Jump to content
Sturgeon's House

Recommended Posts

2 hours ago, Xoon said:

What did you dislike about the AMX-10RC, or armored vehicles in general? 
Everything counts, even lack of space for snacks for that matter. 

Generaly speaking, I never answer to such a question because it’s the start of unrealistic discussions of technology fanboys unknowing real. But, I can say :

- never forget AMX-10RC is a very 80’s light tank. So, any improvement must be cheap provide. 

- the world famous Serge AFV belief is : an AFV chassis push, carry and tow. 

- having a good AFV is good, but without its environment, it’s useless. 

 

FCS, sights, weapons were good.

 

So, I would have :

- modified the seats to have something more confortable and armored. Maybe an harness to sleep ;

- introduced a new TC hatch with an umbrella opening (my priority) ;

- rearrange external storage to increase them ;

- suppress river crossing (both useless and dangerous) to have more storage ;

- add spall liner and mine proof plates under pilot seat and turret floor. 

 

Considering chassis, I would have add :

- 2 rear fuel drop barrels like the Leclerc ones. Fuel drums are compulsory ;

- front tools connector to push mine rollers...

 

Considering it’s environment, I would have :

- add a fourth 10RC per troop (In France, reccon tanks troops are 3 tanks troops. Leclerc : 4 MBT troops) ;

- adopted AMX-10RTT as command post and ARVs instead of VAB and ARV based on trucks.

c080b9187ce9aa61fe7302c881f145e3.jpg

 

With diminution of 10RC number, I would have transformed some of them in general purpose vehicles able to carry dedicated teams for special tasks such as EW....

When dimounting the barrel and ammo racks, you have plenty of room. 

 

Share this post


Link to post
Share on other sites
On 16/04/2018 at 9:43 AM, Alzoc said:

 

I remember reading that they payed a particular attention on mass balance around the trunnion for the Leclerc's gun, so that the strain on the electric drive of the gun would be as limited as possible.

  Reveal hidden contents

 

 

Don't know the final performance level they reached, but Nexter/GIAT commonly marketed the Leclerc as the only tank with a true fire on the move capability (describing the M1, Leo 2 and Challenger 2 as tanks that have merely acquired this capacity at limited speed and only in the frontal arc).

 

When reading on the history of it's development one have the really distinct feeling that they went full retarted on having the best stabilization possible.

The initial aluminum tracks that had awful service life were chosen for their light weight but mostly because they generated less vibrations, for example.

 

Dunno if the M1, Challenger 2 and Leo 2 still use an hydraulic drive for their guns or if their most recent versions switched to electric.

 

 

A sort of mechanical arm that would measure the angular difference?

Well that's a question for a crewman for once. Does the gunner lose the target when the gun is reloading?

@Serge Aren't you the one who knows an ex Leclerc TC?

Or was it @Laviduce?

 

The specs required a highly mobile tank capable to destroy any Warsaw pact (PAVA) tanks at long range with a high hit probability on first shot. This led to the crafting of highly precise system.
To be honnest with you there is no stabilisation on the Leclerc. The gun is slave to the ballistic computer which computes the ideal LOF from the stabilised LOS.
When reloading, the gun goes to the reloading elevation. Meanwhile the LOS is still stabilised to the direction of observation (in the limits of the mirrors amplitude). Unless you release the palm switches, the mirrors go to their mechanical neutral positions.

The gunner sight is mechanically mounted to the main armament. When the gun goes up and down; the sight bows up and down.
Since the both move along with the exact same angle, boresighting can be done automatically with a deviation measurement laser (AMX 10 RC being the first french AFV to be equiped with such device).
Crews do some alignments (what we call "harmonisation" where we keep the parallax in check), but that's not the bullshit stated by Sergei Suvorov where crews were forced to boresight everytime they move their tanks...
 

On 16/04/2018 at 4:06 PM, Alzoc said:

 

There was a shitload of concept for the Leclerc (same for any 3rd gen MBT I guess).

Take your pick:
 

  Reveal hidden contents

 

948baa2e8a4ae5304082a3e24b9f8dcc

c2a0af58e19ef91f9b4d00ae3e3d6659

dacb53df9ff04e126e9e56c34b16aae9

67403526cad3d05ca951b20ae286c18f

d9ef28c84fa495f9adc6d3d325d839a2

0068Ayuagy1fc6caf4g2vj31kw23vb2b.jpg

 

 

At the time engineers were open minded on what could replace the classical tank. Once they defined that their platform was still an AFV, they assessed every kind of compromise to take what was the most favorable and compatible to their specs guideline.
 

20 hours ago, Alzoc said:

On the mass balance topic, here's a citation of a book I (and probably other French speaking members) own.

Even if you don't speak French it's quite a nice book to have with plenty of pictures (all those pictures of the various early EPC concept comes from here), though you have the impression that nobody ever proofread it (screw grammar and the orthograph^^).

 

P58:

 

Comme pour la fonction mobilité, une mécanique de haute technologie est requise pour la fonction feu. Celle-ci est entièrement conçue pour faire du tir en roulant le mode normal d'engagement des cibles.

La précision de la stabilisation est donc au cœur des performances du système. Stabiliser un objet dans l'espace (en l’occurrence la tourelle et son canon) est un défi technique qui requiert de la part de l'ingénieur en mécanique le respect des trois règles d'or:

 

-La recherche des équilibres ;

-Le contrôle des élasticités et des déformations dynamiques ;

-La chasse au jeu entre les pièces.

 

Ces équilibres sont obtenus par conception du canon de 120mm et de la tourelle dont les centres de gravité sont respectivement situés sur les axes de rotation site et gisement.

 

Canon et tourelle sont mis en mouvement à l'aide de moteurs électriques transmettant leur puissance à des boîtes mécaniques de pointage dont les élasticité sont contrôlées en permanence grâce à un montage utilisant des barres de torsion.

Enfin des roulements à billes sans jeu assistent le mouvement du canon dans l'axe vertical.

