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c3k

German Interleaved Roadwheels: An Introspective

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Gents,

The German vehicle designers had a fetish with the interleaved roadwheels that they used on the Tiger, Panther, Tiger II, SPW series, Sdkfz 7, etc. That system had the obvious benefit of weight distribution, as well as a robust level of damage tolerance. The drawbacks would seem to be complexity of maintenance and repair in the field. (It'd be a bitch getting to the innermost wheel.)

An ancillary benefit was the protection the unbroken line of wheels would add to the lower hull's armor.

Why is this system no longer in favor?

In fact, did ANYONE use it post-WWII?

Ken

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I copied this from another forum, but this is the answere as far as I know, weightdistribution and the quality of the suspension.

It would be weight distribution. They made their tanks so heavy they needed to fit in so many axles the tank would be two blocks long. So they had to make wheels interleaved so that they would fit in.

The porsche suspension (not interleaved) on Tiger II and Jagdtigers was not very good at crossing terrain giving a bumpy ride.

So there you go. Indeed repairing a wheel could be a major undertaking.

Did anyone ever use it afterWWII? Not that I know of. Would be interesting to see if anyone can find an example of an after WWII use of interleaved wheels..

.

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Tanks are heavier now than then. They ground has gotten no better at supporting massive amounts of weight, so what has changed with modern engineering?

EDIT: Actually, an Abrams seems to weigh about a ton less than a Tiger II, and a Challenger 2 weighs even less. But modern tanks are heavier than Panthers and Tiger I's.

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It would be weight distribution. They made their tanks so heavy they needed to fit in so many axles the tank would be two blocks long. So they had to make wheels interleaved so that they would fit in.

But then why was the interleaved design also used on German halftracks?

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From URL = http://en.wikipedia.org/wiki/Continuous_track

Many World War II German military vehicles, including all vehicles originally designed to be half-tracks and all later tank designs (after the Panzer IV), had slack-track systems, usually driven by a front-located drive sprocket, the track returning along the tops of overlapping and sometimes interleaved large diameter road wheels, as on the suspension systems of the Tiger I and Panther tanks. There were suspensions with one (sometimes double) wheel per axle, alternately supporting the inner and outer side of the track, and interleaved suspensions with two or three road wheels per axle, distributing the load over the track. The choice of overlapping/interleaved road wheels allowed the use of slightly more torsion bar suspension members, allowing any German tracked military vehicle with such a setup to have a noticeably smoother ride over challenging terrain, leading to reduced wear and more accurate fire. As a tracked vehicle moves, the load of each wheel moves over the track, pushing down and forward that part of the earth, snow, etc. under it, similarly to a wheeled vehicle but to a lesser extent because the tread helps distribute the load. Apparently, on some surfaces, this consumes enough energy to slow the vehicle down significantly, so overlapped and interleaved wheels improve performance (including fuel consumption) by loading the track more evenly. It also must have extended the life of the tracks and possibly of the wheels. The wheels also better protect the vehicle from enemy fire, and mobility when some wheels are missing is improved. But this complicated approach has not been used since that war ended. This may be related more to maintenance than to original cost. Mud and ice collect between the overlapping areas of the road wheels, freezing solid in cold weather conditions, often immobilizing so equipped vehicles. The torsion bars and bearings may stay dry and clean, but the wheels and tread work in mud, sand, rocks, snow and so on. In addition, the outer wheels (up to 9 of them, some double) need to be removed to access the inner ones. In WW II, vehicles typically had to be maintained a few months before being destroyed or captured, but in peace time vehicles must train several crews, over a period of decades.

Bottom line is that more torsion bars improved suspension and vehicle mobility performance back then. Post WW2, advanced metals and better metallurgy improved the torsion bars themselves so that the same suspension benefits are now achieved with simpler designs which also allow for easier maintenance. Breaking track and replacing roadwheels is no small nor easy task.

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It's a bit of a mystery who decided to do it, based upon what. There are many different sources claiming different things.

- The Wirtschaftsministerium liked that the Schachtellaufwerk-equipped machines used less rubber for the roadwheels per kilometer. Also fuel consumption seems to have been better.

- PzII-neu drivers waxed poetic about the new overlapping wheel set shedding track much less often.

- There are unsubstantiated rumours from front units about improved mine resistance, but this is not borne out by the Waffenamt tests.

