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Tracks vs Wheels   General Army topics

Started 26-May by graylion; 15094 views.
schnuersi

From: schnuersi

9-Jun

stancrist said:

Not doing mechanized infantry exactly the same way as Germans or Russians doesn't make the US Army wrong, just different.

I found a nice video showing German mech Inf (Grenadiers) in training. A simulated firefight.
https://www.youtube.com/watch?v=ENipa4fYOSc
Its focussing a lot on the machine gunners but its intresting footage.

TarheelYank

From: TarheelYank

9-Jun

Elbonia is also famous for waist deep mud year round and it's also their major export.

stancrist

From: stancrist

9-Jun

schnuersi said:

I found a nice video showing German mech Inf (Grenadiers) in training.

Nice.  First time I've seen an MG3 with the bipod attached so far back from the muzzle.

schnuersi

From: schnuersi

10-Jun

stancrist said:

First time I've seen an MG3 with the bipod attached  so far back from the muzzle.

The MG3 (and MG42 for that matter) have to attachment points for the bipod. One close the the muzzel and one roughly in the middle. The first one is the one normally used. The second one is for close range shooting. It gives a greater arc of traverse. Close to the muzzle gives a more stable gun.

The spare barrel container is also in the video. The gunner carries it slung on his back. The unit also make use of a weapons teams. The gunner at least once calls for his assistant. He calls for more ammo several times.

WarthogARJ

From: WarthogARJ

11-Jun

Thanks for your very clear reply: I understand what you're saying, and I think it makes sense.

In terms of wheeled vs tracked vehicles getting stuck, I think there's quite a bit that can be done with wheeled vehicle design to improve traction, whilst you're much more inherently constrained with a tracked vehicle.

I think the older wheeled IFV's are not a good measure of what a wheeled IFV can indeed do with careful design.

It would be useful to have a Standard with a controlled range of terrains to assess IFV's on: I am not so sure that tracks are always so great across the board. But it's hard to prove that because from what I can tell (in my admittedly limited exposure) I haven't seen a lot of controlled head-to-head tests.

But as you say, the results are likely kept confidential.

Be interesting to see how the Puma Level C fared against a modern 8x8 with similar Stanag ratings over a range of terrain.

Take muskeg (using the term to include marshland): if the top layers are soft enough so the tracked IFV sinks down, and it doesn't bottom out, it's stuck for good. Maybe even sink! But a wheeled IFV inherently floats, and using a combination of wheel traction and jets, it has a better chance of getting through.

And when a tracked IFV is indeed stuck, it's a HEAVY bastud to pull out.

schnuersi

From: schnuersi

11-Jun

WarthogARJ said:

It would be useful to have a Standard with a controlled range of terrains to assess IFV's on:

Such tests are made. The German MoD for example runs several test facilities for this. There are also test done in artic and desert climates abroad. These are usually done at the same places.

WarthogARJ said:

I am not so sure that tracks are so great across the board.

Sure they aren't. Tracks are pretty bad on roads and hard surfaces.

WarthogARJ said:

I haven't seen a lot of controlled head-to-head test

Yes these are usually classified.

WarthogARJ said:

Be interesting to see how the Puma Level C fared against a modern 8x8 with similar Stanag ratings over a range of terrain.

The thing is I do not know any wheeled vehicle with a comparable protection level. The fully equiped Puma also weights more than the sensible threshold for 8x8 vehicles. This is one thing that makes comparison so tricky. The vehicles themself are quite different.

WarthogARJ said:

But a wheeled IFV inherently floats

No it doesn't. It only would float under the same conditions as a tracked vehicle -> more displacement than weight. Which if both vehicles have comparable or the same protection level is very unlikely.

WarthogARJ said:

and using a combination of wheel traction and jets,

Nope. Tracks are actually better in propelling a vehicle trough water while floating compared to wheels. Propellers or jets are better BUT these usually do not work in mud. Especially jets would be wrecked very quickly.
A vehicles without any amphibious capability is equiped with neither so this is of little concern in the first place.
The threshold for amphibious capability of an 8x8 is 20-25 t. With a protection level similar to Puma a vehicle will be much heavier. In the 40-50 t range. Twice the size. It would sind like a stone.

WarthogARJ said:

And when a tracked IFV is indeed stuck, it's a HEAVY bastud to pull out.

