What the Hell is the Point of Interleaved Road Wheels?

[Thomas Zhang]

On 6/10/2016 at 7:26 AM, Collimatrix said:

Great find legiondude!

 

I'm actually pretty partial to the E-series suspension concept, as it appears to solve or at least ameliorate the big problem with interleaved/overlapping road wheels.

 

 

There are horizontal tubes filled with belleville washers pressing against a piston.  The piston is attached to the swing arm via that rack and pinion toothed mechanism.  This would probably work fine for the E-10 and E-25, but surely I am not the only one who thinks that those teeth would strip right the fuck off if E-50 or E-75 hit a bump.  Especially with late-war German metallurgy.

 

Anyway, to pull a bad road wheel you pull the bogie of two road wheels off.  Even if they're in fully overlapping configuration, you only need to tilt the bogie off diagonally to get it off the hull without disturbing the other road wheels.  This does mean that you have to take the road wheels off as pairs, and with their associated springs, but this is basically the same procedure for changing a road wheel on a tank with Horstmann suspension:

 

 

And you'll see paeons to the centurion raving about how much easier it was to swap out busted centurion suspension units than it was to change out road wheels and torsion bars on the M48.

So is the E-50 suspension independently sprung? How does it compare to torsion bar suspension of Panther and Tiger II (smoothness and pitching issue)?

I am worried about its pressure on tracks since E-50 only has 6 wheels (3 pairs) per track while the Panther has 16 and Tiger II has 18 wheels.

I mean look at the wheels - they are so thin and few it makes me cringe.

[Scolopax]

44 minutes ago, Thomas Zhang said:

So is the E-50 suspension independently sprung? How does it compare to torsion bar suspension of Panther and Tiger II (smoothness and pitching issue)?

I am worried about its pressure on tracks since E-50 only has 6 wheels (3 pairs) per track while the Panther has 16 and Tiger II has 18 wheels.

I mean look at the wheels - they are so thin and few it makes me cringe.

 

To quote Jentz and Doyle in Panzer Tracts No. 20-1:

Quote

 

The suspension was an entirely new design. The individual roadwheels were mounted in Schrittanordung (step arrangement). The crank arms for each pair of roadwheels acted through ratchets and wedge gear segments on a large parcel of Belleville springs contained in a housing with the shock absorbers. The E 50 had three suspension units  on each side, and the E 75 had four suspension units. The combat track for the E 50 was to be used as the transport track for the E 75.
 

 

 

It should be worth noting that this model above is probably not 100% to scale.  The road wheels on it do look noticeably thin, but that seems to me to be a result of the model designers.  They should be more similar, if not the same, as those found on the King Tiger.

 

 

World of Tanks' E-50 model has the suspension units modelled (and can be viewed here), so that should give an idea of what it would have looked like.

[TokyoMorose]

On 6/23/2016 at 5:26 AM, Collimatrix said:

Forczyk mentioned in his T-34 vs panther book that there was some loon in the German armor development bureaucracy who was completely obsessed with torsion bars and interleaved road wheels, and would basically reject any design that didn't have them.  This is apparently why the DB panther design gained them later in development.  But it's not clear to me why this guy had so much say in tank design, and why everyone around him didn't point and laugh.

 

I know I am late here, but the loon wouldn't happen to be Ernst Kniepkamp would it? I know with the half-tracks and Panzer III he was directly the guy responsible for those elements - and the Tiger I work at Henschel was also his pet project of the time.

 

And wait, I have Forcyk's book.... and yep it is Kneipkamp. Head of all tank projects at the Wehrmacht, and had been the chief army engineer even before the Nazi takeover when it was the "Military Automotive Department". Even the tiny Kettenkrad has the interleaved wheels, and yep the patent on that is "E. Kneipkamp".

[heretic88]

Funny that nowadays everybody likes to bash ww2 german stuff. Yes, interleaved road wheels had problems, but it wasnt that bad actually. What about the mythical Christie suspension? In my opinion that was far worse. Took lots of space inside and was a nightmare to repair, much worse than interleaved german suspension. Also the ride quality... I once had the opportunity to ride on a T-34, that thing has horrible,  I felt almost every bump on the road. Compared to it, the T-55 (that I drove lots) has a luxury car quality suspension.

