Reports: Sinkage and Angular Movement of Track Links of A.F.V.s

Discussion in 'Weapons, Technology & Equipment' started by dbf, Jan 6, 2012.

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    TNA Catalogue Reference: DSIR 27/65

    Department of Scientific and Industrial Research: Road Research Laboratory Reports, Reports to Ministry of Supply

    Scope and content: MOS 465 - 478

    Covering dates: 1945 Aug - 1945 Dec

    N.B. There are 3 separate Summaries (or conclusions) on this thread

    Courtesy of Drew
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    Note No. MOS/466/WAL.
    August, 1945.


    Road Research Laboratory




    by W.A. LEWIS
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    Records have been made of the sinkage and angular movement of track links of A.F.V. on soft ground at vehicle speeds of the order of 2 m.p.h. The vehicles tested were "PANTHER", "CHURCHILL", "SHERMAN" and "CROMWELL", some of which in addition to being tested with standard tracks were also fitted with links of special design.

    Comparative measurements showed that the records which were obtained by the method previously described (Note No. MOS/443/WAL.PdeV.) could be measured accurately to within +/- 0.15 in. and +/- 30/4. The sinkages measured by the Road Research Laboratory differed from the F.V.P.E. measurements which were made on the hull of the tank because the "nose-up" couple compresses the springs and may reduce the belly clearance of the tank by as much as 2 in.

    The measurements obtained enabled the various tracks to be compared as regards sinkage and track link movement and the following general conclusions were drawn:-

    (1) Lengthening the pitch of "CROMWELL" tracks reduces sinkage.

    (2) Increasing the spud depth increases sinkage of the short pitch "CROMWELL" tracks but has little effect on the long pitch tracks.

    (3) All the methods of widening tracks by means of platypus extenders or extended end connectors reduce sinkage.

    (4) Decreasing the wheel spacing or reducing spud depth for "CROMWELL" short pitch tracks decreases the range of angular movement of the link.

    (5) A decrease in sinkage of a particular set of tracks is accompanied by a decrease in link oscillation.

    (6) At low speeds, an increase in tank speed reduces sinkage.

    (7) Variations in soil strength as obtained from the A.O.R.G. vane and the Campbell Bog stick do not correlate in general with variations in sinkage of the same tank-track combination (See F.V.P.E. Reports No.s 1553/2 and 3).

    An order of merit of the various tank-track combinations tested, has been drawn up on the basis of the residual belly clearance after one run.
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    At the request of the Committee for the Mud-Crossing Performance of Track Laying Vehicles of the Ministry of Supply, a series of tests of tank track performance has recently been completed on sites in SOMERSET. In the course of these tests, detailed records were made in the case of selected track types of track-link movement by means of the Road Research Laboratory photographic method, details of which have already been reported in Note. No. MOS/443/WAL.PdeV.

    Tank sinkage was also measured by a method explained in the Ministry of Supply's, Fighting Vehicles Proving Establishment (F.V.P.E.)'s reports No.s FT 1552 and 3.

    Object of the Tests
    The object of the tests was to measure and compare the sinkage and angular movement of the various types of track links (both current and experimental) tested on "CROMWELL", "SHERMAN", "CHURCHILL" and "PANTHER" tanks. From the test results the significance (in relation to sinkage) of factors such as spud depth, link pitch, wheel spacing, etc., was to be estimated.

    A secondary object was to obtain a check on the accuracy of the F.V.P.E. method of sinkage measurement.

    Conditions of Test

    - Apparatus employed. The apparatus used for recording sinkage and angular movement of track links was that described in the previous report Note No. MOS.443/WAL.PdeV. except that the recommendations suggested in that report were adopted. These included the use of longer datum pickets, longer link standards with suitable white markings, bulb shields and higher camera speeds.

    - Site and Procedure. All the tests were carried out at St. George's Wharf, SOMERSET. A full description of the site appears in F.V.P.E. report No. FT 1553/2.