This is also independent of the drivetrain. A stuck 45 t vehicle is a stuck 45 t vehicle.
Since there are MBTs that are above 50 t that are considered fast with high cross country mobility there is no reason for other tracked vehicles not to be the same. A 50 t wheeled vehicle on the other hand would perform not nearly as good ob soft ground.
This doesn't mean its impossible to develope a special 50 t wheeled vehicle that has as good or better mobility on soft ground than a 50 t MBT... only the resulting vehicle would most likely not be suitable for military use. The design would end up being a specialised 50 t swamp and mud racer with little practical purpose. It certainly would be a nice engineering excercise.
The German Army currently uses the Puma IFV wich is above 40 t and the 8x8 Boxer APC which is below. The Boxer is less well protected though. It also has a lower power to weight ratio. The cross country mobility of the Boxer under common German conditions does not compare to the Puma. The soft ground capabilities are much worse. Also the ability of the suspension of the Boxer to absorb bounces at high speeds off road is much worse. This last thing is one of the main reasons why wheeled vehicles have worse cross country mobility compared to similar tracked vehicles. The wheeled vehicles bounce around. The shocks and impacts are transmitted to a much higher degree. Which means the occupants are thrown around inside the vehicle. There is only so much a human can tolerate. This limits the realistic top speed. The limit is not technical its biological. It matters little if the vehicle could go faster if the crew can not take it. The smooth ride of torsion bar suspended large wheels with long lever and movement on its own track is allmost impossible to duplicate with wheels. That being said this is not true on smooth and hard surfaced. Here the vibrations of lots of moving parts and masses are a huge drawback. Wheels are much better under such conditions.

In reply toRe: msg 104
WarthogARJ

From: WarthogARJ

11-Jun

I've been looking at the background research on overall off-road mobility, from Becker to Wong and the various off-shoots, and it's clear that there's still a lot that's not very well understood about it. Basically, as soon as you get into anything that needs an accurate assessment of the plastic response from the terrain it gets very fuzzy. Very hard to predict things, you need to do tests and measure the various responses.

That's why all the current models suck when you try to take into account the Multi-Pass Effect, or even slip-effects to any real degree.

For instance with the current NATO Reference Mobility Model (NRMM), first major upgrade in over 20 years, they've given up on using anything that's analytical/rigorous, and are going to use a combination of FEM/DEM.

But then that means trying to model the effects of grousers or lugs with a mesh/particle size that's close to that scale: which is obviously incorrect. So you need to add lots of fudge factors (as in to do it properly, you'd need to model it with a particle size an order of magnitude smaller than the track grouser/tread size scale). The reason why the comprimise is the computing power needed to run a sim if you did use the right resolution.

So my point is that you can do a lot to optimise the mobility of a multi-wheel/AWD vehicle through wheel size & tread geometry, slip/traction control, active pressure control etc etc. After all, you've got control over the torque sent to each wheel, of all 16 in an 8x8, as well as the ability to adjust the contact patch size at the same time.

WarthogARJ

From: WarthogARJ

11-Jun

schnuersi said:

WarthogARJ said: But a wheeled IFV inherently floats No it doesn't. It only would float under the same conditions as a tracked vehicle -> more displacement than weight. Which if both vehicles have comparable or the same protection level is very unlikely. WarthogARJ said: and using a combination of wheel traction and jets, Nope. Tracks are actually better in propelling a vehicle trough water while floating compared to wheels. Propellers or jets are better BUT these usually do not work in mud. Especially jets would be wrecked very quickly. A vehicles without any amphibious capability is equiped with neither so this is of little concern in the first place. The threshold for amphibious capability of an 8x8 is 20-25 t. With a protection level similar to Puma a vehicle will be much heavier. In the 40-50 t range. Twice the size. It would sind like a stone.

Ah, our posts crossed each other.

And BTW, is good discussion.

Yes, I agree with you that to have a reasonable chance, a wheeled IFV needs to be as light as it can get, and be amphibious: as in float.

And again, perhaps I'm optimistic in thinking this, but I think one CAN make a wheeled IFV that DOES float, is lighter than a tracked IFV,  and where both have equivalent Stanag KE/Mine protection levels. Let's say KE Class 4 all round, with maybe 5 on front, and Level 4 for Mines.

Let's say with a good mix of composite/spaced aluminium/ceramic armour, and ERA blocks as needed.

After all, a wheeled vehicle is inherently more resistant to mine blasts because you can have a higher ground clearance, and the wheels don't trap the blast as much as a track assembly does. And you can use a V-shaped hull as well, which with most tracked designs is tricky. My point is that means you can get your desired blast protection but not need as much armour WEIGHT as a tracked vehicle.

In addition, a tracked suspension is a LOT heavier than a wheeled system, comparing a similar "payload" of armamement & crew carried.

I can send you my estimate, but I can see the difference between a wheeled and tracked IFV (with same Stanag/crew/gun system) being as much as 10 tonnes. As in, the tracked variant costs you an EXTRA 10 tonnes.

