1942 Nov - War Diary :

591 (ANTRIM) ARMY FIELD COY R.E.
APPENDIX 2.


54 DIV, ASSAULT DEMONSTRATION.
13 Nov 42
R.E. ASPECT



GENERAL.
1.
The site of the demonstration was low-lying and marshy and a considerable amout of R.E. work was necessary before hand to ensure that Tanks did not get bogged on the day of the Demonstration. Various methods and equipment were used for corduroy roads [roads made of tree trunks] but over the most marshy ground the following was found to be most satisfactory.
(a) A Layer of brushwood (fir tops) fascines [bundles of logs] of approx 8 inches diameter x 6 feet long laid to overlap in the middle of the roadway and form a clear 10 foot roadway.

(b) A layer of chestnut paling. In this case two 5 feet wide coil were used.

(c) A layer of 10 feet x 4 inch diameter forestry poles laid touching as for decking of a bridge.

(d) A layer of chestnut paling as in (b)

2. This roadway successfully took 24 Tanks (in rehearsal and demonstration) over ground where one Tank (the first to attempt it) had previously been bogged for 4 hours and had broken a track in getting out. The roadway was perfectly serviceable at the conclusion of the Demonstration, and the factor of safety may have been high, but the fate of one tank had shown the ground to be more treacherous than had been thought, and it was essential that there should be no fiasco on the day of the Demonstration. Approx 400 yards of this type of roadway was laid. In some cases the initial layer of fascines was omitted and in others the design was modified to suit being spaced out to 2 feet 6 inches.

3. Crossings on the paths of the Tanks over a small drainage ditch approx 4 feet wide by 2 feet deep with a minimum of 2 feet of mud bottom were made by completely filling the ditch with 10 feet forestry poles.

4. Other R.E. work of a general nature prior to the Demonstration consisted in,
(a) Tubular scaffolding stands for spectators, Six stands each for 120 spectators. These were roofed with tarpaulins.

(b) Tubular scaffolding Control Tower 20 feet high with lower platform 13 feet high for 50 spectators.

(c)Tubular scaffolding O.P. for R.A.

(d) Clearing of trees for field of view.

(e) Laying of minefields

(f) Making large letters and numbers for reference in pointing out tactical features.


Description  of Obstacles.
5.
The obstacles to be crossed consisted of.
(a)Wire fence "Double Apron" triple Dannert Double Apron. This was cut by infantry and is not considered in this report.

(b) 1st minefield 60 yards deep of Mk II British Mines (unarmed). One mine per yard of front.

(c) Artificial Anti-Tank Ditch of cross section as at "Sketch A." [see below]


(d) Wire fence as in (a)

(e)2nd minefield 100 yards deep of British Mk IV mines, armed and not fitted with sorbo rings. One mine per yard of front.

Crossing  1st Minefield (Para 5(b))
6.
This was cleared under cover of darkness. (actually by day with dark glasses) in two ways.
(a) With mine detectors (Polish No.2 with long handled search coil)
(b) With probes

7. No particular points of interest came out from this part of the Demonstration. The detector parties consisted of 2 R.E. and 4 Infantry working in two parties of three each. The Sapper using the Detector led each party and the two Infantry following up lifted mines and taped the sides of the cleared lane. The two parties worked in echelon; one about 8 yds behind the other, and cleared a lane 18 feet wide by 60 yds long in approx 14 mins.

8. The probing parties consisted of one R.E. and 7 Infantry, and worked in two parties in echelon; three men probing and one man lifting and taping. In practice they did not progress as fast as the Detector parties; taking approx 17 mins.

Crossing  Artificial Anti-Tank Ditch.
9. Crossings were made for Tanks in the following ways.
(a) By hand ramping with shovels.

(b) By the use of an explosive charge to assist hand ramping.

(c) By the use of a Tank Fascine.

(d) By the use of a Scissors Bridge (not further considered in this report).

Hand  Ramping.
10.
This was carried out by R.E. The strength of the party being 1 NCO and 11 Other Ranks. Practices were carried out before the demonstration on a V ditch 18 feet wide by 9 feet deep. The soil was light sandy soil with twisted roots of heather and other shrubs at original ground level. The excavated spoil was 2 feet above ground level.

11. A ramp was made across this V ditch, by intensive digging, in 13 mins which was passable by Tanks (Valentine). It was found essential to have fascines available in large numbers. These were made up from fir tops and were 6 feet long by about 8 inches diameter so as to be a one man load. It was essential to 'carpet' completely the ramp up out of the ditch on the enemy side with fascines. The number of fascines used, including six held by a maintainance party as the Tanks crossed, was 32.
Contrary to previous experience it was found that a small amount of work on the home side was well worth while. This prevented the Tank descending at too steep an angle of the ditch. Shovels G.S. with blades bent at right-angles were tried but were not a reliable and quick method of breaching a ditch.

Explosive  Charge to Assist Hand Ramping.
12. Experiments which were carried out before the Demonstration showed very clearly that it is essential to carry out preliminary trials in the same type of ground as the obstacle in order to arrive at the optimum size of charge.

