Sherman with Rover Meteor engine

[Kingsman]

Interesting info. It is well known that the first 1690 "small hatch" M4A3s built by Ford - the only Shermans built by Ford - were retained in the USA for training, replacing a similar number of M4A4s, while the Army and Ordnance were gaining confidence in the GAA before decaring it fit for overseas use. These tanks are extremely rarely seen overseas but are among the most seen preserved in the US.

But this all underscores why the Continental radial engine continued in production after the manufacturer and variant rationalisation in early 1944 and the very last Sherman off the line in August '45 was radial-engined. I have seen it written that the radial-engined M4/A1 variants outnumbered M4A3s in US Army service in NW Europe, to the point where remanufactured M4s and A1s were being supplied alongside new M4A3s. I believe that M4A3s were most common in the Pacific.

M4A3s were reserved for US use and not available for Lend-Lease, although Free French units under US command had some and were first to use the 76mm M4A3 in combat. The Soviets would not have wanted them because of the petrol/gasoline fuel. The UK received only 7, never used operationally. Post-war France re-engined the few they retained with the Continental engine, partly for standardisation but also because GAA spares were hard to get.

 

[Scott Kenny]

But this all underscores why the Continental radial engine continued in production after the manufacturer and variant rationalisation in early 1944 and the very last Sherman off the line in August '45 was radial-engined. I have seen it written that the radial-engined M4/A1 variants outnumbered M4A3s in US Army service in NW Europe, to the point where remanufactured M4s and A1s were being supplied alongside new M4A3s. I believe that M4A3s were most common in the Pacific.

I was under the impression that the M4A2 was the Pacific theater tank of choice. Diesel powered, because the USN could easily supply diesel.

 

[CaptianNemo2001]

Interesting info. It is well known that the first 1690 "small hatch" M4A3s built by Ford - the only Shermans built by Ford - were retained in the USA for training, replacing a similar number of M4A4s, while the Army and Ordnance were gaining confidence in the GAA before decaring it fit for overseas use. These tanks are extremely rarely seen overseas but are among the most seen preserved in the US.

But this all underscores why the Continental radial engine continued in production after the manufacturer and variant rationalisation in early 1944 and the very last Sherman off the line in August '45 was radial-engined. I have seen it written that the radial-engined M4/A1 variants outnumbered M4A3s in US Army service in NW Europe, to the point where remanufactured M4s and A1s were being supplied alongside new M4A3s. I believe that M4A3s were most common in the Pacific.

M4A3s were reserved for US use and not available for Lend-Lease, although Free French units under US command had some and were first to use the 76mm M4A3 in combat. The Soviets would not have wanted them because of the petrol/gasoline fuel. The UK received only 7, never used operationally. Post-war France re-engined the few they retained with the Continental engine, partly for standardisation but also because GAA spares were hard to get.

I have this mess... it got ugly at the London Munitions Assignment Board Meeting

This goes all back to LMAB - Army Assignments Sub-Committee Meetings Weapons and Armaments Bidding MINUTES Army (42) 22nd Meeting (A.F.V.2) Copy 50 May 2nd 1942

Image 004. Paragraph 2.

At different points early on the UK does say they don't really want the A57s, but they do change their tune and start to ask for as many as possible. Sadly by this point the A57 is already being slated to be killed in production. As for the Continental, the UK at first wanted it over the A57. They changed fast. Even Canada in its memos on procurement resolved to accepting it because Fords were unavailable and that the US would likely only ship the R975 for the Ram and Grizzly program. The C4 is a massive improvement over the C1.

 

[Kingsman]

I was under the impression that the M4A2 was the Pacific theater tank of choice. Diesel powered, because the USN could easily supply diesel.

Then I am afraid you are under something of a misapprehension. USMC did not particularly want M4A2s but they wanted Shermans fast. The only ones available quickly were M4A2s from the Lend-Lease pool, so it was a forced choice. Fuel supply had nothing to do with it. USMC had their own on-shore supply chain and all their other vehicle types apart from tractors were gasoline. USMC had more gasoline-engined Shermans than diesel-engined by a wide margin, mostly M4A3s but some M4/A1s. However they did have enough diesel-engined tanks to request a quantity of specific diesel M32B2 variants of the M32 TRV.

