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Peter Dow

The catamaran tank - an MRAP which doesn't roll over!

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MRAP (armored vehicle)

 

Mine Resistant Ambush Protected (MRAP) vehicles are a family of armored fighting vehicles designed to survive IED attacks and ambushes. IEDs cause the majority (63%) of US deaths in Iraq.

...

A June 13 report by the Marine Corps Center for Lessons Learned indicated concerns about MRAP vehicles rolling over in combat zones.

 

The V-shaped hulls of the MRAP give it a higher center of gravity and the weight of the MRAP can cause the poorly built or maintained roads in rural Iraq or Afghanistan to collapse.

 

Of the 66 MRAP accidents between Nov. 7' date=' 2007 and June 8, 2008, almost 40 were due to rollovers caused by bad roads, weak bridges, or driver error.

 

In many of the rollovers troops were injured, and in two separate incidents five soldiers have been killed by rolling over into a canal and getting trapped under water. The report said 75% of all rollovers occurred in rural areas often when the road is above grade and a ditch or canal full of water is next to it.[/quote']

OK so that is the problem and there is an obvious vehicle modification to counter the roll-over problem which is to fit stabilisers, adopting the same concept employed in a child's bicycle.

 

sport-direct-bicycle-stabilisers--pair.jpgstabilisedmrap.jpg

 

The simplest and cheapest way to do this would be have bolt on stabilisers which could be partially unbolted to fold up when not required while driving on good flat roads but where the additional width of the stabilisers would cause problems, such as when travelling along narrow roads, needing to negotiate dense traffic such as in urban roads.

 

The high-tech and expensive solution would be stabilisers which fold-up or deploy automatically using hydraulics at the touch of a driver's button.

 

However, when you compare the expense of a good solution to the expense of lives lost by MRAP rollovers then it is a small price to pay.

 

OK that idea is adapting the existing MRAPs but here is an idea for a completely new design of MRAP.

 

The catamaran tank - an MRAP which doesn't roll over!

 

bareboat-catamaran.jpg

A catamaran - the inspiration for a twin-hulled armoured vehicle

 

The catamaran tank or catamaran MRAP or catamaran armoured vehicle or catamaran armored vehicle - you heard it here first!

 

One idea I have for a completely new design to counter ground-blasts yet retain stability would be a double-hull or catamaran tank.

 

To explain, let us describe most simply the current MRAP vehicle design as an

 

M-shape,

 

looking at the vehicle from the front or the rear, with a high middle, and a V-shaped hull, armoured to deflect the blasts.

 

Well the concept of the catamaran tank is to replace the M-shape with something more like a

 

Y''Y-shape

 

which is a lot wider for stability and so may not be so good in narrow streets or traffic admittedly.

 

The central double quotes in the Y"Y-shape represents a line of strong blast-chimneys up through the middle of the vehicle, from front to rear, which some of the blast could go up without splitting the vehicle in two.

 

This twin-hull, double-hull MRAP would give two distinct cabins on the left and right of the vehicle and however high you need the vehicle to get distance from a ground blast then make the Ys bigger and so further apart which keeps stability.

 

The leg of the Ys could have blast ventilation holes so that blast gas under the vehicle can escape to the sides as well as up the central chimneys. The more ways the blast gas can escape from under the vehicle the less force the blast will apply against the vehicle itself.

 

The bottom of the Ys could be either wheels or tracks depending on what ground conditions you are designing the vehicle for and need to cope with.

 

This dear forum members is the catamaran tank - my idea and you heard it here first. Copyright © Peter Dow, 26th July, 2010.

Edited by Peter Dow

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Wouldn't the double hulls make the MRAP even heavier? The increased surface area would all have to be armored, so the weight would go up.

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and you'd also have the middle section subjected to increased blast damage due to shockwave focusing, the very thing the V hull is designed to counteract.

 

and then there's the mobility issue. a wider vehicle can't go down narrow streets etc.

 

put simply the MRAP is, like all designs, a compromise to meet specific design criteria.

