January 1936: British army, you run the show

[Shortround6]

Back to the tanks - on what to bet on?
A 30 ton tank with something better than a 2 pdr should be feasible; the Matilda II was at 27 tons. The lighter tanks might be needed to overcome the budget restraints, though, while using the commercial engines (1x150 or 2x85/95 HP), so we can have enough of decent tanks. The Liberty must be kept at 340 HP, without attempts to increase the power, in order to give good service?

Best service for the Liberty engine is to attach long chains to them and use them as boat anchors

The WW I aircraft engines were made by a number of companies and while a good Liberty engine by a good maker was a decent enough engine, too many of them were junk from the day they left the factory door.
For a brief review : Liberty Notes

Why somebody thought that an engine with a 75 hour overhaul life would make a good tank engine I have no answer for.
The fact that few, if any, commercial operators (not counting rum runners) used the engine for very long, even getting them at surplus prices should have been another clue.

 

[tomo pauk]

Roger that
How the tanks should be looking, on a more affirmative note?

 

[fastmongrel]

Best service for the Liberty engine is to attach long chains to them and use them as boat anchors

The WW I aircraft engines were made by a number of companies and while a good Liberty engine by a good maker was a decent enough engine, too many of them were junk from the day they left the factory door.
For a brief review : Liberty Notes

Why somebody thought that an engine with a 75 hour overhaul life would make a good tank engine I have no answer for.
The fact that few, if any, commercial operators (not counting rum runners) used the engine for very long, even getting them at surplus prices should have been another clue.

The engines used were not Libertys as built originally but a reworked engine developed and built by the Nuffield organisation (Morris Motors). The Nuffield engine wasnt actually too bad by the standards of 1940 it was the ancillaries like transmission, cooling and filtration that let it down. Nuffield Libertys with modified ancillaries carried on in service till 1945 so they cant have been too bad. Some Crusader gun tractors were modified by the Argentinians into SP guns and served until the mid 50s

 

[tomo pauk]

Since the Germans were fond to mount anything or anything, here is what they used the Bren Carrier for (with 20mm Flak, 25mm ATG, 37mm ATG, 2pdr, 47mm ATG (whose in original?), French 75mm):

 

[Shortround6]

The engines used were not Libertys as built originally but a reworked engine developed and built by the Nuffield organisation (Morris Motors). The Nuffield engine wasnt actually too bad by the standards of 1940 it was the ancillaries like transmission, cooling and filtration that let it down. Nuffield Libertys with modified ancillaries carried on in service till 1945 so they cant have been too bad. Some Crusader gun tractors were modified by the Argentinians into SP guns and served until the mid 50s

It still wasn't a good engine to work from.

Each Cylinder has it's own water jacket (welded sheet metal) which is almost a recipe for coolant leaks ( guess what? they leaked). The crankshaft Unless Nuffield changed it, had NO counterbalances and suffered from torsional vibration and broken crankshafts. Please note valve gear hanging out in the open, Common enough in WW I for air cooling of the valve gear but not really what you want in a tank. Nuffield may have thrown a sheet metal box around the valve gear later.

I can also tell you some stories about 1950s fire trucks I was driving in the 1970s, Desn't mean they were any good, just that department had no money to replace them ( to be fair a couple of them were spares and only got driven a couple hundred miles a year, being "in service" can have a lot of meanings).

 

[Shortround6]

Since the Germans were fond to mount anything or anything, here is what they used the Bren Carrier for (with 20mm Flak, 25mm ATG, 37mm ATG, 2pdr, 47mm ATG (whose in original?), French 75mm):

View attachment 276259

Some shop workers had too much time on their hands

The French 75 had an interesting traverse system. There was rack in the axle and the traverse gear would shift the axle housing, to which the gun cradle was bolted, left and right on the axleshaft using the spade of the trail as the pivot point. Has the advantage that the gun is ALWAYS recoiling in line with the trail instead of a few degrees to one side or the other, Not such a good system to try to adapt to an armored vehicle. Where does the trail go even if you shorten it?
You can build a new traverse system

Gun also recoils several feet unless you modify the recoil system.

