Land battleships?

[Doc Yo]

Wow, that was fast-really sharp looking interpretation of the plan....you should e-mail Roger Todd with these-
I know he'd be delighted.

Well if you know how to get his email address I'll send him the pics.

Sorry for the delay in replying-I was on vacation all last week...

I haven't heard from Roger in a couple of years, but the last time we got in touch his eddress was:

rogertodd1@hotmail.com

Awfully nice fellow-I'm a little surprised he's never turned up here...

[ysi_maniac]

Löwe http://en.wikipedia.org/wiki/Panzer_VII_L%C3%B6we BTW have you seen the model in this wikipedia page? I have not seen before 
Ratte: http://en.wikipedia.org/wiki/Landkreuzer_P._1000_Ratte
Monster http://en.wikipedia.org/wiki/Landkreuzer_P._1500_Monster

[Joe C-P]

How about, instead of turrets, a series of pintel machine guns along the hull? An extension of the WW1 British tanks, with a smaller, quieter, more powerful engine for more internal room, and a couple sponsons each side, plus a box up top with a couple more MGs, or maybe a small cannon in a small turret.

[bluedonkey99]

There is a 1/100 paper/card model (free!)  on the Currell Graphics site based upon a HG Wells Story.
http://www.currell.net/models/ironclad.htm

Its actually an interesting site with models in  range of scales, there is an interesting set of 1/700 British airships R101 set, including a 1/700 Aiship Hanger! and a range of other flying and floaty things!

http://www.currell.net/models/mod_free.htm
BD99

[frank2056]

To paraphrase the opening to MST3K:
"If you're wondering how it moves and fights
And other whiffy facts,
Just repeat to yourself "It's just a whif,
I should really just relax"

OK, that said, what would a "realistic" land battleship be like? An M1A1 produces a 15-16lb/sq. in. pressure on the ground, and it's a very big tank. What's the upper range for a realistic ground pressure? Starting with something like a Patrol Gunboat (PGM-84 weighed 285T/570,000lb) that works out to around 36000 sq. in - 38000 sq. in. Let's say 40000 sq. in to have around the same ground pressure as an M1A1. If the tracks have 100 ft (1200in) of ground contact, they would only have to be about 32 inches wide, total. Since there are two tracks, 18 inch wide tracks with 100 feet of ground contact should be enough, if my math is correct, right?

A Spruance destroyer (8373 Tons/1.67M lbs) with 500 feet of ground contact (almost the full length of the hull)  would need tracks 175 inches/14.5 feet wide, total, or  7.3 feet wide.

These numbers don't seem too unreasonable, so I'm guessing I've made a math error, somewhere. Where are my land cruisers?

[rickshaw]

Basically physics prevents them from existing in the format that you want them to. The reason why a ship works is because its relatively easy to move such a large mass through the water because of the low friction of the surface that it is in contact with.   On land, all that mass is bearing down on what is effectively the running gear of the vehicle.  Friction and inertia prevent it from moving easily.  Tracked systems in particular have considerable friction in them and so getting very heavy things on tracks to move requires substantially more power than a wheeled vehicle of equivalent mass would require (less rolling friction on the wheels, AIUI).   The gearbox and transmissions of such a vehicle would be very interesting, whilst the power outputs would have to be phenomenal.  Goods trains which are the heaviest land vehicles available at the moment require special roads (rails) with careful attention paid to gradients and curves to enable them to keep moving.  Overcoming the problems of rough terrain would tend to prevent the creation IMO anything approaching something comparable to a naval ship in size and mass.

Further, on the matter of ground pressure, I understand that according to the research on the subject, it is simply not a matter of dividing the available weight by the surface area of the tracks but is much more complex than that and is dependent not only on the surface area of the tracks but also the number and size of the wheels in contact with the tracks.   I once read a pretty complex paper on the matter, published by some US Army researchers and they went into it in some depth.  If you want I'll see if I can locate it for you.

[Weaver]

Some further points:

Skid steering only works if the length:width ratio of the vehicle is within a certain range, nominally 1.1:1 to 1.8:1. Most normal warships have ratios in the 7:1 to 11:1 range, so if the "warship-shaped" land battleships often portrayed have one-piece tracks and rigid hulls, then they can't steer - better make sure the production line is pointing at the enemy.... To get a 500ft long Spruance steering, it would need to be 278 ft wide, so please don't drive it down my street anytime soon, thanks.

