This is intended for people interested in the subject of military guns and their ammunition, with emphasis on automatic weapons.
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Back to engines.
Napier and Lion have to be the tank engine and engine makers of choice. If the Merlin can be turned into the Meteor then the Lion can be turned into a tank engine. There is enough time and resources available within Napier to fix that issue and get production of the engine started.
Ethanol upping the octane to 95 or 100 seems like a too good to be true solution for the period and well worth standardising it as the fuel type used by the UK military pre-war.
It would probably benefit the nazis more that the Brits but then they have their own traveller so that should not really be a consideration.
The construction of the lion with individual cylinders makes it an excellent candidate for the various sub engines needed for the various pre war contraptions like Crusader. As noted previously I think Crusader should be a utility hull for mounting engineering and SP artillery on and not a tank in it's own right, that should be left to the Churchill. The British army will need the experience with heavier tanks from a logistical and strategic mobility point of view. There is no reason why the Churchill can't be the British T-34 and grow from 24 to 30 tonnes over the war period.
that potential is also needed because the other traveller will revamp their tank production and their armour can be expected to be much better armoured and more effective than historically.
Back to engines.
On the face of it, the Lion should be an ideal choice: it's compact (great for rear-mounting), about the right power, and very reliable. However, somewhere in these posts I recall some specific issues being raised against the Lion in a tank. One was to do with electrics and seemed solvable without much trouble, but the other was do with ignition problems (knocking, IIRC) when using low-octane petrol, even with very low compression ratios. I don't know how solvable that would be (other than by using higher-octane petrol, of course).
Which again raises the question of fuel octanes. How easy is it to make (or buy, in the case of the UK) higher-octane petrols? What logistic problems would it cause if the tanks needed a higher grade of petrol that the other vehicles' engines can happily cope with? When operating abroad, how readily available would higher-octane petrols be at commercial filling stations at that time?
I think we should start putting some octane numbers on all this, to get a feel for the problems.
autogun said...I think we should start putting some octane numbers on all this, to get a feel for the problems.
I have no idea of the cost of raising the octane of pool petrol or the necessary engine modifications to run on either ethanol or lower octane, so seems safer not to rely on it.
Note the big attraction of the Lion was all the RAF surplus engines lying around, so any mods that make them unusable or expensive really spoil the idea. Otherwise what's the advantage over a Kestrel or Meteorite?
More problems with the Lion, apparently:
BTW I spoke to someone who had looked into Napiers for a book (abandoned) on their aero engines and he tells me that they were selling Sea Lions late in the 1930s but made from old stock and new major parts manufacturing had long stopped by then. The surplus RAF ones were scrap price for a good reason as the RAF had cannibalised anything that would keep their Lions going as long as possible so they would need a lot of work to make them fit and there were not enough parts for that and those in hand at Napiers were earmarked to the Sea Lion programme. Napier, of course, would make new Lions for a big enough order but much machinery was already moved onto the Rapier/Dagger/Sabre work so would have to cover the cost of new machinery. You could have spent the entire tank budget on just the engines.
That would probably depend on when the decision was made more than anything else.
And that is interesting, and for our purposes, useful information, because everything else I've seen suggested that Napier were still making Lions possibly as late as 1940, but the refurbishing older ones with scrapped parts and from old stock puts a crimp in plans and suggestions.
Well, that does help to explain why so little interest was shown in the Lion at a time when British tank designers were very keen to get hold of a decent engine!
Quite. It seems that an early meteor is the only option. The Crusader should be the earliest tank and obviously needs the liberty. This could be replaced on later versions by a V6 meteor for commonality and improved reliability. The artillery platforms on the same chassis could follow Marder III route with the driver front, the engine middle and the fighting compartment rear or or just be a convectional tank layout with with a artillery piece in a taller turret.
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?
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.
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!