    The procedure adopted for the recording of track link movement was similar to that described in the previous report Note No. MOS/443/WAL.PdeV. The main difference was in the spacing of the datum pickets and the camera. To reduce errors due to inaccuracies in measurement and to ground movement, the datum pickets were spaced farther apart and father away from the tank track. To simplify the analysis of the records, the relative positions of camera, datum bulbs and test link were maintained constant as far as possible throughout the tests. Corrections were made for any difference in camera height from the height of the datum bulbs.

    In each test three runs past the datum pickets were made; two forward and one backward. Two such tests were carried out, each on fresh ground, for all track types considered with one exception, the long pitched "CROMWELL" link with 2 1/2 in. spuds (C/LP2 1/2S).

    Measurements of sinkage by the Road Research Laboratory and F.V.P.E. methods were made simultaneously.

    - Analysis. The method of analysis of the photographic records is described in Note No. MOS/443/WAL.PdeV. With one or two exceptions, only the records obtained from the first forward runs - two for each track type - were analysed.

    - Soil Tests. Tests with A.O.R.G. vane and Campbell Bog stick were carried out on the test sites before each test. A full description of these tests and details of the moisture content variation with depth on the days of the test (22nd, 24th, 27th and 28th February) may be found in F.V.P.E. Report No. FT. 1553/3/

    The surface of the test site consist of a thick mat of turf while the top soil beneath contained a very high proportion of interwoven grass roots to a depth of about 12 in. The topsoil especially near the surface was completely saturated with water but the moisture-content of the subsoil below about 20 in. was only slightly above the plastic limit of the soil.

    The characteristics of the soil at the test site were as follows:-

    The difference in the consistence of topsoil and subsoil, referred to above, is reflected in the relation between the natural moisture-content and the plastic limit, although at the surface the actual softness of the soil was masked by the presence of a thick mat of vegetables.

    Accuracy of Method

    To determine the errors involved in plotting, a particular photograph was analysed a large number of times. The range of variation obtained was of the order of +/- 0.15 in. for sinkage measurements and +/- 30/4 in angular movement.

    Besides these plotting errors any vibration of the standards and deflection of them due to acceleration forces during angular movement would increase the inaccuracy. The estimated natural frequency of vibration of the standards employed varied from about 300 cycles/sec. in the case of the "CROMWELL" to 160 cycles/sec. in the case of the "SHERMAN". The amplitude of these natural vibrations would be very small since to produce an angular variation of +/- 10/3 a distribution load acting on the standard of over 500 lb. would be necessary in the case of the "SHERMAN". The maximum acceleration forces are very small in comparison and hence vibration and acceleration forces are unlikely to affect the results.

    Movements of the datum bulbs or of the camera would cause errors but these are thought to be extremely small (possibly +/- 0.02 in.).

    The sinkage and angular movement curve of the S/SCEECUG78 (see Appendix for key to the types of track) was closely examined between two wheel centres (Fig. 11). About 100 points were obtained with a time interval of 1/64th second (0.0156 seconds). On these curves bands have been drawn of width +/- 0.1 in. and +/- 10/2 for the sinkage and angular movement curves respectively. On both curves these bands include 78 per cent of the points while to include 91 per cent of the points the bands would have to be +/- 0.2 in. and +/- 1 degree in width respectively.


    Graphs have been plotted on a time base showing the sinkage and angular movement of the test link during the passage of the tank. Figures 2 to 10 show typical curves obtained from most of the various types of track links tested.

    The basis of comparison for sinkage has been taken as the sinkage of the spud bottom below mean ground level. This measurement is equivalent to measuring the decrease in belly clearance of the tank, The total range of angular movement has been used for the comparison of angular oscillation since the position of the zero line depends upon the accuracy of fitting the link standards perpendicular to the track as well as the slope of the tank.

    The main results have been collected and tabulated (Table 1). Table 2 shows sinkage for certain tanks as measured by the F.V.P.E. method and estimated values as would be measured by the F.V.P.E. method obtained from the Road Research Laboratory sinkage figures.