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Wouldn't the double hulls make the MRAP even heavier? The increased surface area would all have to be armored, so the weight would go up.

 

For the same area in the horizontal plane, the catamaran tank and the MRAP have essentially the same surface area and weight.

 

catamarantank.jpg

 

and you'd also have the middle section subjected to increased blast damage due to shockwave focusing, the very thing the V hull is designed to counteract.

To lessen the blast forces tending to split the two V-shaped hulls apart, the Vs can be angled slightly to form a vertical blast chimney.

 

verticalblastchimney.jpg

 

and then there's the mobility issue. a wider vehicle can't go down narrow streets etc.

 

put simply the MRAP is, like all designs, a compromise to meet specific design criteria.

Considering the wheeled version of the catamaran tank only for now.

 

Maybe the left and right sides while separated are 4 wheeled vehicles which you can drive independently, call those "half-vehicles" Y-sides.

 

The Y-sides are tall and narrow and even less stable than an MRAP while separated but loading and unloading on and off transport and manoeuvring the sides in position to connect together the stability is sufficient.

 

Then, when you come to bolt the two Y-sides together there are a number of choices as to how wide apart the left and right hand Y-sides are fixed.

 

I'll type in some figures so you can see what I mean.

 

Say, the separated Y-sides are 4 feet wide.

 

Well for example, the connecting bars or tubes could hold the left and rights Y-sides together separated by these example widths:

 

  • 1 foot, Y1Y so the total width is 4 + 1 + 4 = 9 feet - no wider than a Cougar MRAP and so as stable as todays MRAPs and narrow enough for urban roads and traffic.
     
  • 4 feet, Y4Y so the total width is 4 + 4 + 4 = 12 feet, the same as an M1 battle tank, good for country roads, stable but narrow enough to get across most bridges no problem.
     
  • 8 feet, Y8Y so the total width is 4 + 8 + 4 = 16 feet, super-stable for open cross country off road where the extra width is no problem for crossing bridges or fitting on roads because there are no roads maybe nothing more than a dirt track of uncertain width itself, maybe nothing but rough ground and rivers need to be forded or not crossed at all and then the extra stability is purely a bonus with no disadvantage of extra width.

The vehicle could even carry the different lengths of connecting bars or tubes for the crew to swap round to change vehicle width which they can do themselves anywhere they can find a flat piece of ground - no special facilities required.

 

The deluxe version could have a hydraulic telescoping connecting tubes to change vehicle width at the touch of a button!

 

When the two Y-sides are connected together, the steering mechanisms of the two Y-sides are mechanically coupled together, somehow! There could be power steering as well!

 

The catamaran tank still has V-shaped hulls to deflect the blast. It just has 2 V-shaped hulls, each of half the width of a single V-shaped hull.

 

The catamaran tank can have the same total area of V-shaped hull measured in the horizontal plane as a single-hulled MRAP!

 

There is not much more area for the explosive force to react with in the catamaran tank because the space between the two hulls is mostly empty space with just connecting bars or tubes!

 

The benefit is this - it doesn't roll over!

 

The catamaran tank - an MRAP which doesn't roll over!

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For the same area in the horizontal plane, the catamaran tank and the MRAP have essentially the same surface area and weight.

 

catamarantank.jpg

The total armored area would rise. Rather than two sides of the hull needing thick, heavy armor, four sides would. (Two hulls, two sides.)

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When you change configuration you are changing the connecting bars between the two Y-side vehicles.

 

connectingbars.jpg

 

So the mechanic or the trained crew would

  • unbolt and remove the connecting bars you want to change
  • drive one of the Y-sides to about the right new position for the new bars
  • attach the bars and tighten them up to bring the Y-sides to the right distance apart.

 

 

The total armored area would rise. Rather than two sides of the hull needing thick, heavy armor, four sides would. (Two hulls, two sides.)

Oh you are not talking about the hulls, but the sides above the hulls, the parts not drawn in the above diagram?

 

OK I am with you now. Fair comment. You might get away with the inner sides being somewhat less thick armour than the outside since the chances of getting a hit and a square-on hit especially from an RPG or something are less because the inner side is shielded to some degree by the other side.