 

[fastmongrel]

It still wasn't a good engine to work from.
View attachment 276260

Each Cylinder has it's own water jacket (welded sheet metal) which is almost a recipe for coolant leaks ( guess what? they leaked). The crankshaft Unless Nuffield changed it, had NO counterbalances and suffered from torsional vibration and broken crankshafts. Please note valve gear hanging out in the open, Common enough in WW I for air cooling of the valve gear but not really what you want in a tank. Nuffield may have thrown a sheet metal box around the valve gear later.

I can also tell you some stories about 1950s fire trucks I was driving in the 1970s, Desn't mean they were any good, just that department had no money to replace them ( to be fair a couple of them were spares and only got driven a couple hundred miles a year, being "in service" can have a lot of meanings).

Not saying it was a great engine just that by the standards of 1940 it wasnt too bad and all the reports I have read say that it was what was bolted onto the engine that caused most of the problems. Nuffield would have been better off building a land based Kestrel in my opinion but I dont know if that was ever considered. The Kestrel tank engine could have powered Britains tanks from 1940 to the Comet when the Meteor could be dropped in.

 

[tomo pauk]

Hmm - the Germans and Americans lashed up the French 75mm to the split-trail carriages, so they can have an anti-tank gun in quantity, until better stuff came along. Americans converted over 900 pieces. link

Both the US and German ATG would've better fared with a better ammo - only full bore, full weight ammo seem to be issued.

 

[Shortround6]

Yes, both the Americans and the French "lashed up the French 75mm to the split-trail carriages" but the lash up pretty much just kept the barrel and breech. Not only new carriage but new gun cradle but new traverse and elevating mechanisms.
Even new recoil system. It might have been worthwhile but it was NOT a quick and dirty "grab this old gun out of the warehouse and slap into this spare chassis".
The extra elevation also added about 2500 meters to the max range.

TOADMAN'S TANK PICTURES 75mm FIELD GUN M1897A4 and CARRIAGE M2A3

Edgar Brandt (of mortar fame) was working on sub-caliber projectiles before WW II. The trick is not just making them but getting acceptable accuracy from them. Getting the sabot/s to separate in a uniform, consistent manor so you can actually get the projectiles to hit in a small area at a distance.
The next thing to figuring out if it is going to "work" is figuring out IF the sub-caliber projectile is actually going to go through more armor at the distance desired (they probably will work better at close range) AND have the desired effect on the target. Do you want to poke a 40mm hole in the enemy tank or a 75mm hole? Just because you made a hole in the armor does NOT mean you destroyed what was behind the armor. Crew, ammo, engine, etc.
If made of similar materials ( steel for example) and shape the large shot/shell will retain it's velocity better at long range and it's penetration will fall of less with distance. The sub caliber round may very well be superior at close ranges, where is the cross over point? Don't forget the larger round will penetrate more armor at the SAME velocity as the smaller round due to having more weight/mass per unit ( sq in/sq cm) of frontal area.
Tungsten carbide works so well because it has about twice the density of steel so the smaller projectile can have similar weight (or be bit better?) per unit of frontal area. Helps with both retained velocity and the armor punching.
Even the allies had problems with producing enough Tungsten carbide during the war. Many US tanks and tank destroyers seldom having the 2-5 rounds in the 'official' load out in 1944.

 

[Shortround6]

Not saying it was a great engine just that by the standards of 1940 it wasnt too bad and all the reports I have read say that it was what was bolted onto the engine that caused most of the problems. Nuffield would have been better off building a land based Kestrel in my opinion but I dont know if that was ever considered. The Kestrel tank engine could have powered Britains tanks from 1940 to the Comet when the Meteor could be dropped in.

Maybe by the standards of bolting a couple of bus engines together it wasn't too bad but that isn't exactly a good recommendation.

