Torsion Bar Suspension Analysis: A Panther Primer

[Yoozername]

Very interesting.

http://www.enginehistory.org/Piston/Diesels/CH4.pdf

[HenryCox]

but not always, the drivers side adjusting bolt it ran in further than the passenger. Since the fuel tank is on the drivers side, there needs to be more tension on the drivers torsion bar to get the truck level from side to side. Did you have a full tank when you had the work done?

[Yoozername]

but not always, the drivers side adjusting bolt it ran in further than the passenger. Since the fuel tank is on the drivers side, there needs to be more tension on the drivers torsion bar to get the truck level from side to side. Did you have a full tank when you had the work done?

Thanks. That is very interesting. Are you talking about Panther tanks though?

[critical mass]

Gentlemen,
I have been trying to find information regarding the vertical suspension travel of various AFV. The suspension travel is the amount of maximum deflection (bump + rebound) possible on a road wheel. The amount a roadwheel can freely travel is an important factor in judging the capacity of cross country mobility. Notice that it´s not a direct proxy of cross country mobility, it kind of determines the range of the speed limit, at which crossing an obstacle is feasable, presuming no other limit is encountered before. In practice, floatation, power or transmission limits are frequently encountered long before. Apparently, this information is not easily accessable. Here is what I have found so far:

LEOPARD II, individually mounted single torsion bars: 530mm / bump: 226mm; rebound: 190mm
PANTHER (Ausf.D to -G, incl.), individually mounted dual torsion bars: 510mm /bump: 226mm; rebound: 190mm
CROMWELL, individually mounted Christies suspension: 416mm / bump: 226mm; rebound: 190mm
LEOPARD I, individually mounted single torsion bars, 380mm / 15"
M48, individually mounted single torsion bars: 320mm / bump: 206mm; rebound: 114mm
T54A, individually mounted single torsion bars, 250mm / 10"
T34/76, individually mounted Christies suspension: 240mm / bump: 120mm; rebound: 120mm***
IS-2, individually mounted single torsion bars: 240mm / 9.5"
TIGER (Ausf. E & -B), individually mounted single torsion bars: 230mm / 9.1"
CENTURION, two wheel bogie mounted Horstmann suspension: 172mm/ bump: 83mm; rebound 89mm (235mm total with one wheel only)
M4A, two wheel bogie mounted VVSS suspension: 105mm / 4"
PzIVh, two wheel bogie mounted leafspring suspension: 100mm / 3.9"


***) T34/76 are recorded to have this suspension travel capacity only initially. Due to inferior spring steel used a considerably sagging has been reported after relatively few loading cycles, which may affect suspension travel, too.

[delete013]

Hello Tom, messages #20 & 21 give good points of the Panther's and Tiger's suspension. The downsides were; it ate some armoured volume, was heavy, when damaged was difficult/labourious to repair, especially if inner roadwheels were damaged, same if a torsion bar was damaged, sometimes they had to blow out the damaged torsion bar using explosives. If mud and/or snow was packed between wheels and froze the tank would not move before the mud/snow melted/was melted or was hacked away.

My impression is that torsion bars actually reduced the space needed. In case of a tiger 1 that would be less than 30 cm height. It allows the hull to be expanded in width which I believe was more constrained than the height.

https://www.dropbox.com/s/3opaps5pu9eaz ... a.gif?dl=0

Panthers owed its relative high height to the drive shaft running over torsion bars.

https://www.dropbox.com/s/j9r4i79tmcy6p ... n.jpg?dl=0

On the internet I've seen many claims that torsion bars are hard to replace. I somehow doubt this to be the case. The laborous part is the removal of the road wheels but then they have to be simply pulled out and replaced by a new one. It is certainly less accessible than external boogies but not as problematic.

In exchange for the reduced access one gets the best suspension for the smallest volume. At least in the opinion of Germans.

[delete013]

...
The requirements of either good speed or good floatation usually work against each other, demanding compromises. Churchill and mathilda and valentine do have good floatation but low speed. M4 has speed but low floatation. This AFV tries to squarify the circle, pretty much in response to the T34s demonstration that balancing requirements wasnt impossible.