[EnsignExpendable]

I don't know why you think it was a nightmare to repair, replacement of springs was something that could be done at company repair workshops without much difficulty. As for taking up room inside the vehicle, the British actually praised this solution because it did not increase the height of the tank or require skirts like their own tanks had. Although the British always had a pretty complicated relationship with suspensions.

Actually I wonder, there is nothing stopping one from making a tank with both interleaved road wheels and a Christie suspension...

[Pascal]

That "i felt almost every bump on the road" doesn't look like a Christie suspension problem, more like "not having any shock absorbers" problem.

[Walter_Sobchak]

6 hours ago, EnsignExpendable said:

I don't know why you think it was a nightmare to repair, replacement of springs was something that could be done at company repair workshops without much difficulty. As for taking up room inside the vehicle, the British actually praised this solution because it did not increase the height of the tank or require skirts like their own tanks had. Although the British always had a pretty complicated relationship with suspensions.

Actually I wonder, there is nothing stopping one from making a tank with both interleaved road wheels and a Christie suspension...

 

If they could figure out a way to make a tank suspension out of Beleville washers, anything is possible.

[heretic88]

18 hours ago, EnsignExpendable said:

I don't know why you think it was a nightmare to repair, replacement of springs was something that could be done at company repair workshops without much difficulty. As for taking up room inside the vehicle, the British actually praised this solution because it did not increase the height of the tank or require skirts like their own tanks had. Although the British always had a pretty complicated relationship with suspensions.

Yes, definitely not as time consuming (at least on T-34) as in the case of the Tiger or Panther, but still not an easy task, far harder than changing a bogie on a Sherman or on a Panzer IV, or changing a torsion bar on a tank without interleaved road wheels. Some springs are more or less trouble free, but some are nasty. In case of the british tanks, well, suspension repair is horror, surely worse than interleaved stuff (tracks off, wheels off, side armor plate off). Brits liked all kinds of weird stuff

So yes, you can bash the interleaved suspension, it indeed had problems. But it is unfair if you bash only that, when at the same time, there were other similarly less successful designs, like the Christie suspension. (in fact, you can still find some prototypes after the war with interleaved wheels, but absolutely nothing with Christie suspension)

 

[heretic88]

15 hours ago, Pascal said:

That "i felt almost every bump on the road" doesn't look like a Christie suspension problem, more like "not having any shock absorbers" problem.

Well, yes you can have shock absorbers with Christie suspension but that makes things more complicated, like on british tanks. 

[Pascal]

2 hours ago, heretic88 said:

Well, yes you can have shock absorbers with Christie suspension but that makes things more complicated, like on british tanks. 

Yeah i know about the british tanks, i just noted that the bumpy ride was on the fault of missing shock absorbers in a t-34 not the suspension.

[EnsignExpendable]

There is no issue at all with fitting shock absorbers on Christie suspensions, the British put them in place of the guide rod in the center of the spring.

[Collimatrix]

 

[Beer]

On 8/9/2019 at 9:33 AM, TokyoMorose said:

 

I know I am late here, but the loon wouldn't happen to be Ernst Kniepkamp would it? I know with the half-tracks and Panzer III he was directly the guy responsible for those elements - and the Tiger I work at Henschel was also his pet project of the time.

 

And wait, I have Forcyk's book.... and yep it is Kneipkamp. Head of all tank projects at the Wehrmacht, and had been the chief army engineer even before the Nazi takeover when it was the "Military Automotive Department". Even the tiny Kettenkrad has the interleaved wheels, and yep the patent on that is "E. Kneipkamp".

 

Sorry for being late to the party but I found it interesting that the to my knowledge not a single serial vehicle, prototype or concept coming from ČKD (BMM) or Škoda during the war had interleaved wheels (not even any paper project). In the end only one of those designed during the war made it to serial production - the Pz.38(t) n.A. chassis used on Panzerjäger 38(t) Hetzer (albeit the design was somewhat affected by the deliberate effort of ČKD chief designer Aleksey Surin to sabotage it, especially the early vehicles). It's notable that the companies had German management installed to oversee any development, yet they still insisted on not to use the interleaved wheels. In light of what you wrote it is also possible that Pz.38(t) n.A. lost to Pz.II Ausf.L Luchs for this reason because otherwise it was arguably the better machine for its task.   

