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Jamby

Help me understand tank suspension

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Sooooo...after doing a site-wide search and perusing Google, I'm surprised not to have found anything about tank suspension, other than a somewhat doubtful thread on the WoT forums. Would my learned colleagues of SH be able to assist me in understanding and identifying the different types of tank suspension? I think I've got leaf-spring more or less mastered, as well as both VVSS and HVSS (thanks, JGT!) but was somewhat embarrassed not to be able to differentiate between the suspension of a Type 97 Chi-Ha and an FV4201 Chieftain.

 

UPDATE: I think I understand tank suspension better now. Thanks, everyone!

Edited by Jamby
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@EnsignExpendable wrote a bit about this some time ago.  Technology of Tanks does have a good summary of the matter, but it's such an expensive book that I recommend going straight to the piracy option and getting the shitty OCR version.  Ogorkiewicz's more recent Tanks: 100 Years of Evolution has a condensed, but far less detailed commentary on the development of tanks suspension.

Here is my heavily editorialized summary of tank suspension:

Tank suspension is what gives the track some "give" while the tank is moving at speed over rough terrain.  The main purpose of tank suspension is to keep the crew from being incapacitated by the tank shaking up and down while the tank is moving off-road.  It has some minor benefits to weapon and sight stabilization, but the technology of weapon and sight stabilization is so advanced at this point that it doesn't really matter today.

The very first tanks had no suspension whatsoever; the entire run of the track was rigidly attached to the tank's hull.  This meant that there was no shock absorption whatsoever when these old tanks went over bumps, but this was basically acceptable because the first tanks were also very slow, and tended to poison their crews with carbon monoxide anyway.

In the interwar period, tank suspension tended towards systems where several road wheels share a common spring element.  In some cases, four road wheels would be attached to a common leaf spring by  series of levers and balances.  More commonly, pairs of road wheels would share a common spring as in the HVSS and VVSS suspension of the Sherman, but also the bizarro longtitudinal torsion bar design in the Ferdinand.

 

The interwar period also saw the first independent suspension systems.  In independent suspension each road wheel acts upon its own spring.  Independent suspensions give a better ride quality for the crew at high speed, but they suffer from greater pitching oscillation (nose of the tank rocking up and down) than the older-style suspension where pairs of road wheels share a common spring, especially at lower speeds.  Independent suspensions are also heavier.  Christie suspension is independent, as are the majority of torsion bar systems (the Soviets screwed around with some non-independent systems, and there was the Ferdinand).  The majority of tank designers switched from the older spring-sharing systems to the newer independent systems, as in the US T20 series of medium tanks where the M4 evolved into the M26 and lost its volute spring suspension for torsion bars.  The British went backwards and switched from the independent Christie suspension of Comet to the spring-sharing Horstmann suspension in Centurion.  This is because the British are bad at tank design, although Centurion was a decent tank once you ripped out the old engine and transmission and put an AVDS and Allison tranny in there.  The British would stay with the Horstmann suspension through Chieftain and until Challenger 1.  Again, Chieftain was generally a bad tank, and the British made the world's best tank in 1916, and have been trailing since then.

 

The majority of publications will categorize tank suspension by what springing medium the swing arms are tensioned by.  This is completely stupid and conveys almost no useful information.  It doesn't tell me anything about the comparative automotive performance of the M60 vs the Pz. 68 to know that one has the swing arms tensioned by long, twisting rods of spring steel while the other tensions the arms with a stack of frisbee-shaped discs of spring steel.  The shape of the piece of steel being bent to absorb energy from the suspension elements is literally the least useful piece of information about the suspension performance.  More useful information would be the limits of the articulation of the swing arm, spring coefficients, swing arm length, damping coefficients, and unsprung mass of the suspension components.  Also useful would be the location of the center of mass of the tank relative to each of the road wheels and swing arms and its moment of inertia about the pitch axis.  But this more specific information is hard to come by.

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Why does Horstmann suspension necessarily denote bad tank design? I think it was arguably quite suitable for the speed that tanks like the Chieftain could reasonably reach, given what I've been reading here:

https://archive.org/stream/Janes_Technology_of_Tanks_01/Janes_Technology_of_Tanks_01_djvu.txt

 

The part I'm referring to is about two thirds of the way down the document - section 13 (I figured out how to link it: http://prntscr.com/iu7i68) - and seems to suggest that the appropriate choice of suspension is largely dependent on the speed you're moving at, from leaf-spring at the lowest speeds to torsion bar at the highest.

 

Unless you were bombing along rough country at particularly high speed (even for a vehicle designed to do that to a degree), would the difference between torsion bar and Horstmann suspension really be appreciable? Are there tankers from both sides of the pond here?

