Landships II

TinCanTadpole · Legend

British Pathe films

TinCanTadpole · Legend

Found another: a medium D prototype, or perhaps a Johnson light infantry - something in that family anyway.

It's surprising how close the fighting compartment/turret is to the front of the vehicle - much closer than on the med D mock-up:

mock-up

The sunken tank looks to me like what Wikipedia call Medium Mk DM:

DM

-- Edited by TinCanTadpole on Sunday 1st of April 2012 05:35:59 PM

LincolnTanker · Commander in Chief

It is interesting to see how the tank digs itself into into the bank of the stream but easily ploughs it's way up the other side with little effort.

TinCanTadpole · Legend

LincolnTanker wrote:
It is interesting to see how the tank digs itself into into the bank of the stream but easily ploughs it's way up the other side with little effort.

Yes, it doesn't seem to lose traction, despite the soft mud it has nosed through. I think it's good to see a MkIII for a change - the I,IV and V tend to hog the limelight. If memory serves, the last MkIII was melted down as part of the war effort, early in WW2 - probably without real need.�

TinCanTadpole · Legend

I've just looked at a couple of old threads on the D and there is a picture of one afloat, clearly showing two silencers with the exhausts merging in a Y for a single tailpipe, so I agree that vee engines were used at some point; I may remember wrongly, but I have an idea that the Armstrong-Siddeley referred to was a V8, rather than an I-8/L8 (depending on your preferred terminology for inline motors), and I also think one source said that the A-S was called 'Puma'. Could be someone getting their wires crossed.

There seems to be some confusion as to which D was the D Modified, as James H and I, plus German Wikipedia, think it to be the one with the flat-slope turret roof and circular escape hatches, whilst in an old post, Centurion thought the Modified was the longer-looking machine with the turret roof which is curved from side to side, like the mock-up. Common sense would suggest that the Modified would be a later machine, abandoning the original curved roof for a higher-sided flat-slope roof, yet the floating D I mentioned with the two silencers (therfore a vee engine) had the curved roof.

One begins to wonder if anyone really knows!

The proportions of the floating tank can be estimated fairly well from the men on the tank, and seems to be close to the 30ft by 7ft5 quoted by mailer.fsu; certainly it doesn't look much shorter than 30ft, taking perspective into account.

Charlie - I don't quite follow your meaning about cheap aero engines and tank failures early in WW2; I've understood tin can armour and the tiddly size of the 2pdr pop gun, plus turret ring sizes and the restrictions placed on them by the effect of railway loading gauges on tank width to be the problems with British tanks early in the war. Do you know of engine troubles too? Were the Nuffield Liberty motors unreliable?

-- Edited by TinCanTadpole on Tuesday 3rd of April 2012 12:18:40 AM

James H · Legend

The Tank That Sank looks like the "Medium D Modified."

TinCanTadpole · Legend

James H wrote:
The Tank That Sank looks like the "Medium D Modified."

�Yes, that's what I put, except I abbreviated the 'D Modified' to 'DM'. I should have been clearer.

Since we're on the subject, anyone have any clue whether the data for the Med D is more accurate on mailer.fsu tanks site, or on German Wikipedia?

Mailer.fsu says that the engine was/was to have been an 8cyl Armstrong-Siddeley 240hp, giving 23mph, and quotes dimensions as 30ft long, 7ft5 wide, 9ft 2.5 high.

Wiki quotes shorter, wider dimensions, and says the engine was just a 150hp Ricardo, good for about 8mph.

Presumably the difference in size can be accounted for by mailer.fsu covering the planned/mocked-up tank and Wikipedia looking at the prototypes built; perhaps the engine differences are explained the same way, but I rather think that 8mph would be pathetic for a twenty ton tank with suspension - it ought to have managed 12-15 at least with a Ricardo, unless hampered by the gearing of the Med C?

Any thoughts?

CharlieC · Legend

�

I think the data from both sources should be viewed with some scepticism.

The early Medium Ds were powered by a 230hp 6-cyl Wolseley Puma (ex-Bristol Fighter).