Sans ces technologies mécaniques particulières, la meilleure électronique du monde ne saurait conserver le canon en direction de la cible sans une débauche de puissance peu compatible avec les contraintes d'emport dans une tourelle.

 

Google trad doesn't make too bad of a job translating it but the main points are:

 

-The gun center of gravity lay on the level of the trunnion

-The turret center of gravity is on the axis of rotation of said turret

-The elasticity of the mechanical parts driving the gun and the turret are monitered in real time reduced using torsion bars (don't know exactly how) The backlash is nearly suppressed.

-Ball bearings with minimal backlash (and same apply for most moving parts) are used.

-No hydraulics, everything is electrically driven.

 

20 hours ago, Serge said:

Yes.

The Leclerc MBT barrel is very rearward compared the manualy loaded turret. This way, artillery is naturally balanced. 

 

Yes.

Leclerc MBT was the first tank designed to achieve fire on the move at hight speed. Firing off road at 40km/h to a mobile target is basic.

Maybe Type-10 and K2 are better today. Maybe. 

 

Yes. 

Aluminium tracks can’t last as long as classical steel ones. They were found too much expensive to support for peace time. 

 

You have such a mechanical link. I don’t know the exact purpose. 

 

I was AMX-10RC tank commander. I never served with Leclerc MBT. So, I can’t help for very detailed data. 

In France, you have Leclerc, Darklabor, Totochez, Rescator. They are not bullshiting. 

Fun fact regarding the tracks. They spent quite some time to switch to steel tracks. They initially used the same arrangement as the aluminum alloy tracks (the shape of the rubber trackpads were supposed to reduce the stomping effect). Surprise, surprise, the vibrations at high speed were strong enough to be a handicap. This explains why we transition from V2 (alloy) to V5 (steel). Apparently V4 was also a disappointment.

Even with V5 or DST 840 the vibration is quite awkward compared to V2.

Share this post


Link to post
Share on other sites

Thanks a lot for your answers, and welcome to SH.

 

45 minutes ago, DarkLabor said:

To be honnest with you there is no stabilisation on the Leclerc. The gun is slave to the ballistic computer which computes the ideal LOF from the stabilised LOS.
When reloading, the gun goes to the reloading elevation. Meanwhile the LOS is still stabilised to the direction of observation (in the limits of the mirrors amplitude). Unless you release the palm switches, the mirrors go to their mechanical neutral positions.

The gunner sight is mechanically mounted to the main armament. When the gun goes up and down; the sight bows up and down.
Since the both move along with the exact same angle, boresighting can be done automatically with a deviation measurement laser (AMX 10 RC being the first french AFV to be equiped with such device).
Crews do some alignments (what we call "harmonisation" where we keep the parallax in check), but that's not the bullshit stated by Sergei Suvorov where crews were forced to boresight everytime they move their tanks...

 

So if I understand well, the gunner sight is normally linked to the gun (as it follow the gun when it move up and down) but the mirror inside it can be decoupled from it to allow to keep the LoS intact when for example the gun elevate to reload?

Share this post


Link to post
Share on other sites
1 hour ago, Alzoc said:

Thanks a lot for your answers, and welcome to SH.

 

 

So if I understand well, the gunner sight is normally linked to the gun (as it follow the gun when it move up and down) but the mirror inside it can be decoupled from it to allow to keep the LoS intact when for example the gun elevate to reload?

Just like any contemporary tank, the mirrors are decoupled from the turret/armament in order to offer a stabilised view.
As long as the gunner pushes the palmswitches, the turret is "active", the mirror will compensate the movement of the tank. When you release the palmswitches, the mirror will return to the mechanical zero. In the case of this happenning during a reload, where the gun is mechanically locked in a certain position; means that the LOS will move to realign with the gun (the LOF will certainly not move since the palmswitches are the elementary security switches for turret movements).
 

Share this post


Link to post
Share on other sites
13 hours ago, DarkLabor said:

switches, the mirrors go to their mechanical neutral positions.

The gunner sight is mechanically mounted to the main armament. When the gun goes up and down; the sight bows up and down.

Crews do some alignments (what we call "harmonisation" where we keep the parallax in check), but that's not the bullshit stated by Sergei Suvorov where crews were forced to boresight everytime they move their tanks...

Rezun said this about soviet tanks or french?

Share this post


Link to post
Share on other sites
2 hours ago, That_Baka said:

Rezun said this about soviet tanks or french?

The french ones in UAE (Gulf 2005???).
The documentary was totally bullshit with russian bias.
He also claimed that the emiratis were in love of the BMP-3 (but we know what happenned when they used them in Yemen).

Share this post


Link to post
Share on other sites
21 minutes ago, DarkLabor said:

BMP-3 (but we know what happenned when they used them in Yemen).

 Arab military is all gear no skill to use it meaning they are ridicuously bad performance benchmark for AFV .

Share this post


Link to post
Share on other sites
On 4/17/2018 at 9:30 AM, DarkLabor said:

To be honnest with you there is no stabilisation on the Leclerc. The gun is slave to the ballistic computer which computes the ideal LOF from the stabilised LOS.
When reloading, the gun goes to the reloading elevation. Meanwhile the LOS is still stabilised to the direction of observation (in the limits of the mirrors amplitude). Unless you release the palm switches, the mirrors go to their mechanical neutral positions.

The gunner sight is mechanically mounted to the main armament. When the gun goes up and down; the sight bows up and down.
Since the both move along with the exact same angle, boresighting can be done automatically with a deviation measurement laser (AMX 10 RC being the first french AFV to be equiped with such device).
Crews do some alignments (what we call "harmonisation" where we keep the parallax in check), but that's not the bullshit stated by Sergei Suvorov where crews were forced to boresight everytime they move their tanks...