I don't know enough about how/why Nuffield selected the Liberty engine. Were they at some point an overhaul facility for Liberties in British service in the 1920s or 30s? Were they offered a "deal" on surplus engines/parts/tooling in addition to the blueprints and manufacturing licence?
Problems with the Liberty in aircraft use were well known. While a number of aircraft records were set using Liberty engines it took a lot of support. For instance the first circumnavigation of the world by air was done with Liberty engines, but..."The spare parts included 15 extra Liberty engines, 14 extra sets of pontoons, and enough replacement airframe parts for two more aircraft.[9] These were sent ahead along the route around the world the aircraft would follow."
"The American team had greatly increased their chances of success by using several aircraft and pre-positioning large caches of fuel, spare parts, and other support equipment along the route. At prearranged way points, the World Flight's aircraft had their engines changed five times and new wings fitted twice."
Now counting the engines they started with and a flight of 27,553 miles that is an average of about 4600 miles per engine. Or a bit less, Most the flight was done by three aircraft. One of the first four crashed early on and and second plane was lost over the Atlantic and the original 5th aircraft joined up for the last legs. Average speed was 70mph. Average time on engines was 65 hours (?)

Perhaps Nuffield built the Liberty because that is what the Christie protoypes used but Christie was rather restricted in what engines he had available. I believe he used Both the Liberty and an American LaFrance V-12 firetruck engine is some of his prototypes? The Liberty had power and were available cheap as surplus.

 

[tomo pauk]

...
Edgar Brandt (of mortar fame) was working on sub-caliber projectiles before WW II. ...

There are AP ammo types, better than plain AP ammo, and still not the APSD, that 75mm (or other gun that will be poking holes) can use. Eg. the Germans could use the steel penetrator that weights 3-4 kg, the MV will be much higher than at 570 m/s, but still under 850 m/s (= shatter unlikely to happen). The AP capabilities would've been better. Even better with tungsten carbide, for the ones that can afford it, of course.

The sub caliber round may very well be superior at close ranges, where is the cross over point?

Above 500-600m distance it seems the full-bore AP has better capabilities, penetration wise, for the 'small guns' we're discussing. The sub-caliber, high speed projectile should offer greater hit probability, though, both because of less arcing trajectory (good if the range was calculated with error) and lower time until hit (less target lead needed).

Do you want to poke a 40mm hole in the enemy tank or a 75mm hole? Just because you made a hole in the armor does NOT mean you destroyed what was behind the armor. Crew, ammo, engine, etc.

Problem might be that, where we can make a 40mm hole, we might not have any hole if we want a 75mm wide one. That was many times a problem for 75-76,2mm guns in Allied and German use. Hence the sub-caliber ammo.

Don't forget the larger round will penetrate more armor at the SAME velocity as the smaller round due to having more weight/mass per unit ( sq in/sq cm) of frontal area.

One of the reasons I like the 88mm L/56 much more then the 75mm L/70

 

[fastmongrel]

Done a bit of quick googling on the Nuffield V12 and it seems some major changes were made to the original Liberty. Redesigned heavier crankcases, cast iron cylinders, rocker covers, flanged steel backed white metal big ends, small ends and main bearings, 2 x distributors working off the camshafts and a crank chain drive for the cooling fans which was changed to 2 x driveshafts running off the crank in the mark IV and V. I have also found mention stellite in the valves though not sure whether thats just the seats or the valves as well.

Tank Museum Nuffield Liberty

Liberty L12

Nuffield tank engine left and Liberty aero engine converted to marine use on right crankcases.

There is a fascinating and from reviews exhaustively comprehensive book by RJ Neal on the Liberty which has a big chapter on the Nuffield
Liberty Engine: A Technical Operational History: Robert J. Neal: 9781580071499: Amazon.com: Books

Some nice engine p0rn pics of a Liberty stripped and rebuilt

Liberty disassembly

 

[Shortround6]

Thank you.