When the tank worked, which was rarely, it could achieve 20mph on good ground.�

The DM was powered by a 260hp Rolls Royce Eagle V12.

source - David Fletcher's "Mechanised Force"

Looks like the use of cheap aircraft engines started early in British tanks - the

consequences of this economics based decision would not be felt until the failures of British tanks in the early part of WW2.

Regards,

Charlie

CharlieC · Legend

TinCanTadpole wrote:

Charlie - I don't quite follow your meaning about cheap aero engines and tank failures early in WW2; I've understood tin can armour and the tiddly size of the 2pdr pop gun, plus turret ring sizes and the restrictions placed on them by the effect of railway loading gauges on tank width to be the problems with British tanks early in the war. Do you know of engine troubles too? Were the Nuffield Liberty motors unreliable?

-- Edited by TinCanTadpole on Tuesday 3rd of April 2012 12:18:40 AM

�Big topic but I'll try to summarise:

- WW1 aero engines are designed to produce max. torque at relatively low rpm over a narrow rev range. To adapt these to a tank requires a large (and heavy) transmission which negates any weight advantage the aero engine might confer.

- Many WW1-era aero engines had exposed valve gear which was incompatible with operations in dusty or sandy conditions. The rate of engine failures in the Crusader tanks in North Africa was truely horrible.

- The Liberty engine was a heavy, unreliable piece of junk that most aircraft designers avoided like the plague. One wonders at Nuffield's campaign to keep using it even in the Cromwell (Centaur).

- One of the better tank engines in WW2 was the Rolls Royce Meteor (a derated Merlin) but this engine was a much higher reving engine with better torque spread than the WW1-era engines and was much easier to seal off for desert operations.

- The Russians realised that using aero engines in tanks wasn't a good idea in the 1930s and developed the V-2 diesel - probably the best engine of WW2 tanks.�

I agree with your comments about thin armour and undergunning as well. David Fletcher's "The Great Tank Scandal" explores this topic in detail.

Regards,

Charlie

TinCanTadpole · Legend

Found this pic of one of the Ds, it's new to me:

http://members.fortunecity.com/rwbrown1942//sitebuildercontent/sitebuilderpictures/amedd.jpg

It looks to be the same version as the one seen trundling through town streets in the first pic here:

old thread

But I think it's slightly different from the curved-roof example seen (I think) awaiting the scrapyard at Bovington:

scrappie

Apologies for directing you to a poster sales site - I have no connection with it, but I can't quite remember where I found the same image before; probably somewhere on Landships or else mailer.fsu.

�

I count at least four versions if you include the mock-up, with my suspicion being that the first of the three real�examples was the one seen in the street photo, the second the shorter-nosed one seen on grass (with the background censored - I think this is the heath at Bov where old tanks were put out to pasture) and the flat-roof tank as the final machine, the D Modified.

TinCanTadpole · Legend

CharlieC wrote:
- WW1 aero engines are designed to produce max. torque at relatively low rpm over a narrow rev range. To adapt these to a tank requires a large (and heavy) transmission which negates any weight advantage the aero engine might confer.
�
- The Liberty engine was a heavy, unreliable piece of junk that most aircraft designers avoided like the plague. One wonders at Nuffield's campaign to keep using it even in the Cromwell (Centaur).
- One of the better tank engines in WW2 was the Rolls Royce Meteor (a derated Merlin) but this engine was a much higher reving engine with better torque spread than the WW1-era engines and was much easier to seal off for desert operations.
�
Regards,
Charlie

�

I believe the Centaur only used the Liberty because of shortages of Meteors; being a derated Merlin, there was of course competition from Spitfires and Lancasters at least to overcome, so as the Centaur wasn't meant for a main combat role (if I recall aright), it had to make do with a lesser engine.

It's a shame, I think, that the Black Prince didn't get a Meteor sooner, as it might have been given the go-ahead for production, instead of being sidelined for the (admittedly very good) Centurion.