- Wide wheel sets made the use of wide tracks possible. according to design conference reports. I find this hard to accept as a reason though: they could just have used modern-style wide wheels.

- The track stayed straighter under the roadwheels in muddy ground, which would have made crawling out of a bog situation much easier. Especially with front sprockets.

- Track tension and concomitant wear needs to be lower with the flatter roadwheel surface. This is especially important with the amount of road marching the Germans did.

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Bottom line is that more torsion bars improved suspension and vehicle mobility performance back then. Post WW2, advanced metals and better metallurgy improved the torsion bars themselves so that the same suspension benefits are now achieved with simpler designs which also allow for easier maintenance. Breaking track and replacing roadwheels is no small nor easy task.

Thanks for answering my question!

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I recall waaay back when the upgraded M60A3 got a new torsion bar design, it was hailed as a major advancement. Much better wheel movement, much better cross country performance. M60 series was functionally America's 'Panther', a large heavyweight 'medium' tank that had a nasty reputation for occasionally snapping torsion bars at the worst possible moment in the field.

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I recall waaay back when the upgraded M60A3 got a new torsion bar design, it was hailed as a major advancement. Much better wheel movement, much better cross country performance. M60 series was functionally America's 'Panther', a large heavyweight 'medium' tank that had a nasty reputation for occasionally snapping torsion bars at the worst possible moment in the field.

My school was across the road from the Alvis plant where they used to make the Scorpion/Scimitar etc series of AFVs, and I was fortunate enough to get a tour with the school. Our guide told us an amusing story about Scorpions sold to the Saudis which were suffering an exasperatingly high (and unique to the Saudis) frequency of torsion bar failure. Upon sending a company team to investigate, it was discovered that the Saudi grease monkeys had not been paying any attention to the "install this way round" arrows on the bars, so 50% of suspension elements that were removed were replaced with the twisting stress working against, rather than with, the prestress of the metal. Result: loud "poinging" noises when a light tank hit the deck having caught some air off the top of a dune...

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Bottom line is that more torsion bars improved suspension and vehicle mobility performance back then. Post WW2, advanced metals and better metallurgy improved the torsion bars themselves so that the same suspension benefits are now achieved with simpler designs which also allow for easier maintenance. Breaking track and replacing roadwheels is no small nor easy task.

(Partial quote taken from upstream.)

Sooo. If better metallurgy has improved the torsion bars, wouldn't it be even BETTER to have interleaved roadwheels on the big heavies of today?

Other than maintenance headaches, I'd think the benefits would still be there. It'd be kinda cool to be able to wave a magic wand and have a couple M1's go head to head (mobility and targeting on the move). One set with standard suspension, one with interleaved.

Regardless of how it would fare in testing, it'd look cool. And THAT counts for something on the battlefield. ;)

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Aren't modern road wheels somewhat wider than WW2 ones? Perhaps the advantages of wider rollers with modern tech added to the "care and maintenance" concerns of interleaved wheels trump any potential ride improvements. Other combatants didn't (off the top of my head) make it policy to use interleaved road wheels at all during the same period, so the alternative obviously wasn't entirely rubbish.

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Tanks and the drive train are interesting. In WW2 the British Churchill and the German tanks with very different ideas on heavy tank design. The Germans certainly hit the spot with the agility of the Cats on the battleground . Incidentally most people do not realise the Churchill in length exceeds German tanks as it was designed to traverse difficult terrain. Hence the very large number of bogies.

However with the gun forward the Cats had the barrel projecting between 6 and 10ft which could and was a tactical drawback. However the greater lethality of the gun was perhaps a most useful attribute.

PS - I see that modern tanks to increase their agility, for instance the reworked T-55AGM originally with 6kph, have sufficient reverse gears [4] to reach 31kph. AFAIK in tanks WW2 only the Tigers had multiple reverse gears.

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If better metallurgy has improved the torsion bars, wouldn't it be even BETTER to have interleaved roadwheels on the big heavies of today?

The problem of snow and/or mud collecting between the wheels and then freezing overnight would still remain. Might be a trifle disconcerting if the enemy dropped by unexpectedly and your tanks couldn't move.

Michael

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Sooo. If better metallurgy has improved the torsion bars, wouldn't it be even BETTER to have interleaved roadwheels on the big heavies of today?

<snipped>

Not necessarily. You correctly note that it might be a viable option; one of many. Armor design evolved using the other alternatives.