 

On 4/17/2018 at 11:21 AM, DarkLabor said:

Just like any contemporary tank, the mirrors are decoupled from the turret/armament in order to offer a stabilised view.
As long as the gunner pushes the palmswitches, the turret is "active", the mirror will compensate the movement of the tank. When you release the palmswitches, the mirror will return to the mechanical zero. In the case of this happenning during a reload, where the gun is mechanically locked in a certain position; means that the LOS will move to realign with the gun (the LOF will certainly not move since the palmswitches are the elementary security switches for turret movements).
 

 

Welcome to SH, DarkLabor.  Always good to have someone who can talk specifics.

 

Could you explain more of what you mean when you say that "there is no stabilization on the Leclerc?"

Share this post


Link to post
Share on other sites
3 hours ago, Collimatrix said:

 

 

Welcome to SH, DarkLabor.  Always good to have someone who can talk specifics.

 

Could you explain more of what you mean when you say that "there is no stabilization on the Leclerc?"

Well it's just a certain nuance.
Obviously there is a stabilisation system but it is limited to the stabilisation of the line of sight (within the sights).
The turret itself has no stabilisation system.
A stabilisation system uses a set of gyroscopes located at specific points (hull, turret, armament).
The angular informations gathered by the different gyros is computed by the FCS which gives a set of corrections to the elevation and traverse mechanism (the most early stab systems where the armament remains to the same position no mater how the tank behaves). In addition the FCS adds on top of this another set of corrections related to the ideal LOF (later stab systems that introduces the concept of correction of the position of the tank).

On the Leclerc, the sight being how it is, the number of variables is kept as minimum as possible. You only compute the angular variation between the current LOS and the ideal LOF. The set of values is then dispatched to the "guidance system" (asservissements) which monitors the actual movement of the turret (traverse and elevation) and assess the need to power the electric motors or revert them into generators to brake the movement.
In itself the tank knows on its own the position of the differents elements (hull, turret and armament) with the closed loop elevation and traverse. The sight give the angle of the whole.

Hope it is clear. It's not a whole lot but we make this distinction.

Share this post


Link to post
Share on other sites

Thank you for taking the time to explain this.  Technical discussions across a language barrier are often difficult, because technical terminology rarely translates well!

It sounds like the fire control system on the Leclerc works very similarly to other, modern MBTs.  In English technical jargon it would be described as having a feed-forwards, two-plane, gun-follows-sight stabilization system, but it sounds like the literal translation of the French terminology would give an English speaker a very misleading idea of what's going on.

Share this post


Link to post
Share on other sites
On 4/16/2018 at 11:57 PM, Serge said:

- modified the seats to have something more confortable

 

I've heard that this is especially the case regarding the commander's seat (in terms of lack of comfort).

 

On 4/16/2018 at 11:57 PM, Serge said:

- rearrange external storage to increase them ;

- suppress river crossing (both useless and dangerous) to have more storage ;

 

For what purpose ?

 

More tools ?

More space for the crew personal equipment ?

Or just fitting the tools currently mounted outside (towing cable, entrenching tool, sledgehammer, ...) inside ?

 

 

On 4/16/2018 at 11:57 PM, Serge said:

- add spall liner and mine proof plates under pilot seat and turret floor. 

 

So, it would be a  kind of lightened version of the SEPAR kit ?

 

On 4/16/2018 at 4:06 PM, Alzoc said:

 

There was a shitload of concept for the Leclerc (same for any 3rd gen MBT I guess).

Take your pick:
 

  Reveal hidden contents

 

948baa2e8a4ae5304082a3e24b9f8dcc

c2a0af58e19ef91f9b4d00ae3e3d6659

dacb53df9ff04e126e9e56c34b16aae9

67403526cad3d05ca951b20ae286c18f

d9ef28c84fa495f9adc6d3d325d839a2

0068Ayuagy1fc6caf4g2vj31kw23vb2b.jpg

 

 

 

Notice the difference in weight between the TC 2 (53 metric tons, two-man turret) and the TC 3 (58 metric tons, three-man turret) concepts.

 

Share this post


Link to post
Share on other sites
1 hour ago, Sovngard said:

I've heard that this is especially the case regarding the commander's seat (in terms of lack of comfort).

Both commander and gunner’s seats are identical.

The only difference is the commander adjustment’s got a rear stopper to reduce the setting by 3 cm. Why ? To avoid to pierce fuel tanks. Without the stopper, the seat can protrude from the turret basket. 

My goal is to protect the crew from shrapnel. So, I would have manufactured seats with ballistic materials. 

 

We have to remain that in France, people above 185cm were not permitted to become tankist, but tank commanders.

So my knees suffered a little bit against the gunner’s seat. 

 

Quote

For what purpose ?

 

More tools ?

More space for the crew personal equipment ?

Or just fitting the tools currently mounted outside (towing cable, entrenching tool, sledgehammer, ...) inside ?

Look at any tank at war. You never have enough place.

The only external storage you have (on the RC standard, not the RCR), is a basket designed to carry 4 of the old butyl waterproof tank crew pack. During the Gulf war, crewmen stored MREs between the hull and the add-on armor.

In the French troop, you have a truck per troop to carry burden. But, in the real life you must be as autonomous as possible. 

My solution would have been a mixt between the TML-105 storage for the front and the sides and a Merkava like rear basket. 

amx2.jpg

 

Quote

So, it would be a  kind of lightened version of the SEPAR kit ?

SEPAR is too much heavy. 

I’m just thinking about internal layer on some dedicated places. AMX-10RC can’t be burdened. It’s very dangerous considering its steering system.

In 2002, Australian SAS LRPV received 4cm thick anti-mine composite floor plates. This kind of solution would have been acceptable. 

Share this post


Link to post
Share on other sites
2 minutes ago, Serge said:

SEPAR kit is so heavy, 10RCR is beyond its limits. 

It was designed during Afghanistan but it’s no more used.

 

Well the 10 RCR will be put out of service in a few years anyway.

I doubt we will see any more upgrades on the platform.