As for the first of these points, well I don't think I know enough to comment about WW1 aero engine revs/ torque spread. I suppose nowadays we'd change the cam profile rather than use an overweight transmission to make up the engine's shortcomings, but these things were still on a steep learning curve in WW1; I read a day or so back that the compression ratio of the Daimler-Knight in the Mk tanks was a paltry 4.something:1, and was still only about 4.75:1 after WO Bentley tried fitting higher compression aluminium pistons.�

CharlieC · Legend

�

The low compression ratios were more a product of low octane fuel than anything else. Midgely's discovery of TEL didn't happen until the late 20s.

Combustion chamber shape was an art form in WW1 rather than based on solid science.

The Meteor engines were built in a separate factory, run by the Rover organisation - it took a while for production to ramp up. Lord Nuffield campaigned to use the Liberty in the Cromwell - some of the early Cromwells were Liberty engined - these were either used for training or re-engined with Meteors as they became available.

Regards,

Charlie�

TinCanTadpole · Legend

Yes, 1923 for TEL if memory serves. Harry Ricardo did a lot to improve understanding of internal combustion engines - I've heard that he had test engines built with observation windows to watch the flame front move through the mixture.

Nuffield got the task of building and running a factory to build Spitfires in WW2, at Castle Bromwich; I understand the factory took a lot longer to get going than it was supposed to, and Nuffield didn't like the regular tweaks and changes necessary in aircraft manufacture; according to a book I read a couple of years ago, he got worked up during a phone call to Lord Beaverbrook, who was wanting to sack Nuffield and put someone else in charge at Castle Bromwich; Nuffield apparently threatened to quit, thinking Beaverbrook would back down, only for Lord B to thank him for resigning and put the phone down! Coming to the point, perhaps Nuffield, already having a production line set up for Liberty engines, and seemingly not liking having to keep making changes on a production line, wanted to keep producing what his company already had?

James H · Legend

This is according to Ellis & Chamberlain, as far as I can make out:

Maj. Johnson was asked to design a 20mph+ Tank as envisaged in Plan 1919, working title: Medium Mk D. The wooden mock-up wasn't ready until Nov 1918, and Churchill intervened to stop the project from being scrapped. The plan was for an initial order of 20, rising to 45. The first prototype was built by Foster's of Leeds, the second and third by Wolseley (Birmingham), and the fourth at Woolwich Arsenal.

Apparently, Johnson took one of the Wolseleys to India for "tropical trials" in Dec 1919 (fate unrecorded), and the other was fitted out for amphibious operation and named the Medium Mk D**. It trialled successfully at Christchurch, but sank during trials at Woolwich. Protoype 4 was designated Mark D Modified.

So it looks as if the Tank in the film is the D**, after all. Apologies. The D Modified had, at some point, two cupolas, and there's no mention of its being amphibious. The Light Infantry Tank was similar in appearance but only 21ft long, as opposed to the Mk D's 30ft. It did undergo amphibious trials, at Aldershot, and the smaller scale is obvious from the size of the people around it in photographs. Its suspension is also much more visible than that of the Mk Ds.

The Infantry Tank had a Hall-Scott (American) aero engine, the Mk D an Armstrong-Siddeley 240 HP Puma. The first 2 Mk Ds were delivered to the Army in July, 1921, but E&C don't say how many in total were manufactured. There is a line that says that revisions were made "too late to affect the first 20 vehicles."

Please feel free to contradict. Maybe there's more info in the German Wiki article, which I haven't read yet. Rather poor show, if I might say so, that there's no equivalent article on English Wiki.

TinCanTadpole · Legend

I identify three different tanks in the photos linked to:

1) the fortunecity/streets tank - seems to be the first prototype; probably with Wolseley 6cyl engine, long track horns like the mock-up. Med D?

2) the amphibious tank - similar shape to the above, but shorter horns and a vee engine. Possibly stronger rake front to back, perspective makes it difficult to tell. Possibly a sharper curve to the middle of the roof, almost forming a chine.

3) the D Modified, flat-roofed and at least temporarily fitted with two cupolas.

�

This leaves two types in the middle - the D* and the D**, one of which should be the amphibious tank of point 2. If E&C are correct, the two silencers it has may preclude it from being the D**, which E&C say was built by Wolseley and would probably therefore use the Wolseley straight six.

