Maglev Wheels???

[Creator]

recoil?

 

[Nik]

Ekranoplan flies in 'ground effect'.

Ah, the 'Caspian Sea Monster' and its ilk...

Ekranoplan or Wing-in-Ground-effect aka WIG...

Trick there is the combination of ram-air cushion, and distance to build up speed. IIRC, CSM famously 'hopped' over several fishing boats...

There's a bunch of related vehicles, ranging from blown 'sidewalls' to fast boats with air-trap between multihulls and/or under 'step'...

And, IIRC, the RAF's Victor bombers, big triangular 'flying wings', had some very strange handling characteristics near ground because of the sheer area under the delta...

One feature in common is that they gotta keep a lot of speed to keep that ram-air cushion-- Like any fixed-wing aircraft, if they stop, they drop.

Um, IIRC, some of the earliest (1920~~30 era) flying-boats spent a lot of time in 'ground effect' until they burned enough fuel to climb out. When you look at those designs, they often had fat sponsons / winglets at water level to encourage this. Remember, getting into the air is hard, and big runways did not appear until WW2's big bombers...

Hmm, also research 'Moller' and related ducted-fan VTOL SUVs. Check their power/weight and stability requirements, and wonder at their long and oft-fraught history...

 

[iansales]

Re: Ekranoplan flies in 'ground effect'.

And, IIRC, the RAF's Victor bombers, big triangular 'flying wings', had some very strange handling characteristics near ground because of the sheer area under the delta...

Er, the Avro Vulcan was the delta-wing v-bomber, not the Handley Page Victor.

 

[Creator]

Ok just a little work on my wacom... well the picture says for itself.

 

[Delvo]

recoil?

Recoil is the force pushing the gun back when the ammo goes forward out of it. The momentum of the ammo is exactly equal to the momentum of recoil, in the opposite direction. Momentum is mass times velocity, so a small, light piece of ammo moving very fast equates to a big, heavy object (like a gun and the person/thing holding it) moving much slower (as in, not supersonic and you can actually see the movement).

Recoil is why you can injure your hands or wrists by firing a hand-held gun that isn't properly aligned (and braced against your shoulder if it's a long gun), and why you see the gun, hand, and arm all jerking back and up with each shot, and why it feels like the gun just punched or kicked you in the hand/wrist/shoulder after you've fired.

It also applies to bigger guns. An A-10, an American attack plane, fires such heavy bullets at such a high rate that its recoil exceeds the maximum power of one of its jet engines, so the engines have to increase thrust while the gun's firing, just to maintain the plane's speed. The only way to put a bigger gun (or more of them) on a plane and still have the plane be able to fly while firing it is to use a modified cargo plane like a C-130, because its greater mass makes it harder to push around. A battleship's big guns' recoil rolls the whole ship a bit, and would sink most smaller ships if they foolishly had such a gun mounted on them and foolishly fired it.

And if you watch a video of a tank firing its main gun, you'll see the whole tank bounce and rock due to the recoil.

Now here's the catch: anything sitting on the ground is deceptive about recoil because it directs most of the force into the ground. That way, the momentum mostly goes into moving the Earth instead... by an immeasruably tiny amount, because the Earth is so much more massive. If all of the momentum of recoil went into moving the gun and gun-holder, they'd go falling back out of control much farther and faster. And that's the situation a tank would be in if it were hovering: its own gun would keep pushing it around each time it's fired, away from whatever its target was.

 

[Nik]

Vulcan.... My Bad.

Vulcan, of course, of course...
My Bad.

Yes, the restoration team has just managed to get one back in the air.

Um, I remember being on a camp-site under flight-path of Anglesey's Valley Vulcans. One did a 'bump & go', came over at such low altitude that we felt the pressure wave.

FWIW, the people who fell over did so because they were staring...

---

Um, sorry, that design of the blades with open centre might be dynamically unstable...

 

[Phil Janes]

I see three main drawbacks to this basic concept, as far as tanks are concerned.

1. Terrain. MagLev works wonderfully on a perfectly straight track, but it’s not so good at cornering and bumps.
2. Torque. For quick starts, stops and steep hills, you need a lot of torque which comes from gearing down from a rapidly spinning motor. MagLev is a direct drive motor with a fixed gear ratio of 1:1.
3. Speed. As has been pointed out already, caterpillar tracks can only go around so fast, regardless of how they are driven. For military purposes, they must be designed to withstand an enemy’s attempts to break them. If you design them for greater speed, they will be more vulnerable to attack.

