h a l f b a k e r yViva los semi-panaderos!
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Today's modern car suspension can only let the tire move vertically up and down when it compresses. This is good for hitting round things like speed bumps, but when traversing an object like a curb, the wheels want to move to the up and rear of the car, but since it can only move up, you feel a nasty
thud while going up it.
The solution to give the tires full vertical movement and some horizontal movement is to mount two shock absorbers, in a V- shape, for each tire. This allows the tire to move vertically as a normal suspension would, but also lets the wheel move gently horizontally along the lines of the shock absorber. This also reduces the wear on each shock absorber, as the car's weight is more spread out over the suspension.
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I've had multiple ideas like this one in the past. |
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This would require a telescopic drive shaft or two if its four wheel drive, and probably larger wheel wells (or smaller wheels), especially in the front. |
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I think you should change the name to something more accurate. |
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Trailing arm suspensions (rear end of old beetles, for example), are pretty good at this type of thing, since as they swing, the wheel moves slightly backwards. |
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For normal road vehicles, you don't really need the damper part of the suspension in the fore-aft direction - just the spring component, with a forward stop. You shouldn't be hitting kerbs fast all that often! It would be nice to avoid damage to the suspension, or excessive shocks to the occupants, when you do; but avoiding a bit of vibration on such occasions surely isn't essential. |
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The normal components of a suspension are all elastic to some extent (everything is!), which is why everything doesn't break every time you hit a kerb. What you're asking for is a bit more elasticity in this direction, to reduce the shock a bit. |
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Why not just slow down when you want to climb a kerb? You probably shouldn't be doing it at all... |
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Surely this would produce auful handling? It would allow the car to dive in more than one direction under brakes/cornering. You would also increase the complexity of the system, and crucially unsprung/sprung mass would increase making the handling worse. |
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I think the handling would be doable, [bs0u0155] - you'd just have to arrange that the movement in the extra direction was small under normal loads (there is of course some movement in that direction anyway - things aren't perfectly stiff), and that the steering compensated for the movement - not a terribly difficult piece of geometry/mechanical engineering. |
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You'd certainly increase the complexity, but you might actually reduce the unsprung weight, because the forces the system would have to cope with would be reduced. |
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The increased complexity would come at a significant cost, because not only would you have more bits to make and assemble, they'd have to be higher quality if you wanted to achieve the same level of reliability - that's a general observation about complexity. Yet people have 4x4s, despite the extra complexity. (Even front wheel drive has greater complexity than rear wheel drive. Yet it's almost universal now.) |
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This effect might desirable for off-roading purposes. |
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To reduce the handling problems, the forward and backward direction of movement of each set of wheels could be locked together, meaning that when one wheel hits something it would cause the opposite wheel to move in the same direction at the same time, this would eliminate the problem of the wheels turning when something is hit by one wheel. |
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Have you thought about how this affect can be achieved on a front wheel drive vehicle? |
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you don't have to make the opposite wheel move in tandem with the other, just attach each wheel to the axle by way of a ball joint (like those on adjustable angle drills and such). The only problem I can see with the concept is what was mentioned before with braking and accelleration - it would make the car pitch, roll, and dive in new and frightening ways. |
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maybe you could just make all of the springs really stiff, but that would just kill the point of them in the first place -- to make going over nonround objects smoother. |
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**edit -- why are you running over curbs again? |
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I think it has far less to to with the shape of the curb as the change in the grade. Your average cars front suspension might only have 4 or 5 inches of suspension travel. The Bump is not coming from the backward movement(as the wheel is rolling up and over) but from the limit of travel up and down. Most suspensions actually have a certain amount of rearward angle to their travel(known as Caster) that way they travel forward without constant input(ever try to drive backwards fast?) |
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This is why almost all cars use some sort of Trailing arm type of suspension so that the wheel get dragged over bumps rather than being pushed over them this radically smooths the ride(this was a common problem on certain Jeeps as the shackles were at the front causing the wheel to push down into a bump upon compression rather than being pulled up and over.) |
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I think what would happen is that the wheel would move back then slam into the stop backwards then be forced upwards beyond its travel and slam into the top stop and you would have twice the slamming around. |
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Pains are taken to keep this phenomenon out of conventional suspension: "brake reaction rods" for one example. My knee jerk reaction is that it would be way, way difficult to keep this from introducing a steering force into the suspension while stopping. Plus, once you stop, the suspension will stay loaded as long as you stay on the brakes. I think subsequenlty releasing the brakes would cause some unnerving sensations. |
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"...a common problem on certain Jeeps as the shackles were at the front..." The original solid axle front end on my 1950 Chevy pickup was this way. It really isn't such a good thing to have the axle move forward on the side where the spring was compressed due to chassis lean. At least, that's what I blamed the massive oversteer on. Good riddance to it. Anyone want to buy an axle? |
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Maybe good for offroad handling, appalling for on-road handling. |
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// ...appalling for on-road handling. // On-road, you shouldn't notice any difference, as long as the geometry is correct (steering altered automatically just exactly to compensate for backward movement). The extreme movements caused by hitting kerbs or off-road bumps would be noticeable - but less so than the effect without such a system. Off-road handling would be improved; on road, there'd be no noticeable difference. |
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Complexity and expense are the only objections, as long as it's well engineered. |
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