Share this post


Link to post
Share on other sites
Just now, Alzoc said:

 

Well the 10 RCR will be put out of service in a few years anyway.

I doubt we will see any more upgrades on the platform.

The arrival of Jaguar will not come instantly, there is still room for "operational emergencies"...

Share this post


Link to post
Share on other sites
8 minutes ago, DarkLabor said:

The arrival of Jaguar will not come instantly, there is still room for "operational emergencies"...

 

True.

 

What I said is simply that I doubt that the government will be willing to spend money on upgrades for a vehicles on it's way out.

Especially now that they finally understood that keeping old vehicles in services cost more in the long run than accelerating the delivery of the new ones.

 

There seem to be a will from the actual government to increase the defence budget but 5 years is a short time to make up for the lack of investment over decades and we don't know what will be the stance of the next government.

We'll see I guess.

Share this post


Link to post
Share on other sites
8 minutes ago, Mighty_Zuk said:

So will they be scrapped or just sent to get dust in some remote long term storage?

 

With the habits of the French army, I would say sent to long term storage.

I guess that the first to be retired would be cannibalized for the maintenance of those still in service.

After some time it's possible that they will end in the open market.

Share this post


Link to post
Share on other sites
1 hour ago, Mighty_Zuk said:

So will they be scrapped or just sent to get dust in some remote long term storage?

I think scrapped. 

They will be very old. The upgrade capability is poor and the barrel is not NATO compatible. It fires a light 105mm shell. 

Share this post


Link to post
Share on other sites
On 4/16/2018 at 5:57 PM, Serge said:

Generaly speaking, I never answer to such a question because it’s the start of unrealistic discussions of technology fanboys unknowing real. But, I can say :

- never forget AMX-10RC is a very 80’s light tank. So, any improvement must be cheap provide. 

- the world famous Serge AFV belief is : an AFV chassis push, carry and tow. 

- having a good AFV is good, but without its environment, it’s useless. 

 

FCS, sights, weapons were good.

 

So, I would have :

- modified the seats to have something more confortable and armored. Maybe an harness to sleep ;

- introduced a new TC hatch with an umbrella opening (my priority) ;

- rearrange external storage to increase them ;

- suppress river crossing (both useless and dangerous) to have more storage ;

- add spall liner and mine proof plates under pilot seat and turret floor. 

 

Considering chassis, I would have add :

- 2 rear fuel drop barrels like the Leclerc ones. Fuel drums are compulsory ;

- front tools connector to push mine rollers...

 

Considering it’s environment, I would have :

- add a fourth 10RC per troop (In France, reccon tanks troops are 3 tanks troops. Leclerc : 4 MBT troops) ;

- adopted AMX-10RTT as command post and ARVs instead of VAB and ARV based on trucks.

 

With diminution of 10RC number, I would have transformed some of them in general purpose vehicles able to carry dedicated teams for special tasks such as EW....

When dimounting the barrel and ammo racks, you have plenty of room. 

 

 

9 hours ago, Serge said:

Both commander and gunner’s seats are identical.

The only difference is the commander adjustment’s got a rear stopper to reduce the setting by 3 cm. Why ? To avoid to pierce fuel tanks. Without the stopper, the seat can protrude from the turret basket. 

My goal is to protect the crew from shrapnel. So, I would have manufactured seats with ballistic materials. 

 

We have to remain that in France, people above 185cm were not permitted to become tankist, but tank commanders.

So my knees suffered a little bit against the gunner’s seat. 

 

Look at any tank at war. You never have enough place.

The only external storage you have (on the RC standard, not the RCR), is a basket designed to carry 4 of the old butyl waterproof tank crew pack. During the Gulf war, crewmen stored MREs between the hull and the add-on armor.

In the French troop, you have a truck per troop to carry burden. But, in the real life you must be as autonomous as possible. 

My solution would have been a mixt between the TML-105 storage for the front and the sides and a Merkava like rear basket. 

amx2.jpg

 

SEPAR is too much heavy. 

I’m just thinking about internal layer on some dedicated places. AMX-10RC can’t be burdened. It’s very dangerous considering its steering system.

In 2002, Australian SAS LRPV received 4cm thick anti-mine composite floor plates. This kind of solution would have been acceptable. 

 

Might as well make a new bloody vehicle with all those changes. Maybe something like a 105mm armed VBCI or the Vextra 105? Or maybe just build a totally new vehicle from the ground up specifically for urban/sub-urban combat. Could probably give it MRAP capabilities stock and not have to worry about a damn 2 ton upgrade package... 

 

Thinking about it, the newest Centauro sounds like a pretty good fit, just add some extra boxes to the hull sides/turret bustle and you’re pretty close to those requirements. 

Share this post


Link to post
Share on other sites
2 hours ago, Sovngard said:

 

I demand to see the transmission of this thing.

 

1525108473-btmp-backl.jpg

 

I would think it's similar to the Achzarit's transmission, considering they both have a rear transmission and door: 

 

Spoiler
1280px-Achzarit_APC_rear_view.jpg
File:Achzarit armored personnel carrier, 2011.jpg

 

 

 

On a separate note: what kind of (preferably free) drawing software could I get, or what do you guys use, for making some of these designs? Or would my Mk.1 Hand and Mk.2 Ruler suffice, and I could just scan it into my computer? 

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Similar Content

    • By LostCosmonaut
      Backstory (skip if you don't like alternate history junk)
       
      The year is 2239. It has been roughly 210 years since the world was engulfed in nuclear war. Following the war, the United States splintered into hundreds of small statelets. While much knowledge was retained in some form (mostly through books and other printed media), the loss of population and destruction of industrial capability set back society immensely.
       
