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Hi all,

I was wondering why the German army in WWII loved interleaved wheels on most of their tanks and why most tanks (and US tanks) used front wheel drive, while the Russians favoured rear wheel? I've read up a little but it seems the disadvantages are more numerous than the advantages which seems odd considering the Germans made huge technological strides throughout the war, so I must be missing the obvious.

Cheers

might be wrong on this but...shorter tanks! the shorter the tank, the less armor is needed to cover the flanks--->less weight
German engines of panther and tiger series specialy designed to be short too.

AFAIK interleaved wheels spread the weight more evenly and reduce ground pressure a bit allowing heavier tanks and greater stability. They may also have improved the ride a bit allowing for more accurate fire on the move, although that would have had only a minor effect I would say.

My best guess about USSR using rear wheel drive would be the cheapness and technical simplicity of that design. I don't believe there is any inherent benefit to either system. It may be that you stick with what you know and USA/German started with front wheel drive and just stuck to it.

Edit: one thing to bear in mind is that despite the German "high level of technology" it was the USSR which developed sloped armour first and sometimes, as USA found during the Vietnam war with Phantoms etc, it is possible to get a bit carried away with your supposed "technological superiority" and overly complicate things which I think may also have been a factor with later German tank design

Pere_Ubu_Roi, on 23 February 2012 - 02:18 PM, said:

My understanding is that a rear wheel drive is inherently a bit better since it pulls from the underside when driving forward instead of the from the upper side, therefore reducing stress on the tracks enhancing their lifetime. (Altough this is probably only a small factor in view of the overall quality of a suspension design.)

Today most tanks have rear wheel drive mainly because engine and gearbox form a single block which can be completely removed in a very short time. In WW2 however, the gearbox was a huge piece of equipment and nowwhere near as reliable as gearboxes today, prone to breakdowns and with relativly short lifespans (this is pretty much true for all tanks of ww2).

Therefore, german and US engineers prefered to seperate the engine block and the gearbox for easier maintanance and changing and for a more evenly distributed weight. As for the USSR, either their engine/gearbox design was so small and superior that it didn't matter or they simply gave a damn about a single tank as long as three others roll from the production line in the time it took to change a gearbox.

you have several issues at play, if you have an all around armored tank then having an engine and gearbox at each end of the tank makes for even weight distribution, but if you have extra heavy frontal armor then having both engine and gears in the back helps balance the tank out.

A rear gearbox also allows for a sharper angle to the slope of the front hull, and removing the drive shaft allows the tank to be lower

A frontal gearbox makes for an easier driving situation and a short tank is more square which makes for better turning.

have a look at the tigers transmission

http://www.alanhamby...nsmission.shtml

the Germans did experiment with rear drive units, the DB the 3001p the vk4502A were rear designs and the E75 was most likely designed rear drive even if some argue against it

First question is a pretty easy one, It is for a smooth ride, Look at youtube of panthers driving around and see how very very smooth they go over bumps etc (almost looks like modern air suspension). There is a few downsides thou. First it is a pretty heavy setup (it weights alot) and second becuase the german tanks where pretty short they needed to make it compact therefore the wheels are interleved. And that made changing inner wheels a hell.

Second one, this is alot harder and "experts" are still arguing about this one, But we will to 110% never know why really. There are bad and good things with both of them, But from my own ideas and logic it was a matter of size for the tanks. They could made the tanks alot shorter this way. Ironclad explains it pretty good. And also the weight distribution is better. The centre of mass is pretty much in the middle even with the long guns they have, If they would have made a rear wheel drive with those big turrets and long guns (they would have been moved forward) they would have been very front heavy and uneven centre of mass.

But still the biggest discussion about this is if you gain or loose anything with having the drive sprockets in front or rear. The tracks are getting pulled or driven. That is a hard one. The logic says with a driven track (transmission front) you dont get so much stress. Think of 1 meter long rope. pull on each end 1 meter apart, the stress is even distributed throu the whole rope and the rope also helps with its momentum to even reduce stress further. Now take a rear drive, take this same rope and pull with 1dm apart (last roadwheel to drive sprocket). Wich one stresses most under heavy duty? Wich one brakes first? I dont know.
And you also need to think about how easy it was to throw a track (they fall of the wheels) Logical it says that rearwheel drive should be better but when i watched a few simulations of front wheel drive im not so shure about that anymore. The first pair of roadwheels is kind of steering the tracks so they cant fall of that way. No matter how much you turn around. With rearwheel drive you have a longer way of a "loose" track that can twitch and bend etc. But then you dont have the drivin force instead, So i have no idea but its worth thinking about

Part of the rationale for interleaved wheels was Germany's lack of rubber. Germans decided to improve ride on all-steel wheels by making a large number of large wheels. Both features improve drivability and reduce wear, but complicates maintenance and broken wheels are much harder to remove and replace. Wheel arrangement doesn't effect tank length, because hull is only as long as necessary for interior space.

