Chieftain MK3 Build

[David Battson]

A bit of work on the sprockets to finish off the running gear.

Armortek has done an excellent job of modelling the hub and steel bolt on sprocket rings. Whilst the kit sprocket rings fixings are M2.5 cap heads with hex nuts on the outside, the real thing used some distinctive square headed bolts with nuts on the inside.

The sprocket rings are subjected to quite a bit of stress and so I was keen to make sure any modification avoided compromising strength for the sake of aesthetics, especially having seen a modified (Comet) sprocket ring come off at a show. After much deliberation and looking around for alternatives I decided to bite the bullet and made up a batch of bolts from square bar. Although clearance is limited on the inner face, the thread size was increased to M3 allowing the use of some nice scale looking thin walled nuts.
To finish off, a new inner hub cap was turned up, allowing some of Steve Winstone's excellent smaller sized fixings to be mounted closer to the outer perimeter. The cap is held in place by a central M5 screw which screws directly into the drive gear, avoiding the need to touch any of the small fiddly fixings.

[David Battson]

Final swing arm assembly

A quick mod to the swingarm pivot bolt before final assembly. If overtightened, the pivot bolt will restrict free movement of the swing arm and so it needs to be left slightly loose. However this means there is a possibility of the pivot bolt binding to the swingarm and rotating with it in the suspension housing. To stop this from happening and improve the look of the bolt head, a hole was machined through the head and a short way down the side. A pin was inserted into the hole to act as a parallel key and also giving a rough impression of a grease/oiling point detail. A corresponding notch was filed into the suspension housing. With the bolt head locked in place in the suspension housing, the screwdriver slot in the bolt head was no longer needed and so filled in.

swing arm bolt

suspension housing

Last views of the underside before putting the tank on it's wheels for good. As much as I like to know the detail is there, hopefully I won't ever see this view again in the field !

underside

underside Hortsman units

A couple of articles I have read criticise Chieftain for lack of ground clearance. At first look, this seems harsh as there appears to be good clearance under the hull which is quite slender and has the 'v' shaped bottom specifically design to improve performance through mud. However it is evident the Hortsman suspension units protrude some way below the the hull line and extend well outside of the track base, so presumably it is these which caused the problems.

David

[David Battson]

Glacis Casting
Chieftains's glacis is large and complex casting. I wonder if British industry still has the capacity and expertise to make anything like them today? The size and weight of the kit casting is also very impressive.

At first look, the glacis shape seems quite organic and rounded, but drawings like the one below show that the curves are based around some more readily recognisable geometric shapes. A reflection maybe of the need to be able to specify the shape in a time before powerful 3D computer modelling. The casting shape seems to have evolved over time, with the geometric shapes being quite visible on early vehicles, but completely indiscernible on later ones.

Offering up the kit glacis to my modified front end revealed a step of about 6mm at the rollover between the slope up to the drivers hatch and down to the triangular cover over the toe plate. Whilst there was probably enough metal thickness in the casting to regrade the front, the size of the job far outstripped the capacity of my small mill.
As an alternative the casting was cut just before the drivers hatch and the front end fabricated from aluminium plate.
Around the base of the turret, the side slope to the vertical was reduced to just 6 degrees and given a bowl like undercut, compared to the kit which flares out to 30 degree matching the slope of the side panniers.

Even with the initial guidance, it's still a very complicated shape the make look right and so after much fettling I've called it a day so I can move on with the rest of the build. After all the work, the geometric shapes are just about visible but unfortunately don't show up in the pictures due to the poor lighting.

David

[John Clarke]

Gets better and better David.
I know the original front castings changed over the years and there might have been differences in the casting molds. I actually prefer the smoother vee front ends, the "smiley version" as I call it. the earlier versions did seem come with a pronounced vee.
All the same, an excellent transformation, a lot of skilled hard work being put in, a great achievement.
A lot of the large original castings were probably made by various companies at various plants. One plant, FH Lloyd's was situated in my home town of Burton upon Trent. I believe they did cast the turrets there too. The sign states turret, tracks and glacis plate I believe.
All gone now.
Your right, Great Britain doesn't have the same casting facilities it once had. Nor the major industries we were once renowned for.
If you want castings these days like this, You'd have to put in an order and it should arrive from China in about six weeks.

