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  • Forward sprocket drive.

    Why did so many early tank designers go for forward sprocket driven tracks?

    Try as I might I can't think of any advantages over rear wheel drive.

    Are they less prone to throwing tracks due to the increased tension on the top run?

    Here is a list of what I would consider to be dis-advantages:

    Increased hull height , internal bulkhead penetration , sprockets more vulnerable to damage , very difficult to replace drive-shaft , reduction in fighting and driving space internal volume , added cost , added production time , extra weight , extra complexity and there must be more.

    Here is a list of what I would consider to be advantages:

    Shortened hull length?..............That's it.

    Picture the standard layout of a tank, starting from the front:

    Driver and hull gunner/op compartment--fighting compartment and turret--engine compartment.

    Why go to the trouble of placing the engine at one end and the final drive at the other?

    I suspect there is a good reason, after all these were very bright automotive engineers.

    It's not like it was tried pre-war and found wanting. It DID work.

    The US Sherman and all its derivatives employed it as did the M3 family.

    The entire German tank inventory used it.

    These were two of the most advanced automotive engineering countries in the World at that time.

    Could they both have been wrong?

    The system seems to have been dropped lke a hot potato post-war,the only vehicle apart from front engined APCs that I know of that still utilise it are the front engined Merkava series.

    Anyone enlighten me?

  • #2
    The only thing that comes to mind is that maybe that the size of the transmission made it neccesary to have it up front.
    The reason the Merkava's is up front is because of the front engine layout.
    "You listen to the ol' Pork Chop Express on a dark and stormy night......"

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    • #3
      Yeah, I know what you're getting at,if the transmission is too large to house in the rear hull without making the hull excessively long,you might have to put in the front.
      But all other tank building nations managed to squeeze it aft.
      Why did the USA and Germany alone pursue this method?
      Were German and US transmissions of a similar (bulky) type?

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      • #4
        With a manual transmission it is far easier to make the cluch and shift levers workable for the driver than some long linkage to the rear sprocket drive. Soviet tanks are notorious for being nearly impossible to shift for that reason, among others.

        The US went to automatics fairly early and that allowed moving the transmission to the rear of the tank without the attendent problems of shift and clutch linkages.

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        • #5
          Dirt & other crap shakes off before reaching the drive sprocket???

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          • #6
            Front-drive tanks have more advantages than you list. The tracks will be cleaned of mud and rocks more than a rear-drive layout, and the steering controls (and transmission controls, as TA mentioned) will be shorter.

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            • #7
              Originally posted by flash View Post
              These were two of the most advanced automotive engineering countries in the World at that time.
              Say what?????
              John

              Play La Marseillaise. Play it!

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              • #8
                Originally posted by T. A. Gardner View Post
                With a manual transmission it is far easier to make the cluch and shift levers workable for the driver than some long linkage to the rear sprocket drive. Soviet tanks are notorious for being nearly impossible to shift for that reason, among others.

                The US went to automatics fairly early and that allowed moving the transmission to the rear of the tank without the attendent problems of shift and clutch linkages.
                Hi T.A
                You're quite right,the T34 was a bitch to drive (Good drivers always carried mallets!)

                The problem wasn't rectified until the final 100 Model 1943s rolled out.

                (4 speed box to 5 speed box)

                But rectified it was and one assumes the very successful T34/85 carried on this trend.

                Automatic is definitely the way forward but wasn't that first used on the
                M26,ie late war?

                The Churchill tank had a hydraulically assisted linkage and seemed to work well, this was first produced at the end of 1941.

                I realise that it's not possible to halt production of a perfectly good tank, ie Sherman, but perhaps if a serviceable gearbox and linkage had been designed in from conception it would have been a better tank regarding it's height and armour protection.

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                • #9
                  Originally posted by Carl Schwamberg View Post
                  Dirt & other crap shakes off before reaching the drive sprocket???
                  Yep,that is an advantage alright, gotta help keep the tracks on a bit

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                  • #10
                    Originally posted by DogDodger View Post
                    Front-drive tanks have more advantages than you list. The tracks will be cleaned of mud and rocks more than a rear-drive layout, and the steering controls (and transmission controls, as TA mentioned) will be shorter.
                    I'm open to suggestions regarding pros and cons of front/rear wheel drive.

