to 'school: to re-learn geometry, basic electronics, and how to avoid getting into a frenzied state!

It gets frustrating, not having parts readily available, but what you end up with is so much more special for all the extra work that's gone into it. It's been interesting following along to see how you've tackled (and overcome!) the various obstacles the build's thrown at you. Keep it up, Roy!

[43rdRecceReg]

Again, cheers a thousandfold, Herman and Ram.
Here's what the engine deck looks like with a quick coat of primer and one spray of a rattle can Olive Drab. Note- this is the yankee version of Drab; but it's quicker to get the rattle can out than set the Airbrush up.
When all's done and dusted, I'll be using the MIG British Olive Drab- SCC15 (1944 colour) for the final tarting up process. I've also made and fitted an intercom box (field telephone on rear of tank) for the rear panel; but have yet to make a towing hook, along with that the two smoke candle discharger boxes that sit either side of the Phone. Then...the external build will be complete. Phew... For the benefit of rivet counters, apparently it was only very late
'F' (welded version) Cromwells that sported the odd looking spring leaf towing bar; the one that was also fitted to the Comet and the Centurion. Though some earlier types may have had it retrofitted. My model's meant to be a "D" model ('D' for desperate.. ), with a normal towing hook

Upper hull sporting some trial makeup....

[43rdRecceReg]

Oh, and here's what a real engine deck looks life before a blast of Drab. They're going to need more than a wire brush to sort this one . Curiously, I found this pic under 'Cromwell for sale' on the net. The restorer wanted a cool, but not unreasonable, £185,000 for it in a fully renovated state. Hmm., that's tad more than a Ludwig Cromwell, but these scratch projects can certainly soak up the cash
What I like is the rough and ready finish on WW2 tanks: the painted-over rust pitting; paint runs; casting marks, evidence of repairs etc., I'd like to make mine look like that, without it wearing the 'botched job' patina at the same time. That's much harder than it sounds.
Having seen how some contributors here make their models come alive with authenticity, this will be the hardest challenge yet!

Buckets of elbow grease needed here..

Cromwell real Engine deck- .jpg (78.1 KiB) Viewed 4650 times

[43rdRecceReg]

Have had lots of none-Cromwell related things to sort lately (Life's little maintenance rituals) and, after foot surgery, can't stand up for long. Thus.. progress has been somewhat limited lately.
I've pretty well abandoned not only the idea of using an Asiatam recoil setup (though I'll fit a new motor to the unit, and rewire it just for good practice), but also the mantlet and pivots that came with the kit.
Put simply: they just get in the way. The cannon on the Cromwell is offset to the left, and this complicates the already elusive geometry needed for a scratch built mantlet, and gun pivot arrangement.
Oh, for a Comet turret
Finally, I'm convinced that Clark Universal (short version) recoil and Elevation unit is the solution to the cramped Cromwell turret; and the limited access I have, by virtue of the rear turret roof being firmly bonded (practically welded) in place.
So, I ripped out the Kit barrel pivots/fulcrums, and also found I needed to fabricate a new mantlet to cope with the offset, and the position of the barrel in elevation mode....
I'd like to stress how much a millimetre (out ) here or there in one axis can have a drastic effect on the other axes and internal angles. For a better idea of the intricate nature of the of the planning, improvisation,
calculation, and trial and error involved, just look at Barry C's fascinating effort in fitting a servo operated elevation unit to an Abrams.
viewtopic.php?f=201&t=18880&start=40
For starters, I made new gun pivots/supports after what seemed a torment of speculation and measurement.

Pivot bracket echoes shape of turret

the Right hand one needed an extension to accommodate the gun's offset.

Revised mantlet

The optimum dimensions of the offset mantlet were an absolute bug*er to determine. I had to calculate a gap between the mantlet and the front armour (roughly 3mm) to allow a decent amount of elevation without the mantlet fouling: (a) The Front plate; (b) the roof of the turret (when front section is in place..), and also without the MG mounting hitting the front plate. Nightmare. Less obviously, the old mantlet would not completely cover the gun aperture when the gun was elevated on the new pivots. It was possible to see inside the turret; and that was an absolute no-no. Hence, the revised (larger) mantlet...

Testing gun support assembly

Revised gun supports

Gun setup tested in turret

The drilled Bracket cut outs in the pic are bonded to turret floor to allow retention pieces to be screwed in, without having to drill thought he turret floor to retain the supports. That would have impacted on the Turret's ability to rotate