I somehow doubt the idea about speed vs. floatability to be true. T-34 obviously had both, speed and floatation. The churchill's speed seems more to be due to its design purpose than compromises. It was an infantry tank, meaning that is was expected to keep the speed of the infantry and primarily be able to climb over obstacles of the envisioned trenches. It is a product of the western front of the ww1 experience and similarly to Char B1 has almost no noteworthy suspension. M4's floatation improved quite a bit with HVSS and broader tracks. From about 1 to 0.77 kg/cm^2 (compared to panthers 0.9).

[delete013]

BTW - looking at the suspension on modern MBTs, when and why did interleaving road wheels go out of fashion?

As seen in this diagram: https://www.dropbox.com/s/sgukytu6h77h8 ... d.jpg?dl=0 the individial wheels and suspension arms were stressed much less. According to my info, the limitations of ww2 were mostly due to the lack of sufficient alloys used in bars. The WAllies seem to be limited in using this kind of suspension for lighter vehicles. Soviets bars tended to have short life span and Germans compounded them with another design concept, the road wheel interleaving or overlapping. This became largely superflous during cold war with better alloys but an obvious advantage during the war. Germans could field heavier tanks with better armour and bigger armament while maintaining relatively good vehicle mobility.

[critical mass]

...
The requirements of either good speed or good floatation usually work against each other, demanding compromises. Churchill and mathilda and valentine do have good floatation but low speed. M4 has speed but low floatation. This AFV tries to squarify the circle, pretty much in response to the T34s demonstration that balancing requirements wasnt impossible.

I somehow doubt the idea about speed vs. floatability to be true. T-34 obviously had both, speed and floatation. The churchill's speed seems more to be due to its design purpose than compromises. It was an infantry tank, meaning that is was expected to keep the speed of the infantry and primarily be able to climb over obstacles of the envisioned trenches. It is a product of the western front of the ww1 experience and similarly to Char B1 has almost no noteworthy suspension. M4's floatation improved quite a bit with HVSS and broader tracks. From about 1 to 0.77 kg/cm^2 (compared to panthers 0.9).

I disagree. Floatation is not just ground pressure. Netto ground pressure is a poor indicator for floatation (f.e. Mathilda with very high ground pressure). Relevant is the mean maximum pressure along the tracklength. Smaller diameter roadwheels distribute the weight more equally, which is why You see those often with heavy, and relatively slow vehicle Design (f.e. IS2, Churchill, Maus). However, smaller diameter road wheels increase rolling resistance considerably (You cant scate well on gravel). Larger diameter road wheels focus the weight over fewer contact points, which is negative for floatation but the rolling resistance is low (You can ride a bike over gravel well). The tracks, and their pitch help to distribute vehicle load but the track is not a solid element and the weight is transferred into the soil primarily via contact areas of the road wheels.
The large diameter, interleaved road wheels allowed low rolling resistance over a tight setup of track contact points, thus providing favorable conditions for both, relatively low rolling resistance and good floatation at the expanse of higher weight and complexity.

[delete013]

You are certainly right, mean ground pressure should be mentioned, especially on uneven ground.

So the interleaved wheels, besides lowering the mean pressure along the entire track, also reduce the pressure on the wheels that hit the obstacle first, i.e. locally? This would be somethig that boogies couldn't.

[delete013]

...

Btw, I'm just reading your comments on TankArchives. Do you have a webpage or anything published? I feel compelled to force you into producing something. Your insight into ballistics and materials seems quite higher that anything I have encountered on the internet.

[Yoozername]

On the internet I've seen many claims that torsion bars are hard to replace. I somehow doubt this to be the case. The laborous part is the removal of the road wheels but then they have to be simply pulled out and replaced by a new one. It is certainly less accessible than external boogies but not as problematic.

In exchange for the reduced access one gets the best suspension for the smallest volume. At least in the opinion of Germans.

It would be a little bit more labor intensive than that. The Panther had a torsion bar suspension that went to the other side, locked into a rocker bar, and another torsion bar went from that rocker also, back to the original side.

So, it appears there is a lock down device on the rocker. One would have to clamp this down to do the repair. But for a broken return torsion bar, it would be quite a bit of work.

I am not sure if anyone bothered with such a setup. Even the King Tiger went with single torsion bars.

[delete013]

It would be a little bit more labor intensive than that. The Panther had a torsion bar suspension that went to the other side, locked into a rocker bar, and another torsion bar went from that rocker also, back to the original side.

So, it appears there is a lock down device on the rocker. One would have to clamp this down to do the repair. But for a broken return torsion bar, it would be quite a bit of work.