And I think in many cases, the tracked IFV designers pretty well give up on trying to get a LIGHT vehicle, and don't make vigorous attempts to TRY to keep the weight down. As in, they know it cannot be amphibious, nor will it ever fit into a C-130 etc etc. So they pull out the stretch jeans instead of a crash-diet.

WarthogARJ

From: WarthogARJ

11-Jun

schnuersi said:

This is also independent of the drivetrain. A stuck 45 t vehicle is a stuck 45 t vehicle. Since there are MBTs that are above 50 t that are considered fast with high cross country mobility there is no reason for other tracked vehicles not to be the same. A 50 t wheeled vehicle on the other hand would perform not nearly as good ob soft ground. This doesn't mean its impossible to develope a special 50 t wheeled vehicle that has as good or better mobility on soft ground than a 50 t MBT... only the resulting vehicle would most likely not be suitable for military use. The design would end up being a specialised 50 t swamp and mud racer with little practical purpose. It certainly would be a nice engineering excercise. The German Army currently uses the Puma IFV wich is above 40 t and the 8x8 Boxer APC which is below. The Boxer is less well protected though. It also has a lower power to weight ratio. The cross country mobility of the Boxer under common German conditions does not compare to the Puma. The soft ground capabilities are much worse. Also the ability of the suspension of the Boxer to absorb bounces at high speeds off road is much worse. This last thing is one of the main reasons why wheeled vehicles have worse cross country mobility compared to similar tracked vehicles. The wheeled vehicles bounce around. The shocks and impacts are transmitted to a much higher degree. Which means the occupants are thrown around inside the vehicle. There is only so much a human can tolerate. This limits the realistic top speed. The limit is not technical its biological. It matters little if the vehicle could go faster if the crew can not take it. The smooth ride of torsion bar suspended large wheels with long lever and movement on its own track is allmost impossible to duplicate with wheels. That being said this is not true on smooth and hard surfaced. Here the vibrations of lots of moving parts and masses are a huge drawback. Wheels are much better under such conditions.

I'll answer separately.

Firstly, I would not class the Boxer as a particularly well designed wheeled IFV.

And as I said in my post just before this, to be competitive, the wheeled IFV does need to be LIGHTER (with same Stanag etc). I think that can be done, if not, you are correct.

As for suspension, I don't agree. You can make a wheeled off-road with EXCELLENT suspension. Why not? There's nothing magical about tracks, in fact you can do BETTER when you have full control over the suspension of all 16 wheels of an 8x8. Which you cannot do with a tracked vehicle: it is literally linked by the track.

I ride motorbikes off-road: you can do a huge amount by tuning your suspension right, and with tire selection. And you only need to watch the Paris-Dakar to see what can be done with wheeled vehicles there.

Look at the Patria 8x8, it's got independent hydropneumatic suspension: so that's 16 independents. A tracked vehicle often pairs a set of road wheels together, so that reduces the freedom of movement.

As for torsion bars, from what I understood, the Puma has a decoupled set of tracks: so it cannot have torsion bars from side to side in that case, can it? That sort-of couples it up again. And torsion bars are just a crude spring: you can do better with a non-linear spring as is used in good off-road vehicles.

The wheels on the wheeled IFV are a lot bigger than the road wheels on a tracked one: and in any sort of soft or rough ground the track starts to act like a set of wheels. You go from a uniform contact patch on hard ground to series of high pressure contact areas: one per road wheel.

Plus, pneumatic tires themselves help a lot in suspension, whereas a track's road wheels are rigid and do not.

Since we cannot see test results, we don't know what was actually tested, and how. And I doubt that anyone who has already got firm ideas about needing a "heavy-duty" IFV (and thus automatically it MUST be tracked) is going to spend a lot of time in testing lots of wheeled IFV's. I suspect the only people who test both types are willing to consider a wheeled IFV, and add a few tracked models to compare it to. Like the Australians and Swedes did.

In reply toRe: msg 108
WarthogARJ

From: WarthogARJ

11-Jun

Yeah, but I think the main point is as you said it.

I think it's difficult to do direct wheeled vs tracked when you add in something like the Puma Class C, or the Namer. They start to be moving out of the IFV category, and more into an MBT that carries extra people. Which is how both the Namer and the T-15 were designed: based on MBT-hulls.

However in that case, I think such a heavy, and EXPENSIVE, IFV starts to be an issue as well.

For one, a Euro 17million/43 tonne Puma can be killed by a Euro 1million/25 ton wheeled IFV carrying a 40mm CTAS autocannon. Dang, you start to need to have IFV's protecting your own IFV's from getting whacked, let alone worry about the MBT's being hit!

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