David, Are you sure that's an Armortek Chieftain? and not just click bait.

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[David Battson]

Hi John,
Many thanks for your comments and also providing some inspiration for when I get around to adding the casting numbers. Following your tip off, I've been looking through the articles on FH Lloyd on the historywebsite, incredible stuff. They suggest that the turrets and glacis were cast at their Wednesbury site next the the M6 (now Ikea), however it would be great to think that Chieftain parts were cast at Burton too. I have childhood memories of shopping trips there, my Dinky Toys Chieftain Tank may have even come from 'Toyland' at the back of the market place - I guess that's another place that's also no more. Either way, as my home town is midway between the two, from now on I'll be adding Lloyds casting marks to everything.
From the photos their mark seems to be 'FHL' and maybe just 'FH' and possibly the 'A' star symbol as well - do you know ?

[John Clarke]

Thanks David for putting me right with the castings and their place of manufacture. The info was given to me by an acquaintance who worked at the Burton plant for many years, working with major tank castings the track manufacture too. Continuing with William Cook when FH LLoyds when taken over in the early 1990's. Then it closed for good in the mid 2010's.

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He did give me a semi promotional video, well sort of, which was given to the workers, effectively asking them to make a decent product, on time and not to ask for more money.
It shows different William Cook customers sending the same message, keep productivity up and costs down. This included a Vickers spokesman.
Still, there were some good short clips of casting turrets, (Challenger)

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As for the star on the castings, I couldn't be sure, but it sounds plausible, It seems to appear on a lot castings, fuel filler caps too. It certainly appears on the Mk5, so I've added the detail to my model.

[David Battson]

Seeing Vince's post of the excellent gunner sight he did for me an embarrassingly long time ago, I feel obliged to post some of my meagre recent Chieftain progress.
Before finally fixing the glacis to the hull, I plan to finish as many associated details as possible whilst access to all sides of it is still easy. First up, another another tricky and difficult to make look right detail that I haven't been looking forward to doing - the wade rail which adds the distinctive go faster swoosh to the front of the British Chieftains.
The full size rail measures 1" wide by 1.5" tall so 6mm square aluminium 'u' shaped channel trimmed down to 4.2mm by 6mm makes a good fit. Originally I had planned to use brass channel, but this proved difficult to bend without plenty of heat to soften things up. To get the shape as symmetrical as possible the rail was bent around a wooden template. The template also proved invaluable for positioning the rail centrally on the glacis. Where the rail was in direct contact with the glacis. 9BA threaded pins were used to hold it down. Elsewhere thin alloy sheet was used to infill the gaps.
The top of the wade rail on the righthand side dictates the minimum lift height required for the drivers hatch and so with the rail in place I can now move on to complete the hatch.

David

[David Battson]

Drivers hatch
The opening for the drivers hatch was reworked using scale measurements taken from the real thing as part of the modifications to the glacis when access with the mill was easier. The opening was cut by plunge milling, each corner radius represents about 80 separate cutter set ups, comprising 40 slightly undersized rough cuts and then another 40 fine cuts to the finished radius, all repeated 8 times for the lower and upper parts of the opening - where does all the time go!

As with most things chieftain, the hatch profile isn't straightforward. Looking at a section along the centre line of the tank, the slope gradients for the top of glacis, top of hatch and underside of hatch are all different. This means that and the top of hatch doesn't finish flush with the glacis surface and the hatch is actually wedge shaped. A new hatch and swing arm were fabricated from two blocks of aluminium blended together. The underside was recessed slightly and lugs added for the two pull straps.

The hatch arm is attached to a lifting column which slides in a brass guide tube. On the real thing rubber bellows around the top of the lifting column keeps dirt out of the mechanism. I had hoped by now to have found something suitable to use here, but no such luck. As an alternative the top section of the lifting column was grooved to give a rough approximation of the real thing - by no means accurate, but will have to do for now.
The hatch's movement is controlled by a peg on the side of the lifting column which engages with an 'L' shaped slot in the guide tube. This bolt action effect controls the lift height and swing angle, ensuring that the hatch always drops centrally into it's opening.

