From the Vault: British Report on the US M46 Medium Tank

Today we have something sent to us by British researcher and author P.K. Knight.  Knowing of our interest in anything having to do with US tanks powered by Continental Motors engines, he forwarded us a copy of a British F.V.R.D.E. (Fight Vehicles Research and Development Establishment) report examining a US M46 medium tank.  This is a fairly short report and mainly focuses on automotive performance.  The most interesting thing revealed by this report is just how much difference there is between the stated gross horsepower of the engine, the actual power output taking into account power lost to engine cooling and accessories and then the actual power at the sprocket.  The M46 was the first US tank equipped with a Continental 12 cylinder 1790 cubic inch aircooled engine and the Allison CD-850 transmission.  The report states that while the listed gross HP of the engine is 810, their bench tests show an actual power output of 646 HP, which they attribute to losses from air cleaners, cooling fans and the exhaust system.  The power at the sprocket is measured at 433 HP.  So what does this all mean?  Not much, other than always take those gross horsepower numbers listed in books with a grain of salt, they don’t always tell you all that much about how much power is actually being transmitted to the drive sprocket.

Report below.

From the Vault: Panther Shot to Pieces

dsc02279_exposureThis British Armour Branch report was recently linked to over at the Tanknet forum. We thought it was worth posting here. The document is from 1945 and details British comprehensive firing trials against a German Pz V Panther tank.  A variety of weapons were tested against the Panther, including small arms, mines, the PIAT, and the common tank and anti-tank guns in service with the UK at that time (6pdr, 75mm, 17pdr, 25pdr.)  The results are not particularly surprising, but may be of value for those looking for specific information about vulnerabilities of the Panther.

We have transcribed the conclusions of the report below:

  1. The vehicle is virtually immune to small arms fire from ground level.
  2. Small arms attack directed downward at about 30 degrees into the inlet louvres of the engine compartment causes severe damage to radiators.
  3. Even more severe damage to the radiators may result from 20mm attack from the air from from fragments of HE shell bursting in the air above the vehicle or against the turret above the engine compartment roof.
  4. Projectiles of calibre 6 pdr and upwards, whether AP or HE, which strike below the horizontal centre line of the gun mantlet, are likely to penetrate or blow in the roof of the driving compartment and may jam the turret traverse.
  5. Penetration through the sides of the vehicle will very probably cause cordite or petrol fires.
  6. The rolled armour proved brittle and flaky.
  7. The use of interlocked joints provides a structure which has considerable stability even when the main welds are fractured.
  8. The brittle nature of the roof plates makes these vulnerable to attack from HE grenades or shell which burst in contact with or within a few inches of the plate.
  9. Frontal attack with PIAT is unprofitable, flank attack against pannier (or turret) sides is effective.
  10. Mine with explosive charges between 4 and 15 lbs are likely to break the track if detonated at the centre of its width, but may not do so if detonated by its edge.  Detonations under any part of the track are unlikely to affect the floor plates or their joints with the hull side.
  11. It is probable that a combination of three No.75 grenade mines will have an effect on the track similar to that produced by a single Mk.V H.C. (standard) A.T. mine.  Either will break the track when detonated below the middle third of the track.

Further discussion of the above conclusion will be found in the various parts of this report.

The Trial has confirmed in general the assessment of vulnerability given in D.T.D. Report No. M.6815A/3 No.1, differences between certain predicted vulnerable ranges and actual results being due to the brittle nature of the armour.  Though evidence is available that many other Panther tanks damaged in battle have had armour which has shown similar defects, it should not be assumed that this form of weakness will always exist.

The design of the vehicle is such that its structural stability is considerable, the effective use of interlocking joints being chiefly responsible.

The Panther tank, judged on the results of this trail alone, remains a most formidable weapon with few weaknesses; and its value if used with adequate flank protection should not be underrated.

The full report can be viewed in this photo gallery.

From the Vault: The Japanese 10 ZF engine

A couple weeks ago we presented a description of the Orion engine prototype taken from the 1975 book Some Unusual Engines by LJK Seltright. Today we present another tank engine mentioned in that book, the Japanese 10 ZF V-10 air-cooled two-stroke diesel.  This is the engine that powers the Japanese Type 74 MBT, producing 750 HP.  Compared to western armored vehicles, not much has been published regarding the Japanese Type 74.  This is the first detailed description we have found of this particular engine so we thought it was worth sharing.

10-zf-engine-image10-zf-engine-text

From the Vault: Investigation of the Factors Involved in Steering Tracklaying Vehicles

A couple weeks ago we came into the possession of a 1970 report on factors involved in steering tracklaying vehicles conducted by the Allison division of General Motors for TACOM.  This report will probably be of limited interest to most people, but perhaps a few people will find it worth looking at.  As far as we can tell, this report has not been posted anywhere else.

Download the report at archive.org.

steering-report

From the Vault: CIA Report on The Tank and Assault Gun Industry of the USSR

From the CIA reading room website comes this 1953 report on the Tank and Assault Gun Industry of the USSR.  This is a pretty substantial report, coming at in over 60 pages.  Given the age and nature of this CIA report, obviously not everything found in its pages will be accurate.  However, it is a rather interesting in piece in that it shows what exactly the US thought it knew about Soviet AFVs and AFV production at the time.  There are quite a few tables in this report, with production numbers as well as charts showing the amounts of different types of metals used in Soviet tank production.  Below is an example of this sort of chart.  The report can be downloaded in PDF format here.

metallic-imputs

From the Vault: The Orion Engine

We recently were given a copy of the 1975 book Some Unusual Engines by LJK Seltright.   This is a long out of print and somewhat hard to find book, with used copies going for $125.00 or more on Amazon.  Several tank engines are featured in this book, including the well known A57 Chrysler Multibank and the Mitsubishi 10 ZF ten cylinder engine.  One tank engine mentioned in the book that we were not familiar with at all was the Orion engine designed by General Motors.  This unusual engine never made it past the prototype stage.  Like the Soviet 5TD of the T-64 and the British Leyland L-60 of the Chieftain tank, the Orion utilized an opposed piston, two stroke design.  However, it was a much more unusual design than either of those two engines.  Rather than having the cylinders arraigned in a row, the Orion engine features six cylinders in two rows of three each on top of each other.  Even more unusual was that engine was combined with a turbine and the turbine actually generated the shaft power.  Below is the description from the book as well as an illustration:

orion-engine-descriptionorion-picture

We did our best to find out any other information on this rather interesting engine.  The only thing we found was a brief description in the document Engine Transmission Power Packs for Tactical Vehicles 1967. Interestingly, this report gives more detail on the Orion project, as well as the name “Rigel” for the 600HP version of the engine intended for tanks. This document also gives a date for the project, noting that the program was cancelled in 1955. Oddly, it credits the engine concept to General Electric, rather than General Motors. Below are the pages from the report pertaining to the Orion program. Unfortunately, the PDF these images came from is not of very high image quality.

orion-engine-report-descriptionorion-project-image-1orion-project-image-2

From the Vault: Trunnions on the Move

Today we present an article from the January-February 1986 issue of ARMOR magazine titled “Trunnions on the Move” by Robin Fletcher.  Although thirty years old, this article is still relevant for those with an interest in tank layout design, particularly issues involved in turret design.  With the end of the Cold War, much of the impetus to produce new MBTs using some of the alternative turret ideas explored in this article was lost.   However, the introduction of the new Russian Armata will no doubt reignite interest in some of these turret and gun mounting concepts.  We have posted the pages of the article in a photo gallery below, or the entire issue can be downloaded as a PDF here.