 

But yes, there is no avoiding that 4 sides are always going to weigh more than 2 sides.

 

Look on the bright side then. The upside of more weight is the vehicle will not be accelerated so much by a blast imparting the same impulse.

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But the report you quote in your first post says that part of the MRAP's problem is that its weight causes poorly-built roads and bridges to collapse, causing it to crash. Increasing the weight can't solve that problem.

 

And I am talking about the parts drawn in the above diagram; the sides labeled "2" and "3" are interior walls not necessary in a single-hull design. Because the armor and shape of the MRAP is specifically designed to combat IEDs, you'd have to keep the interior walls very strong -- the primary threat is IEDs, not RPGs.

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But the report you quote in your first post says that part of the MRAP's problem is that its weight causes poorly-built roads and bridges to collapse, causing it to crash. Increasing the weight can't solve that problem.

Well I have got a lot to say on that question.

 

MRAP luggage compartments / trailers / passenger trailers are something I want to feature in my new design.

 

It isn't really a "catamaran" feature particularly because a mono-hull MRAP could have a luggage compartment, outside the armour-protected volume and trailers are already available for today's MRAPs. A trailer is a trailer, right?

 

But I hear complaints from many sources about passenger cabins not being spacious, can't afford to make them smaller and so on.

 

The thing is, if you always put the gear the troops are carrying (heavy guns and ammunition etc.) in a trailer it saves space in the passenger cabin right?

 

So then the armoured passenger cabins could be made smaller, and the gear stored in a non-armoured volume, either a luggage compartment - a boot or a trunk which can be low, lowering centre of gravity, or in a trailer, which also takes the weight off the MRAP wheels which helps to prevent road collapse.

 

So for all kinds of reasons I am thinking that pulling a luggage trailer and a non-armoured boot/trunk should be integral to a good MRAP design, not just an optional extra.

 

So why don't MRAPs use trailers more, when road collapse, heavy weight on the wheels is such a problem?

 

I know that to use or not to use a trailer is an operation decision that the military make but if anyone knew if trailers were a bad idea for some reason, then would you please point that out.

 

OK for existing MRAPs (some of which don't have a fixed gun) I can see why the passengers want to keep their weapons with them so that they can dismount guns blazing.

 

Frankly, a "no fixed gun" APC is a really bad design in my opinion. Even one gun is too little in my opinion.

 

Defence against ambush is why you need fixed guns on every APC roof.

 

My design would include a minimum of one gun on each side of the catamaran MRAP.

 

Actually, I would like 4 guns on top; that is possible and if you read on I will explain how.

 

Only the guns and video cameras (2 per gun, one wide-angle, the other telescopic sights) need to be on the roof. There is no need for a gunner up top in a gunner's turret with all the high up weight and instability that causes.

 

The gunner can be sat in the cabin with the rest of the crew and fire and aim the gun from below.

 

Think of a submarine periscope in terms of turning and aiming the gun, although the gunner would remain seated in one position if he (or she) views the gun camera views on a LCD display. Push buttons to change camera view and push button to fire.

 

For reloading "the periscope" can come down to allow the gunner to reach the gun to reload in safety.

 

2 or 4 guns, medium machine guns can be up top and because there is no armour up there, it could work out with a lower centre of gravity than one gunner with an armoured turret.

 

Of course an armoured passenger trailer would have guns of its own as well.

 

There is no reason why passengers cannot always carry a handgun which takes up no space. That and cover from fixed guns should be sufficient I would have thought.

 

Sure I could imagine a scenario when you'd really like to fire a guided missile the second you open the passenger door.

 

Well you still could do that and carry weapons inside in a smaller cabin if you were not carrying a full load of passengers.

 

MRAP armoured passenger trailers

 

In fact, why not have an armoured trailer with a V-shaped hull (or two V-shaped hulls for a catamaran trailer) and carry some of the passengers there?

 

Then you could really reduce the weight of the MRAP - a much smaller front cabin, much less volume needing protecting in the front vehicle, spreading the weight across more wheels.