US Army also had some M4A2s in training and demonstration units. Of 10,968 M4A2s of all variants the US retained 2630 75mm tanks and had 856 76mm HVSS tanks on its hands when Soviet Lend-Lease ended. Canada bought 280 and the rest were stripped for 76mm HVSS conversions of 75mm M4A3s. Of the rest, the UK was sent 5,046, the Soviet Union 4,029 and Free France 382.

The UK was in a similar position with the M4A4. The USA didn't want it, taking 1600-odd temporarily for training. The Soviets certainly didn't want it. But like USMC we wanted more Shermans in a hurry and M4A4 was the only feasible answer. It became our majority type and we actually liked it. Ultimately we were sent 7,180 of the 7,499 produced with France taking 274, the Soviet Union 2 and the USA keeping 43.

 

[CaptianNemo2001]

As to ODD engines for an M4... Caterpillar drew up but never built a semi-radial duplex. 11 cylinders, with 5 in one bank and 6 in the other. So that the engine could lay flat on the floor of the M4. Mid late 43. Never goes anywhere as far as I know. They said they would give it to anyone as they couldn't spare the engineers to work on the idea.

There is also the Cast Iron Ford GAA from March 1943. Ford proposed but nothing seems to happen.
And the Canadian conversion of a Ford GAA to Diesel. Discussed for a few weeks in Canada and dropped.
As well as the R975C1-C4 or R975C1-4 hybrid. R975C1 with C4 heads. Two months or so of discussion. Dropped because of adding to logistics and because worn out C1s were being replaced outright by R975C4s.

 

[Kingsman]

I can see there being no great advantage to the R974 C1/C4 hybrid. Many improvement proposals during WW2 were dismissed because of the effect on production logistics of what were often marginal improvements. The ultimate US example of this is probably the decision not to take the T23 medium tank into production once it was realised that the main improvement over the M4 - the 76mm gun - could be implemented on the M4 with far less disruption.

Sticking with aluminium for the GAA remains an illogical situation when it was such a strategically important material with many more important uses. The alteration from V12 to V8 was perhaps an opportunity missed, but under time pressures we cannot now really appreciate. Redesign to use cast iron or steel blocks and crankcases was perfectly feasible, as the Merlin into Meteor showed. However, changing the design mid-production might have had consequences for in-service logistics with potential parts incompatibilities. Worse, parts that looked the same but were not: different material or tolerances, for example. There were many Merlin-Meteor parts incompatibilities.

But then iron and steel foundry capacity in the US was at a premium too. When the UK requested US manufacture of aluminium-cased gearboxes and final drives for the Crusader we were told that would only be possible with a redesign to cast iron/steel.

The diesel engine story is a convoluted one. A Caterpillar adaption of the single-row Wright RD-1820 to diesel as the 450 BHP D-200 was adopted for Sherman in the M4A6 but then almost immediately cancelled with only 75 eventually built from an order for 1,500. At one point the M4A6 was touted as the new standard for Sherman and the D-200 was apparently possibly the "best" engine ever fitted to Sherman. The Guiberson 7-cylinder diesel radial used in the M3 Light Tank worked well enough but the 9-cylinder version was a complete failure with only 1 M3A1 Medium Tank converted with it and the remaining engines sentenced for scrapping. While the Guiberson engine fitted the standard M3/M4 engine bay, the D-200 needed the longer M4A4 hull to fit.

The USA, UK and Germany all faced the same diesel fuel problem: lack of it for ground forces use. The USA made a decision in the mid-1930s to adopt diesel propulsion for all military vehicles, but almost immediately rescinded it. Full dieselisation does not happen until the Vietnam war era. All 3 nations were forced to prioritise diesel fuel for maritime use. Germany could synthesise a benzine from coal, using about 7 tonnes of German brown coal (Lignite) to produce 1 tonne of benzine, about 1,300 litres. The UK was forced to adopt diesel engines in the A12 Matilda (AEC) and Valentine (GM) because of lack of suitable petrol/gasoline engines and was effectively given a forced choice to accept mixed petrol and diesel Grants, Stuarts and Shermans from the US to obtain the numbers needed. Diesel Shermans made up almost a third of all those supplied to the UK. The Soviet Union, with its own oil sources, a small navy and almost no merchant navy could afford to use diesel engines in tanks, a decision taken in 1938. But all other Soviet transport remained petrol-engined. From Lend-Lease they wanted diesel tanks (with full fuel tanks!) but petrol trucks.

In Commonwealth forces, diesel fuel remained "packaged" - i.e. supplied in cans - and was not part of the post D-Day bulk distribution system using tankers and pipelines. Despite the relatively high proportion of diesel AFVs and trucks in service.