 

 

 

 

 

Edited by Jamby
Adding link

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Well there's different kinds of suspension that have evolved since WW1 and they offer different tradeoffs (although some have been superseded) such as cost, simplicity/reliability, effectiveness, etc.   but I also think there may be an element of semantics to it (how people define such things, which is where the sources you use and quality of that source) probably applies.  

 

Also there's going to be more issues than just 'speed' to consider in your suspension choice.  For example on page 319 of Jane's:

 

Quote

The advantages of torsion bar suspensions are however accompanied by a number of disadvantages. Thus, while the installation of the torsion bars across the bottom of tank hulls is simple and well-protected, it also increases their height.

 


 

This is undesirable in itself and it can also significantly increase the weight of
tanks, particularly when they are heavily armoured. Damaged torsion bars are also difficult to replace when a hull is distorted by mine blast. Moreover, the fact that torsion bars store a large amount of energy in relation to their weight means that their outside is highly stressed, which makes them vulnerable to surface damage.


Their installation in the hull makes torsion bar suspensions compare unfavourably in some respects with suspensions of the Horstmann type. In the case of the latter the coil springs are outside the hull, mounted together with their associated pairs of wheels and suspension amis on a subframe so that they form a self-contained bogie which can be replaced as a unit in the event of damage. The same applies to the externally mounted suspension of the Israeli Merkava. The latter is however greatly superior to the Horstmann suspension of the British Centurions and Chieftains because the road wheels arc independently sprung, by vertical coil springs, and because they are provided by it with greater vertical travel.

 

 

It would seem tradeoffs and design (complexity, protection, weight, internal space) are drivers over 'good' or 'bad' decisions as how it is implemented (possibly getting back to the 'semantics' again?)   Speed will matter too since that affects comfort/safety/stability of the crew and vehicle vibration and such matters as Collimatrix described (the better a suspension can cancel out the bouncing/shaking of rough terrain, the faster you could in theory go.) but it's still going to be about tradeoffs in the end (including speed.)

 

Also, the suspension itself is just part of a larger system (Wheels for example, which is also discussed in Janes) which can also play a role and probably shouldn't be ignored.

 

Differences in engineering and metallurgy  (especially over time) probably affect things too.

 

Sorry if that isn't answering what you're specifically asking I'm trying to guess at it from your words and where in Janes you're alluding (unless you mean the Damping section?)

 

Edit (again after many):  Maybe this is what you're referring to from 13.4 in Jane's? 

 

https://imgur.com/a/Et56F

 

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4 hours ago, Jamby said:

Why does Horstmann suspension necessarily denote bad tank design? I think it was arguably quite suitable for the speed that tanks like the Chieftain could reasonably reach, given what I've been reading here:

https://archive.org/stream/Janes_Technology_of_Tanks_01/Janes_Technology_of_Tanks_01_djvu.txt

 

The part I'm referring to is about two thirds of the way down the document - section 13 (I'm sorry for not linking the specific screenshot, but I absolutely cannot manage to do it somehow) - and seems to suggest that the appropriate choice of suspension is largely dependent on the speed you're moving at, from leaf-spring at the lowest speeds to torsion bar at the highest.

 

Unless you were bombing along rough country at particularly high speed (even for a vehicle designed to do that to a degree), would the difference between torsion bar and Horstmann suspension really be appreciable? Are there tankers from both sides of the pond here?

 

 

 

 

 

I think its partly an in-joke (the British were about as good at tonk design in WW2 as you would expect given the amount of effort they put into it, which was none) and partly because the Brits have this weird tendency to combine good engineering with contrarian bodging in all their stuff.

 

Going back to a 1920s suspension design for all your tanks just as literally everyone else is embracing torsion bars is... very british.

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3 hours ago, Jamby said:

Why does Horstmann suspension necessarily denote bad tank design? I think it was arguably quite suitable for the speed that tanks like the Chieftain could reasonably reach, given what I've been reading here:

https://archive.org/stream/Janes_Technology_of_Tanks_01/Janes_Technology_of_Tanks_01_djvu.txt

 

The part I'm referring to is about two thirds of the way down the document - section 13 (I'm sorry for not linking the specific screenshot, but I absolutely cannot manage to do it somehow) - and seems to suggest that the appropriate choice of suspension is largely dependent on the speed you're moving at, from leaf-spring at the lowest speeds to torsion bar at the highest.

 

Unless you were bombing along rough country at particularly high speed (even for a vehicle designed to do that to a degree), would the difference between torsion bar and Horstmann suspension really be appreciable? Are there tankers from both sides of the pond here?