My own vision for the future of superconducting MagLev is a long-distance meteor train inside a huge vacuum tube. Theoretically, if the tube is straight enough, such a train could travel faster than a satellite in low-earth orbit. The beauty of MagLev is its ability to use the deceleration of one train to power the acceleration of another train. With a small but steady input power, you could make each train go a little faster the previous one. If you maintain a constant total kinetic energy for all the trains in the system, you hardly need any energy input to keep them running. Temporary changes in kinetic energy would require some sort of short-term electrical storage—perhaps giant superconducting electromagnets. If you have to shut down the system, you’ll have to find some way to dump the excess energy—which might overload the nations power grid.

After the astronomical initial cost, the biggest drawback to my train is vulnerability to terrorist attack. A well-placed IED outside the tube or inside the train would destroy a big piece of the system, killing all the passengers and anyone else within several square miles along the route. There’s good reason to call it a meteor train; a train moving at 18,000 miles/hour is the equivalent of a good-size meteor; its kinetic energy would be equal to its weight in C4 plastic explosive.

 

[ray gower]

Re: Vulcan.... My Bad.

Vulcan, of course, of course...
My Bad.

Yes, the restoration team has just managed to get one back in the air.

Um, I remember being on a camp-site under flight-path of Anglesey's Valley Vulcans. One did a 'bump & go', came over at such low altitude that we felt the pressure wave.

FWIW, the people who fell over did so because they were staring...

---

Um, sorry, that design of the blades with open centre might be dynamically unstable...

For the sake of accuracy .
It was the 'flying wing' bombers (B35/B49) that had extreme problems with low speed low level flight, they had a natural tendency to go arse over tip.
There are very few aircraft of any size that perform as well at low altitude as the Vulcan, rather fewer that size where the driver would dare to perform loops and rolls at 500 feet. They did have a high stall speed compared to Victors.
It was the rather more conventional Valiant that had low-level problems in RAF service, the wings flapped too much, consequently they tended to fall off.
Nor have bombers ever been stationed at RAF Valley, though we did play host for a flight of Shackleton MR1s for a few months in the 80's.

Apart from the mechanical problem of creating blades strong enough to take the forces, the problem with a centreless turbine is you will not be able to compress enough air into the high pressure chamber for efficient burn or thrust. The air will leak back through the centre vortex of the funnel it creates. You need to close off the middle to fill the void

 

[Nik]

Again, my bad...

Again my bad...

We naively assumed if Vulcans routinely went in/out of RAF Valley, they belonged there...

My understanding is Vulcans *loved* the air, were very reluctant to leave it, happy to float on 'ground effect', ready to rise...

And one did come over our camp-site low enough to astonish !!
---

Um, I wasn't so bothered by the air leaking up the middle of that sketch as those blades wobbling. Never mind 'hopelessly inefficient', it is a ticking bomb...

 

[Creator]

Nah it's ok... that one was a failure. Well I am onto hovercrafts and ekranoplans now.... I don't think treads are going to do it for future tanks.... when wars are getting speed on their side.

 

[Delvo]

I am onto hovercrafts and ekranoplans now.... I don't think treads are going to do it for future tanks.... when wars are getting speed on their side.

You might be underestimating the speed of modern tanks. They can match the speeds of most cars and trucks on a highway. They can also go some places where the terrain is too rough for a hovercraft, and are much tougher because they can carry heavy armor while hovercraft need to be light and can't afford armor's weight.

There are already military hovercraft in use, of various sizes. Their most common application is amphibious operations, because they can so smoothly and easily go back and forth between moving over land and moving over water. They do have guns on them, but much smaller relative to vehicle size than a tank's gun is relative to the tank's size, because of the recoil issue; their main job is to move your own side's people and supplies, not to shoot at enemy targets. In other words, it takes a hovercraft bigger than a tank to use a smaller, less powerful gun than a tank's gun. And they're not particularly fast; tanks can outrun them.

If you want to carry tank-like firepower (or more) at a higher speed than tanks can go, you need true aircraft instead of hovercraft because hovercraft aren't so fast. Then you also generally get longer range because of the higher speed, and the ability to work over extremely rough terrain that a hovercraft or even a tank can't handle. Take a look at these:

AH-64 (attack helicopter; uses rockets instead of a big gun but the effect is similar)

A-10 (attack plane; uses rockets & bombs like an attack helicopter, plus a machine gun that throws heavy, non-explosive bullets at a very high rate instead of big exploding shells one at a time like a tank)

AC-130 (attack variant of C-130, a cargo plane; has a combination of different types of guns and bomb/missile launchers sticking out of its cargo area)

 

[Creator]

How about the military vehicle called the Stryker.??

 

[Delvo]

What about it?