Germany made the decision pre-WW2 to standardise on a single quality of benzine/gasoline/petrol for all uses at about 80 octane. No 100+ octane for aviation use. So while the Spitfire's Merlin engine was 27 litres the Me-109's equivalent DB engines were 34 and 36 litres for the same sort of power output. The R-R Griffon at about 37 litres was very much more powerful. Which is why we see Germany pioneering Methanol and water injection in aviation engines to boost power.

 

[EwenS]

I was under the impression that the M4A2 was the Pacific theater tank of choice. Diesel powered, because the USN could easily supply diesel.

The USMC received 493 M4A2(75). Roughly 300 small hatch and the remainder large hatch. 12 were converted to M32B2 ARV. These first saw service at Tarawa.

By Iwo Jima in Feb 1945 two of the three USMC tank battalions deployed had switched to the M4A3(75). For Okinawa one of the three involved had switched to the M4A3, but replacement vehicles for the other two were M4A3s.

The USMC also borrowed some M4A1 from the US Army for the Cape Gloucester campaign.

US Army tank battalions in the Pacific used M4/M4A1 until 1945. For Operation Olympic the plan was to replace them with a mix of M26, M4A3 and M24. Some new M4A3(75) were already in tank parks in Manila in summer 1945, while in Europe others were being readied for shipment to the Pacific.

Europe had priority for the M4A3 with the first turning up on the battlefield around July 1944. But these were being issued as replacement vehicles, so until the end of the war units were operating a mix of M4/M4A1 75mm & 76mm / M4A3 75mm & 76mm tanks.

 

[Kingsman]

I forgot to mention above that the M4A6 was killed off by a US-UK agreement in Nov 43 not to develop any more new diesel tanks for our own joint uses, only for foreign aid. The M4A2 was considered adequate for Soviet supply, although the UK continued to receive them well into 1944. All UK A2s were small- hatch 75mm apart from 6 HVSS 76mm, including a prototype DD Mk III. M4A6 production had barely begun when that agreement was made and the contract was terminated at the 75 built and under construction.

 

[EwenS]

I forgot to mention above that the M4A6 was killed off by a US-UK agreement in Nov 43 not to develop any more new diesel tanks for our own joint uses, only for foreign aid. The M4A2 was considered adequate for Soviet supply, although the UK continued to receive them well into 1944. All UK A2s were small- hatch 75mm apart from 6 HVSS 76mm, including a prototype DD Mk III. M4A6 production had barely begun when that agreement was made and the contract was terminated at the 75 built and under construction.

Except as you noted virtually all the M4A2 & M4A4 received by Britain in 1944 were of remanufactured tanks no longer required for the US stateside training programmes, which explains all the M4A2 delivered that year being small-hatch.

535 M4A2 were remanufactured by Fisher & Federal between April & Nov 1944. Chrysler remanufactured 1,610 M4A4 between Dec 1943 & Oct 1944.

 

[Kingsman]

Indeed. And as an existing design the M4A2 was not caught by the "no new" caveat. The proposed improved DD Mk III for the Japanese home islands assaults would have been based on a 76mm HVSS M4A2. Sherman III AY DD Mk III in UK designations. The M4A6 was unlucky to have only just gone into production, was seen as no longer required and took the full force of the new policy with not enough made to be useful. Relegated to training and then the scrapyard.

As the UK had accepted and made good use of M4A2s and was receiving remanufactured ones as late as September '44, it is perhaps surprising that we didn't bid for any of the large hatch 75mm type still in production as we really did not want any 76mm Shermans. But had to accept about 1,300 76mm M4A1s, mostly in Italy.

 

[EwenS]

Indeed. And as an existing design the M4A2 was not caught by the "no new" caveat. The proposed improved DD Mk III for the Japanese home islands assaults would have been based on a 76mm HVSS M4A2. Sherman III AY DD Mk III in UK designations. The M4A6 was unlucky to have only just gone into production, was seen as no longer required and took the full force of the new policy with not enough made to be useful. Relegated to training and then the scrapyard.

As the UK had accepted and made good use of M4A2s and was receiving remanufactured ones as late as September '44, it is perhaps surprising that we didn't bid for any of the large hatch 75mm type still in production as we really did not want any 76mm Shermans. But had to accept about 1,300 76mm M4A1s, mostly in Italy.