13. In this case advice obtained from the War Office of details to be included in the next issue of F.E.P.10. from S.M.E. and from A.T.E.E. all suggested a charge in the nature of 300 lbs placed on the sloping surface of the ditch approx 2 feet down from original ground level. Trials showed however that this charge was far too large for the type of soil met. Trials as follows were carried out.

1st Trial
105 lbs Ammonal (Five 21 lb tins) were placed 2 feet 6 inches down from original ground level 2 feet 6 inches in from the face of the ditch. This produced a crater 22 feet across, 9 feet deep which was a tank obstacle in itself and no attempt was made to ramp it down.

2nd Trial
9 feet length of 3 inch stove pipe filled with 50 lbs of ammonal placed on a ledge 2 feet 6 inches from original ground level.
Result:- This charge gave the desired type of crater but it failed to blow the heather roots at ground level and so left an overhanging lip to the crater. With the charge dug into the bank 2 feet 6 inches a similar result was obtained but the sides of the crater were still rather steep.

3rd Trial
A 30 lb charge of ammonal was placed on ground level (original) five feet back from the edge of the ditch. An ideal type of crater was blown but owing to the charge being too far from the ditch a slight lip was left between the crater and ditch.

4th Trial
30 lbs on ammonal fastened in a 6 feet board was laid on original ground level 2 feet back from the edge of the ditch. This blew the 'corner' off the ditch and produced a ramp of almost exactly the required slope. It was however not quite wide enough and the final design was fixed at 15 lbs. Of ammonal on each of two 4 ft boards. These were laid 2 feet back from the edge of the ditch at ground level and 1 foot apart (see Sketch A) Similar charges were placed on each side of the ditch and with the addition of fascines and a minimum of ramping an easy passage was prepared for tanks.


Sketch A



14.
In general the use of explosives was again shown to be somewhat incalculable without previous trial. It should be noted that while the explosive can be laid quietly by night, it can only be detonated after 'zero' and there is still some hand work to be done on the crossing before it can be used by tanks.

Tank  Fascine
15.
The tank fascine was made up of a number of 10 feet by approx 4 inch diameter forestry poles. It was mounted on a tubular scaffolding framework on the front of the tank (Valentine) and was jettisoned from within the tank into the ditch. The tank then 'walked' across the ditch using the fascine as a stepping stone.

16. Details of construction are shown in Sketch B [CLICK to open large graphic]. The method of construction and operation is as follows:-

(a) The tubular scaffolding framework is made on the ground and lifted on to the tank.

(b) The lower ends of the outside uprights are supported on loose fitting pins fastened to the towing shackles on the front of the tank.

(c) The upper ends of the outside uprights are fastened back to the turret by means of a 2 inch lashing. In the case of the Valentine this was passed through the revolver parts and was packed out with sand bags to prevent fraying on sharp edges. The turret must be locked with the 2-pr gun facing a flank.

(d)The fascine is made up of a number of bundles of four poles wired together and of single poles. The bundles of four are a convenient size for lifting on to the frame work and the single poles are used to pack in where bundles of four will not fit. These bundles and single poles are loaded on to the frame work, as many will conveniently fit between the uprights of the frame work and the turret. It will be found that this quality produces an irregular shaped bundle approx 4 feet or 5 feet in diameter. The weight should be kept as far forward as possible by leaning the uprights slightly forward.

(e)The bundle of fascine is then lashed in two places with a single 2 inch lashing as tight as possible.

(f)The tank can now travel with the fascine in position. The cross country performance is very little, if at all, impaired. The driver's view is not hampered since the bottom of the fascine is above vision slit. The tank commander can not see out forwards from the turret owing to the height of the fascine.

(g) When the ditch is reached the Driver approaches as near the edge as possible and stops momentarily. The tank commander then releases the fascine by cutting the lashing. The frame work pivots about the towing shackles and the fascine rolls down the frame work into the ditch/ It is appreciated that the method of releasing the fascine is primative and no doubt a special quick release fastening could be developed. Cutting the lashing is however effective and simple in the field.

(h) If there is any tendancy for the fascines not to roll off the tank (owing possibly to the nose of the tank facing up hill) this can be set right by a quick jerk backwards by the tank.

(i) When the fascine has rolled into the ditch the tank draws back about a foot in order to draw the loose-fitting pins out of the lower ends of the frame work. These pins (about 8 inches long) are then the only attachment to the tank.

(j) The tank then drives forward across the ditch, riding over the fascine.

(k) It is important that tanks following the fascine-laying tank should cross the fascine centrally since with poles only 10 feet long there is little margine of error.


A IWM photo taken at Dunwich on 14 April 43 of a churchill asault vehicle R.E.
using fascines to cross a ditch. Dunwich is where Kruschen Demonstration took place.

17. The following points should be noted:-
(a) It is not of great importance that the poles should be straight e.g. young fir trees. The irregularities of slightly crooked poles help to make the fascine large without increasing the weight.

