Shipbucket
http://67.205.157.234/forums/

Tanks!
http://67.205.157.234/forums/viewtopic.php?f=5&t=6201		 Page 1 of 2
Author:  apdsmith [ August 3rd, 2015, 6:44 pm ]
Post subject:  Tanks!
Good evening all,

I think this is the right location for this, but it may not be - if so, please advise.

This started off as a discussion between ezgo394 and myself regarding the various land forces of Denton and NSWE, respectively, as with both sharing a universe and ending up on opposite sides of WWII, it's fairly obvious that they're going to come to blows at some point. This isn't a claim to expertise, and although I've made efforts to make sure I've not posted anything incorrect I have no doubts errors and mistakes will have crept in. Corrections to these, or amplifications (I'm just as sure that I'll have missed the details behind some design effects somewhere) would be appreciated.

With that said, on with the tanks, or, specifically, design decisions for tanks.

The first thing to consider is the environment that your tanks are operating in. This covers everything from terrain (i.e., Russian winters) to the expected threats (i.e., the Allies' discovery that the Axis tanks in Normandy included more Tigers and Panthers than anticipated) - this'll affect both armour requirements and armament requirements.

Terrain requirements will largely be expressed through suspension requirements, which in turn affect the design of the tank:
Leaf springs, as used on the Panzer IV, are one of the more basic systems, having the advantage of predating most of the other available systems by some margin.
Christie suspension, as used on the T-34, provides for long travel in the roadwheels, but intrudes into the interior of the tank along the sides and may complicate placement of ammo racks.
Torsion bar suspension, as used on the Panther and Tiger tanks, requires less space inside the tank than other systems with internal springs but has placement issues of it's own, taking space along the bottom of the tank that may require the turret to be mounted higher than would otherwise be the case. Torsion bar suspension can also preclude installation of any escape hatch in the bottom of the tank.
Vertical Volute Spring Suspension (VVSS) and the successor HVSS (Horizontal...) as used on the M4 family, initially had some issues bearing the load of the tanks, which were resolved with the HVSS system, however, neither system required space within the hull, simply bolting on to the hull, which also greatly simplified maintenance.
Horstmann suspension, as used on the Vickers light tanks and several other British designs, seems to functionally work in a similar fashion to VVSS / HVSS, with units bolted to the side of the hull, however, Horstmann suspension uses coil springs rather than VVSS' volute spring, the extra space required by the coil spring being taken up in laying the spring along an almost horizontal axis.

In addition to the springing, terrain can also have an effect on the number and size of roadwheels - though this can also be affected by industrial requirements - for instance, the Panther and Tiger tanks, constructed under wartime constraints, had larger roadwheels than the Pz III and Pz IV tanks to accommodate rubber of lesser quality. Overlapping and interleaving these roadwheels provided both additional armour protection for the side of the hull and spread the weight of the tank across many points of the track, improving the ride, at a cost of complicating the maintenance requirements of the suspension (in Russian winters, the frozen mud could bind the closely-spaced roadwheels of the Tiger)

Well, that's me for the moment, just writing up something about engines before moving on to armour and turrets \ guns.

I guess the first question is, is there a need \ desire for this on the forum is should this more properly be kept to PMs between myself and ezgo?

Any comments \ corrections appreciated.

Regards,
Adam
Author:  JSB [ August 3rd, 2015, 7:06 pm ]
Post subject:  Re: Tanks!
Quote:
I guess the first question is, is there a need \ desire for this on the forum is should this more properly be kept to PMs between myself and ezgo?
Why not ? would be interesting to read your logic (and annoyingly point out perceived flaws :twisted:)
Author:  apdsmith [ August 4th, 2015, 7:22 pm ]
Post subject:  Re: Tanks!
OK, on with the engines (and transmissions):

Tank engine selection is a compromise between several factors. In no particular order:
Absolute power;
Power-to-weight ratio;
Economy (for tanks and other combat vehicles this is normally expressed as a function of range on a given fuel load rather than the actual cost of the fuel);
Physical size;
Survivability;
Maintainability;

