AFV Loss Rates in US 12th. Army Group

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LWD
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Re: AFV Loss Rates in US 12th. Army Group

Post by LWD » 05 Feb 2010 18:29

Cannonade wrote:...OK,… I had absolutely no idea that the Ordnance Department procured medium tanks powered by the radial engine until the spring of 1945. It must have been out of sheer necessity ...
I beleive the rational was to standardize on as few as possible engines. To that end the Sherman was designed to be able to take an aircraft engine or at least one with many parts in common to one.

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Re: AFV Loss Rates in US 12th. Army Group

Post by RichTO90 » 05 Feb 2010 19:14

Cannonade wrote:Rich,

I finally realized why you asked about Saint Barabara. I picked my screen name sort of at random. It was the first thing that came to mind when I signed up, probably because I just finished reading a book about cannon. :)
I wondered. Of course screen names can seem random or have a reason. Very few have ever figured out mine. :lol:
I’m not much of a tank guy, especially from the technical standpoint. It just seems necessary to have a working knowledge of their development and implementation in order to better the ground war in Europe.
You're doing pretty good though.
OK,… I had absolutely no idea that the Ordnance Department procured medium tanks powered by the radial engine until the spring of 1945. It must have been out of sheer necessity since the R975 Continental engine was found to be underpowered and lacking endurance (reliability) when subjected to off-road conditions in hilly terrain so it was easy to avoid a conflict with the Army Air Force by looking for other, more suitable power plants. By comparison the GAA Ford had more power, and after some minor adjustments to the design, better reliability than the radial. (The GAA had 450 horsepower. Apparently later versions had 500.) The GAA was also viewed more favorably by tank crews as a result of its higher horsepower and torque. The authors of The Ordnance Department: Planning Munitions for War, conclude; “Had production capacity been great enough, the Ford engine would unquestionably have been adopted as the one and only power plant for American medium tanks.” With diesel powered tanks banned by the army for use overseas, and the Chrysler powered tanks were used for lend-lease, I guess the R975 radial was all that was left when Ford was unable to produce enough GAAs.

Cannonade
It's a bit more complex than that and reliability was never the primary issue. The Army had been happily using Continental radials in their tanks since 1933 and had always accepted the maintenance and reliability issues. Realistically, power and torque were only moderately different. The GAA was rated at 500 gross HP at 2,600 RPM and produced 1,040 foot-lbs of torque at 2,200 RPM from 1,560 pounds. The Continental at 400 gross HP at 2,400 RPM and 890 foot-lbs at 1,800 RPM from 1,137 pounds. So 86% of the torque with 82% of the RPM, not a bad trade. And the Continental turned out 1 HP per 2.8 pounds compared to the 1 HP to 3.12 pounds for the GAA.

The number of engines required for the aircraft program was enormous. Eventually, over a half-million radials of various types were produced for them. Since the aircraft program was given higher priority early on than the tank program (largely due to political decisions by Roosevelt), although the tank program was also projected to grow enormously (to a projected capacity of 4,000 medium tanks per month) the decision was made to make up the slack in the tank program.

The first substitute standard approved for medium tanks was the GM 6046 diesel in December 1941. The second was the Chrysler A-57 "Multi-bank" approved a few days later, and the third was the Ford GAA in January 1942. The fourth was the Caterpillar G-200 diesel produced as the Ordnance Engine RD-1820 in May 1943.

Diesels were not actually "banned" for Army use overseas, but since they were considered substitute standard they were only to be issued when standard vehicles (M4, M4A1, and M4A3) were unavailable. In the event, the medium tank shortage in the ETO (more on that probably in my next book) became so severe following the Battle of the Bulge, that small numbers (about 200 off the top of my head) of M4A2 and M4A4 were "reverse Lend-Leased" (i.e. borrowed) from the British to help make up shortfalls.

Postwar the Army decided to standardize completely on the M4A3 since, postwar, they could have the luxury of acting to eliminate the reliability and maintenance issues associated with the radial. Plus of course by that time they were well aware that the radials had reached their limit in terms of tank applications and would be unsuitable for the heavier tanks projected for the future and were dumping all their development funds (what little they had postwar) into the Continental V-12 air-cooled series of engines. At that point most M4 and M4A1 that were still in Army inventory were used as MAP to various countries, which is how Yugoslavia got the M4A1 used in "Kelly's Heroes".

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Re: AFV Loss Rates in US 12th. Army Group

Post by binder001 » 05 Feb 2010 20:11

Trivia on your last line - the Shermans in the movie "Kelly's Heroes" were M4A3E4s, not M4A1s. These were M4A3 75mm Wet Stowage that were overhauled and upgraded by Bowen-McLaughlin-York (and I beieve some at Red River Army Depot). One of the features was the upgunning to a 76mm M1A1 gun. M4A3E4s went to Yugoslavia (where Kelly's Heroes was filmed), Denmark and a couple others under MAP. There were also M4A1E4s that were received by Pakistan among others.

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Re: AFV Loss Rates in US 12th. Army Group

Post by Cannonade » 05 Feb 2010 21:11

Rich,

Thanks for the encouraging words, but I’m pretty sure I am in over my head.

I am going by The Ordnance Department: Planning Munitions for War. The authors say the GAA had 450 net horsepower compared to the 400 horsepower of the Continental radial. Perhaps subsequent versions of the GAA had 500 horsepower?

According to the same source, the reliability problem with the Continental radial became apparent when the engines were used in the M4 medium tank in off-road conditions in hilly terrain. “Endurance of the Continental was unsatisfactory, particularly under full-load operation over hilly terrain. Overspeeding the engine to brake the vehicle while descending hills was responsible for four out of five major breakdowns.” This information appears to be the result of the first large-scale test of the various tank engines used in the M4 medium tank.

