Comparison of tanks on boggy ground.

On 9th December 1944 a series of trials were carried out to compare the abilities of a range of current tanks. They were carried out on Chobham Common at Albany Bottom, where there was a small defile consisting of 100 yards of a churned up mixture of waterlogged loam, sand and clay.

Test 1 was to drive the length of the defile. The six tanks were: a Sherman I with steel chevron tracks and weighed 28tons 12cwt, a Sherman II with steel chevron tracks and single extended end connectors (EEC) and weighed 29tons 6cwt, a Panther weighing 44tons 10cwt, a Tiger weighing 56tons 10cwt, a Churchill IV with manganese tracks weighing 38tons and a Comet weighing 32tons 14cwt. Except for the Churchill and Comet the tanks made their runs in first gear.

The Sherman I negotiated 50 yards before failing with track slip, but was able to reverse out.
The Sherman II was successful but with considerable track slip. The driver commented on the extra difficulty in steering.
The Panther was successful but suffered some slipping when bulldozing.
The Tiger became bogged nose down after 30 yards and had to be recovered.
The Churchill very confidently negotiated the majority of the course in second gear, changing down to first at the end. Track slip could not be detected visually at any time during the run, which was most impressive.
The Comet negotiated the course, then became bogged at the end owing to an inability to steer out of the ruts. Prior to this, track slip was not pronounced.

Test 2 was carried out on the same site; the defile was now a small valley, this test was a transverse crossing and to carry on climbing the far hillside. The same tanks took part along with a T14 weighing 43tons 10cwt, and a T34 weighing 27ton 17cwt.

Both Shermans failed by track slip in identical conditions, that is at the climb out on the far bank, but both were able to reverse out up the equally steep near bank. The T14 failed in a similar position to the Shermans and was also able to reverse out.
The T34 also failed but was slightly better than the previous tanks.
The Churchill succeeded and climbed the hill opposite at an angle.
The Panther succeeded and climbed the hill in the ruts made by the Churchill.
The Tiger failed by slippage on the far bank but reversed out successfully.
The Comet failed by slippage on the far bank in the ruts made by the Panther.

Afterwards both Shermans made a second attempt and succeeded.

Test 3 was carried out on a hillside consisting of 2-6 inches of sandy soil with organic matter but no vegetation on a firm clay underlay changing to compacted sand at the top of the hill. The slope increased from zero at the base to a maximum of 24° near the top. The moisture content was high, causing unwary walkers to slip. Each tank was required to make a straight climb in first gear taking a separate course from the others. A tank was deemed to have failed as soon as track slip was so great that it was stationary. If a tank slid sideways a second attempt was allowed. This trial included a Lynx, weighing 12tons 2½cwt.

The Sherman I failed at 15° with a lack of adhesion.
The Sherman II failed at 16° with a lack of adhesion; the EEC had little effect.
The Comet's first attempt was a failure at 16° with lack of adhesion and sideways slippage; the second attempt was the same but at 14°.
The Lynx failed at 18-19° with lack of adhesion and sideways slippage.
The T14's first attempt was a failure at 13½° with lack of adhesion and sideways slippage; the second attempt was the same but at 14½°.
The Churchill's first attempt was a success with very slight track slip and some sideways slippage; the second was also a success and by the use of some steering, slippage was avoided.
The Panther failed at 22° with a lack of adhesion.
The Tiger failed at 12° slipping sideways badly, and steering could not correct this.

Trial Series 2, 15th December 1944.
The same undulating defile as the previous trial; the churned surface was now 24" deep.

To repeat earlier trials when some vehicles failed, then later succeeded when following in the wake of a successful vehicle.

The Sherman I first attempt failed due to track slip and an inability to bulldoze; the second was successful but with much track slip.
The Sherman II (with EEC) failed due to track slip and an inability to bulldoze on both attempts.
The Churchill VII was successful with no indication of difficulty or track slippage on both attempts.
The Sherman II made a third attempt but failed as before.
A Cromwell with 15" tracks weighing 28 tons made a single attempt and negotiated most of the course but failed at the end on trying to climb out.

The assessment was that the EEC track made the Sherman's performance worse, and that the Churchill was outstandingly superior as on the previous similar trials.

A further test was carried out traversing the defile as in Test 2 of Trial 1; the results were identical to that test.

A long series of tests were carried out on the same piece of terrain to compare the T54 tracks with Extended Edge Connectors and the Skinner Platypus Tracks. Although it showed each type had its advantages, these slight differences in the performance were amplified by the very good abilities of one of the drivers.

The Platypus type track on the Sherman is [considered to be] worth further development but not adoption at present. Although not directly relevant to Trial series 3, the known performance of the Churchill with light tracks, over the same courses, is incomparably better than the Sherman with either of these tracks.

In the Report's summary the vehicles were placed in the following order:

1 Churchill: The only vehicle which did not fail or even exhibit appreciable track slip.
2 Panther: Almost, but not quite, as good as Churchill.
3 Cromwell (with 15½" tracks): Good performance very largely influenced by skill in making the most of its power and speed.
4a Sherman with dry pin Platypus box type tracks.
4b Sherman with T54E1 track and Extended End Connectors.
4c Sherman with T54E1 steel chevron tracks.
All these types can be very easily bogged by comparison with the Churchill and Panther.
5 Tiger: Very poor, assuming the vehicle tested was representative of its type.

The report is signed by Lt-Col E Ward REME, and Brigadier WF Morrogh, Commandant FVPE.

Source: TNA WO 194/845

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