Another AFV design question

Interesting.

Did the germans ever really use rear drive? One of the main disadvantages I can see, and the above hints at is access to the gearbox/tranny/steering brakes. on rear drive thay tend to be under the fuel tanks or buried pretty much under engine and tanks. I think modern vehicles get round this maintaiance access problem by making the whole unit easily removable (a power pack).

Front drive not only makes more fuel space and ammo space but allows easier access to the transmissinon and steering brakes. I think its also worth remember that in the time before differential steering the steering brakes take a real hammering and would need constant adjustment and replacment of the shoes. Maybe this was deciding factor in the Churchil steering???

I guess with more modern designs the maintaince issues becomes less of a factor compared to the advantages hence the almost universal rear drive. Still think the Merkeva?? is an interesting solution

Kev

 

Horizontal entry hatch considered more favourable (??? not at all sure what they mean here yet)
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Just mean the hatch lid on the rotating pivot instead of a hnige dont they, dont see how this is related to front drive??? al la tiger, panther, etc

Kev

 

To be honest though, transmissions and suspensions confuse the hell out of me, spent several hours last night staring at the Panther's double-torsion-bar-per-wheel setup before it started to make sense. The drive systems, electric, hydrostatic, etc. etc. still largely read like witchcraft to me. In a mound of books I still don't have one that satisfactorily gives a basic explanation of all the different systems (suspensions more than transmissions) in one easy to refer to place. Been thinking it's time to build a page just attempting to put 'em all in one place for ready reference...

I dont think there is any one correct answer. A lot of varibles not least weight and speed.

Have you got the twin bars thing? Ive never really looked at it, the panther, its frightening tank, its speed of rough ground impressive. I presume the twin bars system is to get round the problem that torsion bars offer only proportional progression? A helical spring can be wound to offer a more progressive spring. Twin bars with a a lighter and heavier bar to offer 2 spring rates???

My own personal option on it is the that fully damped torsion bars is the way to go on larger tanks (more defensive and tank destoyers can get away with a bogie suspension). not only offering large travel and good damping but effective use of space and good protection for the componants. Its just expensive. See the machining that goes into the torsion bars and swingarms, they are all splined. on slower or lighter vehicles bogie suspension offers adquadate performance at a fraction of the cost.

Kev

 

PantherA

See how one bar runs to the actual wheel crank but is also joined with a collar at both ends to a second bar anchored on the wheel side, both bars pivoting on the collar on the opposite side. So one twists in a nearly direct line with the crank while the other backs up that effort, it was apparently down to the unavailability of the right steel to make strong enough single bars (not sure yet if this was down to Germany's material problem, or if technology simply hadn't reached that point yet).

They were asking for an ability to absorb 500mm movements of each wheel without disturbing the Gun platform too much, the amount of testing of this and other ways to reduce 'bounce' seems to have been phenomenal.

Got to agree on Torsion bars as the way forward (as evidenced by near any other modern tank design) but all that effort on interleaved wheels, theoretically an excellent solution, without considering their lethal tendency to deny the vehicle mobility completely in certain conditions just kind of staggers me. Particularly since the design work was being carried on with while the Russian winter was proving it's effect on such systems.

Oh I get it. I dont think that system is 'that' clever. Its just designed to give a effective longer bar lenght. Yes its a material restriction, but doubling its lenght you get only half the angular twist for the same wheel arm travel. I think it is anyway, its hard to tell how each bar is engaged as its hidden. You can clearly see the attachment points for the damper units. Theres your lack of bounce and control! Appears they still need a few more, though the standard of restoration (or replacement) looks amazing! Probably better made than in 1944!

As said a big disadvantage of torsion bars is offering more progressive springing, which would allow the suspension to work over wider range of forces, Helical springs can do this, torsion bars its very hard. Still think Bars a miles better meself though. Be interesting to see if I am right on the panther system or if it really does offer multiple spring rates. To do it with bars you would have light (read thin) bar for smaller bumps but after a certain amount of travel (read angular movement) a heavier bar would be engaged. That would be a good system.

You know I like the interleaved wheels, though the tiger one is just plain crazy. Still find it hard to beleive that the winter could freeze the wheels, with 750 hp pulling on them?? Not liked the wheels are spoked, the solid discs??

Kev

 

I still think the Christie suspension is much superior. Go for transverse torsion bars and forward drive and you have two factors raising the tank's profile, while the Christie design tucks in to the hull side. It can also have a much larger travel. That's one reason why, for example, Comet was far faster and lighter than Panther whilst carrying comparable gun and armour - just a pity it was 18 months or so later.

Regards,
MikB

 

I still think the Christie suspension is much superior. Go for transverse torsion bars and forward drive and you have two factors raising the tank's profile, while the Christie design tucks in to the hull side. It can also have a much larger travel. That's one reason why, for example, Comet was far faster and lighter than Panther whilst carrying comparable gun and armour - just a pity it was 18 months or so later.