 

While it is true that Chieftain had such a low power to weight ratio that putting independent suspension on it wouldn't much improve its mobility, that hardly speaks well of it.  It meant that Chieftain was generally inadequate, both in terms of power to weight and suspension performance.  Centurion, Conqueror and Chieftain are literally the only tanks designed after WWII without independent roadwheel suspension.  It was a specifically British bit of backwardness.  They were behind on hydraulic torque converters in tank transmissions, behind on smoothbore guns and APFSDS ammunition, and behind on fire control systems too.  The track record of British tank design post 1945 is really not very impressive.

On top of that it was contemporaneous with the T-64, which sported a stereo rangefinder, much higher power to weight ratio, composite armor, and a comparable gun while being something like fifteen tonnes lighter than Chieftain.

The design of Chieftain isn't all bad, and there are several individually good ideas on it.  The mantletless turret is a good idea, the reclined driver is a good idea, and the ammunition stowage is probably the safest of any tank of that generation.  But overall?  It's underwhelming.

 

2 hours ago, A_Mysterious_Stranger said:

Well there's different kinds of suspension that have evolved since WW1 and they offer different tradeoffs (although some have been superseded) such as cost, simplicity/reliability, effectiveness, etc.   but I also think there may be an element of semantics to it (how people define such things, which is where the sources you use and quality of that source) probably applies.  

 

Also there's going to be more issues than just 'speed' to consider in your suspension choice.  For example on page 319 of Jane's:

 

 

It would seem tradeoffs and design (complexity, protection, weight, internal space) are drivers over 'good' or 'bad' decisions as how it is implemented (possibly getting back to the 'semantics' again?)   Speed will matter too since that affects comfort/safety/stability of the crew and vehicle vibration and such matters as Collimatrix described (the better a suspension can cancel out the bouncing/shaking of rough terrain, the faster you could in theory go.) but it's still going to be about tradeoffs in the end (including speed.)

 

Also, the suspension itself is just part of a larger system (Wheels for example, which is also discussed in Janes) which can also play a role and probably shouldn't be ignored.

 

Differences in engineering and metallurgy  (especially over time) probably affect things too.

 

Sorry if that isn't answering what you're specifically asking I'm trying to guess at it from your words and where in Janes you're alluding (unless you mean the Damping section?)

 

Edit (again after many):  Maybe this is what you're referring to from 13.4 in Jane's? 

 

https://imgur.com/a/Et56F

 



There are indeed cost issues to consider, but these days those aren't pressing.  The cost of modern tanks is driven by the fancy composite armor and fire control systems so advanced that they are practically magical.

Again, the type of suspension isn't too useful a piece of information.  The M60 and M1 Abrams both have torsion bar suspension, but the M1's suspension articulates through about double the range of motion that the M60's does, and thus has correspondingly better ride when hauling ass offroad.  Leaf spring suspensions could be used for a high-speed tank.  Indeed, the early Daimler Benz VK. 30.01 prototypes were slated to have leaf spring suspension, and they were only later changed to torsion bars because some asshole in the bureaucracy had a fetish for interleaved roadwheels and torsion bars.  Seriously, that's what the Osprey book on the matter says.

Leaf springs would weigh somewhat more than torsion bars for the same performance.  Imagine bending a leaf spring; the atoms of iron in the outer surfaces on the top and bottom of the leaf spring are being stretched apart from each other the most.  This stretching of the metallic bonds between the atoms is how a spring stores energy.  The atoms in the center of the leaf spring are being deflected apart from each other very little, they're nearly deadweight.  The atoms on the sides of the leaf spring aren't doing much either.

A torsion bar is a big cylindrical tube that gets twisted about its long axis.  Therefore, the entire surface of the cylinder minus the ends is contributing to storage of energy.  The center of the torsion bar isn't storing much work, and there has been the odd attempt here and there to use hollow torsion bars to further improve suspension efficiency.  But for the most part, normal torsion bars are satisfactory and offer a good performance to weight ratio relative to other spring types.

Now, there are all sorts of interesting considerations when it comes to servicing the stupid things.  Torsion bar suspensions have a few problems here.

BZLTede.jpg

Torsion bar suspensions are almost always slightly asymmetrical.

E7XpCjQ.png
This is simply because one bar has to sit slightly in front of the other, which means that one roadwheel will end up sitting slightly in front of the other.  That leading wheel will eat more of the shock from bumps, which in turn means that the leading torsion bar will wear out faster than the others.