�

Update�- the tank exiting the water and the one on the poster are NOT quite the same: there are more stays for the track return on the amphibious tank�than the heath tank; unless extra stays were at some point removed from the amphibious tank, I suggest that these two which otherwise appear similar, are the two Wolseley-built prototypes mentioned by Charlie. If this is so, it appears that at least one was not Wolseley powered, and my guess is that the extra track return stays (which look angled outwards at the top) were intended to help track shoes to centralise (not twist to the side, as snake tracks did) before they entered the water - assuming that it was propelled by it's tracks, that is.

-- Edited by TinCanTadpole on Tuesday 3rd of April 2012 11:36:03 PM

TinCanTadpole · Legend

James H wrote:
The plan was for an initial order of 20, rising to 45. The first prototype was built by Foster's of Leeds, the second and third by Wolseley (Birmingham), and the fourth at Woolwich Arsenal.

Apparently, Johnson took one of the Wolseleys to India for "tropical trials" in Dec 1919 (fate unrecorded), and the other was fitted out for amphibious operation and named the Medium Mk D**. It trialled successfully at Christchurch, but sank during trials at Woolwich. Protoype 4 was designated Mark D Modified.

Please feel free to contradict. Maybe there's more info in the German Wiki article, which I haven't read yet. Rather poor show, if I might say so, that there's no equivalent article on English Wiki.

�I've just run the German Wikipedia article through Google Translate and come up with something passable enough to get the gist of. Actually some bits it translated very clearly, but all online translators struggle over something. If anyone speaks German (I don't), I would definitely recommend reading this article.

�

A summary goes like this:

Johnson was sent back to Blighty in August 1918 to design the tank and four prototypes were ordered straightaway from Fowler's, with another six ordered from Vickers.

The R-R aero engine (Eagle V12) used in the modified fast Whippet was powerful, but too thirsty for the envisaged role - the tank needed a good radius of action, so the Armstrong-Siddeley Puma aero engine (V8?) was used

The wire rope suspension (which I never understood before) had a wire rope running lengthwise inside the track frame and held in tension by a spring/springs at the end(s). The road rollers were free to move vertically and when doing so bore against the wire rope, stretching the spring(s) at the end(s).

It achieved 37km/h on the 240hp A-S engine (23mph - the figure quoted by mailer.fsu)

The envisaged role for Plan 1919 meant crews would spend more time in their tanks, so comfort and space were important; the 6pdr of a male version would have taken up too much space.

First prototype delivered June 1919. The translator struggled with the bit about the reason for the shape of the track frames (I know James started a thread asking about that), but it looks like Johnson said it was something to do with the capacity of the tank (I don't understand, will have to try other translators), and that tall obstacles could be reversed over. It was also supposed to give a better shape for steering.

To make the tank amphibious, an example from Vickers was widened at end of 1919 from 2.2m (7ft2.6) to 2.56m(8ft4.8) to improve buoyancy. This was the D* and it wasn't buoyant enough.

Another Vickers tank was widened further in 1920, to 2.7m (8ft10.3)and worked - the D**, tested at Christchurch.

James's post about E&C says that the initial order was for 20 machines and this was increased to 45; German Wikipedia seems to say that the initial order (for the D Modified, I think) was 45 and that it was reduced�to 20 and then to 3. So it looks like three D Modifieds were built, at least one with two cupolas. Two were apparently taken into service in 1921, If I understand the translator correctly, but the programme cancelled the next year.

One of the D Modifieds sank, according to wikipedia.de - which fits better with what makes sense about whether the flat-roofed tank was the D** or the D Modified.

�

Dutch Wikipedia also has this article; perhaps translators can manage some of the tricky terms better in a different language?

�

Update�- to my surprise, Google Translate actually managed some bits better from Dutch than German.

The explanation of the shape becomes clearer - with the modified Whippet, the height of the engine deck rose to obstructive levels, so Johnson simply turned the tank around and took a reversed Whippet as his basis.

As a reversed Whippet has tracks low at the front and high at the back, that idea carried over to the Medium D and was kept on because of restrictions that the lightweight wire rope suspension placed upon the design when steering. Johnson apparently said that if necessary the tank could reverse over a high obstacle.