[delete013]

On 1/11/2021 at 4:11 PM, Beer said:

 

Sorry for being late to the party but I found it interesting that the to my knowledge not a single serial vehicle, prototype or concept coming from ČKD (BMM) or Škoda during the war had interleaved wheels (not even any paper project). In the end only one of those designed during the war made it to serial production - the Pz.38(t) n.A. chassis used on Panzerjäger 38(t) Hetzer (albeit the design was somewhat affected by the deliberate effort of ČKD chief designer Aleksey Surin to sabotage it, especially the early vehicles). It's notable that the companies had German management installed to oversee any development, yet they still insisted on not to use the interleaved wheels. In light of what you wrote it is also possible that Pz.38(t) n.A. lost to Pz.II Ausf.L Luchs for this reason because otherwise it was arguably the better machine for its task.   

A lot of conjecture here on your part. Afaik, Pz.38 was kept in production due to the great need for armoured vehicles. You might have noticed that most numerous German tanks in 1940 were still Pz2s or earlier and were not considered adequate at the time. The chassis was evidently decent enough to enter the usual German vehicle lifespan cycle. But as a weapon platform.

 

The key to understanding Luchs is its off road mobility, the principal improvement over previous Pz2 at which Pz.38 was no better. Here comes in one of the advantages of overlapping wheels, the ability to traverse rough ground at high speeds, needed for a recce vehicle.

[Beer]

43 minutes ago, delete013 said:

A lot of conjecture here on your part. Afaik, Pz.38 was kept in production due to the great need for armoured vehicles. You might have noticed that most numerous German tanks in 1940 were still Pz2s or earlier and were not considered adequate at the time. The chassis was evidently decent enough to enter the usual German vehicle lifespan cycle. But as a weapon platform.

 

The key to understanding Luchs is its off road mobility, the principal improvement over previous Pz2 at which Pz.38 was no better. Here comes in one of the advantages of overlapping wheels, the ability to traverse rough ground at high speeds, needed for a recce vehicle.

 

Sorry but you shall educate yourself a little bit because Pz.38(t) n.A. is different vehicle than Pz.38(t) just like Luchs is not the same vehicle as usual Pz.II. The "Neue Art" Pz.38(t) is what later became the chassis for Jagdpanzer 38(t). Even the chassis is not completely same as of Pz.38(t) albeit it looks same. The "Neue Art" had much larger and twice stronger engine (from V-8-H aka ST vz.39 medium tank) than the original Pz.38(t) while having only some 1,7-1,8 t more. It reached up to 75 km/h during testing in Kummersdorf. The power to weight ratio was 21,1 Hp/t while Luchs had only 15,2 Hp/t. Unlike the original Pz.38(t) the "n.A." was fully welded. It was better armoured than Luchs while having slightly lesser weight (up to 50 mm on gun mantlet) and it had much stronger armament (37 mm A19 gun - again different gun than in the original Pz.38(t). It had even reasonably better ground pressure than Luchs with its Kniekamp suspension (0,06MPa for the "n.A." and 0,08 MPa for Luchs) and could climb much higher obstacle (1,08 m for "n.A." and 0,6 m for Luchs). Luchs had an advantage of having more comfortable torsion bar suspension, better ground clearance and more crew space in the turret (likely because of the tiny gun it had), that is true but in the end history tells that Luchs ended as a failure. 

 

After all the Germans decided in late 1944 that future light tracked vehicles shall be built on Pz.38(t) n.A. and preferably on its diesel derivate 38 (d) chassis abandoning Kniekamp's interleaved wheels. 

 

 

 

[delete013]

2 hours ago, Beer said:

 

Sorry but you shall educate yourself a little bit because Pz.38(t) n.A. is different vehicle than Pz.38(t) just like Luchs is not the same vehicle as usual Pz.II.

Apparently I should have. I didn't know that a special recon vehicle was built.

2 hours ago, Beer said:

The "Neue Art" Pz.38(t) is what later became the chassis for Jagdpanzer 38(t). Even the chassis is not completely same as of Pz.38(t) albeit it looks same. The "Neue Art" had much larger and twice stronger...

