What exactly is a zero radius turn vehicle?

[banerjeerupak]

Well for my project in 6th sem, I'm planning to make a zero radius turn vehicle. What i understand by a zero radius turning vehicle is that it should keep the centre of mass at a fixed position and then rotate so that it moves 180 degrees. That is the maximum movement i should be able to show i guess.

Am i right in my concept??

 

[DaveC426913]

Certianly sounds like "turn on a dime" to me.

 

[Andre]

A helicopter can do it.

 

[FredGarvin]

So can some lawn mowers and tanks and fork lifts.

 

[brewnog]

And skid-steer loaders, excavators, bulldozers, supermarket trolleys...

 

[Danger]

I'm not sure, but I think that the Jeep Hurricane can as well; it has 4-wheel steering.

 

[banerjeerupak]

so you feel that my idea is correct. i know how to make it work. only thing is that i should not be making something else. and how on Earth does a 4 wheel steering work

 

[banerjeerupak]

by the way, i know a helicopter can do it. but it does not have to rotate wheels to do it. its very different for a helicopter and a 4 wheeled vehicle i guess

 

[FredGarvin]

Yes they're different. That wasn't the point.

For a 4 wheeled vehicle or tracked vehicle to do a zero radius turn, the two opposing sides drive wheels must be able to rotate in opposite directions at the same time.

 

[banerjeerupak]

that is exactly what I'm planning to do...make the two diagonally opposite wheels rotate in opposite directions

 

[Danger]

Here's an article about the Hurricane.
http://www.gizmag.com/go/3599/"

and another:
http://auto.howstuffworks.com/jeep-hurricane.htm"

 

[banerjeerupak]

well the both the articles are a great read. but what the howstuffworks article says is using a different concept of turning all the wheels in particular directions resulting in net 360 degree turn. not the way of couple that i thought or suggested...

 

[russ_watters]

Wow, yeah, I was going to say that 4 wheel steering alone won't get you zero turn radius, but that's crazy how they applied it to that Jeep.

 

[banerjeerupak]

but just give it a thought... how do they plan to move the 4 wheels differently... when in normal conditions they can't do it

 

[Danger]

You probably just switch modes with a dash control and the rest is done by computer. This is not the only on-off road vehicle with 4-wheel steering; it's just the most extreme example of it.
By the way, I didn't realize until I reread the article that it won't be put into production.

 

[Mech_Engineer]

You probably just switch modes with a dash control and the rest is done by computer. This is not the only on-off road vehicle with 4-wheel steering; it's just the most extreme example of it.
By the way, I didn't realize until I reread the article that it won't be put into production.

LOL You do realize it had TWO engines in it, right?! While an interesting concept, what a nightmare if you wanted to buy one.

Exotic, yes. Impractical, absolutely.

 

[Danger]

Not just 2 engines--2 Hemis.
As mentioned elsewhere, my grocery-getter is a 4WD El Camino with 33" tires and a 455 Olds Rocket motor, so practicality has never been near the top of my priority list.

 

[banerjeerupak]

well, this vehicle would be capable of a zero radius turn. but would it be able to do something like a .5 metre radius turn. as probably the dashboard button just fixes the wheels to this angle and then the engine just makes them move... and by the way which other all wheel steering vehicles exist. never heard of them... all wheel drives i know of but all wheel steering... and i am yet to understand the concept of making all the tyres separetely maneuvrable...

 

[banerjeerupak]

and one more thing... what is so special about HEMIS... they are just another breed of engines. what is it in their design that they give the max power. i understand that their combustion chamber is hemispherical in shape...

 

[brewnog]

and one more thing... what is so special about HEMIS... they are just another breed of engines. what is it in their design that they give the max power. i understand that their combustion chamber is hemispherical in shape...

Obviously, if you actually want an answer to this it should be in a thread of its own.


A brief overview:

Getting the best (in terms of performance and emissions) out of a given SI engine requires four main optimisation strategies. A fast combustion process is required which displays minimal cycle-to-cycle variation. This needs to be present over the whole expected duty cycle of the engine in question (speeds, loads ec). A high volumetric efficiency is required at wide-open throttle. Minimum heat loss to the combustion chamber is obviously advantageous, as is the requirement for a low octane fuel.

Naturally, combustion chamber design and geometry has a huge affect on all four of these factors, and steps taken to enhance one will often have a negative impact on others (increasing flow through the valves, or swirl, for instance). Being a pretty novel (for its day) combustion chamber arrangement, it can only be expected that a hemispherical head would have some pretty drastic effects on all four of these factors.

If you want to truly understand why a hemispherical head can work quite well, and where its limitations are, you know what to do!

 

[Panda]

... and by the way which other all wheel steering vehicles exist. never heard of them...

TATRA make a number of truck bodies that were used for military vehicles and commercial vehicles for operation in harsh environments.
I had the honour to have one to play with that had six wheel drive, six wheel steering. The whole arrangement was mechanical driven by hydraulics so that cams automatically reversed certain axels directions as you hauled the wheel round further.
Other good features. If you went on or off soft ground the tyre pressures could be altered using a series of valves on the dashboard, again all mechanical with pressure line going through each hub. Also it had a V12 Diesel for motion and a gas turbine for power generation. If one failed you could generate off the diesel, or even better drive off the turbine although this destroyed the automatic clutches. Both engines ran off the same fuel.
Bad features the cabin heater just diverted the engine exhaust across the dashboard and it leaked diesel fumes into the cockpit. It was built to be driven by midgets so you cut you kness on all the sharp bits of metal and screws sticking out from under the dash.

From what I've seen MAZ do an 8x8 all wheel steering chassis (Designation 7910) again for Russian Military and extreme environments.
These vehicles are very popular in European Off-Road Truck Trials.

 

[Dreamedideas]

Just look under a car at the front wheels and see how they turn...duplicate that for the front and back gearing them to the steering wheel...I'm sure with some effort and a few drawings you can come up with a proper design. Making the rear wheels turn left when the front turn right. The wheels would most likely have to turn at a 90 degree angles.

 

[brewnog]

Just look under a car at the front wheels and see how they turn...duplicate that for the front and back gearing them to the steering wheel...I'm sure with some effort and a few drawings you can come up with a proper design. Making the rear wheels turn left when the front turn right. The wheels would most likely have to turn at a 90 degree angles.

No. Firstly, this would not necessarily create zero radius turning, it would merely reduce the turning circle. Secondly, having all four wheels turn 90 degrees from their 'straight ahead' position would just mean that the vehicle crabs sideways.

 

[Dreamedideas]

Well, if the front wheels turn left and the rear wheels turn right both still pushing in their respective forward direction the vehicle would most definitely be spinning...:)

 

[Ken.Li]

A ZTR ( Zero Turn Radius) vehicle is the machine that can make a zero radius turn with the its turning center which usually is the point of rear wheel which touches ground.

 

[Danger]

A ZTR ( Zero Turn Radius) vehicle is the machine that can make a zero radius turn with the its turning center which usually is the point of rear wheel which touches ground.

Don't you have that a bit bass-ackwards? One front brake locked would enable a powerful enough vehicle to pivot around it.