                    So far we have advantages : Problems with gearbox linkages erased and less crud will accumulate around the sprocket....Anymore for anymore?

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                    • #11
                      This shows why - no room anywhere else:

                      Quis Custodiet Ipsos Custodes? Who is watching the watchers?

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                      • #12
                        Originally posted by JBark View Post
                        Say what?????
                        Errrrm, well they were.
                        I don't want to go into individual vehicular achievements here but I think it's safe to say that USA,Germany,UK and France were streets () ahead of the competition in the late 30s.

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                        • #13
                          Originally posted by Mountain Man View Post
                          This shows why - no room anywhere else:

                          Hi Mountain Man.
                          That's one cluttered tank!

                          If you look at the idlers you will see that thay actually protrude from the hull rear. The area between the left and right idler is known as dead space (The wasted space caused by the juxtaposition of machinery in a confined space) and the box would fit quite snugly between them.

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                          • #14
                            Yes, the components of the M4 could have been arranged to provide a rear drive sprocket, and a concept of an improved version of the Sherman did just that. In fact, while Spielberger notes the Germans discussed the virtues of front versus rear drive, the US built so many front drive vehicles almost as a matter of circumstance instead of policy. Until early/mid-30s, the US had not used a front drive tank. The light tank M2, however, locked the US on the front drive sprocket path: The combat cars M1 and M2 used essentially the same hull as the light tank M2. The light tank M3 was a light tank M2A4 with heavier armor and a trailing idler. The light tank M5 was a light tank M3 with sloping armor and a powertrain that didn't rely on the radial engines being sucked up by the aircraft industry. The light tank M24 used the powertrain of the light tank M5. The medium tank M2 was conceived as a larger light tank M2, and used as many components as possible. The medium tanks M3 and M4 were in turn based on the medium tank M2. The early 1940s were desperate times in the US as far as tank design and production went, and a total redesign was out of the question, especially while the British were wanting tanks to help fight off Panzergruppe Afrika.

                            In contrast, the heavy tank M6 used a rear drive sprocket, and the follow-on series to the M4, which began in spring 1942 and eventually culminated in the M26, all used rear drive sprockets as well. The box-type tank hull with the powerpack at the rear was the most efficient use of space, and this trend has continued almost without exception since World War II.

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                            • #15
                              Originally posted by DogDodger View Post
                              Yes, the components of the M4 could have been arranged to provide a rear drive sprocket, and a concept of an improved version of the Sherman did just that. In fact, while Spielberger notes the Germans discussed the virtues of front versus rear drive, the US built so many front drive vehicles almost as a matter of circumstance instead of policy. Until early/mid-30s, the US had not used a front drive tank. The light tank M2, however, locked the US on the front drive sprocket path: The combat cars M1 and M2 used essentially the same hull as the light tank M2. The light tank M3 was a light tank M2A4 with heavier armor and a trailing idler. The light tank M5 was a light tank M3 with sloping armor and a powertrain that didn't rely on the radial engines being sucked up by the aircraft industry. The light tank M24 used the powertrain of the light tank M5. The medium tank M2 was conceived as a larger light tank M2, and used as many components as possible. The medium tanks M3 and M4 were in turn based on the medium tank M2. The early 1940s were desperate times in the US as far as tank design and production went, and a total redesign was out of the question, especially while the British were wanting tanks to help fight off Panzergruppe Afrika.

                              In contrast, the heavy tank M6 used a rear drive sprocket, and the follow-on series to the M4, which began in spring 1942 and eventually culminated in the M26, all used rear drive sprockets as well. The box-type tank hull with the powerpack at the rear was the most efficient use of space, and this trend has continued almost without exception since World War II.
                              Hi Dogdodger.
                              Do you have any more info on the rear drive concept M4?
                              I agree entirely with your very informative post.
                              I still wonder at how the designer of the original M2 came to the conclusion that front drive was preferable to rear.

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