 

I think the armoured passenger trailer idea is a winner, catamaran or no catamaran and it is a concern that existing MRAPs don't use this concept already.

 

B)

 

And I am talking about the parts drawn in the above diagram; the sides labeled "2" and "3" are interior walls not necessary in a single-hull design. Because the armor and shape of the MRAP is specifically designed to combat IEDs, you'd have to keep the interior walls very strong -- the primary threat is IEDs, not RPGs.

Well admittedly, changing the shape of the V-shape to allow for a vertical blast chimney does also increase the hull area as well.

 

The diagram with sides 1 to 4 doesn't show the "slight" change in V-shape which also effectively negates the claim associated with that diagram of "equal area".

 

So yet again fair comment. Well done. The cross sectional weight of hull goes up and you need to think about using trailers, more wheels to spread the increased weight around, sure.

 

Correct the "interior" hull walls are exposed to blast.

 

The inner hull armour 2 & 3 can afford to be somewhat thinner for the same level of protection because it is shielded from square-on attacks from IED or mine fragments because ground blasts from IEDs and mines are imparting against the inner surface of the vertical blast chimney at an oblique angle which presents less of a danger.

 

Whereas the outer hulls, as with a conventional MRAP, could have fragments heading straight towards them.

 

The penetration threat is mostly from fragments rather than gas blast. The gas of a blast is not so piercing and blows things apart by exceeding tensile strength across a dispersed area of an object's surface - not nearly so problematic for armour designers.

Edited by Peter Dow

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catamaranvehicle640.jpg

Conjoined All-Terrain Anti-Mine Ambush Repellent

 

Armoured Next-generation (CATAMARAN) Vehicle

 

© Peter Dow

The CATAMARAN vehicle concept is the original idea of Peter Dow of Aberdeen, Scotland and was published on 26th July 2010. All copyrights are retained by Peter Dow.

 

More details of the CATAMARAN Vehicle here.

Edited by Peter Dow

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I should think the bigger advantage of that design would be its far greater stability. This stability means that the vehicle's center of mass could be lifted up much higher, so that mines would be largely negated due to distance. However the extra width may make it useless.

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I should think the bigger advantage of that design would be its far greater stability. This stability means that the vehicle's center of mass could be lifted up much higher, so that mines would be largely negated due to distance. However the extra width may make it useless.

I am proposing that the width be configurable by changing the connecting bars between the two sides.

 

The narrowest configuration "Y1Y" will be only 9 feet wide, the same as some MRAPs so it needs to perform as well or better than existing MRAPs therefore its centre of gravity must be no higher than existing MRAPs - preferably lower.

 

The "Y4Y" configuration at 12 feet wide will be as wide as a tank which is not useless.

 

The "Y8Y" configuration at 16 feet wide will be primarily for off-road use with maximum stability - not useless.

 

The idea is to also have a "deluxe" or "transformer" version which will have telescopic tubes for connecting the sides which can be lengthened by hydraulics and shortened by winches, automatically by the driver at the press of a button.

Edited by Peter Dow

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The problem here is cost. MRAPs are meant to be cheap, otherwise you'd buy a APC or AFV. A commercial truck with some steel plate and a light machine gun on the roof is reasonably cheap to build and service. Going beyond that pushes cost into APC/AFV territory, at which point you'd just buy a Stryker or Puma.

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The problem here is cost. MRAPs are meant to be cheap, otherwise you'd buy a APC or AFV. A commercial truck with some steel plate and a light machine gun on the roof is reasonably cheap to build and service. Going beyond that pushes cost into APC/AFV territory, at which point you'd just buy a Stryker or Puma.

MRAP I think has better mine resistance than many APCs and possibly some lighter AFVs as well. MRAP is optimised to counter mines. MRAP is probably not as good against missiles as those other armoured vehicles but it was IEDs that were killing most in Iraq and Afghanistan so mines were the threat to counter and mine-resistant vehicles were the way the military decided to go. See later for my strategic ideas.