Of these, the first, absolute power, is probably easiest to address - the more the better, until it's not better ;) - that is, given that we're generally discussing 20+ tonne fighting vehicles, the power delivered by the engine is probably going to provide the limiting factor in terms of manoeuvrability, with the caveat that "delivered" includes having a transmission that will withstand the power generated by the engine.
An example design that emphasised the power-to-weight ratio would be the M3 Lee and M4 Sherman tanks, with their Continental R-975 radial engines - these were selected, as with aircraft, for their superior power-to-weight ratio, however, physical size constraints - or rather, the placement of the drive shaft, which, unlike a more normal V-engine, is in the middle of a radial - dictated that the drive shaft took a quite high line through the fighting compartment, which in turn necessitated a high turret in order for the turret basket to clear this drive shaft.
Economic measures are valid concerns but a discussion of these turns into a complex discussion about the operating nation's logistical train. It's worth noting, however, that modern tank engines are generally "multi-fuel" and, for instance, the US runs their M1 Abrahams on JP8 jet fuel for logistical commonality. In the WWII timeframe, multifuel engines were not widely available, if at all.
Physical size, for tanks particularly, is a quite significant constraint. Engines of sufficient power to move armoured vehicles have a significant size and given the hostile operating environment, the engine bay must be armoured, in turn feeding into the power-to-weight ratio as the physical size of the engine (and therefore the size of the armoured box necessary to protect it) increases. An example of an engine that prioritised physical size over other factors would be the Maybach HL210 and HL 230 engines, as used on the Panther and Tiger tanks, with their compact cylinder layout, which required a complex and more fragile crankshaft layout, reducing the reliability of the engine.
Survivablity in the WWII timeframe is largely going to be determined by the engine's fuel, with diesel engines as used on the Russian T-34 and the Japanese Type 97 providing a significant benefit compared to petrol engines in the event of the tank being hit, either by anti-tank fire or by more unconventional munitions such as Molotov cocktails.
Maintainability on tanks engines is generally going to be a concern, as whether it's petrol or diesel you're taking about a powerful heat engine that's confined in a steel box and getting shot at (or dunked in a river) from time to time. In addition to concerns fundamental to the engine, the tank design itself can negatively affect maintainability, either through causing issues more frequently through poor cooling systems design, such as on the Panther tank, or through poorly-implemented dust filters allowing dust into the engine, shortening it's service life, as on early T-34 tanks, or through complicating access to the engine to effect repairs.

With regards to transmissions there are a couple of major concerns:
Function;
Reliability.

Function, for instance, would cover the dual-radius steering on the Tiger (and the cheaper, simple single-radius steering on the Panther and a similar system present on the Churchill tank) or the more traditional differential braking seen on the M3 Lee and the M4 Sherman.
Reliability itself would consist of several factors:
The quality of the materials used - tank transmissions are subjected to significant forces, requiring special grades of steel to retain function for a long length of time. Substitute materials, such as those used in the Panther's transmission, will wear and deform quickly, resulting in poor service life.
The design of the transmission - US tanks, with the vast American industrial machine behind them, used herringbone gears, which required specialist gear-cutting machinery to create, to reduce the forces applied to the transmission internally. By the time that the Panther tank was being produced, Germany's industrial infrastructure could not produce these gears in sufficient quantity, nor the epicyclic gearing that the Tiger used, requiring the use of spur gears instead, compounding the metallurgy problems already experienced (herringbone and epicyclic gears both apply the applied power across several gear teeth at any one time. Spur gears apply the power one tooth at a time.)

I think that's it for this one ... it turned quite technical, so there's an increased risk I simply got something wrong, and a significantly increased risk that what I've written, correct or not, is simple incomprehensible. Any comment?

Regards,
Adam
Author:  Tobius [ August 4th, 2015, 7:46 pm ]
Post subject:  Re: Tanks!
Quite good.

