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Comet to Cromwell Conversion

Forum for discussion relating to the Comet
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Steve Stuart
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Comet to Cromwell Conversion

Post by Steve Stuart » Sun Aug 04, 2013 6:51 pm

Having taken on the Cromwell I have been working slowly on the mudguards and have now completed producing a turret gear ring and then installing it. The original system was a lazy-susan.
But I wanted to open out the hull as it is a bit tight for space.
Getting the gear ring made was achieved with the help of a local engineering company who's designer produced the CAD drawing and then referred for the me to someone else to cut the gearing itself.
P7250844.JPG
Gear Ring Bearing and swarf
I had to cut large holes in turret base and the deck of the tank to suit the bearing and the gear ring. I milled the two halves of the bearing out of a thick sheet of nylon and an equally thick slab of aluminium, producing three dustpans full of plastic and metal swarf!
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Bearing in turret and hull
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Turret motor mount and Gun Mounting
Once made it all bolted together reasonably straight forward way, and I then made the mount for the turret motor and rejigged the mountings for gun. Now it is completed it looks no different to how it was originally!
P7250844.JPG
Gear Ring Bearing and swarf
Attachments
P8040867.JPG
As before apart from a new gun barrel

Steve Stuart
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Re: Comet to Cromwell Conversion

Post by Steve Stuart » Sat Nov 16, 2013 10:02 pm

I have used the option packs from my Tiger which I upgraded to the latest generation to go into the Cromwell which only had the motors left in. These motors are quite big and use chain drive which takes up a fair amount of room, which when using the Electronise and 4QD units means there is not much space. So I fitted the Tiger motors into the hull instead. Including fitting new engine mounting blocks, which meant each side of the hull had to be taken apart to get them in, fun and games. This photo shows the end result :)
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Engine Bay
Whilst doing this I have fitted a remote Momentary Switch and Power on Light for the Power Supply Model and using the Component Shops General Purpose Voltage Meter created a means of telling when the battery is switched on. I have fitted a charging socket and a Toggle switch to turn the charge circuit or the power circuit on and have the tank turned completely off. All for safety and to avoid embarrassing mistakes :oops:
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Management!
The next thing is to remodel the Engine Vent, my third one to date.
Steve

Steve Stuart
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Re: Comet to Cromwell Conversion

Post by Steve Stuart » Thu Nov 21, 2013 10:58 pm

The cold spell has not made working in the garage in the evening too pleasant but my next project has been to make a new Engine vent for the Cromwell, in real life it is simpler than the Comet, however the less robust supports for the cover are harder to replicate and caused me more brain strain the ones for the Comet.
The real Engine Vent on Shufti Cush
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Real Engine Vent
The Model Engine Vent
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The Model Engine Vent
I have now to fill the bolt holes and prime the cover and Milliput the welds. Then onto adding a couple of extra hatches on the rear deck, to get the hull to be closer to an earlier D Type Hull.
Now warming up in front of the computer. Steve

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Re: Comet to Cromwell Conversion

Post by Steve Stuart » Mon Dec 02, 2013 8:57 pm

I have now made the extra hatches to make the deck an earlier D type by copying the existing hinges and doing quite a bit of support work under the deck to allow for the new hatches.
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New Hatches
The new vent is also installed, which entailed moving the central line of hatches back a bit with a fillet added to the deck. To improve the engine sound I have cut a hole beneath the vent which allows free passage of noise from the loud speaker underneath.
PC021422.JPG
The Vent in place
More hatch handles are next on the list to be made and fitted, then a whole lot of holes to fill before repainting the deck!
Steve

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Re: Comet to Cromwell Conversion

Post by Steve Stuart » Mon Apr 28, 2014 10:17 pm

Ironically I have just been down to the Garage to photograph the Cromwell and loged on to discover Derek has also posted on the Comet. So here is my contribution to British Tank building!
I have now pretty well finished the top of the rear deck:
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Cromwell Front and Turret
The Rear of the Cromwell had lots of holes drilled and taped for various sizes of bolts to replicate the profusion of fastenings found:
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Cromwell Rear Plates
My latest work has been making, copying Armorpax Comet, Turret Hatch Latches. I have used his fittings as a basis for what are similar but different fittings. I have been experimenting using Tiranti supplies making moulds and casting in white metal, a satisfying challenge.
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Cromwell Top Deck
I hope to have the Cromwell at Shepton Mallet this Saturday so not much more tinkering time.
Steve

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Re: Comet to Cromwell Conversion