      Though the Pacific Northwest was less badly hit than other areas, the destruction of Seattle and Portland, coupled with the rupturing of the Cascadia Subduction Zone in 2043, caused society to regress to a mid-19th century technology level. However, in the early 2100s, the Cascade Republic formed, centered near Tacoma. The new nation grew rapidly, expanding to encompass most of Washington and Oregon by 2239. The Cascade Republic now extends from the Klamath River in the south to the Fraser River in the north, and from the Pacific roughly to central Idaho. Over time, the standard of living and industrial development improved (initially through salvaging of surviving equipment, by the late 2100s through new development); the population has grown to about 4.5 million (comparable to 1950 levels), and technology is at about a 1940 level. Automobiles are common, aircraft are less common, but not rare by any means. Computers are nonexistent aside from a few experimental devices; while scientists and engineers are aware of the principles behind microchips and other advanced electronics, the facilities to produce such components simply do not exist. Low rate production of early transistors recently restarted.
       
      The current armored force of the Cascade Republic consists of three armored brigades. They are presently equipped with domestically produced light tanks, dating to the 2190s. Weighing roughly 12 tons and armed with a 40mm gun, they represented the apex of the Cascade Republic's industrial capabilities at the time. And when they were built, they were sufficient for duties such as pacifying survivalist enclaves in remote areas. However, since that time, the geopolitical situation has complicated significantly. There are two main opponents the Cascade Republic's military could expect to face in the near future.
       
      The first is California. The state of California was hit particularly hard by the nuclear exchange. However, in 2160, several small polities in the southern part of the state near the ruins of Los Angeles unified. Adopting an ideology not unfamiliar to North Korea, the new state declared itself the successor to the legacy of California, and set about forcibly annexing the rest of the state. It took them less than 50 years to unite the rest of California, and spread into parts of Arizona and northern Mexico. While California's expansion stopped at the Klamath River for now, this is only due to poor supply lines and the desire to engage easier targets. (California's northward advanced did provide the final impetus for the last statelets in south Oregon to unify with the Cascade Republic voluntarily).
       
      California is heavily industrialized, possessing significant air, naval, and armored capabilities. Their technology level is comparable to the Cascade Republic's, but their superior industrial capabilities and population mean that they can produce larger vehicles in greater quantity than other countries. Intelligence shows they have vehicles weighing up to 50 tons with 3 inches of armor, though most of their tanks are much lighter.

      The expected frontlines for an engagement with the Californian military would be the coastal regions in southern Oregon. Advancing up the coastal roads would allow California to capture the most populated and industrialized regions of the Cascade Republic if they advanced far enough north. Fortunately, the terrain near the border is very difficult and favors the defender;


      (near the Californian border)


      The other opponent is Deseret, a Mormon theocratic state centered in Utah, and encompassing much of Nevada, western Colorado, and southern Idaho. Recently, tension has arisen with the Cascade Republic over two main issues. The first is the poorly defined border in Eastern Oregon / Northern Nevada; the old state boundary is virtually meaningless, and though the area is sparsely populated, it does represent a significant land area, with grazing and water resources. The more recent flashpoint is the Cascade Republic's recent annexation of Arco and the area to the east. Deseret historically regarded Idaho as being within its sphere of influence, and maintained several puppet states in the area (the largest being centered in Idaho Falls). They regard the annexation of a signficant (in terms of land area, not population) portion of Idaho as a major intrusion into their rightful territory. That the Cascade Republic has repaired the rail line leading to the old Naval Reactors Facility, and set up a significant military base there only makes the situation worse.
       
      Deseret's military is light and heavily focused on mobile operations. Though they are less heavily mechanized than the Cascade Republic's forces, operating mostly armored cars and cavalry, they still represent a significant threat  to supply and communication lines in the open terrain of eastern Oregon / southern Idaho.


      (a butte in the disputed region of Idaho, near Arco)
       
      Requirements
       
      As the head of a design team in the Cascade Republic military, you have been requested to design a new tank according to one of two specifications (or both if you so desire):
       
      Medium / Heavy Tank Weight: No more than 45 tons Width: No more than 10.8 feet (3.25 meters) Upper glacis / frontal turret armor of at least 3 in (76mm) LoS thickness Side armor at least 1in (25mm) thick (i.e. resistant to HMG fire) Power/weight ratio of at least 10 hp / ton No more than 6 crew members Primary armament capable of utilizing both anti-armor and high explosive rounds Light tank Weight: No more than 25 tons Width: No more than 10.8 feet Upper glacis / frontal turret armor of at least 1 in thickness Side armor of at least 3/8 in (10mm) thickness Power/weight ratio of at least 12 hp / ton No more than 6 crew members Primary armament capable of utilizing both anti-armor and high explosive rounds  
      Other relevant information:
      Any tank should be designed to operate against either of the Cascade Republic's likely opponents (California or Deseret) The primary heavy machine gun is the M2, the primary medium machine gun is the M240. Use of one or both of these as coaxial and/or secondary armament is encouraged. The secret archives of the Cascade Republic are available for your use. Sadly, there are no running prewar armored vehicles, the best are some rusted hulks that have long been stripped of usable equipment. (Lima Tank Plant ate a 500 kt ground burst) Both HEAT and APFSDS rounds are in testing. APCR is the primary anti-armor round of the Cascade Republic. Either diesel or gasoline engines are acceptable, the Cascade Republic is friendly with oil producing regions in Canada (OOC: Engines are at about a late 1940s/early 50s tech level) The adaptability of the tank to other variants (such as SPAA, SPG, recovery vehicle, etc.) is preferred but not the primary metric that will be used to decide on a design. Ease of maintenance in the field is highly important. Any designs produced will be compared against the M4 Sherman and M3 Stuart (for medium/heavy and light tank), as these blueprints are readily available, and these tanks are well within the Cascade Republic's manufacturing capabilities.  
       
       
       
       
    • By Jamby
      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!
    • By EnsignExpendable
      The mean goons over on SA roped me into writing an effortpost, so I figured it's only fair that you freeloaders get to enjoy it too.
       
