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Piston Spokes Suspension
piston spokes reduce unsprung weight. making for better suspension, fuel economy and steering in wheelmotor vehicles | |
I admit it, I like the idea of electric vehicles with wheelmotors; individually controlled they could theoretically give the best traction on any road surface. Where they come up short though is the addition of unsprung weight which makes for slower response time and higher fuel consumption.
The
"Be-Spoke" Suspension System uses several staggered rows of pistons between the hub and rim as spokes. The hub is unsprung and remains stationary in respect to the body of the car allowing electric motors and braking systems to be mounted on the frame and not to be subject to vagaries in road conditions.
The basic premise of course is that the spokes are the secondary suspension components immediately after the tires. Car hits a rock, the tire deforms, if it's a big enough rock the tire pushes on the bottom spoke(s) which compresses, etc.
In order to keep the tire rim equidistant from the hub at all times (since normally the weight will be all on the bottom pistons), a governed lightweight mechanical centrifugal pump in the hub ensures that, at speed, the bottom pistons contain more air than the top pistons by scavenging air from the top pistons and pushing it into the bottom. This keeps the hub equidistant from the rim while the car is at speed (barring gravel, stones, etc. which cause the tire and piston-spokes to do their job and keep the body of the car riding smooth).
For an even smoother ride, the piston motions are also electro-mechanically feedback-enhanced.
Weight distribution enhancement is achieved while cornering: by varying the pressure of the inner and outer upper and lower spokes, the tire will tilt in the direction of the steer, thus moving the CG outwards making for tighter, safer turns.
[edit] rather than being bolted to the frame the wheel-hub assembly (and brakes and wheelmotor) is on an adjustable ride-height arm; that way in case the tire and spokes go past their limit the system can invoke that temporarily as a suspension component in an emergency.
[link]
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You can get the same efect by letting most of the air out of your tires, massive rolling resistance. (-) |
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//rolling resistance// where ? I've got it set up so the pistons won't move when the tire rolls (except of course when they're supposed to) |
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Some bits of this are wrong, other bits are unlikely to work as described, but the concept of a non pivoting suspension is very intriguing. (+) |
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the "centrifugal pump" bit is still a work-in-progress; without something the hub will "sag" at lower speeds... and the adjustable ride-height arm I just tossed in there a few minutes ago: a result of it needing more extension in case of a *big* bump or deep pothole. |
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I think I hit the key point though: the braking system and wheelmotor would be stationary in regards to the road surface... only thing is how much more will the wheel weigh because of the new spokes :) |
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Could this not be done much more easily by making the inner part of the wheel a heavy rubber membrane rather than a fixed steel support? That way the axle would be eligible to additional translation from the centre of the wheel. |
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..or replacing the spokes with stiff-ish springs? |
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//inner part of the wheel a heavy rubber membrane(?)//
more than a bit wobbly unless you can find 2d rubber. |
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//stiff-ish springs?//same principle except it'd be more difficult to vary the springs' springiness and that disallows electromagnetic fine control i think. |
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I think that you'll find that (assuming the other problems are solved) if you're not damping the springs/spokes then the vehicle will behave like it's on bed-springs (bouncing for about a minute after that last pothole), but if you do damp it, then there are gonna be a lot of losses as the motor has to work against the damping to keep pulling up as the hub sags. |
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The concept is good, but I think there are reasons why this hasn't been baked! |
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Potentially if you were to use a pre-tensioned rubber sheet system (I'm thinking one vertically each side of the rim and two diagonals), and you could run cables tensioned within slots in the sheeting to give you the control you were after. |
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Bone for complexity.
The easy way to achive what you want is to use chassie mounted motors with short driveshafts to the wheels as is done with front wheel drive vehicles except insted of a diff motors are used insted. |
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//The easy way// which calls for a relatively lossy universal joint and means more junk sticking out under the car, ie: lower ground clearance, which means higher CG, etc. |
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[Sl] I'm not a car-guy but there's an amazing jungle-gym down there in the suspension department. I think what you're proposing is the same as mine but using rubber supports instead of pressurized cylinders(?) (post it) |
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At any good speed the sag problem goes away even without help. I know there's an HB post for (electromagnetic) regenerative suspension which is why I didn't say much about it in my post, but that would be the damper. |
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