"Wide tank tracks" Topic

I have read in various books on the Russian Front that one significant advantage the T34 enjoyed over German tanks was that it had comparatively wider tracks, which thus meant it could traverse softer ground etc.

As the whole point of using tracks on a tank in the first place is to permit greater off-road capability, it would surely stand to reason that they should be as wide as possible to distribute its weight?

This seems so logical to me, that I am left wondering why anyone would build a tank with narrow tracks. Was it really just a case of it being "I can't believe we didn't think of that!" or was there a rational reason behind other tanks having narrower tracks – presumably weight / cost / material shortage or something?

What it really comes down to is ground pressure (pounds per square inch or whatever the metric equivalent is) rather than specific track width. I'm not sure it was even a specific design consideration in early tanks, but apparently it took on greater importance as the war developed. There were many models that had "low" ground pressure, even if the treads weren't considered particularly wide. Believe it or not, the Tiger series, IIRC, had fairly low ground pressure as well. It does have a wide track but it was still a monster. Some models (can't remember which now, but I want to say German) had detachable 'track extenders' for lack of a better term, which widened them a few inches, lowering the ground pressure still further.

Wider tracks put more strain on the drive train, and increase wear and tear. (That's why some tanks had the option to fit a narrower "march" track and a wider "battle" one.)

Sundance

Absolutely – and that is my point. I would suggest that the easiest way to reduce your pounds per square inch is to make your tracks wider: surely this was so obvious to German tank designers that they must have had a valid reason for not making their tanks enjoy the same low ground pressure as the T34 (if the books I have read are to be believed).
I assume the Tiger was given wider tracks as a result of this experience?

Dom Skelton

Yes – that makes sense. Do you know if the T34's drive train suffer as you mention, or did they get round this in other ways?

To be honest the T-34 wasn't really built to last anyway – they pretty much assumed a short service life and built accordingly – I'm pretty sure mechanical breakdown claimed more T-34s than the Germans did. (That said, the T-34 was rear wheel drive, which lessens the issues specifically associated with wider tracks, as you don't have a drivetrain running the whole length of the tank like in many designs.)

Wider tracks put more strain on the drive train, and increase wear and tear. (That's why some tanks had the option to fit a narrower "march" track and a wider "battle" one.)

I was of the opinion that the "march tracks" were only fitted because the Tiger, when loaded onto a railcar, wouldn't fit through narrow tunnels ?

I was of the opinion that the "march tracks" were only fitted because the Tiger, when loaded onto a railcar, wouldn't fit through narrow tunnels ?

This is my impression as well. In fact, if they could get away with it, they'd leave the battle track installed while on trains if there were no clearance issues along its route.

Damon.

"You mean if I just put this armor plate on a sloped angle it works better? Why didn't I think of that?"

The Germans didn't design their early tanks with the conditions of a Russian spring in mind, the Russians did. The Mk III and IV were interim designs that were supposed to be replaced by the early to mid '40s.

The US had 'duckbills' that bolted onto the ends of the track links, giving them another couple inches of track width. The disadvantage of those is that they were fragile and would break off if the tank drove too fast.

Given that tanks steer by slewing the tracks, the wider the tracks, the more resistance there is when turning and hence more stress on the drive system.

Also, the tracks are unsprung, driven mass. The former means that the wider the tracks, the rougher the ride will be (and hence the less stable it will be as a moving gun platform) and the bigger the suspension system needs to be.

The latter again is increasing stress on drive gear -- If you double the width of the track, you've just doubled the torsion forces in the drive-gear shafts. That means bigger engines, bigger gearboxes and heavier parts to service and replace.

Fitting through railway tunnels would be the main consideration, it definitely affected British tank designs as well as German ones. The designer is faced with a number of issues – the lower hull must be 'X' wide to allow a driver and a hull gunner to fit in there but the whole package can only be 'Y' wide and still fit on a train. Then the 'loading gauge' also says that the load cannot be wider than 'Z' at a fixed height above the tracks, so the designer also has to consider what sort of carriage the tank will be carried on, and depressed centre flat cars were almost unknown before WW2, so the tank often had to have a smaller turret for its main armament as well. The list goes on – crane capacity, bridge capacity, rail wheel loads…..

