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The Foresight War Revisited: AFVs   Novel: The Foresight War

Started 16-Feb by autogun; 23262 views.
hobbes154

From: hobbes154

13-Apr

TFW already depends on an early (half-)Meteor meaning that the Centurion is only a bit behind (or theoretically simultaneous with, at the cost of some unreliability) the Crusader.

Liberty is an off-the-shelf design (though will still need new production lines) but only gives a little more power than the half-Meteor. "The Liberty would eventually be up-rated to 410 HP in later versions simply because the power was absolutely necessary. Doing so was at some sacrifice in reliability, however, as such output was pushing the engine to its full capabilities." - Liberty Engine (p.437). It also has the disadvantage of being bigger (similar size to full Meteor). To me that is only a backup option for a tank of the same size, though if you want really cheap and off the shelf use twin 150hp AECs from Cruiser I/II.

V6s are hard to balance so not a great idea at this time in an engine that size (they took a while after WW2 to be common even with much smaller car engines and trucks still use straight 6s).

I gave my preferred tree in post 98 but I can see where Tony is going within his story arc where he can really optimise for a particular point in time (Normandy 1943).

Now let's think about what the Germans would/should do?

In reply toRe: msg 153
hobbes154

From: hobbes154

13-Apr

Now for the Germans...

Like everyone else the real constraint on tank design is the engines and drivetrain. Assuming they stick with the same Maybach engines they have an even bigger power jump from 300 PS to 700 PS so the first generation is always going to be a compromise relative to the T-34 or Sherman. In the absence of detailed knowledge to the contrary I would not like to assume the 700 PS engine could be ready much sooner than OTL (hopefully more reliable though!). That might rule out Panthers for Barbarossa.

The  Panzer III and IV were great for their time, aside from the unnecessary duplication and initial undergunning (but get Ford and Opel involved in production ASAP!). Sloped front armour would be nice, also mundane things like wider tracks and other preparation for the Russian winter. The Germans stuck with front transmission even in the Tiger/Panther so that seems to be a strong preference (and had some advantages). Could get rid of the bow gunner for a stronger front plate and additional ammo storage but again this seemed to be a German preference and the bow gunner was also the radio operator.

The III was never matched to the right gun (50mm HE too small, short 75mm low velocity). IMHO it would have been ideal with the Allied 75mm (152cm turret ring, same as Cromwell, so should fit). However if we are sticking with the menu of OTL German guns the obvious option is the 75mm L/43 and /48 which only fits in the Panzer IV. Note however "The longer 7.5 cm guns were a mixed blessing. In spite of the designers' efforts to conserve weight, the new weapon made the vehicle nose-heavy to such an extent that the forward suspension springs were under constant compression." Maybe III's with a mix of 50mm L/60 and 75mm L/24 (with HEAT as a backup)?

I have already given my opinion that late IVs were underarmoured and underpowered. This was a good tradeoff for the OTL Germans who ended up on the defensive against bigger and more powerful tanks. Less ideal for Barbarossa in 1941 which Hermann will focus like a laser on. Yes the Germans are already facing large numbers of T-34s and KVs, however they managed to deal with them historically with smaller guns. If you do go with the IV might be worth cutting weight by only trying to armour against 45mm AT guns from the front and 14.5mm AT rifles from the sides/rear? (wwiiequipment.com/pencalc/ is telling me the 80mm IV H/J front hull is proof against Soviet 76.2mm but vulnerable to US 75mm out to 1km, which seems unlikely?) It's just not possible to overmatch the T-34 in both armour and firepower with only 60% of the engine power, unless you are happy with an armoured pillbox. And it's a long way to Moscow. With a break of rail gauge.

The other choice between the III and IV is torsion bar vs leaf spring suspension. If we stick with OTL designs leaf springs come with the IV. Advantages: completely external so don't use armoured volume and easier to replace in the field. OTOH since this is a "universal" tank the army might insist on torsion bars for better ride quality as in the III. Not a biggie unless it slows development - time is everything (as I keep repeating, in OTL the III and IV were only 1/3 of German tanks in 1940 and 2/3 in 1941).

The Jagdpanzer can wait a few years, the Germans will want all the medium tank chassis they can build as tanks to begin with. OTL Marders are enough as tank destroyers in 1941 - you will have lots of spare Panzer II and French/Czech hulls.

Panther not much comment except don't skimp on the final drive! Lack of gunner's periscope also an interesting point but not sure if that is plausibly within the range of Hermann's knowledge. 

In fact I think there's a lot of interesting questions about what's plausibly the range of Don and Hermann's knowledge - but that belongs in the general thread.

In reply toRe: msg 154
hobbes154

From: hobbes154

13-Apr

Finally some general comments on tank design and how much it can be speeded up:

Bigger guns and armour are not hard.

