Com-Central.net

Perhaps a link to this thread would be sufficient...

www.physicsforums.com/...?p=2820378

I cannot help but relate to the comment about a "stream of consciousness" design style...

Sorry for the late response, did not have an change to react sooner
And I have the same (bad) habit, all mechanic engineers have: improve an (existing) design or kill it

- Peter_Dow

What I'd like to suggest Michel is that because vehicles are very often designed to have more weight on the rear axle, the designers of such "rear-axle-heavy" vehicles been able to use a lighter front axle, lighter front suspension, lighter front wheels as well. They could have made the front equally strong but since it didn't have to be, they didn't so as to save weight. Fair enough.

However, if like here, I am designing a new vehicle from scratch and I have good reasons to want equal weights on each axle (such as wanting to spread the weight around all the axles evenly to help to cope with poor quality roads which might collapse under the weight) then I can specify an equally as strong front, rear and trailer axle.

True the front axle of most "rear-axle-heavy" vehicle's is much lighter and they could have made it equally strong

The problem, to get an equally strong front axle is that the amount of material needed to realise this, will be much more then for the rear heavy axle's
This because all joints for steering, etc are weak spots so if you could reduce the load on the components this will decrease the amount of material needed
Another advantage of an lighter front axle is that "lighter parts" are easier to control, so steering systems (no matter if they are mechanical, electrical or hydraulic) can be simpler and also lighter

Before we go on, I would also like to say that your definition of heavy is an little different then mine
An Bushmaster IMV for example of 12.5 tons, is not heavy to my standards it would fit in the range of light

- About the steering.
Your solution is something mechanically, whether by a rod or a cables or whatever.
I would suggest to drop the whatever idea, because there is no other mechanical solution and the idea with the cables will be very complicated (with pulley's and a like)
Even the rods will be trouble some, better solutions would be hydraulic or electrical

- Concerning the connecting bars and the components which attach them to the Y-sides will need to be strong enough to cope.
because your design has changed, from a 2x 4x4+2x2 design to an 2x 2x2+1x1, your removeable connecting bars will have to be permanent fixed. Otherwise you will have to halve vehicle's laying sideway's

- Problem may be the overall width of the vehicle
Sorry missed that point in the text, I based my dimension on the dimensions of an average size MRAP

Michel

- Michel_Krauss

because your design has changed, from a 2x 4x4+2x2 design to an 2x 2x2+1x1, your removeable connecting bars will have to be permanent fixed. Otherwise you will have to halve vehicle's laying sideway's

Changed? I have posted a second completely different design, a conventional mono-hull, not a catamaran at all!

Look - one hull, no connecting bars! See large image.

- Peter_Dow

Armoured Personnel Carrier Designed by Peter Dow.

Features

• 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
• Trailer wheel steering
• Telescopic Rear Axle & Wheels
• Rotation on the spot
• Even axle weight distribution
• 5 : 3 weight & length ratio, 5 (vehicle) : 3 (trailer)

More details ...

The second design gets stability from a telescoping rear axle! Look! See large image.

- Peter Dow

Oh I am on to my second design already Michel and you are still discussing the first!

Sorry I don't have a really cool name for my second design yet - I have just called it "Armoured Personnel Carrier by Peter Dow". I will need to think of something better so as to grab people's attention.

Air-Powered Steering for rotation in a vehicle

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.



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.

- Joe_D

Interesting,

Looking at the design, it kinda reminds me of this thing,

Engineer vehicle with Ground Penetrating Radar

Yes I see the resemblance right away.

- Joe_D

Don't ask me the official name.

A very narrow crew compartment with "V" hull providing minimum exposure to blast. Lash two of these side by side, remove the inside set of wheels, and now you have facsimile to your Catamaran vehicle.

Pretty close Joe.

Actually that was the idea I first started with - 2 simple Vs or as I called it Y"Y

The nice thing about the first idea that would have meant that you could use the same amount of hull armour (a bit more for the inner sides, but who is counting?)



But then we got thinking over on the science forum.

www.scienceforums.net/..._p__556702

- insane_alien

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.

Which I have to tell you Joe worried me a lot (and there isn't an easy way to test how bad the effect would be) so I came up with this.

- Peter Dow

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.

So the vertical blast chimney should help a lot with stopping a blast in the middle of the two hulls using a lot of its energy pushing the two hulls apart but ..

... changing the shape of the V-shaped hulls like that does unfortunately mean that they need to be bigger, cover a bigger area than just one V-shaped hull twice the size.

So with bigger armour the CATAMARAN vehicle gets heavier for the same volume to protect.

That is not to say the CATAMARAN vehicle, even if it was heavier could not be useful, but it looks like you need to trade more weight for more stability and so maybe there is another solution?

So that is why I started looking around for a second design - and I came up with the telescoping rear axle.

- Joe_D

With your idea a mine blast coming from below would have a hard time penetrating the hull, being that the inside there is no area for the blast to concentrate on.

Well that is precisely the unknown about how the two V-hulls side by side would react to a blast between them.

If the blast between the Vs was not too damaging then maybe you could use the original VVs without angling them, save weight and the CATAMARAN vehicle would win every way? Hard to know but it is a concern.

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!

HUMPBAC
Hinged Under-floor-Mine-Protection Battle-ready Armoured-personnel Carrier
Copyright © Peter Dow, 7th August, 2010.



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)