Regarding diesel powered tanks, the same source says; “The General Motors diesel was out of the picture for two reasons: first, because of the ban on the use of diesels overseas, and, second because the endurance qualities were unpredictable and its reliability the lowest of all engines tested.” Earlier in the text, there is a reference to a War Department directive to the same effect. “For tanks, development of gasoline engines should be pushed in order to supplant all diesel powered tanks as quickly as possible. The latter were not to be shipped overseas but held for service in the United States and for training.”

As for the use of diesel powered tanks by US forces in the ETO, it would appear the ban was lifted or ignored, officially or unofficially, in the interest of obtaining urgently needed replacement tanks to help alleviate the shortage you mention.

Obviously, I am limited by my reliance on a single source, but the relevant footnotes and citations appear to support the authors’ statements.

Cannonade

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Re: AFV Loss Rates in US 12th. Army Group

Post by RichTO90 » 05 Feb 2010 21:40

Cannonade wrote:Rich,

Thanks for the encouraging words, but I’m pretty sure I am in over my head.

I am going by The Ordnance Department: Planning Munitions for War. The authors say the GAA had 450 net horsepower compared to the 400 horsepower of the Continental radial. Perhaps subsequent versions of the GAA had 500 horsepower?
Always a tricky measure and horsepower does appear differently according to the RPM it was measured at and whether it was gross or net horsepower. I'm using the figures given in the Ordnance Catalog, which are all gross and at a given RPM.
According to the same source, the reliability problem with the Continental radial became apparent when the engines were used in the M4 medium tank in off-road conditions in hilly terrain. “Endurance of the Continental was unsatisfactory, particularly under full-load operation over hilly terrain. Overspeeding the engine to brake the vehicle while descending hills was responsible for four out of five major breakdowns.” This information appears to be the result of the first large-scale test of the various tank engines used in the M4 medium tank.
Quite true, but that was the confirmation that the utility of the radials had reached their maximum, which is why no further attempt was made to develop them as tank engines. But it wasn't until the tests were done in 1942 that it was confirmed and it had no effect that, real world, the US Army initially went to war in M4 and M4A1 (all early production M4A3 dry stowage went to Lend-Lease, while improved M4A3 didn't start coming off the lines until January 1944 and didn't get into the hands of troops until late August. Sometimes you just gotta run with what you brung. :wink:

In any case it doesn't bear on issues and decisions made 1940-1942, which were meant to insure that the tens of thousands of tanks that were intended to be produced had engines of some sort.
Regarding diesel powered tanks, the same source says; “The General Motors diesel was out of the picture for two reasons: first, because of the ban on the use of diesels overseas, and, second because the endurance qualities were unpredictable and its reliability the lowest of all engines tested.” Earlier in the text, there is a reference to a War Department directive to the same effect. “For tanks, development of gasoline engines should be pushed in order to supplant all diesel powered tanks as quickly as possible. The latter were not to be shipped overseas but held for service in the United States and for training.”
Sure...of course we had no problem foisting these upon our Allies though. :lol: And oddly enough they had no problems with the reliability of the diesels - the Soviets positively loved theirs. Nor, oddly enough, did the USMC have any issue withthem. Even more oddly, by most accounts I have seen the Brits actually liked the Chrysler Multibank Monstrosity! 8O
As for the use of diesel powered tanks by US forces in the ETO, it would appear the ban was lifted or ignored, officially or unofficially, in the interest of obtaining urgently needed replacement tanks to help alleviate the shortage you mention.
Again, not precisely a ban, more the way the replacement system simply worked..."standard" was always king.
Obviously, I am limited by my reliance on a single source, but the relevant footnotes and citations appear to support the authors’ statements.

Cannonade
No problem, I think the only difference is we are arguing semantics now and which came first...

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Re: AFV Loss Rates in US 12th. Army Group

Post by ChristopherPerrien » 05 Feb 2010 23:41

Tanks are "hot-rods", their variations in horse-power, are dependant on a variety of factors. Most of them being crew/driver quality ,extent of use, maintenance team quality,and the availibility of new/replacement/better parts and those being installed on a particular tank. Sometimes, simply where or when they were built affected perfomance. I would estimate that any particular model tank hp( of any army, at any time) could easily vary on the the order of 25% to spec based on these factors. I've seen tanks perform better than their listed specs and I've seen same identical/model engined tanks perform much worse.

Chris

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Re: AFV Loss Rates in US 12th. Army Group

Post by Cannonade » 06 Feb 2010 03:52

Rich,

I agree that it is come down to an issue of semantics. Although I will stick with the wording of the War Department memo as an indicator of the developmental history of the M4 medium tank we can agree that when push came to shove the US army went to war with what they had.

Thanks for the additional information and insights. :D

Cannonade

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Re: AFV Loss Rates in US 12th. Army Group

Post by masqqqq » 06 Apr 2010 21:30

What was the average strength compared to autorized strength US tanks. How many was ready to action, in short repair or long-term repair. Anybody has sauch statistics month after month?

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Re: AFV Loss Rates in US 12th. Army Group

Post by Carl Schwamberger » 07 Apr 2010 01:59

masqqqq wrote:What was the average strength compared to autorized strength US tanks. How many was ready to action, in short repair or long-term repair. Anybody has sauch statistics month after month?
I dont have the refernce. My impression is it was very high. While specific battalions had surges of losses over several days the overall available rate was usually over 85%. Between the reliability of the machines, and the robust well trained repair companies damaged & broken tanks did not sit for very long.

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