As has been said, British railway loading gauges definitely affected British tank design until after the war, when the decision was finally taken to move tanks by road instead of rail. However, the whole subject of loading gauges is insanely complicated and we still don't get it right – I once saw the track of a rail-borne Warrior MICV hit a station platform edge at 50mph; showering startled passengers with sparks and dust!

The Wiki page on railway loading gauges is good: link

As above, AFV design is always a matter of tradeoffs. Wide tracks to reduce ground pressure use more material and are higher maintenance on both tracks and drive train. Similarly sloped armour is all very whizzy but reduces the useable internal space, and against modern hyper-velocity rounds doesn't make a blind bit of difference.

Well the reason the german tracks were narrower was because they worked fine in the sort of terrain the designer had in mind.
Fitting on a railcar and across a bridge are significant concerns. You build a tank and it has to be able to move around.
Less of a concern is if it might have some trouble in some terrain that seems unlikely in the mind of the designer.

There is also the problem of narrow road bridges.

"What it really comes down to is ground pressure (pounds per square inch or whatever the metric equivalent is) rather than specific track width."

It's far more complex than that. The number of road wheels, their diameters, and the distance between their axles all matter a lot. If you think about it, the wheels are where the tracks will actually have pressure on them and will press down into soft ground, while the space between them will bulge "up." Having the road wheels going up and down little hills isn't helpful.

The complex interleaved road wheels of the Tiger and Panther allowed very large wheel diameters with very closely spaced axles.

With fewer road wheels, you also want to distribute them according to the weight distribution of vehicle to produce even loading.

The complex interleaved road wheels of the Tiger and Panther allowed very large wheel diameters with very closely spaced axles.

Which then becomes a mechanic's nightmare to fix. You will have to pull a minimum of 3 axles worth of road wheels to fix a single wheel.

So there are a lot of variables that go into tank designs.

Which then becomes a mechanic's nightmare to fix. You will have to pull a minimum of 3 axles worth of road wheels to fix a single wheel.

An inner road wheel. The outer ones most likely damaged. Inner ones will be damaged by mines which is going to damage quite a lot. The interleaved wheels give a very smooth ride. Ever seen a movie of the Panther at speed? It is rock steady.

Some excellent and very interesting points. I had a feeling that the German designs would not be 'stupid' / 'ill considered', so it is great to hear some of the rationale behind them – I had not previously considered the width of railway tunnels as a design restriction.

I remember reading about a (from memory) Argentinian tank / AFV which could only be a certain weight (ie. much lighter than ideal) so as to be able to use the weak bridges found in the country – so I guess things are never as easy as we might at first think.

It wasn't so much the size of railway tunnels – more the other bazillion bits of railway infrastructure such as platform edges, bridge parapets, etc, and more critically, the gap between one train and the train coming in the opposite direction. Even then, the more critical aspect of British tank design that was limited by railway loading gauges wasn't so much the track-width as the size of the turret-ring, which in turn limited the size of tank guns.

German Panzer IV added Ostketten or track extensions which lowered ground pressure. They couldn't be fitted while on railcars and might be torn off on a quick turn.

Going back to something Dom the dancing banana said, why have the drive sprocket at the front when the engine is at the rear? It's got to complicate the transmission so what advantages does it give?

I thought front drive sprockets simplified the transmission and meant you didn't have to fit it in the (rather crowded) back of the tank.
Isn't the rear transmission the reason the t34 has the turret so far forward?
You want the turret in the middle for weight distribution.
It's also a sort of reverse of regular vehicle design at the time which would be rear wheel drive with front engine.
So engineers would probably be more experienced with such designs.

Not a lot of room at the back of the tank for the transmission and final drives. Another reason for the front drive sprocket was to minimize the shock loading on the final drives as the tank moved forward at high speed.