    Table 3 give a comparison of the link pitch and mean ground pressures for the various tracks from which records were obtained. The figures for the mean ground pressure are obtained from overall dimensions, no allowance being made for the cut away areas in plan, of the track.

    The standard code that has been used for the description of the various types of track links is given in the Appendix.

    Attached Files:

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    Table 1
    Sinkage and angular oscillation of typical links in experimental tracks on various tanks

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    Table 2
    Comparison of sinkage as measured by F.V.P.E. method and as estimated shouldl have been measured by the F.V.P.E. method.

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    Table 3
    Comparison of link pitch and mean ground pressure for tracks tested.

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    Comparison of tabulated results.
    By comparing the results for the C/LP2 1/2S with C/S and C/DS (Table 1), it will be seen that although the spud depth of the former lies between that of C/S and C/DS, it sank markedly less. This suggests that lengthening the link pitch is an advantage. It might well be that there is a definite connection between the dimensions of the link and spud and sinkage. Further testes would be necessary however, before such a connection could be definitely established. The performance of the C/DCDS lies between that of the C/S and C/DS as would be expected.

    A comparison of the results obtained from the short pitch "CROMWELL" tracks, C/S and C/DS (Table 1) shows that deepening the spud by 1 in. increases sinkage from 7.4 in. in the case of the C/S to 10/6 in. for the C/DS. However, with the long pitch "CROMWELL" tracks with platypus extenders, (C/LP3 1/4SP and C/LP4SP) increasing the spud depth has no appreciable affect on sinkage.

    Although no direct comparison was mode of the effect of widening tracks with platypus extenders, a very reasonable conclusion can be reached from a comparison of the long pitch "CROMWELL" tracks, C/LP2 1/2S and the C/LP3 1/4SP, the latter track having slightly deeper spuds than the C/LP2 1/2S and platypus extenders. It will be seen from Table 1 that the track with platypus extenders (C/LP3 1/2SP) sank very much less than the track without platypus extenders (C/LP2 1/2S), and this is due no doubt to the lower average pressure on the track.

    An examination of the available data which is admittedly insufficient for firm conclusion, suggest that the range of angular oscillation depends mainly on wheel spacing, wheel loading and spud depth. Referring to Table 1, the "CHURCHILL" with nine wheels oscillated less than the "PANTHER" with eight wheels and still less that the "SHERMAN" with six wheels, all these tanks having similar lengths of track in contact with the ground. In the long pitch "CROMWELL" tracks, increasing spud depth increased angular movement. The probable effect of the platypus extenders in the case of the long pitch "CROMWELL" tracks is to decrease link oscillation but no direct comparison was made. The effect of link pitch on oscillation seems to be small.

    The two "SHERMAN" tracks tested (S/SC and S/SCEECUG78) oscillated through the same range. The universal grouser appears to increase the amplitude of oscillation whilst the extended end connector reduces the amplitude of oscillation. This result agrees with the indications from the "CROMWELL" tracks.

    - Effect of Speed

    To investigate the effect of tank speed on sinkage, two runs were made about 5 m.p.h. with the S/SCEECUG78. Owing to the lack of clarity of the photographic records, no numerical results could be obtained but visual observation showed that the tank sank less at the higher speed. This is confirmed by a comparison of differences in speed and sinkage of the first two runs of each track type which shows that there is a definite tendency for the tank to sink less with increase in speed. (Table 1).

    - General inferences from the graphs

    Examination of the various sinkage and angular movement curves that were obtained show several distinct features.

    In all the "SHERMAN" curves (see Figs. 6-8) more sinkage occurred under the 1st, 3rd and 5th road wheels than under the 2nd, 4th and 6th, having regard to the general slope of the tank. This is possibly due to the irregular spacing of the wheels which causes greater concentration of loading between the trailing wheel of one bogie pair and the leading wheel of the next, the spacing between these being less than between the wheels of each bogie pair. This has been confirmed by tests carried out at the Road Research Laboratory on the distribution of pressure under the tracks of a "SHERMAN". (See note No. MOS/439/CGG).