      So, suspensions. I'm going to introduce the book as well because it's probably the most Soviet book that ever existed. It is called TANK.     What makes this book so Soviet? Well, here's the first paragraph of the introduction:   "Under the guidance of the Communist party of the Soviet Union, our people built socialism, achieved a historical victory in the Great Patriotic War, and in launched an enormous campaign for the creation of a Communist society."   The next paragraph talks about the 19th Assembly of the CPSU, then a bit about how in the Soviet Union man no longer exploits man (now it's the other way around :haw:), then a little bit about the war again, then spends another three pages stroking the party's dick about production and growth. The word "tank" does not appear in the introduction.   The historical prelude section is written by someone who is a little closer to tanks and might be a little less politically reliable, since they actually give Tsarists credit for things. I guess they have to, since foreigners are only mentioned in this section when they are amazed by Russian progress. The next chapter is a Wikipedia-grade summary of various tank designs that gives WWI designs a pretty fair evaluation, then a huge section on Soviet tank development, then a tiny section on foreign tanks in WWII mostly consisting of listing all the mistakes their designers made. The party must have recuperated since the intro since we're in for another three pages of fellatio.   Having read so far, you might think that there is very little value in this sort of book, but then the writing style does a complete 180 and the rest of the book is 100% apolitical and mostly looks like this.     Which is what we care about, so let's begin. Bonus points to anyone who can identify what the diagram above is about. Sorry in advance if my terminology isn't 100% correct, there aren't exactly a lot of tank dictionaries lying around.   The book skips over primitive unsprung suspensions of WWI and starts off with describing the difference between independent suspensions and road-arm suspensions. In the former, every wheel is independently sprung. In the latter, two or more wheels are joined together by a spring. Some suspensions have a mix of these designs. For example, here's a simple road-arm suspension used in some Vickers designs and their derivatives. The two road wheels are connected by a spring and to the hull by a lever. A weight pushing down on top of the pair of wheels is going to compress the spring that's perpendicular to the ground, bringing the wheels closer together.     Here's a more complex road-arm suspension, with four wheels per unit instead of one, also AFAIK first used by Vickers and then migrating to an enormous amount of designs from there. This suspension provides springiness through a leaf spring that you can see above the four road wheels. The two pairs of wheels don't have their own springs. The black circles in the image show where the suspension elements can turn, keeping the tank flat while hugging the terrain.     Here's another road-arm suspension, similar to the first one. In this case, the spring is made of rubber instead of metal. Otherwise, the design is very similar. Two rubber bungs on the bottom of the axles prevent the wheels from slamming into each other too hard. This design was used by French tanks and nobody else.     For some reason, volute spring suspensions are completely absent from this section. This is the best image of a Vertical Volute Spring Suspension (early Shermans) that I could find. It's kind of similar to the first image, except the spring is a volute spring, and it's vertical instead of horizontal. Later Shermans used horizontal volute springs.     Of course, as the book points out, these suspension elements are very easy to damage externally and knocking out one part of the suspension will typically take out the rest of the assembly, so independent suspensions are the way to go. The best way to do this are torsion bars. The bar is attached to a lever that holds your road wheel. As pressure is applied to the road wheel, the bar subtly twists, remaining elastic enough to reset once the pressure is off. This image is kind of weird, but the part in the center is the part on the far left, zoomed in, showing you where the lever and the opposite side's torsion bar are attached. As you can see, road wheels in a torsion bar suspension are going to be a little off on one side, unlike what you're used to on cars and such.     Now, since torsion bars are metal bars on the floor, they are going to make your tank taller. If you want a tank that's as short as possible at the expense of width, you may want to consider a Christie like suspension. Here, much like in torsion bars, the pressure is transferred inside the tank, but instead of a bar to absorb it, it's a spring in a vertical (or angled) tube. In most tanks with this kind of suspension, the springs are on the inside, but if you want to make the tank roomier on the inside, you can have them on the outside too. If you're really fancy, you can put a spring within the spring like in this diagram.     Since this is a Soviet tank book, you gotta have a huge T-34 diagram. Here it is.     The T-34 uses Christie springs, which you can see in the diagram. The road wheel configuration is a mix of the externally dampened and internally dampened "Stalingrad type" road wheels. The former have more rubber for absorbing hits from terrain, but the latter use less rubber. When you're in Stalingrad and you have to make tanks with a rubber deficit, that's the kind you want. When road wheels from other factories were available, they would go in the front and then the back to absorb most of the impact from harsh terrain features, and the steel-rimmed wheels went in the middle. The diagram shows how both types of wheels work.   Rubber can't really take too much punishment, so the KV, being a heavy tank, went with internally dampened road wheels from the very beginning, with a ring of rubber on the inside around the axle.     And finally, idlers. If you don't have big Christie type wheels, you gotta have idlers so your saggy track doesn't fall off. This diagram shows the rubber coating on an idler, and also how the rear idler can adjust to tighten the track. A loose track makes more noise, gets worn more, and is liable to slip off.     Keep those tracks tight, and you'll be zooming towards glorious victory in no time flat!     Now, the book ends and my own stuff begins. I mentioned rubber, but not what a headache it was to tank designers. In hot weather, the rubber in your tracks and wheels tends to fall apart. If you go fast enough, tires that don't have proper ventilation are going to melt too. There was a lot of pre-war panic in the USSR about the German PzIII being able to do 70 kph on tracks, but once the Soviets started building SU-76Is on the PzIII chassis they found out that the speed had to be limited to a whopping 25 kph to keep the wear to a reasonable level.
    • By Collimatrix
      Tank design is often conceptualized as a balance between mobility, protection and firepower.  This is, at best, a messy and imprecise conceptualization.  It is messy because these three traits cannot be completely separated from each other.  An APC, for example, that provides basic protection against small arms fire and shell fragments is effectively more mobile than an open-topped vehicle because the APC can traverse areas swept by artillery fires that are closed off entirely to the open-topped vehicle.  It is an imprecise conceptualization because broad ideas like "mobility" are very complex in practice.  The M1 Abrams burns more fuel than the Leo 2, but the Leo 2 requires diesel fuel, while the omnivorous AGT-1500 will run happily on anything liquid and flammable.  Which has better strategic mobility?  Soviet rail gauge was slightly wider than Western European standard; 3.32 vs 3.15 meters.  But Soviet tanks in the Cold War were generally kept lighter and smaller, and had to be in order to be moved in large numbers on a rail and road network that was not as robust as that further west.  So if NATO and the Warsaw Pact had switched tanks in the late 1950s, they would both have downgraded the strategic mobility of their forces, as the Soviet tanks would be slightly too wide for unrestricted movement on rails in the free world, and the NATO tanks would have demanded more logistical support per tank than evil atheist commie formations were designed to provide.
       

