New steering system concept to minimize aerodynamic drag

[hummingbird]

Another point here is a low mass, high CG narrow three wheeler - unless there is some kind of banking mechanism included, there is a real possibility of this matchbox toppling/tumbling on its side while negotiating a tight turn at some speed.

Bomber, did you take this into account?

[aerohead]

Originally Posted by Blue Bomber Man

Ya have the curve flipped would make more sense. What sort of results did they have with this sort of steering mechanism?

Blue Bomber Man,the comment was made in the context of the aerodynamics of the articulation.GM's work revolved around the forward structure being the tractor,and the following structure,the trailer.The tractor's steering was conventional.

[aerohead]

Originally Posted by Blue Bomber Man

LOL Frank, was not my intention. This is exactly why I love posting about stuff like this on these boards. You can toss an idea around and get a lot of different insights to the benefits and complications of a scenario.

After all this talk I've decided to stick with a traditional steering system and will probably just design a part that attaches to the steering system that fills in the wheel wells at the body to smooth airflow.

I might consider making the wheels internal, but probably won't because it would require a larger wheel base/more frontal area. No sense killing the all the benefits of shielding the airflow from the wheels.

Have you seen the HONDA Dream II solar car? They put the steering wheels on lazy-Susan turntables,mated to double-wishbone suspension,where the wheels turned with their respective fairings.There is no conventional "wheel-house" as in conventional cars.The apparatus is rotated like an outboard motor on a boat.Perhaps a bit of toe-in is provided for "centering".Whatever you do,it's got to be very robust,unbreakable,zero-defect.Too much is riding on it!

[DonR]

The Honda Prelude's rear wheel steering had two modes of opperation.
1) Slow speed 0-15 or 20mph. The rear wheels turned opposite of the front. Not near the angle of the front wheels. This aided in maneuverability, shortening the turning radius. At higher speeds you have too much oversteer.

2) High speed 15 or 20 mph on up. Parallel to the front. Not near the angle of the front wheels. This induces an increased slip angle in the rear tires reducing oversteer.

Wagon steering.
Wagons have 2 rear wheels. Pivoting a front "axle" reduces the track width on the front axle leading toward tipping issues with a single rear wheel. Under normal driving conditions you would probably be ok. Evasive maneuvers would get real hairy real quick.

Personally I would go with a manual rack & pinion steering of the front wheels. Mount the wheel pants to the upright so they travel up & down as well as turn with the wheel. With a dual wishbone suspension with coil over shocks, you would not have any suspension components higher than the tire by the outside of the vehicle.

[Blue Bomber Man]

Unfortunately you cannot have the wheel skirts travel up and down with the suspension. If you did that it would collide with the body that is fixed to the frame. If I left enough gap there to allow for full suspension travel, it would avoid that issue, but it would negate much of the aerodynamic benefit.

I think I have a solution though. Very hard to explain without a visual, but the basic idea is there will be two sets of steering linkages. One goes to the wheel, the other to the wheel skirts. The wheel skirt linkage will not be hard fastened to the wheel skirt pivot point, rather it will be free to travel up and down. This might require some small sets of bearings or something to prevent binding but I think some variation of this concept will be an adequate solution.

I probably won't make a solidworks drawing of the idea until I have finalized the rest of the steering and front suspension. Which might require me to design the frame as well

So it might be a few weeks before you see something for this idea.

On a different topic regarding 'wagon steering' Aerohead had mentioned the research done on it in the 60's regarding that and indicated that the pivot point was behind the wheels rather then ahead of the wheels as my earlier sketch showed. The problem I see with having the pivot point behind the wheels is the steering system will always pick a side and try to pull that way. So unless the system was design to prevent that the driver would always be forced to counter steer some.

If the pivot point is ahead of the wheels the system should want to self center. Of course this requires a less favorable body design that leaves an edge out of the body during a turn unless the width of the body is the same as the diameter of the turn.

BTW guys, if this vehicle ever comes to be, I am certain it will be because you all provided so much advice on different concepts and had different perspectives.

[Christ]

for a nice electric self contained drive unit, see "reach truck". The drive and steering units are in the same self contained area. Could be made to fit just about anything else, although they haven't ever been designed with too much power or speed (about 15 mph tops, IIRC, due to the relatively tiny, solid tire used.)

Some of them have had the drive and steering wheels placed on opposite sides, with the drive wheel acting like the front wheel of a shopping cart as far as lateral movement, but still being capable of driving, while the steering wheel freewheels, and can be powered to move laterally.

[Christ]

Very little lateral movement is required to steer at any speed when high caster angles turn toe-movement into camber... the problem with that, is that camber-based steering requires suspension correction to not kill tires... i.e. when you steer, the vehicles suspension needs to counteract centripetal force, so the body of the vehicle either remains mostly straight, or leans into the turn.. see "T-Rex 3-wheeled vehicle"

It steers from the front wheels, the suspension is set at a high camber angle, and allows the rear wheel to be a pivot point, which makes the chassis lean into corners. This makes it so that while the tires are losing contact patch due to over-cambered turning (leaning up on their sidewalls), the vehicle's suspension correction helps the vehicle "dig in" to the corner, so that it helps to correct the contact patch of the tire.

[Piwoslaw]

Originally Posted by DonR

The Honda Prelude's rear wheel steering had two modes of opperation.
1) Slow speed 0-15 or 20mph. The rear wheels turned opposite of the front. Not near the angle of the front wheels. This aided in maneuverability, shortening the turning radius. At higher speeds you have too much oversteer.

2) High speed 15 or 20 mph on up. Parallel to the front. Not near the angle of the front wheels. This induces an increased slip angle in the rear tires reducing oversteer.

I remember an ad of some car showing how the rear wheels turned in the same direction as the front, aiding in changing lanes. I wondered that it would make turning in a full parking lot quite tricky. I wonder how Honda's Prelude switched from one mode to the other, say if the 15-20 mph were exceded with the wheels turned?

Steerable front and back wheels make the car more complex, but it would allow a smaller angle of turn, making it easier to cover the wheels with skirts.