Regards,
MikB


Mik,
Not sure how CHristie has more travel, you think it would be less since there is much more restricted space between the arm the hull side top to get the a large Christie unit in. Its limited by the units stroke and thr stoke is normally considorably less than the units lenght. Not sure travel is suficently different between the systems to make that much difference.

Torsion is mainly limit (for a given material) by the lenght of the bar and the dampers stoke, assuming th hull is thr same depth inside as outside then its about the same.

The big advantage with the Christe is the spring can easily be wound at two rates since its a helical spring???

Kev

 

I accept your argument that there may have been less difference in travel, though Christie designs seem to have had more deflection room above the track than the German TTB designs. The crowded wheel assemblies must have shortened the swinging arms and hence their arc of travel.

But it seems to me very likely that Fritz had to go for interleaved and overlapping wheels at least partly because the torsion bar assemblies were so heavy. He'd got himself into an engineering spiral that seemed to lead him by the nose to the 150 ton unbuildable monsters he was playing with by the end.

With the Christie, you can put the coilspring roughly vertically inside the hull, or, better still, between the walls of a double skin, giving extra protection against any hollow charges that might find their way there.

The other - and I think most significant - argument in favour of Christie is that it's enormously easier to make and maintain.

Panther is sometimes classed as a medium, but that was only a relative truth in comparison to the other big cats - in anybody else's book it'd definitely've been a heavy. Despite being more automotively capable than the Tigers it could never match a Sherman, Cromwell or T34 in agility and was only a little better armoured than they were - scarcely at all at the sides.

If Panther had been a Christie tank it could perhaps have been 6 - 8 tons or more lighter than it was, and soaked up maybe 25% less production capacity to build it, without any real loss of fighting capability at all.

I doubt that would've made much difference to the final outcome, but I think much of the reputation this tank gained as a formidable adversary is owed more to its skilled crews, good gun and the defensive positions it was deployed in than to its design excellence.

Regards,
MikB

 

I accept your argument that there may have been less difference in travel, though Christie designs seem to have had more deflection room above the track than the German TTB designs. The crowded wheel assemblies must have shortened the swinging arms and hence their arc of travel.

But it seems to me very likely that Fritz had to go for interleaved and overlapping wheels at least partly because the torsion bar assemblies were so heavy. He'd got himself into an engineering spiral that seemed to lead him by the nose to the 150 ton unbuildable monsters he was playing with by the end.

With the Christie, you can put the coilspring roughly vertically inside the hull, or, better still, between the walls of a double skin, giving extra protection against any hollow charges that might find their way there.

The other - and I think most significant - argument in favour of Christie is that it's enormously easier to make and maintain.

Panther is sometimes classed as a medium, but that was only a relative truth in comparison to the other big cats - in anybody else's book it'd definitely've been a heavy. Despite being more automotively capable than the Tigers it could never match a Sherman, Cromwell or T34 in agility and was only a little better armoured than they were - scarcely at all at the sides.

If Panther had been a Christie tank it could perhaps have been 6 - 8 tons or more lighter than it was, and soaked up maybe 25% less production capacity to build it, without any real loss of fighting capability at all.

I doubt that would've made much difference to the final outcome, but I think much of the reputation this tank gained as a formidable adversary is owed more to its skilled crews, good gun and the defensive positions it was deployed in than to its design excellence.

Regards,
MikB

Mik,

Wouldnt argue with any of that mate, I think your dead right.

 

Here we go. Still limited interleaving but rather different to what went before.

(from Spielberger)







Hello Mr Porcshe.

Bit horrible that picture. The sectioned springs have come out like folds. See exactly what the old fraud was up to here. He was trying to get longer units in a smaller space (as you say like HVSS) by mounting them horizontally. Have the advantage/disadvantage of easy access. One would pressume in the event of problems you just jack up and take the whole unit off. CLever the way he has got the damper and sping on each arm/plunger.

Kev

 

Hello Mr Porcshe.

Bit horrible that picture. The sectioned springs have come out like folds. See exactly what the old fraud was up to here. He was trying to get longer units in a smaller space (as you say like HVSS) by mounting them horizontally. Have the advantage/disadvantage of easy access. One would pressume in the event of problems you just jack up and take the whole unit off. CLever the way he has got the damper and sping on each arm/plunger.

Kev

Yes, this is a neat and economical design and compares well with Christie. Counting the b100dy Belleville washers might've been a bit of a headache for field service units.

And you'll need a big, thick baseplate for your jack when your tank weighs 150 tons My back is hurting just thinkin' about it...

Despite my earlier comments about vertical Christie springs, I've seen from a TV tank restoration documentary that the springs in Comet and, presumably, Centaur/Cromwell suspensions were far from vertical, being tucked in parallel to the dampers at around 45 degrees between double hull skins. But then, by using suitably angled lugs, the Christie can be disposed at whatever angle suits the design. Doesn't really change the argument vs TTBs.

Regards,
MikB