British bridge classification of Sherman tanks

Discussion in 'Weapons, Technology & Equipment' started by Gary Kennedy, Aug 18, 2023.

  1. Gary Kennedy

    Gary Kennedy Member

    I was looking at the info on bridge classifications for British Army vehicles recently, and found myself confused by a particular point (no real surprise as military bridging is not one of my strengths!).

    MTP No.74 (supplement on "A" vehicles") of Mar 1944, and MTP No.74 of Sep 1945 both list all marks of Sherman with a classification of 33, which rises to 35 for the Vc. The RE Reconnaissance Pocket Book states that an Armoured Division needs both Class 9 and Class 30 bridges.

    If I'm understanding it correctly though, a Sherman with a classification of 33 should not attempt to cross a Class 30 bridge. The Divisional Bridging Troop (or Platoon) carried sufficient Bailey equipment to build a Class 40 bridge of 80-foot, so in that respect could accommodate tanks of up to (and I presume including?) 40 classification anyway.

    I had a quick look in Bellanger's British Soldier, as I recalled it has a section on markings, and he shows all Shermans with a bridge classification plate of 30.

    Any thoughts on what appears to be a discrepancy in the available figures?

  2. Aixman

    Aixman War Establishment addict Patron

    Hi Gary,

    TNA's WO 33-1941 "Bridge load classification of 'A' vehicles, 1942" (19.10.1942):
    Cruiser Tank, General Sherman - classification 30.

    My guess: It depends on time. Later Sherman types might have been heavier. Probably a question for the Sherman specialists in here.

    The same classification 30 applied for
    Cruiser Tanks
    - General Lee I - VI
    - General Grant I - IV
    - Ram I - II

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  3. Don Juan

    Don Juan Well-Known Member

    My understanding is that oversized loads could pass over a bridge if they were adequately spaced out, i.e. 33 ton Shermans could use a Class 30 bridge, but with greater spacing between vehicles than for sub-30 ton tanks.
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  4. Gary Kennedy

    Gary Kennedy Member

    Thanks both for the above. I asked over on another forum, which has a high density of tank obsessives, and had a few more suggestions.

    As mentioned above, it does seem there was an ongoing weight increase for the Sherman that had altered the bridge classifications. A British summary from 1942 had the Sherman as approximately 30-tons (British long) so a bridge classification of 30 would be expected. Later models then creep up, from around 66,500-lbs (Sherman I) to 69,000-lbs (Sherman III) and 71,000-lbs (Sherman V), at least as given in the US Ordnance Items catalogue.

    Military Training Pamphlet No.74 states that standard vehicle spacing should be maintained at 50 yards (150-foot) in convoy, and should never be closed to less than 80-foot. That would certainly mean an 80-foot Bailey put up by an Armoured Division should only need to handle one tank at a time.

    The figures I've seen re Bailey bridging equipment in particular, as carried by Divisions and RASC Bailey Platoons, do all centre on constructing a Class 40 bridge, which should have been able to handle Shermans, Cromwells, Comets and Churchills alike. Possibly the reference to a Class 30 bridge for an Armd Div in the RE Recce pocket book was referring to the earlier British cruisers, which mostly came under 30-tons.

  5. Wg Cdr Luddite

    Wg Cdr Luddite Well-Known Member

    I've seen Shermans with both 30 and 33 plates.
    From memory a whole Infantry Divsion can cross Class 9 bridge, whereas an Armoured Division requires a Class 40.
    I'm not sure Class 30 bridges were much of a thing. Class 9 and Class 40 seem to have been the standard.
  6. Not sure whether this is useful, but the Combined Operations Staff Notebook dated September 1945 (but written earlier in view of the expected landings in the Far East) lists the weights (in tons) of the various marks of Sherman as follows:

    Mark — Tanks (US) — Shermans modified for British use
    Sherman I — 30.50 — 30.80
    Sherman IB — 30.97 — 30.97
    Sherman IC — 30.55 — 32.75
    Sherman II — 30.50 — 30.80
    Sherman IIA — 31.20 — 31.20
    Sherman III — 31.20 — 31.20
    Sherman IV — 30.50 — 31.50
    Sherman IV (up-armoured) — 37.70 — N/A
    Sherman V — 32.00 — 31.75
    Sherman VC — 34.75 — 34.75

    This would explain the 33 tons Bridge Classification for all British Shermans except VC (and IC). The 30 ton one might derive from the Sherman II weighing only slightly over 30 tons.

    Last edited: Sep 3, 2023
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  7. Trux

    Trux 21 AG

    An interesting topic, and one worthy of further study (if only one had unlimited time and mental energy).

    Some stray thoughts.
    Some published works have given lists of classifications as if they were absolute and invariable. In fact over the years and in various theatres a large number of such lists were issued.

    Bridge Classifications did not only apply to military bridges. Engineers also calculated weight limits for civilian bridges.

    Towards the end of the war it seems that lists were issued using a vehicles axle loading rather than its total weight. I must admit that the concept is beyond me but a 6 wheel 3 axle 3ton vehicle would be rated lower than a 4 wheel 2 axle vehicle, and a tracked vehicle rated lower still.

  8. Don Juan

    Don Juan Well-Known Member

    Most tanks in 1944-45 are going to be overweight anyway, because they will be carrying lots of extra stowage, protective track links, spare wheels, in many cases excess ammunition etc. In the well-known Charles Dunphie report on British armour from early 1945, he states that all British bridging east of the Rhine was based on the 40 ton Bailey Bridge.

    The standard bridges at the beginning of the war were the Class 18 and Class 24, which the Crusader and Matilda were respectively supposed to meet, although in the event they both exceeded these limits by about a ton. I suspect that the Class 30 and Class 40 were developed with the Cromwell and Churchill in mind, and these both successfully stayed within their respective bounds (possibly only just with the Churchill VII), but as the Sherman was not developed by the British it strayed over the 30 ton line.

    But there will be a significant safety factor employed with military bridges - a Class 30 bridge will not immediately crack in two if a 30.00001 ton load passes over it. So the extent to which a blind eye might be turned to excess loads will depend upon the degree of excess and the urgency. I have certainly read a German account where they successfully took tanks over an existing bridge at a severe overload condition in an emergency.
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