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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 Proyas
      Hi guys,
       
      Does anyone know of any military studies that analyzed the reload speeds for different tanks? The question occurred to me when I watched this video tour of the T-55's interior: 
       
      https://youtu.be/TEDhB9evPvw
       
      At the 10:00 mark, Mr. Moran demonstrates how the loader would put a shell into the tank's cannon, and the effects of the turret's small size and of the loader's awkward seating make it clear that the process would be slow. My question is: how slow? 
       
      Side question: Am I right to assume that storing the tank shells all over the inside of the turret like that is an inherent design flaw of the T-55 that makes it inferior in that regard to modern tanks? 
       
      Thanks in advance. 
    • By N-L-M
      ATTENTION DUELISTS:
      @Toxn
      @LostCosmonaut
      @Lord_James
      @DIADES
      @Datengineerwill
      @Whatismoo
      @Kal
      @Zadlo
      @Xoon
      detailed below is the expected format of the final submission.
      The date is set as Wednesday the 19th of June at 23:59 GMT.
      Again, incomplete designs may be submitted as they are and will be judged as seen fit.
       
      FINAL SUBMISSION:
      Vehicle Designation and name

      [insert 3-projection (front, top, side) and isometric render of vehicle here)



      Table of basic statistics:

      Parameter

      Value

      Mass, combat


       
      Length, combat (transport)


       
      Width, combat (transport)


       
      Height, combat (transport)


       
      Ground Pressure, MMP (nominal)


       
      Estimated Speed


       
      Estimated range


       
      Crew, number (roles)


       
      Main armament, caliber (ammo count ready/stowed)


       
      Secondary armament, caliber (ammo count ready/stowed)


       

       
      Vehicle designer’s notes: explain the thought process behind the design of the vehicle, ideas, and the development process from the designer’s point of view.

      Vehicle feature list:
      Mobility:

      1.     Link to Appendix 1- RFP spreadsheet, colored to reflect achieved performance.

      2.     Engine- type, displacement, rated power, cooling, neat features.

      3.     Transmission- type, arrangement, neat features.

      4.     Fuel- Type, volume available, stowage location, estimated range, neat features.

      5.     Other neat features in the engine bay.

      6.     Suspension- Type, Travel, ground clearance, neat features.

      Survivability:

      1.     Link to Appendix 1 - RFP spreadsheet, colored to reflect achieved performance.

      2.     Link to Appendix 2- armor array details.

      3.     Non-specified survivability features and other neat tricks- low profile, gun depression, instant smoke, cunning internal arrangement, and the like.

      Firepower:

      A.    Weapons:

      1.     Link to Appendix 1- RFP spreadsheet, colored to reflect achieved performance.

      2.     Main Weapon-

      a.      Type

      b.      Caliber

      c.      ammunition types and performance (short)

      d.     Ammo stowage arrangement- numbers ready and total, features.

      e.      FCS- relevant systems, relevant sights for operating the weapon and so on.

      f.      Neat features.

      3.     Secondary weapon- Similar format to primary. Tertiary and further weapons- likewise.

      4.     Link to Appendix 3- Weapon system magic. This is where you explain how all the special tricks related to the armament that aren’t obviously available using Soviet 1961 tech work, and expand to your heart’s content on extimated performance and how these estimates were reached.

      B.    Optics:

      1.     Primary gunsight- type, associated trickery.

      2.     Likewise for any and all other optics systems installed, in no particular order.

      C.    FCS:

      1.     List of component systems, their purpose and the basic system architecture.

      2.     Link to Appendix 3- weapon system magic, if you have long explanations about the workings of the system.

      Fightability:

      1.     List vehicle features which improve its fightability and useability.

      Additonal Features:

      Feel free to list more features as you see fit, in more categories.

      Free expression zone: Let out your inner Thetan to fully impress the world with the fruit of your labor. Kindly spoiler this section if it’s very long.


       Example for filling in Appendix 1
    • By Collimatrix
      Sturgeon's House started with a community of people who played tank games.  At the time, most of us were playing World of Tanks, but I think there were a few Warthunder and even Steel Beasts players mixed in there too.  After nearly five years, we must be doing something right because we're still here, and because we've somehow picked up a number of members who work with, or have worked with tanks in real life.

      I know that @AssaultPlazma served as an Abrams loader, @Merc 321 and @Meplat have helped maintain and restore privately-owned armor, and @Xlucine has volunteered in a tank museum.  I'm sure I'm missing several more!

      So, what are your favorite personal tank stories?
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