Building an engine, drivetrain, suspension and tracks that can move then around with the desired mobility and reliability is.

Engine (and associated fuel requirements): have done this to death for British, don't have much more info on Germans except they maybe went to 70+ octane sooner?

Drivetrain: steering is the hard bit (see Panther's final drive above). Ideally want a system that powers both tracks through the turn but the Soviets got away with clutch and brake in the T-34 and KV (!). Meritt-Brown seems the gold standard for the Brits but too late for the Crusader, in OTL they had some kind of bolt on (i.e. not integrated with the rest of the transmission) epicyclic steering system for the earlier Cruisers. Germans seemed to do OK (again except the Panther, I think they spent the money to get a stronger component in the Tiger).

Suspension: Horstmann seems good enough for the Brits (takes up less room than Christie and we're not going for 30mph+ top speeds), leaf spring/torsion bar for Germans.

Tracks: British tracks were particularly prone to breaking early war, this needs to be fixed and presumably will be if you just throw more development money at tanks in the '30s.

Another important point is when to change from riveting to welding. Germans went for welding early and apparently had some problems (12:15), British a bit later. Seems safer to do initial designs with riveting and take welding as a bonus (training more welders should be a priority). The Cromwell and Valentine switched from riveted to welding but I guess you're not getting the full weight savings that way?

So at a very general level engines (and fuel) seem to be the biggest problem? Plus the length of development time to work out the inevitable bugs.

For the Germans, might be a good idea to aim for less power out of the HL210/230 to begin with? At 21-23L it is a smaller engine than the Meteor or Liberty. 500hp and a 35 ton tank with 75 or 88mm would still be pretty good (just enough for frontal overmatch vs T-34). Unlike the British if they are going to win they really have to optimise for 1941-42. But they are still mainly relying on the III/IV in that timeframe IMO.

My ideal 2nd generation German tank would be of Tiger II appearance but 35-40 tons and 75mm L/70 or 88mm L/56 (or even 75mm L/48 to begin with to allow a bigger ammo load). When the Germans who fought in WWII got to build their ideal tank it was the Leopard!

larrikin2

From: larrikin2

14-Apr

If Australia could cast entire tank hulls with its limited industrial capabilities then the UK should be able to as well.

That takes the rivetted/bolted/welded problems pretty much out of play for the main body of the tank and turret.

mpopenker

From: mpopenker

14-Apr

Each time I read those TFW threads I imagine a Russian guy like me being time-bombed to the 1939 in the same story line :)

Red7272

From: Red7272

14-Apr

hobbes154 said:

V6s are hard to balance so not a great idea at this time in an engine that size (they took a while after WW2 to be common even with much smaller car engines and trucks still use straight 6s). I gave my preferred tree in post 98 but I can see where Tony is going within his story arc where he can really optimise for a particular point in time (Normandy 1943).

Apparently Kestrel was also considered as a possibility so a kestrel or meteor V8 is also possible (The Metorite is a V8 version of the meteor but derated with a power output of 260 BHP)

As for my vehicles is an 18 ton liberty engined design with the 3"/20 hwt and as much armour as is practical around 1937. This is basically a training tank. 

Next is a V8 meteor engined 25 ton tank that is superficially similar but slightly shorter and much better armoured with the 77 mm gun. In service this tank might grow over time to 28/30 tons as more armour becomes necessary. 

Third design is the 87 mm MTB.

Red7272

From: Red7272

14-Apr

mpopenker said:

Each time I read those TFW threads I imagine a Russian guy like me being time-bombed to the 1939 in the same story line :)

I believe Tony's observation was that would probably be shot as a spy. 

mpopenker

From: mpopenker

14-Apr

With all due respect, it's an observation of a person who have very little idea about real life in USSR.

In fact I'd surrender to the NKVD in the 1st place, prove them that I indeed have some futire tech with me, and ask to bring me to the attention of the Beria. Yes, it still poses certain risks, and my life would be spent somewhere well guarded, but I think chances of being heard by the Beria and Stalin are much greater than zero.

hobbes154

From: hobbes154

14-Apr

Not much of a story though. A Red Army with throwback assistance and forewarning... I give the Nazis until mid '42. It's almost as bad as Foresight America which I think some guy actually wrote. 

I do Ike the T-34M and the Polikarpov I-180.

I read somewhere about the screening the NKVD did on returning POWs. Contrary to legend only a small percentage ended in the gulag. 

hobbes154

From: hobbes154

14-Apr

I recall the Matilda's cast hull front was very labour intensive though - one reason it was replaced by the Valentine. I assume there is a reason no one else did a fully cast hull until the M48?

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