 

The Stryker doesn't have the mine resistance ability of the MRAP I am guessing otherwise why this?

 

LAV-H Stryker upgrade

The US Army plans to improve its fleet of Stryker vehicles with the introduction of improved semi-active suspension, modifications reshaping the hull into a shallow V-shaped structure.

 

Note "shallow" - it may have to be shallow because maybe Stryker does not have room for a deeper V-shape?

 

Stryker does have some nice features though. Like that sloping front armour. Future MRAPs and my CATAMARAN vehicle could have sloping front armour too, perhaps shaped as a bow of a ship?

 

Puma is quite a bit heavier therefore not transportable by Hercules C-130 transport. MRAP at around 14 tons can be flown around.

 

http://www.army-technology.com/projects/puma_tracked/

 

The vehicle is built with the option of three levels of protection to suit the operational requirements. The versions weigh 29.4t, 31.45t and 43t.

 

The advantage of my CATAMARAN vehicle is it splits in half and the trailer comes off so it is very easy to transport.

 

Anyway if cost was the priority, for say Afghanistan, we'd be putting the Afghans to work creating secure supply routes which would mean that most of the important roads our troops would use would be IED and mine free.

 

Here's my plan for a strong defence via secure supply routes.

U.S. funds our enemy Taliban's Afghan war. Afpak strategy.

 

 

 

 

The CATAMARAN vehicle can rotate on the spot!

 

It is proposed that the CATAMARAN vehicle will have impressive manoeuvring and tight turning abilities, despite its size - including an ability to rotate on the spot as tracked tanks can do.

 

The trailer, although optional, when it is fitted, it will be attached to the powered and driven front of the vehicle by hinges allowing the front and rear parts of the vehicle to pivot relative to each other in the vertical plane thus keeping the driven rear wheels on the ground but the hinges will not allow any relative movement to the left or right, so as to keep the body and the wheels in alignment.

 

There are 3 pairs of axles -

 

  1. front wheel drive steered axles, (left and right)
  2. rear wheel drive fixed axles, (left and right) and
  3. trailer wheel steered axles, (left and right).

The trailer wheels will steer coupled to the front wheels but in an opposite clockwise / anti-clockwise sense to the front wheel.

 

Each Y-side of the vehicle will have 4-wheels driven so with "4-wheel drive" on both the left and right Y-sides, one might note that the whole vehicle has 8 driven wheels, not just the 4.

 

CATAMARAN Vehicle Steering Geometry Normal steering

catamaransteeringnormal.jpg

 

What this arrangement allows is that even with the trailer fitted, the vehicle can be reversed easily. Normally trailers are a nightmare to reverse. The CATAMARAN vehicle will be a dream to reverse.

 

In addition the CATAMARAN vehicle can rotate about a spot in the middle between the powered rear wheels. It achieves this special ability by virtue of certain design features -

 

  • A first gear which is a low gear for manoeuvring and has a gearing ratio precisely the same as the reverse gear
     
    Two additional rotational gear modes -
     
  • Clockwise - when the left side gearbox of the vehicle is automatically put into first gear and the right side gearbox of the vehicle is automatically put into reverse gear.
     
  • Anti-clockwise - when the left side gearbox of the vehicle is automatically put into reverse gear and the right side gearbox of the vehicle is automatically put into first gear

When either clockwise or anti-clockwise gear is selected, the mechanical coupling normally engaged between the left and right hand steering is automatically disengaged and the left hand wheels are automatically turned to hard right hand turn lock and the right hand wheels are automatically turned to hard left hand turn lock; those two hard turn lock stops are designed so that the steered wheels are pointed in the correct direction for vehicle rotation.

 

Whenever either of the two rotational gear modes is deselected and the gear shift is put into neutral, the mechanical coupling between left and right hand steering is re-engaged and the wheels returned to the appropriate direction as determined by the driver's steering wheel which was redundant during the selection of either of the rotational gears.

 

CATAMARAN Vehicle Steering Geometry Rotational steering

catamaransteeringrotate.jpg

Edited by Peter Dow

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The CATAMARAN Vehicle vs. the MRAP. Which is better?