In addition to the mechanical, manufacturing and environmental factors, you should look at your HUMAN factors.

For one thing, your choice of the tank main armament determines turret layout and how you service the gun. Will the gun loader be the vehicle commander/radioman (France) and will he have a semi-automatic or automatic gun to service? Will the main gun be a gun/howitzer (Americans and Russians), so needing a dedicated crewman to feed it or will it be a high velocity rifle (some of those guns were naval rifles in that you needed two loaders; one for the shell and one for the bag charge!)? (Germans, Russians and British fielded examples). Will the gun be loaded from the wrong side? (Germans and British again?)

Will the gun use a screw breech block or a sliding wedge breach block? The Germans liked the sliding wedge breech block when they could use it. It made even side/odd side loading easier.

I assume that aside from the South Americans, who don't count because they horribly misused their Vickers 6 tonners in their mid 30s wars, that nobody starts out with the right answers, so your fictional guesses along these lines will be interesting to compare with real results.
Author:  JSB [ August 4th, 2015, 9:58 pm ]
Post subject:  Re: Tanks!
It might be interesting to look at the limits to your Tanks!

- Budgeting both pre war peace time development and war time total available ?

- Weight size ? limits on transport (rail/road) or loading (cranes onto ships) ?

- etc
Author:  ezgo394 [ August 4th, 2015, 11:23 pm ]
Post subject:  Re: Tanks!
Hey, this looks great! Lots of good info here! :)
Author:  apdsmith [ January 6th, 2016, 10:20 pm ]
Post subject:  Re: Tanks!
Well, this has been a while coming.

To resume, this post is going to detail armour considerations. This, particularly, is a response to the environment, but while suspension choices are heavily affected by the physical environment (though the armour, due to the effect it has on weight, also plays a part here) armour is largely defined by the threat environment and the intended response to that. This is visible from the very first tanks, the Mark I's 12mm armour being upgraded to 16mm by the time of the Mark V due to some losses to German infantry weapons utilising "K-bullet" armour-piercing rounds. This also actually represents a good illustration of varied responses to differing elements of the threat environment - British tanks were vulnerable to artillery fire, with gravity-fed petrol tanks up high in the front of the track frames. While the threat from German AP rounds was relatively easy to address with a little additional armour, the vulnerability to artillery was much harder to fix - alternate designs were proposed, such as the Flying Elephant, but this was tank with poor mobility (even by the standards of the Mark I tank) and massive expense and was deemed less useful than a greater quantity of heavy tanks following the existing pattern.

Armour tends to follow a pattern of escalation - German-designed Pz.III and Pz.IV tanks were protected well enough to face Soviet forces when they consisted of T-28 and BT-7 tanks, however, the introduction of the T-34 by the Soviet Union and the M4 Sherman and M3 Lee led to an increasingly unsurvivable battlefield for the Pz.III and Pz.IV. These tanks were up-armoured but quickly reached the limit of their engine and suspension, requiring a new German tank to survive the more modern battlefield - the Tiger and Panther. The Allies did encounter Tiger tanks in Tunisia, however, they underestimated the quantities they would be fighting later on and did not assign a high priority to their own efforts to defeat the Tiger's armour. The Soviet Union, rather than designing an entirely new tank (this was attempted, but the resultant T-43 was cancelled) instead designed a new turret with a re-designed 85mm AA gun as the existing 76mm could only penetrate the Tiger's armour by closing to suicidally-close range of the side of the Tiger. Something of a counterpoint to the "escalation" argument, the T-34-85 was still outmatched by both the gun and the armour of the Tiger but came close enough for the vast numbers of T-34-85s produced to overwhelm the German tanks.