       
      So instead of wading into a deep and subtle subject, I am going to write about something that is extremely simple and easy to describe in mathematical terms; the top speed of a tank moving in a straight line.  Because it is so simple and straightforward to understand, it is also nearly meaningless in terms of the combat performance of a tank.
       
      In short, the top speed of a tank is limited by three things; the gear ratio limit, the power limit and the suspension limit.  The tank's maximum speed will be whichever of these limits is the lowest on a given terrain.  The top speed of a tank is of limited significance, even from a tactical perspective, because the tank's ability to exploit its top speed is constrained by other factors.  A high top speed, however, looks great on sales brochures, and there are examples of tanks that were designed with pointlessly high top speeds in order to overawe people who needed impressing.
       

      When this baby hits 88 miles per hour, you're going to see some serious shit.
       
      The Gear Ratio Limit
       
      Every engine has a maximum speed at which it can turn.  Often, the engine is artificially governed to a maximum speed slightly less than what it is mechanically capable of in order to reduce wear.  Additionally, most piston engines develop their maximum power at slightly less than their maximum speed due to valve timing issues:
       

      A typical power/speed relationship for an Otto Cycle engine.  Otto Cycle engines are primitive devices that are only used when the Brayton Cycle Master Race is unavailable.
       
      Most tanks have predominantly or purely mechanical drivetrains, which exchange rotational speed for torque by easily measurable ratios.  The maximum rotational speed of the engine, multiplied by the gear ratio of the highest gear in the transmission multiplied by the gear ratio of the final drives multiplied by the circumference of the drive sprocket will equal the gear ratio limit of the tank.  The tank is unable to achieve higher speeds than the gear ratio limit because it physically cannot spin its tracks around any faster.
       
      Most spec sheets don't actually give out the transmission ratios in different gears, but such excessively detailed specification sheets are provided in Germany's Tiger Tanks by Hilary Doyle and Thomas Jentz.  The gear ratios, final drive ratios, and maximum engine RPM of the Tiger II are all provided, along with a handy table of the vehicle's maximum speed in each gear.  In eighth gear, the top speed is given as 41.5 KPH, but that is at an engine speed of 3000 RPM, and in reality the German tank engines were governed to less than that in order to conserve their service life.  At a more realistic 2500 RPM, the mighty Tiger II would have managed 34.6 KPH.
       
      In principle there are analogous limits for electrical and hydraulic drive components based on free speeds and stall torques, but they are a little more complicated to actually calculate.
       

      Part of the transmission from an M4 Sherman, picture from Jeeps_Guns_Tanks' great Sherman website
       
      The Power Limit
       
      So a Tiger II could totally go 34.6 KPH in combat, right?  Well, perhaps.  And by "perhaps," I mean "lolololololol, fuck no."  I defy you to find me a test report where anybody manages to get a Tiger II over 33 KPH.  While the meticulous engineers of Henschel did accurately transcribe the gear ratios of the transmission and final drive accurately, and did manage to use their tape measures correctly when measuring the drive sprockets, their rosy projections of the top speed did not account for the power limit.
       
      As a tank moves, power from the engine is wasted in various ways and so is unavailable to accelerate the tank.  As the tank goes faster and faster, the magnitude of these power-wasting phenomena grows, until there is no surplus power to accelerate the tank any more.  The system reaches equilibrium, and the tank maxes out at some top speed where it hits its power limit (unless, of course, the tank hits its gear ratio limit first).
       
      The actual power available to a tank is not the same as the gross power of the motor.  Some of the gross horsepower of the motor has to be directed to fans to cool the engine (except, of course, in the case of the Brayton Cycle Master Race, whose engines are almost completely self-cooling).  The transmission and final drives are not perfectly efficient either, and waste a significant amount of the power flowing through them as heat.  As a result of this, the actual power available at the sprocket is typically between 61% and 74% of the engine's quoted gross power.
       
      Once the power does hit the drive sprocket, it is wasted in overcoming the friction of the tank's tracks, in churning up the ground the tank is on, and in aerodynamic drag.  I have helpfully listed these in the order of decreasing importance.
       
      The drag coefficient of a cube (which is a sufficiently accurate physical representation of a Tiger II) is .8. This, multiplied by half the fluid density of air (1.2 kg/m^3) times the velocity (9.4 m/s) squared times a rough frontal area of 3.8 by 3 meters gives a force of 483 newtons of drag.  This multiplied by the velocity of the tiger II gives 4.5 kilowatts, or about six horsepower lost to drag.  With the governor installed, the HL 230 could put out about 580 horsepower, which would be four hundred something horses at the sprocket, so the aerodynamic drag would be 1.5% of the total available power.  Negligible.  Tanks are just too slow to lose much power to aerodynamic effects.
       
      Losses to the soil can be important, depending on the surface the tank is operating on.  On a nice, hard surface like a paved road there will be minimal losses between the tank's tracks and the surface.  Off-road, however, the tank's tracks will start to sink into soil or mud, and more power will be wasted in churning up the soil.  If the soil is loose or boggy enough, the tank will simply sink in and be immobilized.  Tanks that spread their weight out over a larger area will lose less power, and be able to traverse soft soils at higher speed.  This paper from the UK shows the relationship between mean maximum pressure (MMP), and the increase in rolling resistance on various soils and sands in excruciating detail.  In general, tanks with more track area, with more and bigger road wheels, and with longer track pitch will have lower MMP, and will sink into soft soils less and therefore lose less top speed.
       