I am not sure if anyone bothered with such a setup. Even the King Tiger went with single torsion bars.

You're right. Double torsion bar suspension is situated entirely inside the hull. Thanks for the reminder.

Double torsion bar with longer travel has obviously superior performance, particularly at smoothing vehicle during higher speeds. The question is, as often discussed, where does the increased complexity still pay off. Mr. Schneider in his book on the panther mentions that the aim of the design was to give at all costs a superior weapon, to anything available and upcoming. Perhaps is this the reason why they deliberately refused to go for simpler solutions. Comparison with tiger B is, imo, less appropriate, since the vehicle wasn't mant for high speeds. That the panther 2 was to have single bars has its own reasons that might have been a better trade off but also due to a much more desperate situation, which called for simpler vehicles. I habe yet to find what the official reason was. There were a number of simplifications introduced on German vehicles past 1943. I think it made sense to maximise a design in 1942-43 when Germans fielded best crews.

The other day I had a consideration comparing the panther's fate with that of a cromwell. For the former, design was expected to have problems but in worst case they would still end with at least a mass-produced, well protected and deadly platform that moves. Cromwell on the other hand had a higher mobility, less problems with drive train, sleek layout and well balanced armour and firepower.. but for some two years before it was actually introduced. This way it was balanced to have no tactically useful advantage at all past the role of a light tank. On top of it, it appeared nearly impossible to upgrade. Pretty much a similar story to that of Pz3.

[Michael Kenny]

Cromwell on the other hand had a higher mobility, less problems with drive train, sleek layout and well balanced armour and firepower..

Cromwell is just the name for the mark that got a good engine. All the others models had serious mobility issues. One of the differences between UK and German tanks is that one nation would reject a whole class of tank that had drive problems whilst the other would build and field it anyway and hoped it would sort itself out.

[Yoozername]

An overall opinion is that the Panther design just tried too hard. Basically, the Germans went for a trifecta, and should have sacrificed the mobility (speed) aspect and just went with an excellent gun (among the best) and decent armor (facing within an arc of enemy fire).

[Yoozername]

It would be a little bit more labor intensive than that. The Panther had a torsion bar suspension that went to the other side, locked into a rocker bar, and another torsion bar went from that rocker also, back to the original side.

So, it appears there is a lock down device on the rocker. One would have to clamp this down to do the repair. But for a broken return torsion bar, it would be quite a bit of work.

I am not sure if anyone bothered with such a setup. Even the King Tiger went with single torsion bars.

You're right. Double torsion bar suspension is situated entirely inside the hull. Thanks for the reminder.

Double torsion bar with longer travel has obviously superior performance, particularly at smoothing vehicle during higher speeds. The question is, as often discussed, where does the increased complexity still pay off. Mr. Schneider in his book on the panther mentions that the aim of the design was to give at all costs a superior weapon, to anything available and upcoming. Perhaps is this the reason why they deliberately refused to go for simpler solutions. Comparison with tiger B is, imo, less appropriate, since the vehicle wasn't mant for high speeds. That the panther 2 was to have single bars has its own reasons that might have been a better trade off but also due to a much more desperate situation, which called for simpler vehicles. I habe yet to find what the official reason was. There were a number of simplifications introduced on German vehicles past 1943. I think it made sense to maximise a design in 1942-43 when Germans fielded best crews.

The other day I had a consideration comparing the panther's fate with that of a cromwell. For the former, design was expected to have problems but in worst case they would still end with at least a mass-produced, well protected and deadly platform that moves. Cromwell on the other hand had a higher mobility, less problems with drive train, sleek layout and well balanced armour and firepower.. but for some two years before it was actually introduced. This way it was balanced to have no tactically useful advantage at all past the role of a light tank. On top of it, it appeared nearly impossible to upgrade. Pretty much a similar story to that of Pz3.

Your welcome...but how is it a 'reminder' in your calculations?. I am adressing your assertion that it is so easy to change out the torsion bars. I have stated that it is more complicated in a Panther. You have ignored the technical issue. So, don't 'thank me'.... it doesn't bode well for you.....

But you are probably missing the apparent (obvious) point. It is only 'obvious' to you that the Panther tank 'enjoyed' such great mobility. They did not. They also did not 'enjoy' the overly complicated transmission either.

Not sure what your points are...or if you even think you have any?