Interesting info. I see that there was a contest between Pz.2 L, Pz.38.n.A. and T15. I doubt however that politics were involved. Germans used Škoda for TDs.

2 hours ago, Beer said:

After all the Germans decided in late 1944 that future light tracked vehicles shall be built on Pz.38(t) n.A. and preferably on its diesel derivate 38 (d) chassis abandoning Kniekamp's interleaved wheels. 

This is your assumption or a fact? The idea that interleaved wheels were abandoned due to Czech light tanks is highly unplausible to me.

[Beer]

3 minutes ago, delete013 said:

Interesting info. I see that there was a contest between Pz.2 L, Pz.38.n.A. and T15. I doubt however that politics were involved. 

 

There is not enough known to me about what was the decisive factor. From a book I read the Kummersdorf comission allegedly recommended Pz.38(t) n.A. but Waffenamt selected Luchs. There could have been a lot of reasons for that (performance, lobbing, planning of supplier workload, Kniekamp's preference of his suspension design etc. etc.). We will likely never know. We only know that Luchs as a program failed. 

  

3 minutes ago, delete013 said:

Germans used Škoda for TDs.

 

The only Škoda AFV design used by Germany was pre-war Pz.35(t). All those other Czechoslovak vehicles used by Heer or SS were designs of ČKD (BMM per Germans). Škoda was co-producer of ČKD vehicles but it was mainly occupied with various artilery. The only other Škoda design which made it to production during WW2 was the T21 medium tank. This tank was produced under a licence in Hungary as 40M Turán (with Hungarian armament) and the chassis was used for 43M Zríniy assault gun. Other Škoda WW2 AFV designs didn't make it past paper (WoT players know T25 tank but the only actually existing thing of it was the gun with the autoloader, the rest was only on paper). 

  

3 minutes ago, delete013 said:

This is your assumption or a fact? The idea that interleaved wheels were abandoned due to Czech light tanks is highly unplausible to me.

 

Based on various sources I read it was decided by the AFV comission on 4th October 1944 that all new light tracked vehicles will be built on 38 (d) chassis. 38 (d) was a modification of 38 (t) n.A. done by Alket and using Tatra air-cooled diesel engine instead of petrol ČKD/BMM ones (in fact two of five Pz.38(t) n.A. prototypes already had Tatra diesel). I don't think that it was because of Czech light tanks. It was IMHO because interleaved wheels where wrong idea especially from production and mainteanance point of view and also because of the ever planned optimization of the AFV production - to have high level of standardization and to use best the Czechoslovak factories which were largely unaffected by Allied strategic bombing (the first successful air raid on Škoda happened only in December 1944 and there were only two others following in April 1945, when it was irrelevant already, and ČKD/BMM was bombed (hard) only once at the end of March 1945). 

 

I think that it can be confirmed for example by the development of the never materialized successor of Sd.Kfz.251, the APC Kätzchen. The original design K1 by Auto-Union had Kniekamp's suspension. Later Auto-Union was ordered to test ČKD suspension as well (K2 prototype wa built). In the end the whole project was transefered to ČKD for redesign (and use of the diesel engine) but only a wooden mockup was built before the war ended. That happened despite the fact that in APC use the relative discomfort of the ČKD suspension was a signifficant drawback.  

 

For your information Surin's ČKD/BMM suspension was considered as one of three options also for the E-50 and 75. The final decision about which suspesnion would be used was never done. 

[delete013]

On 6/23/2016 at 2:26 PM, Collimatrix said:

 

I'm actually not 100% clear on why the Germans were so obsessed with this suspension design.  It wasn't just the big cats that they stuck with these silly things, it was every single Sdkfz 251.  That was probably even worse for them, since those were supposed to be mainstay medium transport.

251 would eventually be replaced by smth akin to Gep. MTW Kätzchen, which has what? [The interleaved wheels.] One prototype had them apparently. The rest were based on Pz.38 karosserie.

Quote

If the Germans ditched the stupid suspension and were able to make a few hundred extra tiger IIs in 1944, I can't see how that would make much difference.  If they had ditched the stupid suspension and made a few thousand more Sdfkz 251s in 1939, that might have material impact.

The [theory] idea is pretty straightforward, as has been mentioned. Larger wheels with narrower gaps in-between offer better absorption of terrain and better carrying of the weight at any speed. In fact, almost every late-war German design had overlapping wheels. The E-Serie study is full of them, not only the heavies.