      The largest loss of power usually comes from friction within the tracks themselves.  This is sometimes called rolling resistance, but this term is also used to mean other, subtly different things, so it pays to be precise.  Compared to wheeled vehicles, tracked vehicles have extremely high rolling resistance, and lose a lot of power just keeping the tracks turning.  Rolling resistance is generally expressed as a dimensionless coefficient, CR, which multiplied against vehicle weight gives the force of friction.  This chart from R.M. Ogorkiewicz' Technology of Tanks shows experimentally determined rolling resistance coefficients for various tracked vehicles:
       

       
      The rolling resistance coefficients given here show that a tracked vehicle going on ideal testing ground conditions is about as efficient as a car driving over loose gravel.  It also shows that the rolling resistance increases with vehicle speed.  A rough approximation of this increase in CR is given by the equation CR=A+BV, where A and B are constants and V is vehicle speed.  Ogorkiewicz explains:
       
       
      It should be noted that the lubricated needle bearing track joints of which he speaks were only ever used by the Germans in WWII because they were insanely complicated.  Band tracks have lower rolling resistance than metal link tracks, but they really aren't practical for vehicles much above thirty tonnes.  Other ways of reducing rolling resistance include using larger road wheels, omitting return rollers, and reducing track tension.  Obviously, there are practical limits to these approaches.
       
      To calculate power losses due to rolling resistance, multiply vehicle weight by CR by vehicle velocity to get power lost.  The velocity at which the power lost to rolling resistance equals the power available at the sprocket is the power limit on the speed of the tank.
       
      The Suspension Limit
       
      The suspension limit on speed is starting to get dangerously far away from the world of spherical, frictionless horses where everything is easy to calculate using simple algebra, so I will be brief.  In addition to the continents of the world not being completely comprised of paved surfaces that minimize rolling resistance, the continents of the world are also not perfectly flat.  This means that in order to travel at high speed off road, tanks require some sort of suspension or else they would shake their crews into jelly.  If the crew is being shaken too much to operate effectively, then it doesn't really matter if a tank has a high enough gear ratio limit or power limit to go faster.  This is also particularly obnoxious because suspension performance is difficult to quantify, as it involves resonance frequencies, damping coefficients, and a bunch of other complicated shit.
       
      Suffice it to say, then, that a very rough estimate of the ride-smoothing qualities of a tank's suspension can be made from the total travel of its road wheels:
       

       
      This chart from Technology of Tanks is helpful.  A more detailed discussion of the subject of tank suspension can be found here.
       
      The Real World Rudely Intrudes
       
      So, how useful is high top speed in a tank in messy, hard-to-mathematically-express reality?  The answer might surprise you!
       

      A Wehrmacht M.A.N. combustotron Ausf G
       
      We'll take some whacks at everyone's favorite whipping boy; the Panther.
       
      A US report on a captured Panther Ausf G gives its top speed on roads as an absolutely blistering 60 KPH on roads.  The Soviets could only get their captured Ausf D to do 50 KPH, but compared to a Sherman, which is generally only credited with 40 KPH on roads, that's alarmingly fast.
       
      So, would this mean that the Panther enjoyed a mobility advantage over the Sherman?  Would this mean that it was better able to make quick advances and daring flanking maneuvers during a battle?
       
      No.
       
      In field tests the British found the panther to have lower off-road speed than a Churchill VII (the panther had a slightly busted transmission though).  In the same American report that credits the Panther Ausf G with a 60 KPH top speed on roads, it was found that off road the panther was almost exactly as fast as an M4A376W, with individual Shermans slightly outpacing the big cat or lagging behind it slightly.  Another US report from January 1945 states that over courses with many turns and curves, the Sherman would pull out ahead because the Sherman lost less speed negotiating corners.  Clearly, the Panther's advantage in straight line speed did not translate into better mobility in any combat scenario that did not involve drag racing.
       
      So what was going on with the Panther?  How could it leave everything but light tanks in the dust on a straight highway, but be outpaced by the ponderous Churchill heavy tank in actual field tests?
       

      Panther Ausf A tanks captured by the Soviets
       
      A British report from 1946 on the Panther's transmission explains what's going on.  The Panther's transmission had seven forward gears, but off-road it really couldn't make it out of fifth.  In other words, the Panther had an extremely high gear ratio limit that allowed it exceptional speed on roads.  However, the Panther's mediocre power to weight ratio (nominally 13 hp/ton for the RPM limited HL 230) meant that once the tank was off road and fighting mud, it only had a mediocre power limit.  Indeed, it is a testament to the efficiency of the Panther's running gear that it could keep up with Shermans at all, since the Panther's power to weight ratio was about 20% lower than that particular variant of Sherman.
       
      There were other factors limiting the Panther's speed in practical circumstances.  The geared steering system used in the Panther had different steering radii based on what gear the Panther was in.  The higher the gear, the wider the turn.  In theory this was excellent, but in practice the designers chose too wide a turn radius for each gear, which meant that for any but the gentlest turns the Panther's drive would need to slow down and downshift in order to complete the turn, thus sacrificing any speed advantage his tank enjoyed.
       
      So why would a tank be designed in such a strange fashion?  The British thought that the Panther was originally designed to be much lighter, and that the transmission had never been re-designed in order to compensate.  Given the weight gain that the Panther experienced early in development, this explanation seems like it may be partially true.  However, when interrogated, Ernst Kniepkamp, a senior engineer in Germany's wartime tank development bureaucracy, stated that the additional gears were there simply to give the Panther a high speed on roads, because it looked good to senior generals.
       
      So, this is the danger in evaluating tanks based on extremely simplistic performance metrics that look good on paper.  They may be simple to digest and simple to calculate, but in the messy real world, they may mean simply nothing.
×