Jump to content
Sturgeon's House

Recommended Posts

17 hours ago, Toxn said:

Sadly no - I used the 1972 MMP equations and noodled around a bit with variables. From a gaming sums perspective, what they do is introduce a new term (tire deflection) which increases effective track contact area. Even a few centimetres makes a big difference here.

 

Realistically, of course, you're right - having soft, flexible bits on road wheels seems like a recipe for issues unless the vehicle is very light to begin with (at which point MMP more or less sorts itself out). 

 

Some of the French 40s and 50s prototypes had pneumatic roadwheels, and I wonder if that was influence from the German 'expertise' they agglomerated post war. They did after all, also build some interleaved suspensions at this time - as well as desperately tried to get the HL 230 family to work to spec.

Link to post
Share on other sites
  • Replies 198
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

I'm sure that all the SH regulars will know this backwards and forwards, so this is more for the benefit of newer people, or people who stumble in via google, or people who want a quick link they can

It's rarely pointed out because it is an absolute load of bullshit, and most self respecting people have enough of a brain to not embarrass themselves in public by making such inherently absurd claims

9 hours ago, TokyoMorose said:

 

Some of the French 40s and 50s prototypes had pneumatic roadwheels, and I wonder if that was influence from the German 'expertise' they agglomerated post war. They did after all, also build some interleaved suspensions at this time - as well as desperately tried to get the HL 230 family to work to spec.

I was wondering about that myself, actually.

 

I think part of it was that they had a bunch of hulls, plans, jigs and engineers on hand who'd worked on the things. So, you know, use what you have.

 

I think the other thing (as can be seen with the AMX 50 and Bat Chat) is that they were on a big drive to put a really powerful gun on a mobile chassis and still have it come out to less than 50mt (presumably while also being rail-transportable). So pneumatic road wheels and torsion bars must have appealed simply to keep dimensions down.

 

Pity that, like most German wunderwaffle tech, it was all a technological dead end.

Link to post
Share on other sites

So here's a question: is it better, without using interleaving or whatever, to have a few big road wheels or lots of little ones in terms of MMP? Here I'm going to ignore things like travel and have no spacing between the roadwheels.

 

For a 5m track contact length, 40t vehicle with the other specs kept the same (track width 0.6m, track pitch 0.15m), you find that ground pressure rises quickly and then tails off as the size of the road wheels decreases. This rapidly leads into diminishing returns: 25 axles with 20cm roadwheels gets you an MMP of 95KPa, 50 and 10cm road wheels gets you 67, and 100 axles with 5cm road wheels gets you 48.


If you restrict things further to sane territory (12-4 axles), on the other hand, you get the following:

  • 12 axles/0.42m roadwheels: 137 KPa
  • 11 axles/0.45m roadwheels: 143 KPa
  • 10 axles/0.5m roadwheels:  150 KPa
  • 9 axles/0.56m roadwheels:  159 KPa
  • 8 axles/0.63m roadwheels: 168 KPa
  • 7 axles/0.71m roadwheels: 180 KPa
  • 6 axles/0.83m roadwheels: 194 KPa
  • 5 axles/1.00m roadwheels: 213 KPa
  • 4 axles/1.25m roadwheels: 238 KPa

So in this part of the range the relationship is more or less linear. It's also clear that the easiest way to improve ground pressure, mutatis mutandis, is to pack as many wheels as possible onto a given length of track.

 

 

Link to post
Share on other sites

You can see from the MMP equation that the term for number of wheels is linear but the term for diameter is a square root.

Seeing as the tradeoff between the two is inverse linear, it evidently makes sense to maximize the linear one at the cost of the square root one, all else being equal. 

Now, where do we see this in practice? In heavy earth moving or construction equipment, primarily.

CatD9T.jpg

 

Link to post
Share on other sites
44 minutes ago, N-L-M said:

You can see from the MMP equation that the term for number of wheels is linear but the term for diameter is a square root.

Seeing as the tradeoff between the two is inverse linear, it evidently makes sense to maximize the linear one at the cost of the square root one, all else being equal. 

Now, where do we see this in practice? In heavy earth moving or construction equipment, primarily.

CatD9T.jpg

 

Exactly. Earthmovers also don't have to worry about suspension travel and such, meaning that you can pack your extra wheels in aggressively.