Actually changing out torsion bars ranges from a pain to a giant pain if the hull is somehow warped, as noted above.  The Israelis noted that the Horstmann suspension on their Centurions was faster to swap out than the torsion bars on their M48s.  This should not be construed as a defense of Horstmann suspension in TYOOL 1973, however.  There were plenty of other suspension systems that were completely external to the hull of the tank that offered independent roadwheel suspension, like the Belleville washer suspension in the Pz 68 and the external coil spring suspension the Israelis ultimately adopted for the Merkava.

Another problem of torsion bar suspensions is that the bars themselves take up space inside the hull, and thus force the turret basket to be a little higher:

88xAInV.png

But there are ways around this; as in the AMX-30:

FKMkxku.jpg

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One thing that have always surprised me is that even on new tank designs we still see torsion bars suspensions (T-14 I'm looking at you) while hydrogas seem to be superior in every single way but cost.

 

I mean that it allow for a smoother ride, doesn't intrude into the hull (most important point from a design perspective), add some metal on the sides where there is usually none, is external so it's not too much of a pain to replace and finally allow you to play with ground clearance and hull pitch (IMO the last part is more of a nice gimmick than something really useful combat).

 

How expensive are hydrogas compared to torsion bar (but as Collimatrix said, suspensions doesn't make up for a lot of the price in a modern MBT)?

Or is there another major downside I overlooked?

 

Same could be said about Israli coil spring suspension (which seem close to hydrogas but are maybe cheaper)

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You can see in some of the pictures in the T-14 thread that the side armor under the top run of the track is ridiculously thick.  Any sort of external suspension would probably have taken up too much room there.  So that is one advantage of torsion bars.

Aside from that, hydropneumatic seems generally superior.  I'm not even sure that it's more expensive.  Some modern torsion bars are made of very fancy and expensive VIM/VAR or electroslag steels.  I suspect (but don't know for sure) that the reason the Leo 2 and Abrams have nearly double the range of motion in their suspensions is that their torsion bars are made of these low-fatigue steels.

 

I don't know why the independent external coil spring suspension wasn't more popular.  It seems like a good and logical design.  The US T49 tank destroyer prototype used it:

iSPvaWq.png

And as you can see, it also had a rear sprocket drive.  But the production M18 Hellcat went with torsion bars and a frontal drive sprocket for reasons I do not ken.

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10 minutes ago, Collimatrix said:

I don't know why the independent external coil spring suspension wasn't more popular.  It seems like a good and logical design.  The US T49 tank destroyer prototype used it:

And as you can see, it also had a rear sprocket drive.  But the production M18 Hellcat went with torsion bars and a frontal drive sprocket for reasons I do not ken.

 

My guess would be steel fatigue, the section of a coil spring being smaller than the one of a torsion bar probably meant that coil spring could endure less cycles.

But metallurgy has come a long way since WWII.

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6 hours ago, A_Mysterious_Stranger said:

(. . .)

 

Sorry if that isn't answering what you're specifically asking I'm trying to guess at it from your words and where in Janes you're alluding (unless you mean the Damping section?)

 

Edit (again after many):  Maybe this is what you're referring to from 13.4 in Jane's? 

 

https://imgur.com/a/Et56F

 

 

This is the bit I meant - I think I finally figured out how to link it:

Screenshot

Edited by Jamby
Fixing broken link

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7 hours ago, Alzoc said:

 

My guess would be steel fatigue, the section of a coil spring being smaller than the one of a torsion bar probably meant that coil spring could endure less cycles.

But metallurgy has come a long way since WWII.

 

I'm no mechanical engineer, but as I understand it coil springs are basically torsion springs that are coiled into a helix.  So torsion bars and coil springs should have similar energy density and fatigue properties.

That said, fatigue in springs is largely dependent on how smooth the surface of the spring is kept.  As I said above, it's the surface of the spring that is storing the most work, so the bonds between the atoms are at their most stretched there.  Any imperfections in the surface of the spring, like little micro-nicks or corrosion tend to spread and accelerate fatigue.

So the fact that a torsion bar is safely tucked into the hull of the tank where it is less likely to develop such imperfections may give them an edge in fatigue life.  So... score another point for torsion bars, I guess.

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48 minutes ago, Collimatrix said:

 

I'm no mechanical engineer, but as I understand it coil springs are basically torsion springs that are coiled into a helix.  So torsion bars and coil springs should have similar energy density and fatigue properties.

 

As you said, both work in flexion.

So for the same energy absorbed, the coil spring will absorb it over a smaller section (in each "floor" of the spring) but at the same time the amplitude of movement on the thread should be smaller.

 

Edit: They work in torsion my bad, I wasn't thinking (and reading) straight. :wacko:

Time to stop for today

 

Since fatigue comes from the propagation of defects in the structure of the material, which makes it stiffer and stiffer (until it fail), I think that the amplitude of the movement should have some importance.