 

Compare and contrast the features of the CATAMARAN Vehicle against the MRAP it is designed to replace.

 

  • The CATAMARAN vehicle is not taller than an MRAP with a gun turret.
     
  • Yes the CATAMARAN vehicle will be taller including the height of its guns than an MRAP without a gun turret but the CATAMARAN vehicle's automatic guns are quite light and don't raise the height of the centre of gravity much and maybe has a lower centre of gravity than an MRAP with a gun turret with armour and gunner up top as well.
     
  • The CATAMARAN vehicle can be the same width as an MRAP when configured narrow, such as Y1Y at 9 feet wide. It can be narrower, the same width or wider than a tank to suit the roads or terrain.
     
  • The CATAMARAN vehicle will be as fast as an MRAP without the trailer on a straight road. It will be much faster off road, with or without trailer, because it won't roll over and a rolled over MRAP is a slow as you can get; you'd be faster on a donkey!
     
  • The CATAMARAN vehicle will be as well armoured as an MRAP.
     
  • The CATAMARAN vehicle will have as much internal cargo space without the trailer and more internal cargo space with the trailer compared to an MRAP.
     
  • The CATAMARAN vehicle offers the possibility, depending on the width configuration, of additional external cargo space by strapping certain loads, which don't require armoured protection, to the connecting bars in between the two halves of the vehicle.
     
  • The CATAMARAN vehicle will very manoeuvrable even with the trailer attached so its length is no big deal.
     
  • The CATAMARAN vehicle will have more firepower than an MRAP. Two roof mounted machine guns without the trailer, 4 guns with the trailer.
     
  • The CATAMARAN vehicle is "ambush repellent". whereas the MRAP is only "ambush protected".
     
  • Terrorists going up against a CATAMARAN vehicle with RPGs and the like is a more risky proposition for them because the defenders have got 2 or 4 pairs of eyes watching for ambushes with their fingers on triggers to fight the attackers off.

 

Conclusion

 

The CATAMARAN vehicle is a better vehicle than MRAPs for any conflict where MRAPs are now the vehicle of choice.

 

 

 

CATAMARAN Vehicle & trailer - 6 machine guns, 16 seats!

 

catamarangunswieghtpeop.jpg

 

The image shows some vital statistics for my proposed CATAMARAN vehicle, only one Y-side is pictured.

 

The front powered and driven vehicle seats a maximum of 10, 5 in either Y-side.

 

Each side seats 5 =

  • 1 - one driver or reserve driver or front passenger +
  • 2 - one front gunner and one rear gunner +
  • 2 - two passengers

The trailer seats a maximum of 6, 3 in either Y-side

 

Each side seats 3 =

  • 2 - two passengers +
  • 1 - one tail gunner

So the vehicle with trailer attached seats a maximum of 16, 8 in either Y-side.

 

Each side seats 8 =

  • 1 - one driver or reserve driver or front passenger +
  • 3 - one front gunner, one rear gunner and one tail gunner +
  • 4 - four passengers.

The driver can be either on the left or on the right Y-side and then the reserve driver or front passenger would be on the right or left Y-side, respectively.

 

Weight distribution

 

The image also shows the ideal weight distribution in relation to the axles.

 

Each square represents the same weight and length which is

  • one eighth of the weight and length of the combined vehicle with trailer,
  • one fifth of the weight and length of the front powered and driven vehicle and
  • one third of the weight and length of the trailer.

Designing the vehicle to have this weight distribution helps to keep the vehicle well balanced in terms of equal weights over each axle which allows for the same suspension and tyres to be used through-out and maintains this balance with or without the trailer attached.

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Telescopic rear axle armoured vehicle - easy!

 

OK well I have to admit there are a few problems with my CATAMARAN vehicle design.

 

  • Heavier armour for the same volume protected
     
  • The inner sides required to be armoured and connected together and that all adds weight. Precisely how much more weight is difficult to predict but a significant thickness of additional armour required certainly

Therefore I am now turning to a different and easier idea to solve the roll-over problem for MRAP armoured vehicles - telescopic rear axles.