 

[tomo pauk]

The British were installing coupled engines on their tanks Matildas and Valentines. Unfortunately, the power was still under 200 HP. The two 6-cylinder AECs coupled together will bring 300 HP to the table - should be enough for 20 to 25 ton tanks, even for the ones between 25 and 30 tons.
Granted, less elegant solution than a good V-12.

 

[Shortround6]

The Valentine used a single engine. Either an engine similar to that use in the A9/A10 or later a GMC 6-71 diesel was often used. These GMCs were paired up the M3A3 and M3A5 Grants, M4A2 Shermans and M10 tank destoyers.

while a pair of 150hp gas engines will move a 30 ton tank it won't very "sprightly" Germans had 265-300hp in the MK 1Vs. adding another 6tons or so isn't going to be kind.

Disadvantage to using a pair of SIX's is you need to leave a bit or room between them for maintenance.

The big engines also had a LOT of torque which meant you needed fewer gears or had better acceleration or both. Unless you are dealing with 800 cubic in (13 liter) Sixes two of them probably will not have the torque of the Liberty.

 

[tomo pauk]

Back to the tanks/AFV.
The lighter designs I've proposed (under 15 ton cruiser, above 15 ton I-tank; powerpack transmission all-front) can serve as carriages for the artillery, once they are obsolete to serve as 1st line tanks (talk 1942). The I-tank can have the big anti tank gun or/and the 25pdr, mounted in a well armored superstructure; use both for direct fire (shades of the StuG/StuH). The rear installation should give more useful volume. Cruiser can also receive the big AT gun or 25 pdr (high elevation), the resulting vehicles being a 'better Marder' or 'not quite Wespe'. Either vehicle can be modified to serve as an APC, in lieu of the various Kangaroo APCs. The Cruiser can also receive the multiple 20mm for AA duties, if not already the Bofors.
Once the halftracks are received from the USA, install the 25pdr on those, much like the T19 vehicle was used by the US Army. The 25 pdr will not have as great the recoil as the 105mm (even lower with muzzle brake installed), so no problems with that.

 

[Shortround6]

Uh, Tomo. Above 15 ton I tank engine in front.

Problem with 15-25 ton I tanks is that they are small as in almost tiny.

65mm armor (2.5in) weighs 100lbs per sq ft. you don't get a lot of sq ft to the ton so light I tanks are tiny. And even the T19 was smaller than what was wanted.

They commonly towed ammo trailers.

The British and Americans very seldom used old tank chassis for SP guns, new manufactured obsolete chassis yes.

The British could have done themselves a world of good by dumping the Covenanter in the rubbish bin early on and building tanks they could actually use.

1771 tanks of which only a handful were ever used in action at that was to carry bridges.

 

[tomo pauk]

Uh, Tomo. Above 15 ton I tank engine in front.

Problem with 15-25 ton I tanks is that they are small as in almost tiny.

65mm armor (2.5in) weighs 100lbs per sq ft. you don't get a lot of sq ft to the ton so light I tanks are tiny.

'My' I tank, with 6-cyl engine compartment aside the driver, should allow more space for combat compartment if the tank is overall as long as Valentine. Compared to the Archer, it should be able to fire during the advancement phase, in support of attacking tanks and infantry, not just to use it for ambushes.

And even the T19 was smaller than what was wanted.
They commonly towed ammo trailers.

Ammo trailer is a good thing. The 25pdr gun and ammo is much lighter/smaller than the 105mm ammo, that combined with ammo trailer should mean plenty of ammo per vehicle.

The British and Americans very seldom used old tank chassis for SP guns, new manufactured obsolete chassis yes.

Indeed.

The British could have done themselves a world of good by dumping the Covenanter in the rubbish bin early on and building tanks they could actually use.
1771 tanks of which only a handful were ever used in action at that was to carry bridges.

Agreed again.

 

[Shortround6]

'My' I tank, with 6-cyl engine compartment aside the driver, should allow more space for combat compartment if the tank is overall as long as Valentine. Compared to the Archer, it should be able to fire during the advancement phase, in support of attacking tanks and infantry, not just to use it for ambushes.