German 'school' of tank building preferred centrally-mounted turret with minimal gun overhang; Soviet tanks have turret in front and large gun overhang. This means gearbox is placed in front where it's also easily operated by driver. One reasoning I've heard is that front sprocket gives better tractive effort, but I don't understand why. Driveshaft running under tank turret increases tank height which adds weight, and part of the reason why Germans tanks are much taller than Soviet ones.

Gearbox seems to be very 'dense' component, which determines much of tank's weight distribution. T-34 and T-54 have rear drive, but even with front turret, overhanging gun and heavy glacis plate front wheels are positioned further apart than rear wheels, which indicates centre of gravity is rearwards. IS-4 seems to have a 'notch' on the back to house gearbox, drive sprocket and a pair of road wheels.

Kyphe, on 10 March 2012 - 03:15 AM, said:

Source for this? You can clearly see that rear-drive tanks you mentioned have turret in front like in Soviet tanks, while front-drive German tanks have middle turret. E-75's layout was heavily based on KT, having middle turret and front drive.

Vlevs, on 31 March 2012 - 09:14 PM, said:

True. Actually I read that was one of the reasons, the PzIII was initially only refitted with the L48 5cm gun, because they feared that the already developed L60 was to long and unwieldy.

Having served as a Leo2a4 gunner I can say that gun overhang can be problematic with tank-unfriendly enviroment, like woods etc....so I guess considering france and germany this is certainly understandable. Russia is much more open so that wouldn't be really a problem there, I think.

depends on what part of russia you are fighting Bombastikus

the steppes are open but there is plenty of forest in russia. i guess that most of the fighting would have taken place over the steppes into eastern germany if "ww3" had actually happened

i guess its one of those rl vs in game situations you encounter, front mounted turrets are great in game because of the 90degree angles we encounter a lot, (buildings/rocks/other tanks) with out having to worry about hitting trees etc that irl tankers/designers have to worry about, (i am looking at you revolver system)

Germans made extensive testings of both front and rear driven tracks...

the plus and minus were minimal

plus for front wheel drive...
lower wear and tear of the drive sporcket wheel because the track has more time to get clean befor it reach it
short way of gearbox shifting system
front mounted gearbox could be designed longidutinal (not much different to well known truck gearboxes)
the driveshaft through the crew compartment could easly be used to power the turret travers system
additional crew protection
easy access for fine adjustments of the shiift system

minus
drive shaft through crew compartment means in average 10cm higher hull...
cost space in the fighting compartment
needs a large removable plate over the driver radio operator to get replacet
slightly higher risk to jam the track while backing up
slightly higher risk to get immobile if hit at the track from the front

rear wheel drive
plus
more space in the crew compartment
gearbox could be more easy replaced
lower hull because no drive shaft goes through crew compartment
allows free design of frontal armor

minus
higher wear and tear on the drive sporcket wheel because of mor dirt on track
needs long gear shifting system that could pretty easy jam by shocks if tank gets hit
adjustments at the shift system needs more work
shiffting needs much more strengh which reduce ´driver performance quicker
adds no additional crew protection


as a final result from the tests the germans saw no advantage disadvantage of both layouts... they choose front wheel drive because f the simpler gearbox design layout and the abilty to place the turret into the center of the tank which gave the tanks a good balance
Edited by Schiltron, 03 June 2012 - 09:13 PM.

oh and interleaved wheel layout was choosen because form the avaible materials for the Germans it was the only solution to build heavy tanks with good suspension and nicely balanced groundpreasure spread over the whole track. That benefits outweight the drawbacks of higher maintenance and cleaning work

Hello, i hope this topic is not dead already. And sorry for my bad english, i had few training over the last year ; )

The question about why FWD was used is like comparsion of FWD Cars or RWD Cars. Both have plus and minus.
When i was in the German Army i was a Tankdriver and trained on the Leopard 2A4 to Leopard 2A6. In the Driving School for that Tank we learned much about this Tank and advatages and disadvantages.
One of the Points to use FWD is, that you can't "throw" down the Tracks of your Frontwheel when driving a narrow curve with low speed. If you do so with a RWD you will loose your Track, even if not hit by an Enemy and you need about 1-2 hours to put it back on the Tank. In German its called "Kette schmeißen" and i had it once while drining to heavy ground, which is worst case that can happen ; )
But the Bonus of RWD is, that you can't loose your Tracks while driving backwards even though you drive very slow.
That's why they use FWD still. The German APC Marder has it, so there is more space in the back and the Tank is able to maneuver very quick while driving forward not having the problem of loosing a Track.

The Rest of the Points others wrote are also right (smaller Engine compartment, short gearways, ...)

Ah, one thing more. The Panther is not driving so smoothly because of FWD, its because of the suspension they used. Still today they use tension Bars for the suspension of Tanks.

I hope you understand the Point i mensioned.

Cabal

will front drive, tension the top of the tracks +make them less likely to come off the top rollers?
while the lower part of the tracks are under road wheel weight +not going anywhere...
Edited by tigerstreak, 04 July 2012 - 09:44 PM.