Link to post
Share on other sites
15 hours ago, N-L-M said:

 

Seeing as the tradeoff between the two is inverse linear, it evidently makes sense to maximize the linear one at the cost of the square root one, all else being equal. 

 

By god, the British were right all along, Churchill coming in with the best MMP suspension of all time.

Link to post
Share on other sites
20 hours ago, Toxn said:

Exactly. Earthmovers also don't have to worry about suspension travel and such, meaning that you can pack your extra wheels in aggressively.



Small wheels also have higher rolling resistance, and at high speeds tend to wear their rubber out faster.

Link to post
Share on other sites
8 hours ago, TokyoMorose said:

 

By god, the British were right all along, Churchill coming in with the best MMP suspension of all time.

The Churchill did indeed have very good MMP for its time, combined with a track link design with very aggressive grousers meant a good ability to cross muddy ground. That, combined with the low low gear ratios allowed it to slowly but surely cross obstacles many other tanks couldn't.

The British didn't get everything wrong.

Link to post
Share on other sites
1 minute ago, N-L-M said:

The Churchill did indeed have very good MMP for its time, combined with a track link design with very aggressive grousers meant a good ability to cross muddy ground. That, combined with the low low gear ratios allowed it to slowly but surely cross obstacles many other tanks couldn't.

The British didn't get everything wrong.

If only any of their vehicles had had a turret ring worth talking about, something decent could have emerged before war's end.

Link to post
Share on other sites
2 hours ago, N-L-M said:

The Churchill did indeed have very good MMP for its time, combined with a track link design with very aggressive grousers meant a good ability to cross muddy ground. That, combined with the low low gear ratios allowed it to slowly but surely cross obstacles many other tanks couldn't.

The British didn't get everything wrong.

That sound more usefull for WW1, not exactly as crucial in WW2.

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

That sound more usefull for WW1, not exactly as crucial in WW2.

Let's just say that the British hedged hard against the possibility of WW1 breaking out again. I mean, look at TOG's original requirements...

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


The French did, too

Indeed. Not a good bet, as it turned out.

 

But you can't blame them for at least hedging. The French, at least, went into WW1 adamant that it would a war of offensive manoeuvre (based on their previous experience with the Prussians), and it was for a month or two. And then it wasn't and they lost a generation of young men.

 

If I'd been bled white and had chunks of my country rendered permanently uninhabitable because I didn't put money on the defensive being dominant in the last war...

Link to post
Share on other sites
5 hours ago, LoooSeR said:

That sound more usefull for WW1, not exactly as crucial in WW2.

 

It was indeed meant to climb trenches in a fashion of 1918. It seems that climbing was still quite useful for infantry support in ww2. Churchills made it much easier for the British to evercome the hills around Tunis. Germans felt safe on the peaks and the British simply drove up to them including to the 754th Grenadier Regiment HQ, bagging the officers. Navigating heavy terrain widens the maneuver space and the tactical solutions available. Lowlands are not everywhere.

But as the rest already mentioned, the small turret ring dictated the size of a weapon in the turret and Churchill's ended up being woefully undergunned, which is not very healthy for such a slow vehicle.

Link to post
Share on other sites
28 minutes ago, Toxn said:

Indeed. Not a good bet, as it turned out.

 

But you can't blame them for at least hedging. The French, at least, went into WW1 adamant that it would a war of offensive manoeuvre (based on their previous experience with the Prussians), and it was for a month or two. And then it wasn't and they lost a generation of young men.

 

If I'd been bled white and had chunks of my country rendered permanently uninhabitable because I didn't put money on the defensive being dominant in the last war...

 

It is still quite untypical of the French to behave so timidly. They won ww1 but apparently lost the battle of the will, because Napoleon was precisely the opposite.

Link to post
Share on other sites
On 4/9/2021 at 3:19 AM, Toxn said:

I think part of it was that they had a bunch of hulls, plans, jigs and engineers on hand who'd worked on the things. So, you know, use what you have.

 

That's exactly what happened in all sectors. The French (for a time) absorbed the German small arms collective as well, and played around with adapting their late war designs. In the end, like the tanks, they didn't end up using any of the German ideas, partly because unlike the French tank sector, the French small arms developments were still quite technologically competitive.