You are confusing two different roles.
Using direct fire "able to fire during the advancement phase, in support of attacking tanks and infantry" and being a self-propelled artillery piece.

Granted some armies did try to blend the two but it leads to compromises.
Like.

Great for following the tanks by 200-600 meters and blasting strong points, Lousy at being back 2,000-6,000 meters from the battlefield and providing support fire and absolutely useless at providing support fire at around 8-12KM. The design of the chassis and gun installation limit the elevation to 26 degrees which cuts several thousand meters from the max range. It has either 10 degrees total or 20 degrees (10 either way) traverse without moving the vehicle and cramped crew compartment limits rate of fire. Not too important blasting pillboxes/strong points at 500-1000 meters range but a real limit in support fire.

Compare to

Late or end of war M-37 on M24 light tank chassis, replacement for the M-7.

Not very good for shooting it's way into a city or town but a dandy weapon/chassis for supporting an armored advance. Able to move swiftly from firing position to firing position and lay down HE or smoke on demand from forward units. This of course assumes a decent radio net. Without the radio net you may have to depend on close accompanying guns rather than remote artillery.

BTW, it appears from trying to measure scale drawings that the Valentine hull was only about 5 ft wide, about the same width as the light tanks and around 1/2 ft narrower than the early cruisers and a 1 1/2ft narrower than a Cromwell (Cromwell then sucks up some of the space with the Christie suspension). Grants and Shermans were actually rather narrow between the tracks but then so much of the tank was above the tracks.

Edit: British had a far greater need in NA for artillery able to move from firing position to firing position to keep up with the advance than they did for bunker blasters. One of the more famous slaughters of Matilda tanks by 88s occurred when the battery of 25pdrs assigned to support the attack got bogged down in a sand waddie tying to reach it's position and in order to keep to the firing schedule skipped it's first fire mission. Of course this also speaks to a lack of communication ( and a bit too much emphasis on radio silence) and a bit to much "press on regardless" attitude but 3-4 25pdr armed "assault" guns/tanks a few hundred yards behind the Matildas would have made little difference to the outcome of the battle. An 88 or two knocked out/destroyed, a Matlida or two more saved (at the cost of how many of the assault tanks?) but the position still in German hands.
Even SU-122s weren't going to do much trying to advance across several kilometers of open dessert against dug in 88mm guns. Best they could do was fire smoke and get the Matildas to withdraw but then how many smoke rounds do these 'assault' tanks carry?
And "smoke" was much more difficult to use than most (all) war games would have us believe. And unfortunately for use in the desert, both types of common smoke used by the British need (or are helped) by moisture in the air. Dry air reduces the effectiveness of smoke shells.

 

[tomo pauk]

You are confusing two different roles.
Using direct fire "able to fire during the advancement phase, in support of attacking tanks and infantry" and being a self-propelled artillery piece.

Hopefully I'm not that confusing. My comment starts with 'Compared to the Archer, it should be able to fire...', and Archer was, despite all of it's virtues, lousy in doing that when compared with AFVs with the gun pointing forward. The 'real' SP artillery piece will not have the 17pdr, of course, but the mentioned 25prd.

BTW, it appears from trying to measure scale drawings that the Valentine hull was only about 5 ft wide, about the same width as the light tanks and around 1/2 ft narrower than the early cruisers and a 1 1/2ft narrower than a Cromwell (Cromwell then sucks up some of the space with the Christie suspension). Grants and Shermans were actually rather narrow between the tracks but then so much of the tank was above the tracks.

The Valentine was some 25 cm narrower than Matilda II, so the I tank does not need to be that narrow. We can shave some length (due to engine placement) in order to keep the tabs on the weight.

The British tanks certainly needed sponsons (Matilda II have had them) in order to receive the bigger turret with a bigger cannon. The external mantlet layout (say, T-34, Panther, M4; Matilda, again), instead of internal (Cromwell, Comet, just to name a few), should also provide more space for a bigger cannon, for a given turret ring diameter.