I've never seen anything to suggest that the US Army had any interest in the DD built on the M4A2(76mm) HVSS Sherman chassis for use in either Operation Olympic or Coronet, the planned invasions of Japan.

Britain ordered 300 (reduced to 200) against its 1945 Lend Lease allocations. Production was to be 50 per month starting in Sept 1945. By then two things had happened in relation to British plans in the Far East-

1. Operation Zipper, the invasion of Malaya, had gone ahead as a re-ocupation exercise on 9 Sept, without any partticipation from the old model Sherman III DD of the 25th Dragoons that had been planned. SEAC had no amphibious operations planned beyond that.
2. At Potsdam, Commonwealth Army participation in the invasions of Japan, had been whittled down to a Commonwealth Corps of 3 infantry divisions, not in the initial assault waves, only as part of the follow up.

So the need for a new batch of DD tanks was fast evaporating.

The M4A1(76) also went to the 1st Polish Armoured Div in NWE in some numbers (reportedly increasing from 51 in Dec 1944 to 181 by May 1945), not just armoured units in the Italian theatre.

M4A2(75) production was ended in May 1944. After that the only 75mm variant in production was the M4A3, which the US Army wanted to keep for itself. Curiously, the large hatch M4A2(75) did not receive the "wet" ammunition storage that was applied to other Sherman models from early 1944, including the M4A2(76). Britain also had to take 593 105mm howitzer armed Sherman IB/IBY in 1944/45 that weren't wanted either. Very few were issued in either the Med or NWE.

 

[Scott Kenny]

Then I am afraid you are under something of a misapprehension. USMC did not particularly want M4A2s but they wanted Shermans fast. The only ones available quickly were M4A2s from the Lend-Lease pool, so it was a forced choice. Fuel supply had nothing to do with it. USMC had their own on-shore supply chain and all their other vehicle types apart from tractors were gasoline. USMC had more gasoline-engined Shermans than diesel-engined by a wide margin, mostly M4A3s but some M4/A1s. However they did have enough diesel-engined tanks to request a quantity of specific diesel M32B2 variants of the M32 TRV.

Ah, thank you for that!

 

[CaptianNemo2001]

I can see there being no great advantage to the R974 C1/C4 hybrid. Many improvement proposals during WW2 were dismissed because of the effect on production logistics of what were often marginal improvements. The ultimate US example of this is probably the decision not to take the T23 medium tank into production once it was realised that the main improvement over the M4 - the 76mm gun - could be implemented on the M4 with far less disruption.

Sticking with aluminium for the GAA remains an illogical situation when it was such a strategically important material with many more important uses. The alteration from V12 to V8 was perhaps an opportunity missed, but under time pressures we cannot now really appreciate. Redesign to use cast iron or steel blocks and crankcases was perfectly feasible, as the Merlin into Meteor showed. However, changing the design mid-production might have had consequences for in-service logistics with potential parts incompatibilities. Worse, parts that looked the same but were not: different material or tolerances, for example. There were many Merlin-Meteor parts incompatibilities.

But then iron and steel foundry capacity in the US was at a premium too. When the UK requested US manufacture of aluminium-cased gearboxes and final drives for the Crusader we were told that would only be possible with a redesign to cast iron/steel.

The diesel engine story is a convoluted one. A Caterpillar adaption of the single-row Wright RD-1820 to diesel as the 450 BHP D-200 was adopted for Sherman in the M4A6 but then almost immediately cancelled with only 75 eventually built from an order for 1,500. At one point the M4A6 was touted as the new standard for Sherman and the D-200 was apparently possibly the "best" engine ever fitted to Sherman. The Guiberson 7-cylinder diesel radial used in the M3 Light Tank worked well enough but the 9-cylinder version was a complete failure with only 1 M3A1 Medium Tank converted with it and the remaining engines sentenced for scrapping. While the Guiberson engine fitted the standard M3/M4 engine bay, the D-200 needed the longer M4A4 hull to fit.