 

Telescopic Rear Axles. Extended - Wide.

telescopicrearaxles.jpg

 

Telescopic Rear Axles. Collapsed - Narrow.

telescopicrearaxlesnarr.jpg

 

Hydraulic cylinders components are available to be adapted for this purpose.

 

The axles would need to be braced vertically to stop them bending under the weight of the vehicle.

 

Certain design concepts I have previously described for the CATAMARAN vehicle which I do want to retain for the telescopic rear axle design, such as

 

  • Trailer wheel steering
  • Armoured passenger trailer
  • Rotation on the spot
  • Roof mounted remote-controlled machine guns
  • 5 : 3 ratio, 5 (vehicle) : 3 (trailer), weight and length distribution

Therefore the telescopic rear axle design although it is perhaps a less radical and innovative mono-hull design than the CATAMARAN Vehicle design, nevertheless it has many excellent features which greatly enhance the performance over the standard MRAP.

 

So I await with interest to see if anyone can identify flaws with my second major design iteration.

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Here is an idea. If you need to, please review this diagram of a steering mechanism from Wikipedia on Steering.

 

OK my idea is you replace parts of the steering rod with pneumatic pistons, either side of the connection to the steering column as follows.

 

rotationalsteering.jpg

 

There is an air tank topped up by an air pump which when its valve is turned on inflates the pneumatic pistons now integral to the steering rod. (This should only ever be done while the vehicle is at rest and the driver has selected clockwise or anti-clockwise gear - some kind of safety cut out.)

 

The air pressure quickly rises (that is why you use air, not hydraulics, it is so much faster if you supply from an air pressure reservoir - there is not a need for huge force, just speed, so pneumatics is the driver of choice I think) and when the air pressure exceeds a critical amount, retaining catches, which normally hold the pistons firmly closed against all manner of road bumps, suddenly break open and the pressurised air forces the pistons open against a spring and the steering rod lengthens to a maximum and the wheels are turned inwards to their respective stops - hard right hand turn for the left hand wheel and hard left hand turn for the right hand wheel, ready for rotation.

 

It is clear to me that the 45-50 degrees or so maximum turning angle normally is limited by the steering rod at full stretch - not by the wheel bumping into the axle - so 75 degrees in this diagram looks easy.

 

When you want to revert to normal steering, the system simply releases the air pressure in the pistons and the pistons close with the spring and the pistons snap shut into their retaining catches ready for normal steering.

 

As you can see this is for rotation about a point mid-way between the rear axle. It is only when I add on my trailer to my armoured personnel carrier that the vehicle does zero turning radius, strictly speaking.

 

Hence I have always called it "rotation on the spot".

 

So do you think that would work? I would doubt that is the way that lawnmowers do zero turning radius. :)

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Introducing HUMPBAC - an armoured personnel carrier with a connecting doorway from the rear of the vehicle to walk through into the armoured passenger trailer. Tickets please! :D

 

HUMPBAC

Hinged Under-floor-Mine-Protection Battle-ready Armoured-personnel Carrier

Copyright © Peter Dow, 7th August, 2010.

 

humpbac780.jpg

 

 

HUMPBAC Features

  • Trailer bolts firmly to the rim of the vehicle forming a rigid joint
  • Rear section of vehicle is hinged to articulate the trailer's vertical motion
  • Movement of hinged rear section accommodated by a hump in the roof
  • Vehicle rear door can serve as a connecting doorway to the trailer section
  • Front vehicle seats a maximum of 11 people
  • Armoured passenger trailer seats a maximum of 7 people
  • Vehicle with trailer seats a maximum of 18 people
  • Roof mounted remote-controlled machine guns- front, top & tail gun
  • Trailer wheel steering
  • 6-wheel drive
  • Telescopic Rear Axle & Wheels
  • Rotation on the spot
  • Even axle weight distribution
  • 5 : 3 weight & length ratio, 5 (vehicle) : 3 (trailer)

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