 

On top of that there is also the problem of surface defects, and here it would make sense for springs to be more vulnerable as you said.

 

I think it's a non trivial problem and I'm not a mechanical engineer either so I haven't done this kind of calculation since school (and when I did it was in simple configurations anyway).

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55 minutes ago, EnsignExpendable said:

Foam core or air filled? Air filled tires offer a smoother ride, but are obviously easy to shoot out. Foam core tires are bulletproof, but have the downside of settling if you're parked for too long, so the first few minutes of your ride will be very bumpy.

Are they cheaper than conventional roadwheels? 

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On 3/21/2018 at 4:04 AM, Collimatrix said:

You can see in some of the pictures in the T-14 thread that the side armor under the top run of the track is ridiculously thick.  Any sort of external suspension would probably have taken up too much room there.  So that is one advantage of torsion bars.

Aside from that, hydropneumatic seems generally superior.  I'm not even sure that it's more expensive.  Some modern torsion bars are made of very fancy and expensive VIM/VAR or electroslag steels.  I suspect (but don't know for sure) that the reason the Leo 2 and Abrams have nearly double the range of motion in their suspensions is that their torsion bars are made of these low-fatigue steels.

 

I don't know why the independent external coil spring suspension wasn't more popular.  It seems like a good and logical design.  The US T49 tank destroyer prototype used it:

iSPvaWq.png

And as you can see, it also had a rear sprocket drive.  But the production M18 Hellcat went with torsion bars and a frontal drive sprocket for reasons I do not ken.

Torsion bar, likely because of the increased weight of the M18 (T70) over the T49 & T67, and front drive because of weight (re) distribution, and it allowed the engine and transmission to be easily serviced/replaced as independent units. (the engine and trans will "slide out" on tracks.).

 

 

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On 21/03/2018 at 9:52 AM, Collimatrix said:

 

While it is true that Chieftain had such a low power to weight ratio that putting independent suspension on it wouldn't much improve its mobility, that hardly speaks well of it.  It meant that Chieftain was generally inadequate, both in terms of power to weight and suspension performance.  Centurion, Conqueror and Chieftain are literally the only tanks designed after WWII without independent roadwheel suspension.  It was a specifically British bit of backwardness.  They were behind on hydraulic torque converters in tank transmissions, behind on smoothbore guns and APFSDS ammunition, and behind on fire control systems too.  The track record of British tank design post 1945 is really not very impressive.

On top of that it was contemporaneous with the T-64, which sported a stereo rangefinder, much higher power to weight ratio, composite armor, and a comparable gun while being something like fifteen tonnes lighter than Chieftain.

The design of Chieftain isn't all bad, and there are several individually good ideas on it.  The mantletless turret is a good idea, the reclined driver is a good idea, and the ammunition stowage is probably the safest of any tank of that generation.  But overall?  It's underwhelming.

 



There are indeed cost issues to consider, but these days those aren't pressing.  The cost of modern tanks is driven by the fancy composite armor and fire control systems so advanced that they are practically magical.

Again, the type of suspension isn't too useful a piece of information.  The M60 and M1 Abrams both have torsion bar suspension, but the M1's suspension articulates through about double the range of motion that the M60's does, and thus has correspondingly better ride when hauling ass offroad.  Leaf spring suspensions could be used for a high-speed tank.  Indeed, the early Daimler Benz VK. 30.01 prototypes were slated to have leaf spring suspension, and they were only later changed to torsion bars because some asshole in the bureaucracy had a fetish for interleaved roadwheels and torsion bars.  Seriously, that's what the Osprey book on the matter says.

Leaf springs would weigh somewhat more than torsion bars for the same performance.  Imagine bending a leaf spring; the atoms of iron in the outer surfaces on the top and bottom of the leaf spring are being stretched apart from each other the most.  This stretching of the metallic bonds between the atoms is how a spring stores energy.  The atoms in the center of the leaf spring are being deflected apart from each other very little, they're nearly deadweight.  The atoms on the sides of the leaf spring aren't doing much either.

A torsion bar is a big cylindrical tube that gets twisted about its long axis.  Therefore, the entire surface of the cylinder minus the ends is contributing to storage of energy.  The center of the torsion bar isn't storing much work, and there has been the odd attempt here and there to use hollow torsion bars to further improve suspension efficiency.  But for the most part, normal torsion bars are satisfactory and offer a good performance to weight ratio relative to other spring types.

Now, there are all sorts of interesting considerations when it comes to servicing the stupid things.  Torsion bar suspensions have a few problems here.

BZLTede.jpg

Torsion bar suspensions are almost always slightly asymmetrical.