The USA, UK and Germany all faced the same diesel fuel problem: lack of it for ground forces use. The USA made a decision in the mid-1930s to adopt diesel propulsion for all military vehicles, but almost immediately rescinded it. Full dieselisation does not happen until the Vietnam war era. All 3 nations were forced to prioritise diesel fuel for maritime use. Germany could synthesise a benzine from coal, using about 7 tonnes of German brown coal (Lignite) to produce 1 tonne of benzine, about 1,300 litres. The UK was forced to adopt diesel engines in the A12 Matilda (AEC) and Valentine (GM) because of lack of suitable petrol/gasoline engines and was effectively given a forced choice to accept mixed petrol and diesel Grants, Stuarts and Shermans from the US to obtain the numbers needed. Diesel Shermans made up almost a third of all those supplied to the UK. The Soviet Union, with its own oil sources, a small navy and almost no merchant navy could afford to use diesel engines in tanks, a decision taken in 1938. But all other Soviet transport remained petrol-engined. From Lend-Lease they wanted diesel tanks (with full fuel tanks!) but petrol trucks.

In Commonwealth forces, diesel fuel remained "packaged" - i.e. supplied in cans - and was not part of the post D-Day bulk distribution system using tankers and pipelines. Despite the relatively high proportion of diesel AFVs and trucks in service.

Germany made the decision pre-WW2 to standardise on a single quality of benzine/gasoline/petrol for all uses at about 80 octane. No 100+ octane for aviation use. So while the Spitfire's Merlin engine was 27 litres the Me-109's equivalent DB engines were 34 and 36 litres for the same sort of power output. The R-R Griffon at about 37 litres was very much more powerful. Which is why we see Germany pioneering Methanol and water injection in aviation engines to boost power.

The R985C1-C4 hybrid did have one advantage... it operated at a much lower temperature due to the lower inherent compression ratio. C1s pistons with the C4 head reduced the ratio downwards.

The Ford GAA based Diesel was expected to produce 550 hp. Which is a bit of a surprise but there's only about a page worth of documentation so far found. (I wrote it up for a book). March 14th 1943 to June 28th 1943.

As to the Wright RD-1820... oof. I have most of it logged, but I have yet to start writing it. It has some faults but it was slowly working out the bugs.

 

[Kingsman]

Interesting about the later DD. As 1 was kept in the US and handover to the UK was refused (although we wanted it for free!) I had believed the US had an interest. The T6 flotation device worked well enough but was completely ungainly out of the water, only used once.

The US prototype still exists, last known at Anniston Army Depot. The UK one was apparently scrapped.

 

[EwenS]

Interesting about the later DD. As 1 was kept in the US and handover to the UK was refused (although we wanted it for free!) I had believed the US had an interest. The T6 flotation device worked well enough but was completely ungainly out of the water, only used once.

The US prototype still exists, last known at Anniston Army Depot. The UK one was apparently scrapped.

The T6 device does not appear to have been quite as successful as you suggest.

At Okinawa the US Army planned to use one company in each of 3 tank battalions with the T6 device. In the end only one was landed using the device. The after action report concluded:-
"the T6 flotation devices were not considered very satisfactory due to their small angles of approach and departure. Difficulty was experienced in crossing the reef when the front pontoon struck the reef and prevented the tracks from getting a firm footing."

12 tanks with T6 devices went ashore from 6 LSM about 500 yards out.

The USMC 6th Tank Batt seems to have deployed its 12 T6 equipped tanks without problem, including one fitted with a dozer blade. On the other hand 6 T6 equipped tanks from 1st Tank Batt were subject what can only be described as a massive cock up. Eventually launched 40 mins late and from 10 miles out instead of the departure line. 5 reached shore after 5 hours in the water. The sixth rammed a destroyer, damaging its pontoons and sinking near the shore after running out of fuel for its bilge pump.

None of these vehicles were launched as part of the initial assault waves, and with the Japanese having decided to place most of their troops inland rather than just behind the beach, the capacity of the T6 to absorb damage does not appear to have been thoroughly tested, although the US Army considered it better than a DD, particularly as it could use its main gun on the run in to the beach.

The other problem with the T6 device was the amount of space it took up. So while an LCT could carry 4 DD tanks it could only carry 2 T6 equipped Shermans. This was a problem in the first half of 1944 with asssault shipping at a premium in Europe. However by spring 1945 in the Pacific it was less of a problem. Even so an LST that would normally carry 18x30 ton tanks on its tank deck was limited to 6 Shermans with T6 devices and an LVT as a guide vehicle.

With intelligence showing that Japanese tactics to defeat an assault landing would once again change for Operation Olympic (back to trying to defeat it on the beach) both the US Army & USMC intended to make "extensive use" of the T6 device for those landings, but I've not seen anything quantifying the numbers being proposed. But then both the US Army & USMC had many battalions of the LVT(A)4 to accompany their assault waves.

LVTA4