Link to post
Share on other sites
1 hour ago, delete013 said:

It was indeed meant to climb trenches in a fashion of 1918. It seems that climbing was still quite useful for infantry support in ww2. Churchills made it much easier for the British to evercome the hills around Tunis. Germans felt safe on the peaks and the British simply drove up to them including to the 754th Grenadier Regiment HQ, bagging the officers. Navigating heavy terrain widens the maneuver space and the tactical solutions available. Lowlands are not everywhere.

 

You have absolutely lost the privilege of speaking authoritatively on anything, even if you're right.

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

Indeed. Not a good bet, as it turned out.

 

But you can't blame them for at least hedging. The French, at least, went into WW1 adamant that it would a war of offensive manoeuvre (based on their previous experience with the Prussians), and it was for a month or two. And then it wasn't and they lost a generation of young men.

 

If I'd been bled white and had chunks of my country rendered permanently uninhabitable because I didn't put money on the defensive being dominant in the last war...


True, but from my understanding, the Renault FT had a better showing than the British Marks and Saint Chamond: being faster, cheaper, requiring fewer crew, and generally more reliable. 

Link to post
Share on other sites

 

2 hours ago, Toxn said:

Indeed. Not a good bet, as it turned out.

 

But you can't blame them for at least hedging. The French, at least, went into WW1 adamant that it would a war of offensive manoeuvre (based on their previous experience with the Prussians), and it was for a month or two. And then it wasn't and they lost a generation of young men.

 

If I'd been bled white and had chunks of my country rendered permanently uninhabitable because I didn't put money on the defensive being dominant in the last war...

 

I think that it's a bit of misconception. The French certainly saw that tanks and airforce were very important in the modern warfare, after all they had the largest tank force in the world by 1940 and their airforce was pretty well equipped. The issue was that for various reasons they mostly stayed basically with FT-17 and its more modern clones and on top of that had completely disfunctional command and communication chain. 

 

24 minutes ago, Lord_James said:


True, but from my understanding, the Renault FT had a better showing than the British Marks and Saint Chamond: being faster, cheaper, requiring fewer crew, and generally more reliable. 

 

FT was for sure the best tank of WW1 but by may 1940 there were still 1300 of them in French army service, of that roughly 530 in frontline units facing the German invasion...  

 

Link to post
Share on other sites
57 minutes ago, Beer said:

 

 

I think that it's a bit of misconception. The French certainly saw that tanks and airforce were very important in the modern warfare, after all they had the largest tank force in the world by 1940 and their airforce was pretty well equipped. The issue was that for various reasons they mostly stayed basically with FT-17 and its more modern clones and on top of that had completely disfunctional command and communication chain. 

 

Ya, but part of the reason for that is because the Char B1 was sucking up all of the resources that should have gone into making more modern medium designs.

 

As for their doctrine and C&C, it was perfect for fighting WW1 all over again - built around a process of slow, deliberate, centrally-coordinated movements focused around artillery fire massing and coordination. It just wasn't up to the task of orchestrating manoeuvre warfare (and the very real dysfunction didn't help).

Link to post
Share on other sites
14 minutes ago, Toxn said:

Ya, but part of the reason for that is because the Char B1 was sucking up all of the resources that should have gone into making more modern medium designs.

 

Tend to disagree here. Up to the very last moment the military kept buying literally thousands of 2-men tanks both for the infantry support and cavalry eqipped with the same vintage gun as the FT-17 (R-35, H-35, H-38, FCM-36). That means that by may 1940 the military had close to 3000 2-men tanks with useless guns which were by large majority produced during late 30'. That's a looot of resources vasted. 

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Similar Content

    • By Monochromelody
      IDF had kept about 100 Tiran-6/T-62s since 1973, and remain service until 1990s. 
       
      I wonder if there's any modification on Tiran-6, like changing the powerpack into 8V71T+XTG-411, adapting steering wheel. 
       
      I also heard that British ROF had produce a batch of 115mm barrel for IDF, while MECAR or NEXTER produced high-performance APFSDS for 115mm gun. Did IDF really use these barrels for original barrel replacement? 
       
      And about protection, did IDF put Blazer ERA on Tiran-6? Or they use more advanced APS like Trophy? 
       