Stability as well as buoyancy was the aim of the enlargements from D to D* (width) and then D* to D** (width AND length), with the D** being somehow compartmented for stability.

�

PS - there's a version on Hungarian Wikipedia too...

-- Edited by TinCanTadpole on Wednesday 4th of April 2012 02:09:28 AM

TinCanTadpole · Legend

That's interesting, James. Confusion is easily come by, because you've found E&C to say that the sunken tank was the D**, that the two-cupola tank was the D Modified; yet photographic evidence shows that the two-cupola tank had the flat roof of the sunken tank, so either they were one and the same, or there were two flat-roof tanks, or E&C were as confused as the rest of us and made a mistake.� confuse

Photographic evidence also tells us that there were at least two amphibious specimens - the 'tank that sank', obviously, but also - some way down the old thread I linked to yesterday - one with a curved roof, pictured afloat and similar in shape to the one pictured emerging from some water at a steep angle (which can be seen in PhilthyDirtyAnimal's Med D video).

Charlie C's reading says that early Ds had Wolseley 6cyl aero engines, which would make sense if the second and third prototypes were built by Wolseley. Charlie's source is a David Fletcher book, so ought to be as reliable as any source we're likely to find.

The curved-roof D amphibian had two silencers, one either side, indicative of a vee engine, which could make it the D Modified - which Charlie stated to be powered by an R-R Eagle V12. However, if the D Modified had at some point two cupolas, and photos show a two-cupola D to have the flat�roof, then the curved-roof example is probably something else - either a D or a D* or a D**.

E&C say that the amphibious D** was a Wolseley-built tank? If so, it would seem sensible for it to have the Wolseley 6cyl engine, yet the curved-roof amphibian has the twin silencers of a V8 or V12, and I think the 'tank that sank' did also; so if neither of these, by engine, appear to be the D**, does that mean there were THREE amphibious prototypes? Or am I making two plus two equal five?

I would also ask, James, if you meant to write "Foster's of Leeds"? Did Foster's have an operation there, as well as Lincoln, or is it a different Foster's, or perchance did you mean to write Fowler's? I've no idea if a Fowler's was involved in tanks, but I ask because the fortunecity site where I found that "new-to-me" Med D pic I linked to said it was built by "Fowlers and Wolsley (sic) Motors", and I wasn't sure if the chap had meant to say Foster's or not.

James H · Legend

Sorry, yes, Fowler's, not Foster's.

The rest of it I need to absorb for a while.

TinCanTadpole · Legend

James H wrote:
The rest of it I need to absorb for a while.

�Hmmm - I seem to have a habit of writing unintelligible posts� smile

James H · Legend

Pas du tout.� It often happens that accounts have elements in common along with contradictions. A bit of comparing and contrasting can usually sort it out, but this one is more complicated than some. I'll scan the E&C photos in the next day or so to see if any more light can be thrown.

TinCanTadpole · Legend

Okay, been looking at photos again, and since my posts can be hard to follow I'll keep it simple:

1) the curved-roof amphibian I referred to exiting water, looks to be the tank awaiting scrappage on a grassy heath.

2) tank at fortunecity site linked to earlier seems to be the one on town streets at mailer.fsu - which their pic title suggests is the first model.

3) mailer.fsu, like German Wikipedia, identifies the flat-roof tank with two cupolas as the D Modified

4) both the D Modified (as identified above) and the one exiting water have two silencers - hence vee engines, not straight sixes. This agrees with DFletcher book checked by Charlie - that the D Modified had a V12.

5) the tank on the fortunecity site (point 2) is described as built by Fowler's and Wolseley and likely has Wolseley engine, in keeping with DF book.

6)Fortunecity tank/streets tank (point 2) has long front track horns like the wooden mock-up...

7)...but flat-topped D Modified and curve-topped amphibious tank have shorter front horns - perhaps the D Modified in particular.