As your hull gets longer, it covers more terrain within it's length, but the scale of the terrain doesn't change, which means the chances of finding 500ft of flat terrain decrease. A 25ft long real tank frequently sits "inside" the terrain, either at the bottom of the dips or at the top of the crests, and only rarely hits problems where the middle or end of it's hull are left unsupported. A 500ft long land battleship would find substantial parts of it's hull unsupported for much of the time, thus greatly increasing ground pressure, not to mention ground destruction as it squashes the crests and high-points while sinking to a point where it's supported.

All of this can be dealt with to an extent by making the land battleship articulated, but the limits still apply to the individual units, which means that what you end up with is something like a string of real MBTs linked together. These MBT-sized units would have the same limitations on turret-ring diameter, gun size, recoil etc.. as individual ones, so you'd have to wonder what advantage they'd gain by being linked into one vehicle.

[nev]

Basically physics prevents them from existing in the format that you want them to. The reason why a ship works is because its relatively easy to move such a large mass through the water because of the low friction of the surface that it is in contact with.   On land, all that mass is bearing down on what is effectively the running gear of the vehicle.  Friction and inertia prevent it from moving easily.  Tracked systems in particular have considerable friction in them and so getting very heavy things on tracks to move requires substantially more power than a wheeled vehicle of equivalent mass would require (less rolling friction on the wheels, AIUI).   The gearbox and transmissions of such a vehicle would be very interesting, whilst the power outputs would have to be phenomenal.  Goods trains which are the heaviest land vehicles available at the moment require special roads (rails) with careful attention paid to gradients and curves to enable them to keep moving.  Overcoming the problems of rough terrain would tend to prevent the creation IMO anything approaching something comparable to a naval ship in size and mass.

Reminds me of a Russian report on a captured King Tiger that I read.  It could do 12mph on good, flat road.  On gentle countryside (ie flat firm grassland) it could go walking pace.  Anything remotely "rough" and it was immovable.  Not to mention all the problems it had with broken drivetrains, gearboxes, cracked wheels etc, all due to the sheer weight that was trying to me moved.

But as Radish likes to say, if your whiff is unrealistic, just alter your backstory   Too much weight is nothing that can't be solved by anti-grav devices or advanced lightweight materials

[Jschmus]

This is one of those topics where cold, hard reality brings our dreams crashing to the ground.  Fortunately, a lot of different fiction sources give us assorted kinds of "handwavium" to counteract the natural effects of physics.  That's what anti-grav, repulsorlift and mass effect field generators are for.

[Weaver]

Oh absolutely: put it on another planet with less gravity and big, flat spaces and off you go! Or you can just say "to hell with science, it's art" and file it with the steampunk laser guns....

[jcf]

The Canaveral Crawlers are the best 'real world' example of a large self-powered tacked vehicle
and amply demonstrates the realities and limitations.
http://en.wikipedia.org/wiki/Crawler-transporter

In my own mental noodlings on 'land battleships', I don't take battleship literally and tend to stick with
the Wellesian conception of 'land ironclads', perhaps expanded, at most, to something half again as large
as the Char 2C or T-35.

[proditor]

Oh absolutely: put it on another planet with less gravity and big, flat spaces and off you go! Or you can just say "to hell with science, it's art" and file it with the steampunk laser guns....

And you've hit upon my method.    I just grabbed a couple more 1/72 armor kits to scale to 1/700.

[Sisko]

Sorry I refuse to believe this won't work!

[frank2056]

Further, on the matter of ground pressure, I understand that according to the research on the subject, it is simply not a matter of dividing the available weight by the surface area of the tracks but is much more complex than that and is dependent not only on the surface area of the tracks but also the number and size of the wheels in contact with the tracks.  

I didn't even realize how short the NASA crawlers are compared to even a small ship, like a Patrol gunboat (PGM-84 was 50m long). I guess it's like a submarine aircraft carrier - nice idea but doomed to fail.

[ysi_maniac]

What about Land Nagato?