      Thank you. 
    • By Sturgeon
      The LORD was with the men of Deseret. They took possession of the hill country, but they were unable to drive the people from the plains, because they had chariots of steel.
      —The Book of Latter Day Saints, Ch 8, vs. 3:10, circa 25th Century CE
       
      BULLETIN: ALL INDUSTRIAL-MECHANICAL CONCERNS
       
      SOLICITATION FOR ALL-TERRAIN BATTLE TANK
       
      The Provisional Government of the Lone Free State of Texas and The Great Plains issues the following solicitation for a new All-Terrain Battle Tank. The vehicle will be the main line ground combat asset of the Lone Free State Rangers, and the Texas Free State Patrol, and will replace the ageing G-12 Scout Truck, and fill the role of the cancelled G-42 Scout Truck. The All-Terrain Battle Tank (ATBT) will be required to counter the new Californian and Cascadian vehicles and weapons which our intelligence indicates are being used in the western coast of the continent. Please see the attached sheet for a full list of solicitation requirements.
       

       
      Submissions will be accepted in USC only.
       
       
      Supplementary Out of Canon Information:
       
       
      I.     Technology available:
      a.      Armor:
      The following armor materials are in full production and available for use. Use of a non-standard armor material requires permission from a judge.
      Structural materials:
                                                                    i.     RHA/CHA
      Basic steel armor, 360 BHN. The reference for all weapon penetration figures, good impact properties, fully weldable. Available in thicknesses up to 4 inches (RHA) 8 inches (CHA). 
      Density- 0.28 lb/in^3.
                                                                   ii.     Aluminum 5083
      More expensive to work with than RHA per weight, middling impact properties, low thermal limits. Excellent stiffness.
       Fully weldable. Available in thicknesses up to 4 inches.
      Mass efficiency vs RHA of 1 vs CE, 0.9 vs KE.
      Thickness efficiency vs RHA of 0.33 vs CE, 0.3 vs KE.
      Density- 0.1 lb/in^3 (approx. 1/3 of steel).
      For structural integrity, the following guidelines are recommended:
      For heavy vehicles (30-40 tons), not less than 1 in RHA/1.75 in Aluminum base structure
      For medium-light vehicles (<25 tons), not less than 0.5 in RHA/1 in Aluminum base structure
      Intermediate values for intermediate vehicles may be chosen as seen fit.
      Non-structural passive materials:
                                                                  iii.     HHA
      Steel, approximately 500 BHN through-hardened. Approximately 1.5x as effective as RHA against KE and HEAT on a per-weight basis. Not weldable, middling shock properties. Available in thicknesses up to 1 inch.
      Density- 0.28 lb/in^3
                                                                  iv.     Fuel
      Mass efficiency vs RHA of 1.3 vs CE, 1 vs KE.
      Thickness efficiency vs RHA of 0.14 vs CE, 0.1 vs KE.
      Density-0.03 lb/in^3.
                                                                v.     Assorted stowage/systems
      Mass efficiency vs RHA- 1 vs CE, 0.8 vs KE.
                                                               vi.     Spaced armor
      Requires a face of at least 1 inch LOS vs CE, and at least 0.75 caliber LOS vs fullbore AP KE.
      Reduces penetration by a factor of 1.1 vs CE or 1.05 vs KE for every 4 inchair gap.
      Spaced armor rules only apply after any standoff surplus to the requirements of a reactive cassette.
      Reactive armor materials:
                                                                  vii.     ERA
      A sandwich of 0.125in/0.125in/0.125in steel-explodium-steel.
      Requires mounting brackets of approximately 10-30% cassette weight.
      Must be spaced at least 2 sandwich thicknesses away from any other armor elements to allow full functionality. 81% coverage (edge effects).
                                                                  viii.     NERA
      A sandwich of 0.25in steel/0.25in rubber/0.25in steel.
      Requires mounting brackets of approximately 10-30% cassette weight.
      Must be spaced at least 1 sandwich thickness away from any other armor elements to allow full functionality. 95% coverage.
      The details of how to calculate armor effectiveness will be detailed in Appendix 1.
      b.      Firepower
                                                                    i.     Bofors 57mm (reference weapon) - 85,000 PSI PMax/70,000 PSI Peak Operating Pressure, high quality steel cases, recoil mechanisms and so on are at an equivalent level to that of the USA in the year 1960.
                                                                   ii.     No APFSDS currently in use, experimental weapons only - Spindle sabots or bourelleted sabots, see for example the Soviet BM-20 100mm APFSDS.
                                                                  iii.     Tungsten is available for tooling but not formable into long rod penetrators. It is available for penetrators up to 6 calibers L:D.
                                                                  iv.     Texan shaped charge technology - 4 CD penetration for high-pressure resistant HEAT, 5 CD for low pressure/ precision formed HEAT.
                                                                   v.     The subsidy-approved GPMG for the Lone Free State of Texas has the same form factor as the M240, but with switchable feed direction.. The standard HMG has the same form factor as the Kord, but with switchable feed direction.
      c.       Mobility
                                                                    i.     Engines tech level:
      1.      MB 838 (830 HP)
      2.      AVDS-1790-5A (908 HP)
      3.      Kharkov 5TD (600 HP)
      4.    Detroit Diesel 8V92 (400 HP)
      5.    Detroit Diesel 6V53 (200 HP)
                                                                   ii.     Power density should be based on the above engines. Dimensions are available online, pay attention to cooling of 1 and 3 (water cooled).
                                                                  iii.     Power output broadly scales with volume, as does weight. Trying to extract more power from the same size may come at the cost of reliability (and in the case of the 5TD, it isn’t all that reliable in the first place).
                                                                  iv.     There is nothing inherently wrong with opposed piston or 2-stroke engines if done right.
      d.      Electronics
                                                                    i.     LRFs- unavailable
                                                                   ii.     Thermals-unavailable
                                                                  iii.     I^2- Gen 2 maximum
                                                                  vi.     Texas cannot mass produce microprocessors or integrated circuits
                                                                 vii.    Really early transistors only (e.g., transistor radio)
                                                                viii.    While it is known states exist with more advanced computer technology, the import of such systems are barred by the east coast states who do not approve of their use by militaristic entities.
       