    A feature common to all angular movement curves is the quick flick of the link as the wheel passes over it. The link then returns to its initial position more slowly. To aid in the comparison of the various tracks the ration of:-
    has been obtained. (See angular movement curves for Fig. 3).

    The ration tends to unity in the case of the "PANTHER" and "CHURCHILL" and is smallest in the case of the "SHERMAN" and short pitch "CROMWELL" tracks, the long pitch "CROMWELL" tracks occupying an intermediate position. Thus a reduction in the spacing of road wheels and a lengthening of the track pitch tends to produce more uniform link movement. One would expect better sinkage performance to correspond with smoother link oscillation since it will reduce impact effects to a minimum.

    Fig. 6 shows the first three runs of the S/SCEECUG78 made on the same piece of ground. It will be seen that the tank sank at a decreasing rate after each successive run in the same rut the range of angular oscillation slightly increased after each successive run due probably to disturbance of the surface soil.

    - Sinkage in relation to general performance.
    The performance of a tank (as distinct from the track alone) in the crossing of soft ground depends not only on link sinkage and on the resistance of the track to slip but also upon the initial belly clearance of the tank. In considering tank performance on soft ground, the basis of comparison should include, in some way, the initial belly clearance of the tank. Thus in comparing the performance of the various tanks as a whole, the residual belly clearance after one pass has been taken as the basis of comparison.

    It will be seen from Table 1 and Fig. 1 that the most satisfactory tank from the viewpoint of sinkage was the "PANTHER" with a sinkage of 3.4 in. and a residual belly clearance of 16.1 in. The best "CROMWELL" tank-track combination was the C/LP4SP with a residual belly clearance of 14.6 in. which was only slightly superior to the C/LP3 1/4SP. On the basis of residual belly clearance the "CHURCHILL" is slightly superior to the "SHERMAN" and much superior to the short pitch "CROMWELL" tank-track combinations. In the case of the "SHERMAN", the S/SCEECUG78 sank more than the S/SC but owing to the greater initial belly clearance of the former it has greater residual belly clearance.

    The Road Research Laboratory sinkage measurements give the track profile (assuming homogenous soil) and the actual sinkage figure quoted in Table 1 is the distance below the mean ground level of the link centre or spud bottom under the last wheel. The F.V.P.E. sinkage measurements give directly the distance of a point (arbitrarily chosen) marked on the tank hull above mean ground level.

    It should be possible from the geometry of the tank to estimate from the Road Research Laboratory data what the F.V.P.E. measurement should have been for the same run and these calculated results are given in Table 2. A comparison of the figures so estimated with the actual F.V.P.E. recorded measurements shows a definite bias of the order of 2 in. with a scatter of the order of +/- 1 in.

    One neglected factor which may account for this bias is the spring compression which occurs when the tank is in motion. This spring compression which is due to the "nose-up" couple, is believed to be of the order of 2 in. which would account for the difference.

    From the viewpoint of estimated residual belly clearance after on run it is possible to place the various tank-track combinations in order of merit. The following groups differ from each other by the order of 2 in. but there is little difference between the individual track types in each group.

    The estimated residual belly clearances are subject to corrections due to spring compression which are not yet known. Hence the order of merit may be subject to revision although this would be of minor nature. This grouping is in substantial agreement with the results given in F.V.P.E. Reports FT. 1553/2 and 3.

    - Correlation with soil measurements.
    A comparison of the soil results taken prior to each test by A.O.R.G. and given in the F.V.P.E. report No. 1553/3 shows that differences in sinkage of two first runs cannot be explained by reference to the values obtained from the Campbell Bog stick or the A.O.R.G. vane. In fact, in about half the cases, where stronger ground was indicated from the measurements, greater sinkage took place.