A notable exception to this is the French tanks of the early 1960s - by now the threat environment included HEAT ammunition and in a period before the development of composite armour or ERA it was difficult indeed to adequately protect a tank from these high-penetration rounds - so AMX decided that they wouldn't, instead making their tank as small, light and nimble as possible - again, showing the requirement to realistically assess which threats can economically be defeated by the tank's armour and which must be evaded or simply accepted (as in the case of the British WWI tanks' vulnerability to artillery fire)

As fundamental to the concept of a tank as armour is, it's been a subject of considerable interest over the years and the available technologies have changes considerably over the time that tanks have been a feature of the battlefield. Early tanks, required to protect themselves largely from machinegun fire, had thin, flat plates riveted to each other. By the start of WWII, most countries were dividing their tanks into separate tanks - tank destroyers and medium tanks for the US, infantry and cavalry tanks for the UK and similarly for the Germans and the Soviet Union - all with their own armour requirements. The British Matilda II was an excellent example of the infantry tank, with a low speed (6mph cross-country) and armour that was functionally impervious to enemy guns during the early actions of the North African campaign. The T-34 is probably the canonical example of a mid-war medium tank, with it's sloped armour permitting the use of thinner plates and light weight than would otherwise be the case. Even after the introduction of the Tiger, the T-34-85's armour was assessed as good enough and retained because the tactical benefit the large numbers of T34s provided outweighed the individual shortcomings of the tank in the newer threat environment. Similarly, the M4 Sherman had adopted a sloped front plate as well, the angle requiring a shot into the Sherman's 51mm front plate to travel through 90+mm of steel on early models and more on later models as improvements to the engine and suspension permitted heavier armour to be carried. Since WWII, many more advances have been made, both in tank arrangements (the Chieftan tank introducing a supine driver position, allowing a very heavily sloped upper glacis plate) and to the composition of armour itself, with modern tanks transition away from plain RHA steel to spaced armour or one of a few variants of composite armour, with ERA explosive reactive armour "bricks" carried in high-threat environments to further bolster protection, with "cage armour" a possibility to defeat infantry support weapons too. Active defence systems are starting to be introduced as well, these last intended to destroy an infantry support weapon, for instance, before it reaches the correct range to damage the tank that the active defences are protecting.

Well, I think that's as close as I can come to a good write of up tank armour, any comment would be appreciated.

Regards,
Adam
Author:  JSB [ January 7th, 2016, 5:48 pm ]
Post subject:  Re: Tanks!
My only comments would be to question the wording of,

1-
Quote:
Armour tends to follow a pattern of escalation - German-designed Pz.III and Pz.IV tanks were protected well enough to face Soviet forces when they consisted of T-28 and BT-7 tanks, however, the introduction of the T-34 by the Soviet Union and the M4 Sherman and M3 Lee led to an increasingly unsurvivable battlefield for the Pz.III and Pz.IV. These tanks were up-armoured but quickly reached the limit of their engine and suspension, requiring a new German tank to survive the more modern battlefield - the Tiger and Panther.
Was it driven the armour race or more driven by the larger guns (and towed AT guns) coming into use ?

2- Not just French also Leopard I and Soviet tanks etc ? (ie most people until the development of fancy composite designs)

3- "cage armour" was spaced plates not fitted to some WWII types? (assuming that's what you mean ?)

Hope that makes sense
Author:  apdsmith [ January 7th, 2016, 6:52 pm ]
Post subject:  Re: Tanks!
Hi JSB,

1) I'd understood that both the Tiger and Panther were in their own ways responses to the T-34 rather than a more general improvement in anti-tank weaponry, though I'd welcome any information you had on it.

2) True, I'd meant that to be an example, one of many, but on re-drafting it completely lost that, will re-do.

3) by "cage armour" I was specifically referring to the type of stuff on modern armour in an urban environment, are you referring to "schurtzen" on WWII German tanks? As before, would be interested in any further information you've got on it.

Regards,
Ad
Author:  Tempest [ January 7th, 2016, 7:52 pm ]
Post subject:  Re: Tanks!
Also a point that you might consider is if the tank is forward or rear drive.
Page 1 of 2 All times are UTC
Powered by phpBB® Forum Software © phpBB Limited
https://www.phpbb.com/