Ironsides · Legend

Engine notes:

BHP(Beardmore-Halford-Pullinger) 230HP�(built by)Siddeley-Deasy (name)"Puma"�(post 1919�Armstrong-Siddeley "Puma")

Siddeley Puma�article from Flight March 1919

specs: 6 cyl water cooled inline, power 230Hp at 14,000 rpm, fuel consumption:�.55 pints per�bhp per hour.

More detail can be found in "Janes fighting Aircraft of WW1"

Armstrong bought Siddeley-Deasy in 1919 forming Armstrong-Siddeley.

Wolseley was a Vickers*�company�but it may be the Wolseley Puma refered too is the same engine, Wolseley Built Vipers during WW1 a 200HP V8 engine basically the Hispano Suiza V8.

*Edited Vickers instead of Armstrong

both engines would likely have been surplus in large numbers following the end of the war.

Hall-Scott (American) 1917 212 HP 6cyl inline water cooled, bore and stroke 5"x 7"(Janes)

Rolls-Royce Eagle�article from Flight Dec 1918

Cheers smile

-- Edited by Ironsides on Friday 6th of April 2012 08:11:11 AM

CharlieC · Legend

�

The answer to that one is in "Mechanised Force" - I think the Dutch wikipedia article used David Fletcher's text - the Medium D was based on

Whippet track frames but the engine bay grew to such a height that the driver wouldn't be able to see over it. The solution was to reverse the track frames and�put the engine behind the driver. The downside of this was that the track was very low at the front and the tank couldn't climb over obstacles unless it did so in reverse.

I've never figured out the thinking behind persisting with a design (or designer) that was so fatally flawed as Medium D.�

Regards,

Charlie

-- Edited by CharlieC on Thursday 5th of April 2012 02:22:23 PM

James H · Legend

D. Fletcher's account in British Tanks 1915-1919 is even longer and more convoluted. Apparently, some of the medium Ds were widened.

It's all too much for me.

TinCanTadpole · Legend

Ironsides - thanks for that. I'm not sure about the Wolseley and the A-S being the same Puma, because the A-S is usually described as an 8 cylinder or perhaps sometimes a V8; need to look into that.

James - widened is what German and Dutch Wikipedia says, although in an old post Centurion contradicted that, saying that he'd looked at photos and saw no evidence of widening unless the turret was widened too. He seemed to think there was evidence in photos of lengthening though, which Dutch Wikipedia says happened with the D** (Google Translate didn't manage to extract that bit from the German entry) in addition to widening. Haven't yet looked at Wikipedia's reference list, but I wouldn't be surprised if it lists a DF book.

I have noticed that the front track horns on later versions are shorter; I believe this is because the turret has been moved forwards between the horns, rather than the horns shortened. (I can't help thinking of Texan cattle when I write about long and short horns

)

James - since you started a thread some weeks ago asking why the med D was low-fronted, does the Dutch Wikipedia explanation in my last post satisfy your curiosity?

Ironsides · Legend

The Armstrong Siddeley Puma is pretty well documented for Aircraft at least...

Flight magazine is a good place to look

The pic below if from an old�Guide... notice the odd engine size... typo?

Cheers smile

�

TinCanTadpole · Legend

Ironsides - probably a typo, 235hp would be in the right region.

Charlie - what you've written is more or less what I gleaned from Dutch Wikipedia, if you look at my last post but one. I think you're doing Johnson and the design a disservice though: it may appear low at the front, but that is relative - I believe it's actually four feet or more to the top of the idler, so cross-country performance ought to be much like any tank from the 20s onwards.

Okay, the Western Front is known for being a cratered mess, but by summer and autumn 1918 when the design work started, the war had changed in nature and the fighting was more open; crossing heavily-cratered ground was no longer the game, as I understand things, so obstacles would have been less of a problem. Also, as a medium, the tank was intended to chase around behind trench lines which had been breached by heavies.

Going through a few stages, they seem to have come up with an excellent idea - a decently-sized amphibious tank - and got it to float nicely, but were sunk (no pun intended) long term by mechanical gremlins.

I see the D as a great opportunity lost; it may not have had a revolving turret, but otherwise the concept seems good to me, despite the lower front. It's a shame it wasn't made to work properly.