Suspension roll

[Black_Moons]

Today I wonder about suspension roll in turns, Namely if it can be used to good effect in a 4 wheel vehicle instead of the typical negative effect it has.

I'm thinking in an ultra light vehicle where its only a fraction of the drivers weight and siting low enough, Could someone link the suspension somehow to the driver such that it rolls into a turn (Like a bicycle), instead of out of?

I'm thinking with enough rear suspension travel assuming a trailing arm suspension, if you drop the outside wheel enough you can actually get a wider wheelbase as you tilt the vehicle.

With mushy enough suspension and narrow wheelbase, It also might just be practical for the driver to lean over into the turn and shift enough weight to make the vehicle lean and shift CG enough.

My other idea is linking the steering to some kind of suspension bias springs, But I fear that might make it very difficult to steer and result in bumps having a lot of feedback into the steering.

A 3rd thought was having the seat/occupant on a pivot that would lean him into the turn via G forces as the pivot point would be above his center of mass. But I realised that would actually worsen the center of gravity of the vehicle by moving it to the outside. Maybe if it was connected to the suspension in a way such that tilt of the driver caused the suspension to react... Seems like a lot of work and compromise of the design however, but it would be G force based so it would not excessively tilt the vehicle at low speed when unneeded. It might be rather unsettling to the driver however.


Also with the very large wheel like the 26" wheels I plan to use, the front wheels using double A frame suspension can be set to camber outwards regardless what direction the frame is designed to roll in a turn, slightly improving wheel base.

Although that then requires that the ride height be well tuned to the load to prevent excessive negative or

[The Artful Bodger]

There are a number of 'tilting three wheeler' vehicles and no doubt a few 'tilting four wheeler' vehicles too.

Some are active tilting where a motor or hydralic system tilts the wheels or vehicle body and there are passive ones too where the turning forces tilt the vehicle.

One configuration that interests me is a tricycle with two wheels at the rear which support the engine and transmission, the passenger cabin is attached to this via a pivot and a single wheel for steering is up front. So what it is in effect is the front of a motor cycle coupled to a stable two wheeled power pack. The axis of the pivot passes through the ground contact patch of the front wheel. This would be a passive leaner.

Google is your friend, example 'GM Lean Machine'

[darryl]

Oh, man. This was one of the first ideas I wanted to incorporate into the tadpole. Someone talked me out of it, otherwise I'd probably have some feedback to give.

I wanted to articulate the whole thing so as I leaned my body the front wheels would also lean. I wanted the front chassis to remain flat at the same time, while the rear would lean. Then I started to think about what would happen if you were stopped- you would fall to one side or the other just like you would on a bike. You could put your feet down on the ground to prevent that, like with a bike, or you could have some kind of lock-up happen at very low speeds. If you sat low and reclined, putting your feet down would be a good way to hurt yourself if you were still moving.

Anyway, my original thinking was that you could have the best of both worlds- it would ride like a bike, but be stable at a stop. As long as the front chassis stayed at the same height when you leaned, the tendency to flop over would be minimal to none. If the front chassis raised slightly as you leaned either right or left, the tendency would be to self-settle in the upright position. In my case, the front chassis would have carried the batteries, so you sure would not want to be fighting that weight just to stay upright. In any event, if the front was self-centering to the vertical position, it would tend to bring the back part to center as well. I think you could get used to that quite easily.

With all the articulation, you'd want to use a method that didn't allow any play in any of the junctions. I can see where some tapered roller bearings would be very useful.

All my ideas so far have been with the single rear, two front wheels. It has been and still is my opinion that this is the best configuration. It's a lot easier to do it the other way around though.

[Black_Moons]

I wonder what happens when you stick someone in a car on a seat that has curved rails, such that they have to keep themselves balanced and upright via feet and arms on the steering wheel. Do they tilt themselves naturally after learning? Can I fit enough tilt into the seat?

It would be more comfortable if you can eliminate lateral forces on the driver by allowing him to tilt easily.

[Black_Moons]

Oh, man. This was one of the first ideas I wanted to incorporate into the tadpole. Someone talked me out of it, otherwise I'd probably have some feedback to give.

I wanted to articulate the whole thing so as I leaned my body the front wheels would also lean. I wanted the front chassis to remain flat at the same time, while the rear would lean. Then I started to think about what would happen if you were stopped- you would fall to one side or the other just like you would on a bike.

I wonder how successful linking the wheel tilt to the steering would be? You would naturally try and keep upright at stops, and as long as you don't start to fall over, it should be easy to maintain it upright.

Basically the equivalent of lots of caster producing lots of camber when steering.

Found this about the existing leaning vehicles:

However, unlike the Carver One, which uses high-tech hydraulics to calculate angle of lean based on speed and cornering force, the Lean Machine was much more physical to drive.

