Landships II

Rather than editing the lengthy first post: I have just looked again at the photo of the D** afloat at Christchurch (about two thirds down the page, attached to a post by Centurion), which I had thought showed the back view of the usual turret; it looks like it actually has that turret extension I mentioned in the first post, minus the cupola which is not fitted. You have to look carefully to see it, the evidence is around the point at the back of the main-turret roof, where the driver/commander's cupola would go.

Hello TincanTadpole,

I too have seen a photocopy of the drawing and in corespondance with Dick Harley a few years ago he mentioned that the small extention on the turret rear was based on a photo of the D* in the junk yard with a Medium C parked behind it. The draughtsman had mistakenly included the Medium C's turret on the rear of the medium D* turret! I have not seen that photo (maybe I have but it has the background removed in the reproduction process) so cannot confirm. Dick does "lurk" this site so he might be able to comment if he is able (his masters at work frown on that kind of thing).

I particulary like the original medium D with the turret further back on a shorter hull giving a graceful look due to the longer front horns. Does anyone know if a hatch was included on the Medium D turret rear...some photos of trials in India appear to show "something" at the rear below the commander/driver hood.

R Simmie

R Simmie - you've seen photos of the trials in India?!! That vehicle, I presume was the D* (with one star), which I've never seen any pictures of. The vehicle I've been referring to is the D** (with two stars) which followed the D* and finally had stability on the water (which seems to be what the widening and lengthening was about, rather than buoyancy).

This photo of the D** at Bovington scrapyard might show evidence of a turret extension - the dark patch behind the turret is ambiguous, but may be the hole that would be left after removing the extension.

This one of the D** exiting water is equally ambiguous, as the crucial area behind the turret is underexposed and it is rather grainy too. The open hatches for the engine bay (I presume) mask any turret extension if it is there, but the front edge of the right half of the engine deck hatch can just be seen if you look closely, and it may be far enough back to allow space.

I shall look again at the photo Centurion posted (link in my first post) showing the D** afloat at Christchurch: the photo is not sharp enough to be certain, but I do think it worth considering that whatever Medium C may have been in the background of the draughtsman's reference photo, there is sufficient reason in the rear quarter view of the floating D** to keep that option open - it may have been a forerunner of the separation of driver's and commander's jobs that was demanded by the head of the Tank Corps, Elles. For reasons I shall explain, the D** should have had space between the turret and the engine compartment, and it may be the case that an early attempt was made to introduce a separate commander by installing him in a turret extension built over this unused space, with MG positions  and a cupola of his own. A cupola in this position would require minimal modification of the existing design, however the view forwards would be slim-to-non-existent; this would then have required a more thorough redesign of the turret to instal a commander, perhaps including a rearrangement of the driving controls, as the driver may well have been moved too (resulting in the D Modified).

I too like the original Medium D for the further-aft location of the turret; I'd be interested to know if the D* shared this feature, as the Wikipedia articles (Dutch and German) say that the D* was widened - there is no mention of lengthening.

Much of the lengthening of the later models seems to have taken place within the 30ft (9.14m) length of the original (according to MM, the D* was also 30ft long) - a feat achieved by moving the fighting compartment forwards between the track frames. An increase in volume of the tank without making it any longer overall; this is what would have created an internal space behind the fighting compartment of the D**.

The D** I believe may indeed have been lengthened overall as MM says (the mag quotes 31ft 10in), as my track shoe counts suggest that when fitted with the shorter-pitch tracks (likely 7.5 inches), there are about three extra links on the return run, which would add about 22.5 inches to the length of the vehicle if the pitch is indeed 7.5 inches.

I haven't seen any photos of the back of the D's turret, if there was a hatch there it is beyond my ken. MM comments that the tanks were lacking in provision of hatches. 

Whether the tank trialled in India was a D or a D* I would like to know; very little is said about the D*, except that it was widened to improve stability on the water. As far as I know it may have had the original turret location, or the later forward one; it may have been the machine sent to India, or that may have been a D.