    The methods adopted for measuring the condition of the soil in the tests are not therefore at present sufficiently good to permit any further conclusions to be drawn regarding the present sinkage measurements.

    See SUMMARY.

    Attached Files:

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    Key to description of track links.

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    Figure 1
    Showing Residual Belly Clearance (unshaded) and Sinkage (shaded) after one run.

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    Figure 2
    Figure 3

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    Figure 4
    Figure 5

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    Figure 6

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    Figure 7
    Figure 8

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    Figure 9
    Figure 10

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    Figure 11

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    Note No. MOS/467/WAL.
    August, 1945.


    Road Research Laboratory



    by W.A. LEWIS


    A small experimental soil bath was constructed at CHINGFORD in order to explore the major difficulties likely to be encountered in preparing and handling soil in a soil bath intended for full-scale A.F.V. mud-crossing trials. The soil used in the trials was a soft heavy clay.

    It was found that the clay could be placed most satisfactorily by dropping it into the bath from a height of about 12 to 16 ft. This resulted in a reasonably homogeneous clay containing only about 4 per cent of air. The air voids were slightly reduced by tamping or punning the clay with the bucket of a grape.

    The experimental work also suggested that the clay surface could be levelled either by the use of some automatic tamping plant or by means of a suitable blade made to traverse the bath. Ruts caused by the passage of an A.F.V. were removed either with a special rut-filling blade or by tamping.


    Before satisfactory full-scale tests on A.F.V. can be carried out in a soil bath it is necessary to devise methods of:-

    (1) placing the soil evenly in the bath,
    (2) reducing the air voids in the soil after placing,
    (3) levelling the soil before a test,
    (4) removing the ruts and reconditioning the soil after a test.

    These problems were studied at the request of the Committee for the Mud-Crossing Performance of Track Laying A.F.V., by means of a trial soil bath contracted at CHINGFORD, on the site of the new Metropolitan Water Board reservoir.


    Trial soil bath
    The trial soil bath consisted of a pit some 60 ft. long, 18 ft. wide and 6 ft. deep excavated in the ground. The pit had practically vertical sides and ramped ends.

    The soil used in the bath was London Clay as used in the core walls of the reservoir now under construction. It was obtained from a bank when it had been well weathered and it had the following characteristics:-

    Soil preparation
    The clay was passed through crushing rolls and a pug-mill to give puddled clay of approximately the desired water content and consistency. The water control on the pug-mill was hand operated; this resulted in the occasional very wet mixes particularly after a stoppage of the mill. The puddled clay was conveyed to the pit by dumper or Athey wagon (a tracked wagon of about 6 cu. yd. capacity drawn by tractor).

    Placing the clay in the pit
    The clay was placed in the pit in three 2-ft. layers. It was tipped from dumpers and spread by hand with grafting tools to form the bottom layer, and was dropped from Athey wagons into the pit from various heights with a 3/4 cu. yd. grab to form the upper two layers. These layers were constructed in three sections, the heights of drop being 8 ft., 16 ft., and 24 ft. for the middle layer, and 6 ft., 12 ft., and 18 ft. for the top layer.

    Removal of air voids
    The clay after placing was treated in one or other of the following ways to reduce the air voids (the percentage of voids being calculated from the bulk density of an undisturbed core cut from the soil, the moisture content of the soil, and the specific gravity of the dry soil particles).

    (1) Flat plates of various sizes both round and square were attached to the chisel of a pneumatic hammer and were driven or vibrated into the clay.

    (2) The clay was punned with a "frog-rammer".

    (3) The clay was rolled with two sizes of roller and a few measurements of voids were made after various numbers of passes.

    (4) Tracked vehicles of low nominal track pressure were run backwards and forwards across the clay (David Brown Tractor and Athey wagon)

    (5) The clay was punned or tamped by dropping the bucket of the grab on to it from a height of about 2 - 3 ft. (Figure 3)

    Levelling the clay
    The clay was levelled by rolling it, by tamping it with a grab or by drawing a bulldozer blade across it. The blade was arranged either to "back-blade" the clay (the effect being the same as if a bulldozer was driven over it in reverse), or to skim the surface of the clay.