E7XpCjQ.png
This is simply because one bar has to sit slightly in front of the other, which means that one roadwheel will end up sitting slightly in front of the other.  That leading wheel will eat more of the shock from bumps, which in turn means that the leading torsion bar will wear out faster than the others.

Actually changing out torsion bars ranges from a pain to a giant pain if the hull is somehow warped, as noted above.  The Israelis noted that the Horstmann suspension on their Centurions was faster to swap out than the torsion bars on their M48s.  This should not be construed as a defense of Horstmann suspension in TYOOL 1973, however.  There were plenty of other suspension systems that were completely external to the hull of the tank that offered independent roadwheel suspension, like the Belleville washer suspension in the Pz 68 and the external coil spring suspension the Israelis ultimately adopted for the Merkava.

Another problem of torsion bar suspensions is that the bars themselves take up space inside the hull, and thus force the turret basket to be a little higher:

88xAInV.png

But there are ways around this; as in the AMX-30:

FKMkxku.jpg

Off topic, but how is a mantlet-less turret better?

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23 hours ago, Toxn said:

Off topic, but how is a mantlet-less turret better?

 

For various reasons the edge of an armor array is always a weak point.  There's free edge effect, the fact that the moving elements in NERA/ERA usually don't go all the way to the edge, and the fact that their range of intersection of incoming threats is smallest at one edge.  A mantlet-less turret presents the smallest possible weakened zone in the turret frontal armor from this edge.

 

Most mantlets don't have very much armor.  Look at the picture of the Leclerc's mantlet in the Contemporary Western Tank thread if you want to see the worst example.  Even on tanks with relatively thick, and presumably well constructed mantlets like the Leo 2A5 and up, there will still be a weak point where the edges of the mantlet touch the edges of the hole for the gun.

 

There are two objections to the mantletless design.  The first is that it will make gun replacement harder.  This is only true if the gun tube can't detatch from the gun breech.  On some guns the tube can loosen from the breech and come out forward, and on some it cant.  Obviously, a mantletless turret ought to use one that can.  The second objection is that the trunnions will intrude into the armor package and create a weak point (although this is obviously true of designs with mantlets too).  The solution to that is just make the package a bit thicker on top of where the trunnions are.

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11 minutes ago, Collimatrix said:

 

For various reasons the edge of an armor array is always a weak point.  There's free edge effect, the fact that the moving elements in NERA/ERA usually don't go all the way to the edge, and the fact that their range of intersection of incoming threats is smallest at one edge.  A mantlet-less turret presents the smallest possible weakened zone in the turret frontal armor from this edge.

 

Most mantlets don't have very much armor.  Look at the picture of the Leclerc's mantlet in the Contemporary Western Tank thread if you want to see the worst example.  Even on tanks with relatively thick, and presumably well constructed mantlets like the Leo 2A5 and up, there will still be a weak point where the edges of the mantlet touch the edges of the hole for the gun.

 

There are two objections to the mantletless design.  The first is that it will make gun replacement harder.  This is only true if the gun tube can't detatch from the gun breech.  On some guns the tube can loosen from the breech and come out forward, and on some it cant.  Obviously, a mantletless turret ought to use one that can.  The second objection is that the trunnions will intrude into the armor package and create a weak point (although this is obviously true of designs with mantlets too).  The solution to that is just make the package a bit thicker on top of where the trunnions are.

Thank you!

This makes a lot of sense, but then raises the question of why big mantlets used to be a thing?

Is edge effect just a lot less of an issue than movement in a NERA array?

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    • By Walter_Sobchak
      Since Xlucine suggested it in the general AFV thread, here is a new version of the old Tank ID thread that used to exist at the WoT forums, back before the great exodus to SH.
       
      The rules are simple.  Post a picture of some sort of AFV and everyone has to try to name what it is.  Try to avoid posting a new picture until the previous picture is identified.  Generally, the person who was first to correctly ID the picture in question gets to post the next picture, unless they want to pass.  If a picture is not ID'd in a day or two, the person that posted it should say what it is and bask in their own sense of superiority.   They should then post a new picture for the sake of keeping the thread moving.  Please, no fictional tanks, paper napkin drawings that never made it to prototype or pictures where the vehicle in question is obscured or particularly hard to see.  Also, if posting a picture of an unusual variant of a relatively common vehicle, be sure to note that you are looking for the specific variant name, not just the general family of vehicles it belongs to (for example, if I post a picture of a Panzer IV with the hydrostat drive, I would say in the post something like "What makes this Panzer IV unusual?" since everyone can ID a Panzer IV)
       
      It is perfectly ok to shame those that make spectacularly wrong guesses.  That's just how we roll around here.  
       