Regarding the MM plans, the errors I see (apart from the extension which may not have existed) are: 

1) The drawing is essentially of a D**, with turret further forward and a pent-roof chine to the top, but the length is given as 30ft rather than the 31ft 10in in the data section.

2) The width is narrow, like the original D.

3) The idler is too small, as Centurion thought.

4) The rear overhangs too much as the track rises up from the ground; it should be more of a two-stage rise, with a shallow start and a steeper second stage, probably at more than 45 degrees.

That's probably enough for one post! Are there any photos of the trials in India that could be posted (bearing copyright in mind)?

Okay, at some point, hopefully soon, I'll try some basic drawings to see how things go; they'll be done the old-fashioned way, as I don't have a vector-based drawing package and it should be easier and quicker drawing by hand. The difficult variant is the Mk D*, because there seems to be more info about the Mks D, D** and DM.

R Simmie - are you sure about the D* having the turret further forward? I know that the D** (D-two-star) and DM did, but since I've seen no photos of the D* (D-one-star), the only info I have on it is from various versions of Wikipedia (mainly the German and Dutch ones), which say it was widened; no mention is made of lengthening.
One of these accounts states that the modification was not to increase buoyancy, but stability - which is no surprise given the 4:1 length/beam ratio of the narrow Mk D. It states that the buoyancy of the original D was sufficient, although confusingly it also says that the original D was not amphibious!
Apart from the Wikipedia accounts, James H wrote in an old thread that Ellis and Chamberlain say the second and third prototypes were built by Wolseley and that the second was sent to India for testing; since the third was the D**, it stands to reason that the second was the D*.

I have therefore thought that the D* (D-one-star) might have retained the aft-turret/long-horns layout of the D, with just the hull being widened to improve stability, and the forward turret being introduced on the fully amphibious D** (D-two-star) in 1920. If you know this to be incorrect, I'd be pleased to know, as I can only guess at present what the D* (D-one-star) looked like.

I've just tried the Tank Museum website, to see if you can find pics online using the negative numbers, but the answer unfortunately is no; as for "Mechanised Force", I don't have a copy.

On a different note, there seems uncertainty about the number of tanks built: some say four prototypes; "A New Excalibur" says five tanks were built; Wikipedia says two production tanks were delivered in 1921, I think it implies these were built to DM standard, but Ellis and Chamberlain say alterations to the design were too slow in filtering through to production, and suggests the two tanks were built to the original design.

-- Edited by TinCanTadpole on Saturday 5th of January 2013 12:06:42 AM

Hello Tincantadpole

David Fletcher in "Mechanised Force" definiely says they are Mark D sent to India in 1922. He even quotes an Officer who witnessed these 2 machines in England being surprised to see them again in India! You say you have a copy of the MM article, if you look at the second picture on the first page, that is one of the Mark D in India with Asbestos covering.

The only pic captioned Mark D* I have is the same as your "This photo of the D** at Bovington scrapyard" I'll admit it does look similar to Mark D** in the water trials (turret roof made of 2 plates joined to a point). Looking at this picture is why I said the turret had been moved forward. If it is not the mark D* then you are probably right about only the hull being widened in Mark D*. So somewhere among all the Medium D pictures there may lurk the coy Medium D*.

Production figures I have via David Fletcher:

10 mild steel pre-production machines ordered on:

A. John Flowler & Co. Leeds (contract date 17-8-18)
4 tanks ordered, 3 completed. One destroyed by fire and incomplete machine stored

B. 6 tanks ordered from Vickers Ltd. Wolseley subsidiary. (contract for first 2; 10-09-18. Remaining 4; 27-09-18)
2 completed, 2 cancelled and other 2 finished as Medium D* and Medium D**

C. Ruston & Hornsby Ltd also contracted for 1 Medium D which was stored incomplete. This makes 11 contracted for instead of 10 stated above?

A total of 75 production machines originally ordered, reduced to 45 then cancelled.

 

I have nothing on the Medium DM, it may be a rebuild of one of the pre-production machines or a completely new construction.