<snipped>

Other than maintenance headaches, I'd think the benefits would still be there.

<snipped>

Never underestimate the impact of such "headaches" nor trivialize the real life costs they produce.

<snipped>

It'd be kinda cool to be able to wave a magic wand and have a couple M1's go head to head (mobility and targeting on the move). One set with standard suspension, one with interleaved.

Regardless of how it would fare in testing, it'd look cool. And THAT counts for something on the battlefield. ;)

Logistics really matter. Don't denigrate them. Lives depend on reliability, maintainability, standardization, and resupply.

Your final sentence almost made me angry. For that I apologize. The only thing that counts on the battlefield is winning. The cost of winning is usually high and always in blood. Looking cool counts for nothing. It's wrong and silly to think so.

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Yup.

Great initial reply post Badger73 but I thought it was pretty obvious that c3k was clearly joking with his subsequent post.

Lest's face it, the Germans in WWII made it an art form building things that looked kewl but it didn't help them at all in the long run. Another way of looking at it is their almost fanatical devotion to over engineering things when the simpler solution is usually best when all things are considered. I'll concede there were exceptions. The V1 was a classic example of a really basic but deadly flying bomb.

Regards

KR

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Lest's face it, the Germans in WWII made it an art form building things that looked kewl but it didn't help them at all in the long run. Another way of looking at it is their almost fanatical devotion to over engineering things when the simpler solution is usually best when all things are considered.

Especially on the battlefield, where things that run fine all the time tend to suddenly develop ills that require attention right now. At such times, it's really nice to be able to fix something just by sliding it out, spitting on it, wiping it on your sleeve, and then sliding it back in.

;)

Michael

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As others have already so stated, the use of ;) was, perhaps, overlooked.

Logistics is the key. However, logistics need to be USED. Keeping men supplied with crappy gear is not the way to win.

I'm reminded of a quote by Creighton Abrams when he was Chief of Staff of the Army. They were working on the design of the tank which would eventually bear his name. He tried explaining that all the bells and whistles had to take into account how difficult it is to keep things working in the field. He said, and I paraphrase, "you can take a soldier into the desert and drop him off with an anvil. When you come back the next day to pick him up, the anvil will be broken in half. If you ask him how it broke, he'll shrug his shoulders and say it just happened."

Back to interleaved roadwheels. In combat accounts, and period testing, they took amazing amounts of hits before they would fail. That, surely, must be worth something, especially with the standoff distance they would create for shaped charge warheads.

Ice and mud freezing: the US contractor solution would be heated wheel rims with an active IR cloaking system to hide them from the enemy. ;) <--- See?

With all the new design tools, is there any way that ice/mud would not be such a hazard? Obviously, it did not immobilize all the tanks in the winter. Why, then, were some immobilized and some not? Did it take constant work to keep them mobile, or was just a few extreme cases which immobilized them? I don't recall reading anything about the Tigers in Tunisia (or elsewhere, for that matter) having the need to be overly cautious around areas with small stones. (Conflating a big chunk of ice to a small rock.)

Obviously, wet material jammed amid the running gear, and then freezing, is far different than a few odd rocks flying about.

Do modern tankers NOT have to clean out their running gear prior to sitting in a freezing location if they've been running about in the muck first?

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Does anyone have the primary sources indicating that the Schachtellaufwerk was more susceptible to freezing/mudding up? I've been looking, and I only find one very short mention of Pz IV's getting mired in frozen mud. And they didn't have the overlapping wheels.

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Interleaved roadwheels was a compromise to a string of self-imposed problems. Limited swingarm movement for first generation torsion bars required longer swingarms to amplify the shock absorbing effect. But long swingarms with tiny wheels comes with its own set of problems. So they opted for long swingarms with large wheels. Again, another problem arises - large wheels meant fewer wheel stations per side and poor distribution of weight. So they compromised again, more wheel stations by overlapping the big wheels. Its interesting that they apparently got fed up with the whole affair and most 'paper panzers' on the drawing board at war's end had reverted to external-mounted leaf-spring sprung wheels. Many based on the old Czech Panzer 38(t) drivetrain.

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Unfortunately I cannot remember or find who said this and are somewhat loath to post it but it does seem appropriate.

A good Commander knows strategy and Tactics.

A great Commander knows logistics.