The lack of any external handles makes open the hatch difficult, so as a feature I decided to make the hatch servo controlled. Two servos are attached to a bracket clamped to the bottom of the guide tube. One servo acts directly on the bottom of the lifting column via a swivel bearing and the other servo rotates a sleeve on the outside of the guide tube which also engages with the peg on the lifting column. The hatch is opened and closed by a single switch on the transmitter activating an aeroplane landing gear sequencer which allows for fine adjustment of the servo's speed and travel.

To finish off, all the associated exterior details around the hatch were added, such as travel stops and locking catches. The distortion to the wade rail alignment in the picture of the Chieftain at Elvington shows the dangers of using the zoom for reference pictures.

David

[John Clarke]

Incredible workmanship, Chieftain certainly throws a few curved balls. All you need now is a Bone dome to pop up out of the hatch!

[Robert E Morey]

David,
Your glassis plate mods are incredible, but especially the hatch. Brilliant! That could be useful on Panther A hatches which open in similar fashion. Very nice work - thanks for sharing!
Bob

[David Battson]

Hi John,

All you need now is a Bone dome to pop up out of the hatch!

Well funny you should say that...... I didn't have any pictures of it when I did the last post, but now below are photos of a lifting platform I made and fitted to the underside of the glacis. The platform rises up to just below the drivers hatch. Currently it's supporting an excellent Armorpax head and shoulders sculpt, but maybe in the future an FPV camera for the all immersive driving experience. The model is based on an early MK3 1969 which I believe predates the bone dome (?) so current headwear is acceptable.
I couldn't find a 3 channel landing gear sequencer, so currently the lift is on a 'Y' lead with the hatch rotation servo. It's a close run thing, but no decapitations so far !

David

top view

down position

up position

[David Battson]

Hi Bob,
Thank you for the comments, glad the lifting mechanism was of interest - it has worked well for me so far. With regard to adapting for a Panther A, unfortunately the hatch rotation angle on the Panther A is about 190 degrees, so an alternative method of rotation is required instead of levers. I had looked at this briefly for my Panther and was thinking maybe a geared or belt drive connection between hatch and servo. The landing gear controller I used provided a good degree of fine tuning to the servo start and stop positions, which reduces the need to work out exact servo arm lengths and gear ratios. etc.

David.

[John Clarke]

There's a bit of deja vu with the camera and bust David, nicely built
Sadly, mine is not as sophisticated on Chiefy, all hand operated.
Still, no chance of eddy getting a lobotomy if the hatch jams or closes early

[David Battson]

More details for the glacis.
There are two versions of the drivers vision block housing on Chieftain, I copied the earlier version taking measurements from the one on display at Elvington. Later versions had a more rounded top, presumably to stop the mantlet cover from snagging on it at as the turret traverses.

early drivers vision housing

Late drivers vision housing

The housing for the drivers vision bock is made up from a number of interlocking parts which I wanted to replicate in the build. These went together surprising well, so on assembly I had to exaggerate the joints slightly to stop the from detail being lost under the first coat of paint. I'm not planning on adding interior detail, so the underside was finished off with a removable cap which will allow the actual vision block to be inserted from inside at a later date.

Drivers vision housing

The wash/wipe cover housing plate was also fabricated. The rather fiddley to make looking wipers will be added later on with the vision block glass housing.

Wash - wipe mount

Further to the front, I made up the fixing base for the dozer blade control box. I have read somewhere that the bracket was also for a support jack for the barrel to allow replacement in the field- is this true ? - I have never seen any photos of this in use.
Also added was one of the guide line tie down points for the very precarious looking commanders conning tower for when the tank was set up for wading through rivers. I try and avoid relying on glue alone for fixing details, so wherever possible details are either screwed on or in this case, pins added so they can be firmly embedded in place.

David

Dozer control box mount

glacis view 1

glacis view 2

[Mark Heaps]

My understanding is that it was not used as a bracket to aid barrel replacement.
On Challenger 1 & 2, likely the same on Chieftain, the NBC compartment was opened and the barrel went out the back of the turret.
Not something we would do as a first-line (Squadron or regimental level) repair on Challenger 1 or 2 due to the amount of time needed.
The tank would have gone back to a REME ECP (Equipment Collection Point ), barrel changed and then come back to us.
I believe a skid rail was placed on the back decks during the process.