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Parallel steering car

Great for parking. All wheel drive. No differential needed, and no slip.
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This vehicle is basically round, with maybe 5, 6 or 7 wheels. The wheels are mounted on the arms of a spider like the wheels of an office chair, and the body of the car swivels on the spider like the chair does – except that the rotation of the body is linked directly to the castoring of the wheels – so all the wheels are always pointing in the same direction as the body.

The drive runs vertically down the centre pivot of the body, then via bevel gears to shafts out along the arms of the spider, then bevel gears again and vertically down the middle of the (vertical) steering axes of the wheels, and finally bevel gears again to drive the wheels. Steering is accomplished by rotating the body on the spider (and the steering axes of the wheels in sync).

You can have a simple steering mechanism, in which case steering is a little unorthodox from the driver's point of view: you keep turning the steering wheel further and further all the way round a bend, faster for a sharp bend or if the car is moving fast, slower for a gentle bend at low speeds. Alternatively, you can have a more sophisticated, motorized steering system, where the driver's steering experience is normal, and the steering motor is driven at a speed proportional to the speed of the vehicle multiplied by the steering wheel position. (There is another option, where the steering motor speed is proportional only to the steering wheel position. This might actually be nicer to drive, and possibly safer, too.)

There is of course no magic about having to have the body always pointing in the same direction as all the wheels. The most obvious time you might want to disengage this lock would be to reverse direction, when you might turn the body through 180°, but reverse the gears rather than scrubbing the tyres round 180°, but you could if you liked simply face sideways relative to the direction of travel for a while. Great for disconcerting fellow motorway users, or for glaring at the chap tailgating you!

Also good for driving sideways into and out of a parking space, requiring no space in front or behind at all (tough on the folks each end!)

Good for loading and unloading, and getting in and out – always at the kerb side.

The main drawback is that the vehicle is as wide as it is long – meaning probably a maximum length of 2.4m for a road vehicle. (The body can be longer, of course - but the wheelbase is always a regular polygon.)

The other noticeable drawback is that you either have small wheels, which are okay on good roads but no good off road, or the whole vehicle is rather high off the ground and consequently difficult to make stable on or off road. Maybe a small wheeled version would be good on good but icy roads, and possibly a very big (more than 2.4m diameter) version for completely trackless country.

Cosh i Pi, Apr 15 2007

Auto-rotating vehicle Auto-rotating_20vehicle
I was reminded of this old idea of mine by (link) [Cosh i Pi, Apr 15 2007]

Lego Mindstorms NXT Synchro Drive Description http://www.youtube....watch?v=rL6xx6DDZ9o
[BJS, Apr 16 2007]

Lego Minstorms RCX Robot http://sparky.i989....ik/firefighter.html
with synchro drive [BJS, Apr 16 2007]

Nissan Skyline GT-R http://en.wikipedia...Nissan_Skyline_GT-R
Laptop optional [Ling, Apr 17 2007]

[link]






       I believe it is called a synchro drive.   

       I think an electric drive system would be better for this application.
BJS, Apr 16 2007
  

       Electric drive? Possibly, but I like the fact that all the wheels always rotate at exactly the same rate, which is great for traction.
Cosh i Pi, Apr 16 2007
  

       You could do that with an electric drive, but it might require rotation sensors.   

       In fact, why not make the whole thing drive by wire.
BJS, Apr 16 2007
  

       How does the efficiency of electric drive compare with mechanical drive? Unsprung weight? Total weight?   

       Mind you, if you go to drive by wire, you can steer all the wheels by wire, too, and allow non-parallel steering, with any centre of rotation you like, and all the wheels driven at calculated speeds according to their distance from the centre. Exactly how the driver would control this I'm not sure - it's hard to imagine an intuitive user interface. Nor do I know WHY you'd want to do it.
Cosh i Pi, Apr 16 2007
  

       I think an electric drive would be lighter (depending on the power source). I think it would be more efficient because it has less friction and weight, and it could have regenerative braking, it would be computer controlled, yada yada. There would be more unsprung weight, but I think it would have more traction and a lower center of gravity. The total weight would probably be comparable to a normal drive system, but it would have many more advantages
BJS, Apr 16 2007
  

       Mechanical transmissions don't actually have very much friction, and there are electrical losses in electric transmissions. The biggest disadvantage of mechanical drives is lack of flexibility in spatial arrangement.   

       You can't really get better traction than a system where all the wheels rotate in lockstep - that's achievable on electric systems, but it's an intrinsic feature of the mechanical version.   

       Regenerative braking is good, but to take any real advantage of it on a vehicle that isn't connected to an electricity grid requires big batteries - with a nasty weight penalty.   

       It's true that the weight of electric motor/generators has come down a lot with improved magnetic materials, and the efficiency of the control systems is improving all the time. I don't know that they can yet match the efficiency of mechanical transmissions though, although my design is a bit nasty with all those bevel gears, it's true.
Cosh i Pi, Apr 17 2007
  

       Not quite the same, but "Quadrasteer, GM" and "Hicas, Nissan" systems have 4 wheel steering.
Ling, Apr 17 2007
  

       Quite a lot different! 8~) This one can change direction at right angles if it's going slowly enough.
Cosh i Pi, Apr 17 2007
  

       Sure, but if you like cars, take a look at the Nissan Skyline which had 4 wheel steering and up to 1000bhp with the appropriate laptop. Wikipedia has a good read.
Ling, Apr 17 2007
  

       8~) I have to admit I don't really like cars. To me, they're a method of getting from place to place when there's no bus or train, or I've got too much to carry, or public transport's too expensive, and I can't use a bike for some reason. Option of last resort - sadly only too often.   

       <i>Laptop</i>? What's that about?? 8~)
Cosh i Pi, Apr 17 2007
  

       I'm not talking about dancers. Some Jap cars can be modified without even looking under the bonnet.
Ling, Apr 17 2007
  

       Oh, I've seen some British cars pretty dramatically modified, while travelling at speed, by someone with a mobile phone. He didn't even need a laptop.
Cosh i Pi, Apr 17 2007
  
      
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