Did any Mk V tanks get converted to Mk V* or were they all new builds?
I ask this because Dick Harley's reference drawing of of tank tracks states that Mk V tanks had either 201/2" tracks or 261/2" tracks, while Mk V* had only the larger size.
Why were Mk V built with two different sizes - were they anticipating that some would be converted?
In total 400 tanks MK-V, on 200 females and males from the end 1917 till May, 1918 have been constructed. The part from them has been altered in version MK-V* in repair shops of the tank case in France. Since May 1918 and till the end of war 200 males and 432 females MK-V* have been constructed. Originally on tanks the wide caterpillar was established, but then began to use and narrow of stocks as the caterpillar resource made all 80êì.
Production Mark V tanks were built as Mark Vs. Production Mark V*s were built as Mark V*s. The wider tracks reduce ground pressure, other things being equal. A Mark V* might therefore have been considered to have had a greater need for wide tracks.
The idea for wider tracks was to reduce ground pressure and thus improve manoeuvrability, but they weren't introduced with the Mark V. Fitting them meant the cab couldn't extend the full width of the (inner) hull and in fact all rhomboids from the Mark II onwards could have used these wider tracks. That they didn't is, I think, down to problems in manufacturing track links at all, never mind two different types. So, the standard track used was the narrow type fitted to the Mark I and it was only much later when track link manufacturers had developed the techniques and trained their staff that a sufficient supply could be maintained of the wider type. By that time, the Mark V was the standard battle tank, the Mark IV having been declared obsolete. Consequently we associate the wider tracks with the Mark V, but that hadn't been the intention at the time.
On the subject of ground pressure, some of you may recall that I did some rough calculations last year on just that subject. I'd need to look for the thread if anyone wants figures, but without checking I can still say that the Mk V* would have substantially lower ground pressure than the Mk V. A quick check by calculator suggests a Mk V* with the narrower 20.5" track would have a ground pressure half that of a Mk V on the same track, perhaps slightly less.
Even adding 26.5" tracks to a Mk V would not reduce the ground pressure anywhere near that of a V* with 20.5" tracks - which, if I am not mistaken, a small number of early V*s may have been fitted with? I'm sure I read as much somewhere on Landships/the forum, last year.
The ground pressure figures I worked out were for a vehicle on firm ground; in muddy conditions sinkage would bring a lot more of the track into contact with the ground, thereby spreading the load. I suspect the V* would still have a lower ground pressure than the shorter rhomboids (which were extremely poor in this respect), but the difference is probably much less marked than on firm ground.
I have seen records of tests of Mark V performance carried out by MWEE in 1930 - 1931 (honestly, goodness knows why they were testing Mark Vs then!). Some record details of ground pressure on a hard surface and when sunk to the belly, others on a hard surface and with a 4 inch sinkage. A Mark V Male had a ground pressure of 28.7 lbs/sq inch on a hard surface, but 12 lbs/sq inch when sunk to its belly. Note that I'm not quite sure what type of tracks this tank had, all that's recorded to describe the track type is "AP special".
From my calculations, Gwyn, the 28.7psi figure would be on the 20.5" track; changing to the 26.5" item would drop that figure by 6.5lbs, to 22.2psi. 12psi when sunk to the belly in soft mud would be a great improvement, but then again such soft mud would be poor for traction, and if the belly of the vehicle was dragging in the mud, there would presumably be plenty of stiction.
Re Charlie's point about the curvature of the lower track: it depends how you look at it! My calculations were based on the ground contact length on hard ground, which is the length of the flat centre section. Early rhomboids may have been slightly more curved, but certainly Mks IV and V had a proper flat section in the middle of the tank, with a slight kink upwards (going by the armour plating - it would look smoother in overall effect) for the rising aft section. It looks in overall effect as though the lower run is a varying curve, but the part the tank sits on on hard ground is definitely flat.
Gwyn, I agree it sounds odd that tests would be done on old Mk Vs in 1930-31, but since MWEE was busy testing 16 tonners (A6 series, leading into Vickers Medium Mk III), with various steering systems and transmissions under test (a sorely neglected area of tank design - when it comes to oily bits, books always seem to focus on engines and power outputs, forgetting that a tank is useless if you can't steer), perhaps they thought it would useful to measure the Mk V to provide a comparison showing how much better new designs were. Expenditure on tanks was low at the time, so perhaps there was a political motive for showing how tanks had improved?
Gwyn,
As the industrial revolution had been going for a while by 1916, I find it strange that a relatively simple thing like a tank track could present manufacturing problems. It's either a pressed-metal plate or cast in a sand mould, both of which had been around for a long time. My own feeling is like what happened in WWII, resources are strictly limited and there is a great inertia to overcome for anything new. Look how manufacturing turned around once Lord Beaverbrook started kicking arse!
The comments above on ground pressures are very pertinent - in WWI did they know enough about ground pressures and length of track in contact with the ground (with the associated steering problems)?
There was no comparable data to go on, and tests carried out at home would not necessarily be the same conditions as on the battlefield. More than likely things were produced by rule of thumb and only changed when gross inefficiencies had been identified.
An interesting piece of engineering history here for anyone with the resources to research it!
The Official History of the Ministry of Munitions (or at least the drafts of it that I read at The National Archives at Kew) do cite track link manufacturing problems as being a major issue. It was fine if that was your business, but many firms brought into tank production lacked the expertise needed. Also skilled labour had been lost due to recruitment processes not protecting skilled workers sufficiently.
I think, though I don't know with certainty, that there would have been more to it than pressing or casting: I read not long ago that British interwar tanks (the designs with the Vickers Medium style of track, still used up to the A12 Matilda) used a chemically hardened surface rather than heat-treated, and it may well have been the same during the war.
Nevertheless, such processes should have been in place to manufacture 20.5" tracks, so indeed it should in theory have been a simple matter to produce a wider 26.5" plate instead. Why the idea was in place by the beginning of 1917, but the tracks didn't appear until - what, sometime in the middle of 1918? - is anyone's guess.
The news given to me by Bovington was that the tank tracks were armour plate steel. This might explain the problems with making the wider track.
The tracks, according to Philippe Gorczynski, were never seen to have been bent, but always broken tracks had unbent, jagged edges where the plates had been hit and shattered.
Presumably then, the problem was one of two things:
a)Â getting armour plate of the new width; and/or
b)Â Â bending and moulding the basic plate to the required shape.
Can anyone throw any light on the production of the tracks?