A handle-bar controlled the steering, and separate foot-pedals had to be pressed to control the car’s cable-operated tilting mechanism.

Hmm found even more food for thought:
http://www.gizmag.com/sway-motorsports-scooter/22117/

http://www.ballerride.com/2009/01/27...-four-wheeler/ Has some nice videos.. that thing is really a sexy beast of a... whatever it is!


http://www.piaggiousa.com/scooters.h...s=home/mp3-250 2 front wheel motorcycle?

Hmm interesting sub note, apparently the 650mm min seat height restriction is only for motorcycles and not tricycles, I wonder why?

Also thats unladen, So all you need is lots of suspension travel... heh.

[darryl]

I don't know if you can link the steering to the lean. Since speed plays a crucial role, the amount of lean is going to vary, even though the steering input might remain the same. Taking a tight corner at speed is going to require a lot of lean, while taking it very slowly would take the same steering input, but almost no lean. You steer by vision, but lean by sense of balance.

I better get to bed. I'm out of here at 6am for a couple of days.

[Black_Moons]

Uh oh...

'Bicycles and motorbikes can have tall thin spindly wheels because they don't have to handle the same side loads that a conventional four wheeled non-leaning vehicle does.'

That does not bode well for my design.. I do recall seeing a number of bicycle tires folded in half at the bike shop too..

[Peter S]

I remember when Top Gear tested the Carver they were very impressed. It had very steep tilting, I think linked to steering and speed:

http://www.3wheelers.com/carver.html

The Top Gear clip is probably on the internet.

[EVguru]

Imagine putting two bicycles side by side.

Link the two frames with paralellograms so they will tilt together.

Link the steering.

The result can be ridden and balanced just like a single bicycle.

There's some good stuff on the now defunct Millenium Motorcycle website;

http://members.iinet.net.au/~jsulman/tracer/

It's accessable via the Wayback machine;

http://web.archive.org/web/200710131...sulman/tracer/


Try here too;

http://www.maxmatic.com/ttw_index.htm

[The Artful Bodger]

My thinking for my, maybe, project went something like this..

Having the front lean like a motor cycle means I could make the seating position as high and upright as I liked without compromising stability and this would also pretty much negate the, very valid, concerns that 'one front two rear' is not as stable as the other way around.

While the front half would have the stability of a motor cycle the rear would have two wheels that would always be perpendicular to the road and the entire rear ensemble would have a low centre of gravity and hence good anti roll characteristics.

I thought I would make something like a disk brake mechanism on the 'roll pivot' between the front and back sections so instead of trying to put my foot on the ground when stopped I could just lock that brake and keep the front upright.

One of my friends predicted that it would be possible to lean the front section right over when getting in and out and that a dab on the throttle would cause it to stand up automatically! I think he is probably right.

Riding sensation would be very much like a motor cycle except that a fully enclosed cabin would possible, there would be good isolation between the engine and the cabin and possibly a quiet ride with heater/air con and stereo etc.

[john hobdeclipe]

Honda Gyro

Google "honda gyro" and learn about this unique little leanable 3 wheeler.

[EVguru]

Google "honda gyro" and learn about this unique little leanable 3 wheeler.

Copied from the Ariel 3, but slightly better.

[john hobdeclipe]

Honda Gyro Pix





We bought this back in 2008, rode it around a bit and enjoyed it, but we sold it when we realized that it had to be tagged and insured, and we couldn't afford that because we didn't have a title for it. I liked it, but it had no provision to carry any cargo.

[The Artful Bodger]

The Arial and Honda are not the only examples of the genre as I recall another Japanese one for sale in 1973 (sorry, cant remember the name but it might have been marketed by Daihatsu).

They have a torsion bar to stop the front falling right over and if I recall correctly the pivot line is not exactly through the front wheel contact patch which has the effect of steering the rear slightly as the front is leaned. This could be an area for research!

[justanengineer]

Today I wonder about suspension roll in turns, Namely if it can be used to good effect in a 4 wheel vehicle instead of the typical negative effect it has.

I'm thinking in an ultra light vehicle where its only a fraction of the drivers weight and siting low enough, Could someone link the suspension somehow to the driver such that it rolls into a turn (Like a bicycle), instead of out of?

Many vehicles do this today, and it is one of the reasons why "A arm" independent suspension on all wheels has become so popular.

If you look at an independent suspension, typically you have either two A arms or one lower with a driveshaft acting as a second upper link, ie connections top and bottom of the hub. These two links are typically not parallel and swing in arcs independent of each other. The links also typically arent of equal length and consequently the arcs they swing arent of equal radii. By having a greater distance between the two links at the hub than at the frame, or by having a shorter upper link (ie, tighter upper arc), or other geometric "arc analysis," its rather simple to make a car "lean" into the turns.