They weren't considered as good as interleaved but a compromise had to be made. Any other form of suspension was an emergency improvisation, especially bogies that were considered obsolete. Lucky for the WAllies, rarely is pointed at the fact that they largely dispensed with tactical maneuver mid-war, do no need for fancy drive trains. Infantry tanks suddenly didn't need speed or agility, cruiser tanks no armour. Sounds perfect for that doctrine, too bad Germans didn't abide to it.

 

Quote

Forczyk mentioned in his T-34 vs panther book that there was some loon in the German armor development bureaucracy who was completely obsessed with torsion bars and interleaved road wheels, and would basically reject any design that didn't have them.  This is apparently why the DB panther design gained them later in development.  But it's not clear to me why this guy had so much say in tank design, and why everyone around him didn't point and laugh.

You don't understand, is not on your favourite tank, so it is stupid? Lol. Overlapping wheels on tiger 2 were not considered as optimal as the interleaved would be. But they still offered that needed weight distribution, across the chassis but also on individual wheel. This reduced strain on roadwheel arms and individual torsion bars when hitting several bumps on uneven terrain. Which is one clue to understanding that IS-2 with its small wheels couldn't be anything but slow, unless one wanted to incapacitate the crew or the drive train. Hence, faster off-road speeds for Germans, better maneuvering, more flanking surprises, better combat performance. And it is pretty clear what the Allies were the worst at, maneuver warfare. There is no reason to think that the design wasn't the best around. Everyone else ran about with lighter or slower vehicles.

 

There is however another reason. Germans had to include the limitations of their steel into calculations.

[Lord_James]

45 minutes ago, delete013 said:

better maneuvering, more flanking surprises, better combat performance. And it is pretty clear what the Allies were the worst at, maneuver warfare. 

You must be taking-the-piss, the allies out maneuvered the Germans far more than the reverse, as demonstrated by the great many, successful pincer movements used by the allies during the war. 

[delete013]

22 minutes ago, Lord_James said:

You must be taking-the-piss, the allies out maneuvered the Germans far more than the reverse, as demonstrated by the great many, successful pincer movements used by the allies during the war. 

Great many? Which ones?

[Lord_James]

38 minutes ago, delete013 said:

Great many? Which ones?

Other than the incredibly successful pincer movement the Nazi’s got themselves into when they went to war on 2-3 fronts, against 2 pier level (Russia and Britain) and one superior (USA) opponents? Successful insomuch that the person on the inside of the pincer is suppose to lose, right? 
 

But I’m sure you’re not talking about that, you’re talking about tactical maneuver, in which case I will remind you of: Arracourt, Stalingrad, Leningrad-Novgorod, Riga, Ruweisat ridge (part of first battle of El Alamein), the Falaise / Mons / Colmar pockets... the Nazi’s we’re outmaneuvered again and again, on all fronts, while they couldn’t do the same back due to highly immobile vehicles, many of which were using the inter leveled wheels. I would argue that their most maneuverable vehicles were the panzer 2, 3, and 4 (and derived vehicles) which didn’t have that overly complicated and maintenance intensive wheel system.

[Beer]

3 hours ago, delete013 said:

251 would eventually be replaced by smth akin to Gep. MTW Kätzchen, which has what? The interleaved wheels.

 

No. Only the very first prototype Kätzchen K1 had interleaved wheels. Read please again my post. Second prototype had Surin's suspension and the final vehicle which was never finihed was supposed to be this (yes, only wooden mockup but this is the final vehicle). 

 

  

3 hours ago, delete013 said:

 

The theory is pretty straightforward, as has bees mentioned. Larger wheels with narrower gaps in-between offer better absorption of terrain and better carrying of the weight at any speed. In fact, almost every late-war German design had overlapping wheels. The E-Serie study is full of them, not only the heavies.

 

Never ever was taken any final decision about anything related to E-series. In fact they were canceled before they even got to any final design. Still there were three suspension options and none of them was of Kniekamp style interleaved wheels á la Panther, Sd.Kfz-251 or Tiger. I have already once gave you this link. Please read it finally.