(b) The tubular scaffolding frame work must be rigidly jointed.

(c) The frame-work crushes under the weight of the tank and does not hinder the passage of the tank over the fascine.

(d) It is not necessary to lash the fascine with any more than a single 2 inch lashing. In some cases the lashing will break under the load of the tank but this is rather to be desired than otherwise as it allows the fascine to conform to the slope of the Ditch.

(e) If the poles are prepared in bundles of four beforehand the fascine can be loaded and made fast in 1/2 an hour with a party of 12 men.


2nd  Wire Obstacle (Para 5 (c))
18.
This obstacle was approx 28 feet wide. Gaps in it were made with Standard Ordnance pattern Bangalore Torpedoes 2 inch Sectional (A.C.I. 2202/42). Six 5 feet lengths were used giving a length of 30 feet. This produced a gap 30 feet wide.

.

19. It is considered that these Ordnance pattern torpedoes are an excellent store for dealing with obstacles of this type. As carried by Pioneer Platoons of Infantry Battalions they provide a ready made store which is easy to transport and quick to lay.

2nd  Minefield
20. This minefield was dealt with by Snakes constructed and operated in accordance with W.O. letter 57/Engrs/3658 (W.V.1) dated 5 Oct 42. The following points are recorded:-

(a) The water pipe used should be new pipe. In one case on a rehearsal the pipe which had been supplied was old pipe which had been laid underground. Failure resulted in the middle of the Snake, through the thread of one pipe stripping, the Snake breaking in two.

(b) A quick way of filling these sections of the Snake which have to be filled with sand is to wrap the sand in paper cartridges similar to P.B.G. cartridges.

(c) It was found that one 400 foot Snake complete could be prepared in 5 hours by 1 NCO and 5 men.

(d) On the Demonstration one Snake fouled a tree stump with it's nose while pushing. To avoid this it is considered that the nose should be slightly larger. It must not be too large or it will not force it's way through low banks. It is suggested that the nose be formed round a 4 inch coupler, not a 3 inch coupler as at present.

(e) The 'Pushing' chain as supplied by the War Office in accordance with Drawing T.D. 6663 worked very well. The R.A.C. welded a tack pin to this chain to act as the bar across the floor of the tank. The only possible objection to this is that it may catch in obstructions in the ground.

(f) It is not considered that a shackle and towing collar are necessary on the nose. The arrangement for pulling as shown on Drawing T.D. 6663 worked well.

(g) Failure by buckling occured in one case in the empty length of pipe at the tail of one snake. This occured when the nose had become jammed. To avoid this it is considered that the pipe used should always be thick walled or heavy-weight. Alternatively there appears to be no reason why the last length of pipe should not also be filled with sand to give added strength.

(h) Failure occured in one towing chain by a link breaking. This link was one of the original links which had been opened out to take a toggle pin and then re-made. It is essential that any links so altered should be re-forged as strong as the remainder of the chain.

(i) The towing chain is made fast by passing one end through a ring, as in Drawing T.D. 6663, will normally slide down the Snake when pushing begins, This is an additional reason for not having a collar and shackle which retain the chain near the nose of the snake, and increase the friction when pushing.

(j) The rear 40 feet of the Snake should be white so that the Tank Driver can see where the explosive filled part of the Snake begins. The rubber hose covering the electric loads should also be painted white so that it can easily be picked up.

(K) The Dynamo Exploder Mk VII was found to be an entirely suitable method of detonating the Snake.


21. In the demonstration three Snakes were used to clear three lanes through the minefield. These were towed across the Anti-Tank ditch before reaching the minefield. It is believed that this is the first time on which Snakes have been towed across an Anti-Tank ditch. It was found by experiment that there was no difficulty in towing across a ditch provided that a chain 36 feet long was used. This length of chain also worked satisfactorily when towing across country, although there are certain advantages in using the 15 feet length recommended in W.O. Letter, since in this latter case the nose of the Snake is kept well off the ground. It might be possible to devise some method of paying-out chain from the tank when coming to a ditch. It is however considered that this is an unnecessary complication and that it will be better to use either the 15 feet length or the 36 feet length having decided beforehand from reconnaisance whether or not a ditch has to be crossed.

22. During a practice a Snake was pushed across the Anti-tank Ditch without difficulty. It may be of use to know that this can be done with the Snake if a minefield is suspected immediately on the far side of an anti-tank ditch.

23. The pathway cleared through the minefield by the Snakes was not as wide as is suggested in the W.O. letter of 5 Oct 42. The ground was very light loam and the Snake may have dug itself in somewhat before being detonated. Mines up to 54 feet on one side of the Snake were detonated, but in two cases the clear pathway was only 30 feet wide, and in the third case it was 48 feet wide. It will clearly be advisable in operations for all tanks to keep rigidly to the blast mark of the Snake since it is thought that varying types of soil will cause the clear path to vary in width.

19 Nov 42
(Sgd). P.A.WOOD Major R.E.
Commanding 591 (Antrim) Field Coy R.E.



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