    Removing the ruts
    The following three methods were employed in an attempt to remove ruts caused by the passage of track laying vehicles.

    (1) The special rut filling blade (see Figure 6) was loaded with various weights and was dragged along over each rut.

    (2) A disc-harrow was pulled along the rutted surface so that it cut up the surface which was finally rolled.

    (3) The ruts were closed and the surface levelled by tamping the clay with the grab (Fig. 8).

    Tables 1 and 2 give the moisture content and air voids in the two top layers of clay for various heights of drop of the clay in placing and for two methods of surface finishing. Table 2 gives, for comparison, similar measurements or samples taken from the puddled clay core wall of the new reservoir. This was spread in 4-in. layers and compacted by treading.

    No air void measurements were made on the bottom layer, as placing with dumpers resulted in air voids and was clearly unsatisfactory, as seen in Fig. 1. This clay had to be levelled by hand, a procedure which was impracticable on a large scale, being extremely hard and slow.

    The results given in Table 1 are individual observations while those given in Table 2 are each the average of four individual results and are thus more representative. The accuracy of any individual determination of air voids is estimated to be within +/- 0.5 per cent voids, i.e., if the figure given for voids is 5 per cent the true value will lie between 4.5 per cent and 5.5. per cent.

    TABLE 1
    Screen shot 2012-01-08 at 15.08.04.png

    TABLE 2
    Screen shot 2012-01-08 at 15.32.15.png

    Placing the clay
    The percentage of air voids in the clay after it had been dropped from from a height was low, ranging from 2.0 per cent to 5.8 per cent. There is a slight tendency for the lower voids to be associated with the higher moisture contents: thus is Table 2 the extreme results after placing but before finishing are respectively 3.1 per cent air voids for 42 per cent moisture content and 4.7 per cent air voids for 40 per cent moisture content.

    The height of the drop has little influence on air voids (Tables 1 and 2) but a drop of 12 to 16 ft. was found to give the most uniform surface. When dropped from 6 ft. the clay remained in large lumps and had to be tamped; when dropped from 24 ft. is spread violently on striking the ground leaving crater like depressions.

    Reducing the voids
    In the clay as dropped, the percentage of air voids was small - a mean value of 5 per cent - but this was reduced to 3.8 per cent over a portion of the surface by punning it with the empty grab bucket (weight 1 1/2 tons), letting it fall from a height of 2 ft. in a controlled drop. (Rows 1 and 3 of Table 2).

    This reduction of air voids is as great as that obtained by treading in 4-in. layers, the air voids in the puddle clay forming the reservoir embankment being 4 per cent (see Table 2).

    Another portion of the surface was rolled to reduce the air voids. The two rollers used were both approximately 50 in. wide and had diameters and weights respectively of 21 in. and 1 ton, and 46 in. and 1 1/2 ton. The large roller reduced the mean air voids from 5.0 per cent to 3.9 per cent. (Rows 1 and 4 of Table 2) but pulled up the clay surface in patches, thus spoiling the finish (see Fig. 5). To reduce the adhesion of the clay the smaller roller was covered with rubber sheeting. This was not satisfactory, as the sheeting was torn off after a few passes and the roller was subsequently clogged up after a shorter distance of travel than that covered by the larger roller before clogging.

    A David Brown tractor (track pressure 6 lb. / sq. in.) and an Athey wagon (track pressure 4 lb. / sq. in.) were run over another part of the clay surface but produced no sensible diminution in the air voids. Cores were taken from the ruts left by the wagon gave 4.6 per cent air voids compared with a mean value of 5.0 per cent air voids in the clay as freshly dropped. The tractor would not steer out of its own ruts and left the surface badly rutted and the performance of the wagon was little better.