Looking forward to your drawings as this machine has been sadly long neglected!

regards,

R Simmie

-- Edited by R Simmie on Sunday 6th of January 2013 01:02:22 AM

Ah! No, that's not a Medium Mk D, that's the Vickers Medium Mark D: a totally different machine, and far less easy on the eye.

The Vickers was a one-off built for Ireland, based on the 1926 Vickers Medium Mk II.

I have some more from John Glanfield's "The Devils Chariots":

Royal Ordnance Factory Woolich: 3x Medium DM built, cost 30,000 Pounds from cancelled order. So Mark DM is not a rebuild of a Pre-prodution mild steel prototype.

I have re-read David Fletcher's various books that mention the Medium D series and he states that Medium D* was only widened. So D* would have long front horns like D and a section inserted between the tracks and the original hull? It would be difficult to identify in photos unless it was from the front.

Would you mind if I pm you concerning the Indian trial photos?

Wish you well on the drawings, if you want them printed in 1/72 it is usual to draw them initially in 1/36 and have them printed at half scale.You might want to entice Wayne to do a paper rendition...imagine all those "wee divils" of wooden sabot track pads to fold!

regards,

-- Edited by R Simmie on Monday 7th of January 2013 07:54:20 AM

Not usually a rivet-counter, but counting rivets has shed light upon the length question: one of the tanks does seem to have been lengthened, and the increase from 30 feet (9.14m) to 31ft 10in (9.7m) seems about right. The vehicle lengthened was not the D** as stated in the Military Modelling article, but the D Modified, which also had two extra track-frame spacers and two extra bogies each side.

Given the apparent lack of photos of the D*, and MM saying that there were three prototypes (for which we can perhaps read 'three variants' of prototype), rather than four, I wonder whether someone became confused over the variants at some point?

My theory is that what we know as the D** may actually be the D*, and the D** may actually be an alternative designation for the D Modified - or perhaps the D Modified is so called because it was essentially the sole D** built, but with the turret redesigned at some point to meet the new army requirements; hence four designations, but only three different shapes easily found in photos.

I came across that clip last year and posted a link to it - and PDA knew about it years earlier. It is very useful, because if you click on "view as stills", some of the images show the angle between upper and lower track runs quite well. This helps to show that the distinctive profile of the mockup must have been retained on all variants; it can appear in many photographs as though the front/back rake is much shallower than on the mockup - but "The Tank that Sank" clip shows this is not true, it is a trick of perspective.

It was also very useful to me last night when I was counting rivets and comparing panel lines - reaching the conclusion that the D Modified was longer than its predecessors.

-- Edited by TinCanTadpole on Monday 7th of January 2013 11:10:22 PM

Thanks for your replies, gents.

Re card model, I think it would be easier to cut track shoes from thin sheet balsa and have a narrow flap folded over horizontally from the running gear to glue the shoes (sabots) onto - folding card would be a nightmare!

I don't know how long the drawings will take, as it is but one of many things fighting for my attention at present, but a conservative hope is to have it done by the end of the year; if it can be done in a few weeks, great!

R Simmie: since the photos are copyrighted (or presumably so, by Bovington), perhaps it's best to rely on what you can see in them? If they show long front horns, they must be either Mk D or Mk D*; if the front, or enough of it, can be seen it may be possible to distinguish between the two. The centre hull of the D drops straight down from the plate-joining strips at the front 'corners' of the turret. Beyond this on either side is the slope of the mud shutes; there is no horizontal section at track-top height between the front 'corner' of the turret and the slope of the mud shute.

So if some of the front can be seen, any little horizontal ledge sticking out from the front corner of the turret (about six-seven inches wide/15-18cm) would indicate a widened hull.
I would ask if any of the rear or engine deck is visible in the photos, as the D** tested at Christchurch is the only machine I've seen from the back?

At the risk of writing another very long post, the info from "The Devil's Chariots" therefore brings our understanding to something like this:

1) Eleven pre-production mild steel tanks ordered from Fowler's, Vickers (Wolseley), and Ruston & Hornsby; seven completed, five as Ds and one each of D* and D**.