      I'll start 
       

    • By Monochromelody
      各位最近可能在WT论坛上见过这张图片,在一些争论陆上自卫队90式战车的讨论串里:
      Some of you may have seen this pic recently on WT forum, in some thread arguing the protection of JGSDF Type 90: 
      Discussion on WT forum
       

       
      我就直说吧,表格里的中文注解说了,这不过是个“猜想”,GUESSING。
      To be straight, the Chinese annotation in the table said it is just a GUESSING.
      注解内容可能完全是编造的,但不幸的是,不同语言间的障碍使你们无法看穿这点。
      This annotation could be totally nonsense but unfortunately a barrier between languages prevent you guys see throught it. 
       
      实际上,这又是一份关于陆上自卫队10式战车的文件,说的并不是90式。
      In fact, again, this document itself is about JGSDF Type 10 MBT, not Type 90.
      同样的花招,不一样的人,是吧?
      Same trick, different people, huh?

      ↑陆上自卫队的10式战车规格书
      JGSDF specification handbook of Type 10 MBT

      ↑59页,附录B,性能(规定)以及诸元
      page 59, Appendix B, performance (regulations) and data
       
      下面简要说说这些性能规定如何编写、如何加密。
      Let's talk about these regulations and how they were made and encrypted. 
       
      大家可能知道日语中有平假名和片假名,和拉丁语中的字母还有大写字母是差不多的。
      You may know that Japanese have Hirakana and Katakana, like Latin have letters and capital letters. 
       
      正如图中所示,一些最关键的数值和描述用平假名、片假名、罗马字(拉丁字母)隐去了。
      As you can see, some of the most crucial numbers and descriptions are covered by a Hirakana or Katakana or Romaji(Latin letters).
       
      这些数值和描述被归在一起,编入附属的手册,称为“别册”。
      These numbers and descriptions were collected and listed in some append book, called Bessatsu(別冊). 
       
      在查阅别册时,就好比在看试卷的答题卡。但如果把别册里面的数值和描述涂黑,你就根本不知道说啥。
      When you look up to the append book, just like viewing the answer sheet of an exam paper. But when numbers and descriptions were censored, you'll never know what it said. 
       
      比如说,正面防护:
      For example, the frontal protection: 
       
      “耐弾性 - 正面 - 正面要部は、【あ】に射距離【え】m相当存速において、貫徹されない。”
       
      读起来是这样的:
      耐弹性 - 正面 - 正面重要部位可抵御【あ】以相当于射击距离【え】米存速的射击,不会贯穿。
      It read like this: 
      Protection - Frontal - Frontal crucial part should withstand 【あ】 firing at a distance of 【え】meter speed reduce equivalent, and not penetrate. 
       
      【あ】代表某种弹药,可能是尾翼稳定穿甲弹,但不知道是量产弹种还是实验弹种。
      【あ】stands for certain type of ammunition, probably APFSDS, but don't know whether it is production shot or experimental.
       
      【え】代表某个射击距离,可以是1000、1500或2000(米),但这么远的距离,炮弹会受到风力和重力影响,故无法精确瞄准靶车的防护区域。
      【え】stands for certain firing distance, could be 1000 , 1500 or 2000 (meters), but on such a long distance, shot could be effect by wind and gravity, thus cannot aim on the protection area of target vehicle precisely.
       
      一个常见的解决方式是在更近的距离上开火,比如说200到550米,同时减少推进药量,使得穿甲弹的终点速度符合特定距离的速降。这是一种等效方法。
      The usual solution is to fire from a much closer range, from 200 to 550 meters, while reducing the propellant charge so that the end speed of AP shot could match the speed drop on certain distance. This is an equivalant method. 
       
      有的人争辩说90式战车可以抵挡另一辆90式战车发射的穿甲弹(JM33),距离大约250米。这一说法源自一段未知视频片段,具体什么视频他们自己也没看过。较近的射击距离是为了能更好的瞄准,为此可能使用了减装药来模拟远距离终点速度,但也无法证明。
      Some people argue that Type 90 MBT can withstand AP shot (JM33) firing from another Type 90 MBT, on a distance about 250 meters. The source of this statement came from an unknown video clip, which they have never seen. Firing on closer range is for better aim, and they could have use reduced charge to simulate a much longer range, but we cannot prove. 
       
       
    • By Toxn
      Part 5 of a multi-part series. This one's got the goods.
       



      Sherman and firefly.
       


      Early crusader.
       

      Early Valentine. The British really went through a phase where they slapped 2 pounders onto everything.
       



      Father.
       


      Son.
       

      Holy ghost.
       

      Comet, aka Hipster Centurion.
       