 

The theory is nice but it was proven to be just a theory. People told you that million times alrerady - nobody else ever used that suspension for plenty of very good reasons. Pz.III suspesnion is used by tanks till today, more than 80 years after it was designed. Kniekamp's suspension was dead and burried by May 1945. In next nearly 80 years nobody used it again. Think about why. 

 

1) It adds several tons of weight itself (and therefore also fuel consumption which is kinda bad when you don't have fuel). 

2) it takes more space inside and makes the internal volume of the vehicle larger and therefore even heavier (and often also prevents having floor emergency hatch (Panther)

3) It needs twice more manhours, twice more material and therefore most likely costs about twice more than standard torsion bar suspension. 

4) You know which steel absolutely needs all those chemical elements which Germany lacked? Spring steel. Think about how good idea is to have twice more springs on every fucking vehicle than what is needed.

5) It is terrible for mainteanance. 

6) It likes to collect several hundreds of kilos of mud which adds more weight to the whole thing and tends to freeze in winter 

 

The zig-zag variant used on Königstiger was not better because it added fast track destruction by twisting (this would happen to most of considered E-series suspension too). 

 

Is-2 has lower ground pressure than Panther. IS-2 0,0785 MPa, Panther 0,09 MPa. The reason why Panther was faster in terrain was not interleaved wheels but the double torsion bars (which added another quantum of issues). Geez... 

 

 

[TokyoMorose]

3 hours ago, Beer said:

 

There is not enough known to me about what was the decisive factor. From a book I read the Kummersdorf comission allegedly recommended Pz.38(t) n.A. but Waffenamt selected Luchs. There could have been a lot of reasons for that (performance, lobbing, planning of supplier workload, Kniekamp's preference of his suspension design etc. etc.). We will likely never know. We only know that Luchs as a program failed.

 

As far as I understand it, the rather key reason that the Luchs won over the n.A. (and the Luchs actually *failed* to meet requirements, the program required a 50mm gun and the best MAN could weasel out was they would have a new 50mm turret 'sometime' in the future for it) - was quite simple. MAN was both German and had lots of friends in the brass making decisions. The great irony is that they would basically have to beg for something to replace the nonexistent Luchs (as MAN was so overloaded with higher priority work, they never made more than the LRIP 100 tanks, and it was an epic feat for them to do that - more than a year at WW2 build pace!)... which resulted in the Sd.Kfz 140/1 being churned out for a few months before all Czech production was ordered to change to JgPz 38(t).

 

Always recommend the translated Pasholok piece here: https://www.tankarchives.ca/2018/07/reconnaissance-cats.html

 

It covers the sordid tale of Luchs and Leopard, and ends up discussing the 140/1 (Aufklärungspanzer 38(t)) at the end.

[Beer]

4 minutes ago, TokyoMorose said:

 

As far as I understand it, the rather key reason that the Luchs won over the n.A. (and the Luchs actually *failed* to meet requirements, the program required a 50mm gun and the best MAN could weasel out was they would have a new 50mm turret 'sometime' in the future for it) - was quite simple. MAN was both German and had lots of friends in the brass making decisions. The great irony is that they would basically have to beg for something to replace the nonexistent Luchs (as MAN was so overloaded with higher priority work, they never made more than the LRIP 100 tanks, and it was an epic feat for them to do that - more than a year at WW2 build pace!)... which resulted in the Sd.Kfz 140/1 being churned out for a few months before all Czech production was ordered to change to JgPz 38(t).

 

Always recommend the translated Pasholok piece here: https://www.tankarchives.ca/2018/07/reconnaissance-cats.html

 

It covers the sordid tale of Luchs and Leopard, and ends up discussing the 140/1 (Aufklärungspanzer 38(t)) at the end.

 

Yes, I read this article. I read also the book of Francev about Czechoslovak vehicles but neither source gives a definitive answer. Sure Luchs failed. That's the only thing we know for sure. 

[TokyoMorose]

12 minutes ago, Beer said:

 

Yes, I read this article. I read also the book of Francev about Czechoslovak vehicles but neither source gives a definitive answer. Sure Luchs failed. That's the only thing we know for sure. 

 

I just find it very amusing that MAN was able to submit a vehicle that did not meet the hard requirements (the 5cm gun), and still managed to win. That is some grade A favoritism.