2) Three D Modified (armoured?) ordered from ROF Woolwich.

3) D was 30' long, probably 7' 3" wide (maybe 7' 5", although MM gives 7' 7" on its plans. It may depend whether an overall width is meant, over the chain casings, or a width over the tracks without the protrusion of the casings) and powered by a 235-240hp Siddeley Puma six cylinder. If correct, MM states the transmission was by three-speed epicyclics (the steering gearboxes) without a primary gearbox as the Mk V, Mk B and Mk C had. Height probably 9' 2.5". Tracks 20.5" wide according to Ellis and Chamberlain; MM says 21". Pitch estimated at 7.5" (by myself). Not amphibious. Crew of three, with driver also commanding. First run in March 1919, says MM, with demonstration occurring in May.

4) D* probably as D, except for centre hull being widened by adding in spacer plates between hull and track frames. Width now 8' 5", and according to MM transmission now four-speed compound epicyclic (compounding is apparently necessary to get more than three speeds from an epicyclic unit), still the steering gearboxes controlling overall speed, but with hydraulic control. Amphibious, but lacking stability. Possibly complete by Dec 1919?

5) D** still 30' long, but turret moved forward between front horns. Turret altered, with sides more closely resembling mockup, but chine down centre of roof. Hull widened again, probably to 9', although MM claims 9' 10"! This may depend on factors already mentioned. Hull said by German and Dutch Wikipedia to now be compartmented. Amphibious, stability good. Tracks appear to have changed at some point to a longer pitch, likely 9" specified by MM. Completed 1920? MM says transmission changed to have primary gearbox with four speeds, steering by clutches (and brakes, presumably). Open compartment behind engine, with exhausts coming together to run side-by-side over the open space to the rear of the tank. Small open-topped compartment behind this, between sprocket wheels. Engine now a 260hp Rolls-Royce Eagle (Eagle VIII is likely) V12.

6) DM lengthened, probably to 31' 10" quoted by MM for D**. Width may be as great as the 9' 10" MM quote for the D**? Hull is longer overall, with twelve track frame spacers per side instead of ten (the upper row of u-bolted fastenings on the lower side plating); eleven fixed pulleys per side for the wire rope suspension, rather than nine (the lower row of what look like axle bearing caps on the side plating). Open compartment behind engine (through which transmission must run), described on MM plans as "open hold", now plated over, with double hatches at rear between separated exhaust pipes. Open compartment at extreme rear still present. Wikipedia (German and Dutch) states two delivered to army in Jun 1921 (Ellis and Chamberlain also say that two tanks were delivered at this time, but say they were built to an earlier design, probably Mk D! Circular/rounded escape hatches added to hull sides abreast turret. One of these sank in the Thames at Woolwich on trials.

7) At least a couple of tanks, probably Ds but perhaps D*s trialled in India, in 1922 according to David Fletcher, with external asbestos covering on at least one. One (at least) of these tanks had two curved hoops over the rear compartment; these may have been tilt hoops for a tarpaulin to cover what MM suggests is a hold at the back of the tank?

Very interesting discussion. Just wondered whether any of the views in this help at all?  (It's probably well known to all). 

Gwyn

While searching for a photo of a model at Bovington I knew I took many years ago, I found some more photos from that trip (in 1990 - how time flies!) of the model Medium D. I know there are differences between the model and the real thing, but they may be of use to someone, so here they are.

The recent digging into the IWM collection made me curious enough to look through the Tank Development series. One of the more interesting

items was a prototype based on a Willys Overland car - the caption says it's a test of tracks. Looking closely the Overland prototype has fairly conventional

tracks but the suspension is a version of the cable suspension used on the Medium D. The compliance of the cable suspension can be seen even on

this prototype. I don't know how the Overland car prototype was steered.

Can anyone help with the licence plate "LB 8536" - is this a military or civilian registration no.?

Regards,

Charlie

 

-- Edited by CharlieC on Tuesday 28th of July 2015 08:29:09 AM