Post by Steve Stuart » Mon Aug 31, 2015 10:59 pm

Breaking Tracks have been bad news so the Cromwell has been on the back burner with occasional careful use.
However this summer has seen the solution a with a new set of Tracks made.
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Track Assembly
I have gone for something that is less delicate and so is more of a Stand Off rather than precise scale as I want reliability. (Plus greater detail would have cost an arm and leg for this sort of small number) Having linked them up and fitted them to the tank I was very pleased with how they came together.
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Tracks On
The proof has been the running where I have rapidly gained confidence in how strong they are, the only problem is that the sharp unworn corners really chop wet grass and it then gets caught up. So the solution is to run them in!
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Test Run
Bill of Carron Tooling in Boscombe has done a great job and also I need to give a big thank you to Barry for finding him and setting the whole project up, a real star!
Getting ready for October 8) Steve

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Re: Comet to Cromwell Conversion

Post by Steve Stuart » Fri Jun 08, 2018 10:50 pm

DSC_0843b.jpg
New Turret Bearing
The new Tiger with its annular Lazy Susan Bearing set me an example to follow it really does turn with ease. The bearing I made using a 'nylon' ring has suffered from the material expanding over time and so causing binding. It was a bit of a nightmare to maintain concentricity of all of the component parts in a retro fit, but the result is worth it, the strain on the Turret Turn Motor is gone!
Steve

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Robert E Morey
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Re: Comet to Cromwell Conversion

Post by Robert E Morey » Sat Jun 09, 2018 11:40 pm

Steve,
Really nice work on the conversion. The Cromwell is a very seldom modeled subject. Nice job on the new tracks, were these die cast, or spin cast?

I really like these bearings - they are not very expensive, I'm going to try and retrofit all of my older Armortek models (Sherman, 2007 Late Tiger 1) with this type of turret bearing.
Best regards,
Bob

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Re: Comet to Cromwell Conversion

Post by Steve Stuart » Sun Jun 10, 2018 10:21 pm

Bob, the tracks were machined from bar as a commission from an engineer in Boscombe, Dorset, no casting involved! They remain obstinately shiny despite being given a colour wash. Maybe the problem is that the Tank gets driven alot? Another issue is that the edges don't round off, so they are sharp which means grass gets cut and caught up something chronic and then clogs up in between the drive sprockets and wheels.
However, like the Comet it drives extremely well, and has a good turn of speed. It would make a great addition to the Armortek stable, for those who can get over it not being German, and who want a model that could be further modified to represent a whole range of variants, plus have a cracking Tank to drive at displays and events :D I rest my case!
Steve

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Pete Mallett
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Re: Comet to Cromwell Conversion

Post by Pete Mallett » Sun Jun 10, 2018 11:07 pm

Nice work on the new tracks, Have you also changed the sprocket drive? IIRC the Cromwell sprocket has less teeth than the Comet and is narrower, 14 " for the MkIV with a D Type rear deck plate.
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Steve Stuart
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Re: Comet to Cromwell Conversion

Post by Steve Stuart » Wed Nov 28, 2018 10:26 pm

Comet drive sprocket centre cover made me react to the naked 5mm cap head bolt to produce something more like the prototype.
DSC_0501Resize.jpg
Cromwell Prototype
I have now got my Rotary Table sorted so that I could produce the indentations.
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The New Centre

The sad thing is that the weathering has been lost so more running through muddy water is going to be needed.
DSC_0525crop.png
Center in place
I hope this sequence effectively shows that a model is a work in progress. There is always something that can be looked at again and worked on.
Steve

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Stephen White
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Re: Comet to Cromwell Conversion

Post by Stephen White » Thu Nov 29, 2018 9:27 am

Steve, how refreshing to see such an innovative build as yours. The custom builds always bring something new to absorb, so thanks, Steve. It also redressed the balance on this Forum, which has been a bit focused on das Wehrmachtfieber recently. Regards. Stephen

Steve Stuart
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Re: Comet to Cromwell Conversion

Post by Steve Stuart » Thu Nov 29, 2018 11:47 pm

Stephen, I must at this point acknowledge that this conversion was initially David Skeldon's. What I am doing is running with what he has started.
The Cromwell shares the running gear of the Comet and so is a great Tank for running in the 'arena'. I would be very pleased if Armortek when working out what non German Tank could be on offer, settled on the Cromwell as there are many possibilities for variants to keep us happy.
All in all I am pleased to be the custodian of an almost unique model which is giving me a great deal of satisfaction as a means of working on improving my model making skills. Plus I am pleased to be a 'Green' :wink:
Steve

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