      Centurion, aka The entire History of South African tanks post-WW2.
       




      T-shirt cannon Churchill.
       

      Combat engineers get no respect.
       

      This thing is tiny and has an insane steering system.
       


      Somehow this thing is even smaller. Those twin barrels are for a flamethrower of some sort, because the Italians were world-class optimists.
       
       
       
    • By Darjeeling
      Greetings  I am Darjeeling and I come from Hong Kong. Recently as Turkey launched the OB so I investigate in the TAF as I am a apoist.
       
      The following article will mainly focus on the best armoured unit of TAF. All the data are collected from internet and I need help to complete it.
       
      [Introduction on armour unit organisation]
       
      Turkish tank brigades included three tank battalions while in the mechanised brigades just 1 tank battalion. Each tank battalion consists of 41 tanks. The staff and management team consists of 2 tanks, 39 armored rest distributed to 3 tank Wrotham. Each tank company consists of 13 tanks while 1 tank company commander and platoon 4 to 3 tanks. 
       
      Since the showing the TO&E of all armoured units should be too long, the following will only present some  "Ace armoured unit".
        =====   Version 1.1 
       
      Welcome for any suggestions/addition on this issue
       
      1)M60T units
       
      M60T is a modernised M-60 which is capable with T-72s. Turkey utilizing large numbers of these tanks have been seen deploying to the southern border in the previous years. They were used during incursions into Syria and Iraq in earlier operations to combat Kurdish forces in both nations.
       
      Here are what I confirmed:
       
       
      - 5th Armoured Brigades
      (Confirmed in internet data)
       
      - 20th Armoured Brigades
      (Confirmed in internet data)
       
      - 172nd Armoured Brigades
      (Confirmed in internet data)
       
      They are believed to have equipped with M60T. As each Turkey tank battalion consists of 41 tanks, a total of 123 out of 170 should have counted. I believe there maybe one brigades unknown.
       
       
      Example in real combat:
      >M60T act as spearhead and attaching a YPG town but being ambushed. Two tanks were destroyed.
       
       
      https://m.youtube.com/watch?v=78lnBhcA_n0
       
      2) Leopard 2 units
       
       Turkey has 354 of highly capable Leopard 2 German manufactured tanks. Leopard are currently deployed in Syria in OB and the previous OB. It is most likely that these more capable MBTs are with units tasked with guarding Turkey’s border with Russia and the Caucasus, where they would have to fight against a much more capable adversary. 
       
      Here are what I  confirmed:
       
       
      - 2nd Armoured Brigade
      (Confirmed in Operation ES as casualties)
       
      - 3th Armoured Brigade
      (Confirmed in the 2016 failed coup)
       
      - 5th Armoured Brigade 
      (Confirmed in Operation OB as casualties)
       
      So it is obviously that more efforts needed to be done on Leo2. Only half of them counted.
       
      The Leo2a4 of TAF is the outdated version that it's last update is in 1992. So this explained why it performed so bad in ES. Total 10 tanks were confirmed lost in the battle and even captured by ISIS.
       
      Yet, while facing the poor equipped and trained YPG/J, only 3 Leo 2 was destroyed in OB. 2 was taken out because the engine was penetrated and taken out by Air Force (prevent captured by YPG/J). The only effort of YPG/J is penetrating a Leo 2 from flank and lead to the blow. 
       
       
      Example in real combat:
       
      >Leo 2 receive a direct hit by YPG but it was not destroyed. High survivability showed. 
       
       
      https://m.youtube.com/watch?v=YafzmkvVRiI
       
      3) M60A3 units 
       
      M60A3 is a 2nd Gen-MBT in TAF. They are mostly used as supporting fire unit to assist the infantry. Yet, the performance of M60A3 relatively bad.
       
      Here are what I confirmed:
       
       
      - 16th Mechanised Brigade 
      (Confirmed in Operation ES as casualties)
       
      - 39th Mechanised Brigade 
      (Confirmed in Operation OB as casualties)
       
       
      Example in real combat:
       
      >M60A3 being hit as no soldiers protect it in ES
       
       
      https://m.youtube.com/watch?time_continue=28&v=pg-rbEC0jXI&ebc=ANyPxKqRFXar7bNqSS5wcCJspZFJMnyoQD0qixyUheJgMdLHy5q0eQakNmCBv16NSoGjfAoNbcP4cGDbJHXTpR7eJhobZW8EPw
       
      —————
       
      PPS:This is my post about order of battle of OB about TAF
       
      https://www.reddit.com/r/syriancivilwar/comments/81nml8/keep_updateturkish_order_of_battle_of_ob_up_to/?st=JEE2UT1F&sh=d04daee9
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