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Interleaved roadwheels was a compromise to a string of self-imposed problems. Limited swingarm movement for first generation torsion bars required longer swingarms to amplify the shock absorbing effect. But long swingarms with tiny wheels comes with its own set of problems. So they opted for long swingarms with large wheels. Again, another problem arises - large wheels meant fewer wheel stations per side and poor distribution of weight. So they compromised again, more wheel stations by overlapping the big wheels. Its interesting that they apparently got fed up with the whole affair and most 'paper panzers' on the drawing board at war's end had reverted to external-mounted leaf-spring sprung wheels. Many based on the old Czech Panzer 38(t) drivetrain.
I disagree entirely. As war progressed, the Krauts put Schachtellaufwerk on the latest Pz II and Pz III models to improve their speed and reliability. With big wheels, because big wheels means big radii of curvature, which in turn means less churning of mud, and thus better off-road capability.

As to the Schachtellaufwerk on the heavies being overengineering of a bad idea, just have a look at the VK4501 project, which culminated in the Ferdinand. This machine used 'traditional' suspension, although also with large wheels. It burned out motors at the least provocation, didn't want to turn well offroad, shed tracks, and was an automotive liability that made the Tiger and Panther look like Toyota Landcruisers.

The whole story of the Tiger [and by extension, the Panther] being designed with Schachtellaufwerk seems to stem from the early realisation by the overall design team that they weren't going to be able to power such a big machine if it wasn't optimised for light running. A consideration the French did with one of their questionable designs post-war [AMX 50?]. The rest of the world just switched to high-power Diesels, and powered out of the problem.

The Paper Panzers never got to the point where a decision was reached about such technicalities as suspension, armament, engines, or any other considerations. To say that they 'went back' is a bit quick.

Finally, let us not forget that the Tiger B was designed from scratch based upon experience with the Tiger, and they kept Schachtellaufwerk, although they went to steel rimmed wheels to keep maintenance to a minimum.

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ArgusEye,

If I understand you correctly as to the "S" word (which I'd probably botch), I believe you mean a Panzer V (Panther) or Panzer VI (Tiger).

Panther woes with interleaved roadwheels.

http://en.wikipedia.org/wiki/Panther_tank

"The Panther's suspension was complicated to manufacture and the interleaved system made replacing inner road wheels time consuming (though it could operate with multiple missing or broken wheels). The interleaved wheels also had a tendency to become clogged with mud, rocks and ice, and could freeze solid overnight in the harsh winter weather of the Eastern Front. Shell damage could also cause the road wheels to jam together and become extremely difficult to separate.[29] Interleaved wheels had long been standard on all German half-tracks. The extra wheels did provide better flotation and stability, and also provided more armor protection for the thin hull sides than smaller wheels or non-interleaved wheel systems, but the complexity meant that no other country ever adopted this design for their tanks.[30]"

Achtung Panzer has this to say of the Tiger 1's suspension problems.

http://www.achtungpanzer.com/panzerkampfwagen-vi-tiger-ausf-e-sd-kfz-181.htm

(Fair Use)

"Tiger’s suspension was composed of driving sprocket, rear idler and interleaved roadwheels (36 in total). Interleaved roadwheel arrangement used in Tiger I caused mud, ice and rocks to jam the track mechanism and as a result immobilize the tank. To overcome this problem, running gear needed constant attention, especially on the Eastern Front."

(Fair Use)

I've read of Tiger crews using blowtorches to both warm up the engine compartment and thaw out great clots of frozen mud and ice between the interleaved wheels during winter on the Eastern Front. Believe that was in one of those killer Fedorowicz Tiger books which a friend had.

Regards,

John Kettler

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Tiger P (Ferdinand) is a bit of a red herring since it was such a peculiar beast from stem to stern. Running off big electric motors like a trolleycar with petrol engines used to provide electrical current. Transverse externally mounted pod-type torsion bars - there's nothing 'traditional' about that. The machine was an engineering disaster waiting to happen. Tiger I, Panther, Panther II and Tiger II were all variations on the same theme. Like the US and its volute spring suspension they were wedded to a design idea come hell or high water. Planning ahead, they abandoned torsion bar suspension for (Porsche-type) bolt-on suspension for their E-1, E-25, E-50, E-75 and E-100 designs. Interestingly, the most famous post-war Brit tank, the Centurion, their 'British Panther', also used external bolt-on suspension units instead of torsion bars.

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