    None of the other devices tried was satisfactory. The "frog-rammer" would not always fire, the reaction of the soft clay after a tamp being sometimes too small to compress the charge in the cylinder to the firing point. The largest sized plate (18 in. x 18 in.) vibrated with a pneumatic hammer made no impression on the soil after a minute, a 12 in. x 12 in. plate was little better, and an 8-in. diameter circular plate sank rapidly into the clay; its removal was difficult and left the clay badly disturbed. Rapid vibrations of small amplitude on this type of material are believed to produce little diminution in air voids (see Note No. RN/590/AH.).

    Levelling the clay
    The surface of the clay after it had been tamped was very nearly level (see Fig. 4). Some automatic means of tamping in which the apparatus slowly traverses the bath might produce a perfectly level surface.

    Both rollers tended to level the clay especially when they ceased to revolve due to clogging by the clay and were then dragged along the surface.

    The bulldozer blade could not be loaded really satisfactorily but the results obtained definitely indicated that it would be possible to level the clay either by back-blading or by skimming off the surface irregularities provided that a suitable arrangement of blade and suitable loading were used.

    Removal of ruts
    The removal of the ruts caused by the passage of a track-laying vehicle proved to be the most difficult problem to solve. This was probably due to the absence of a suitable travelling bridge.

    The special rut-filling blade could not be weighed sufficiently nor could it be steered along the ruts which were by no means straight. Where the blade did run centrally over the rut and where the loading was reasonably satisfactory, the rut was filled (Fig. 7). From experiments with various weights on the blade, a vertical load of about 3 tons would appear to be necessary for the satisfactory operation. One David Brown tractor was capable of providing the necessary traction for the blade.

    A disc harrow was of little use in removing ruts. The ruts were partially obliterated but it is doubtful whether the resulting torn-up surface was any improvement. In any case after travelling a short distance the harrow became so clogged that it merely rode on the surface of the clay.

    A much more satisfactory method of rut removal was to tamp the ruts out by using the grab. The method of operation is clearly shown in Fig. 8. The ruts were were filled and the surface reasonably levelled.

    See Summary.

    Figures 1 - 4

    Figures 5 - 8
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    Note No. MOS/467/WAL.
    October, 1945.


    Road Research Laboratory



    by C.G. GILES

    The load-distributions beneath track-laying vehicles of nine different types on similar soil, have been investigated by means of piezo-electric gauges buried in the ground; the vehicles were a CROMWELL, CHALLENGER, A.41, SHERMAN, CHURCHILL, BLACK PRINCE, PANTHER, UNIVERSAL CARRIER, and a T-16 CARRIER with skid rails in place of the normal bogie wheels. Typical records obtained beneath these vehicles are reproduced and the main features of the records for each vehicle are summarised in tables.

    The results showed that under the test conditions, vehicles with a ration of wheel-spacing to track-pitch of less than 4 gave a more uniform load distribution than those in which this ratio was higher.

    Over the speed range of 5 - 15 m.p.h. used in the tests, vehicle speed had little effect upon uniformity of load distribution.
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    Object of Tests
    These measurements were made in order to obtain comparable information about the load-distribution characteristics under the tracks of different track-laying vehicles representing types with both fundamental and dimension differences in the design of their track and suspension.

    Details of Vehicles
    Vehicles of the following types were used in the present tests|:-
    (1) Cromwell Mark V
    (2) Challenger
    (3) A 41 (pilot mode)
    (4) Sherman I
    (5) Churchill Mark VII
    (6) Black Prince
    (7) Panther (without turret)
    (8) Universal Carrier
    (9) T-16 Carrier with Skid Rails

    The main features of each vehicle are illustrated in Figs. 1 - 9 by photographs of the vehicles employed in the tests, whilst particulars of each vehicle are given in Table I.

    The T-16 Carrier with skid rails was that employed in the SOMERSET soft ground trials which are described in F.V.P.E. Report No. F.T. 1553/2.
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    Figure 1 - Cromwell ( CW 77 )
    Last edited: Sep 3, 2019

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