      Armor calculation appendix.
       
      SHEET 1 Armor defeat calculator 4in-54 1200 yd
       
      SHEET 2 Armor defeat calculator 4in-54 2000 yd
       
      SHEET 3 Armor defeat calculator 6in HEAT
       
      Range calculator
       
    • By Beer
      I haven't found an appropriate thread where to put some interesting rare stuff related to WW2 development, be it industrial one or makeshift field modifications. 
       
      Let's start with two things. The first one is a relatively recently found rarity from Swedish archives - a drawing of ČKD/BMM V8H-Sv tank. The drawing and a letter was found by WoT enthusiasts in Swedish archives in 2014 (the original announcement and the drawing source is here). The drawing is from a message dated 8th September 1941. One of the reasons why this drawing was not known before may be that the Czech archives were partially destroyed by floods in 2002. Anyway it is an export modification of the V-8-H tank accepted into Czechoslovak service as ST vz.39 but never produced due to the cancelation of all orders after Münich 1938 (for the same reason negotiations about licence production in Britain failed). Also later attempt to sell the tank to Romania failed due to BMM being fully busy with Wehrmacht priority orders. The negotiations with Sweden about licence production of V8H-Sv lasted till 1942, at least in May 1942 Swedish commission was present in Prague for negotiations. The tank differed compared to the base ST vz.39 in thicker armor with different front hull shape (armor 60 mm @ 30° on the hull front and also 60 mm on the turret; all sides were 40 mm thick). The tank was heavier (20 tons) and had the LT vz.38 style suspension with probably even larger wheels. The engine was still the same Praga NR V8 (240-250 Hp per source). The armament was unchanged with 47 mm Škoda A11 gun and two vz.37 HMG. The commander's cupola was of the simple small rotating type similar to those used on AH-IV-Sv tankettes. It is known that the Swedes officially asked to arm the tank with 75 mm gun, replace the engine with Volvo V12 and adding third HMG to the back of the turret. In the end the Swedes decided to prefer their own Strv/m42. 

      Source of the drawing
       
      The second is makeshift field modification found on Balkans. It appears Ustasha forces (and possibly some SS anti-partizan units) used several Italian M15/42 medium tanks with turrets from Pz.38(t). There are several photos of such hybrids but little more is known. On one photo it is possible to see Ustasha registration number U.O. 139.

      Few more photos of such hybrid.
       
      It appears that the source of all those photos to be found on the internet is this book, Armoured units of the Axis forces in southeastern Europe in WW2 by Dinko Predoevic. 
       
    • By SuperComrade
      I was recently looking at the Japanese wikipedia page for the Chi-Ha tank, and it had this section on the name of the tank:

       
       
      I have never heard of such nomenclature, and obviously I don't have access to such documents since I don't live in Japan. There is no reference for this part, so can anyone confirm that they actually did use "MTK" etc.?

×
×
  • Create New...