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Tilting 4WD 'Spider Car' Makes Light Work of Bizarre Terrain
Zothecula writes: The Swincar Spider is a remarkable tilting 4-wheeler concept that boasts absolutely ridiculous rough terrain capabilities. Each wheel has its own electric hub motor and is independently suspended on a spider-like limb. The result is a vehicle that leans into fast turns like a motorcycle, but can also happily go up or down a 70-percent gradient, ride across a 50-percent gradient that puts the left wheels a couple of feet higher than the right ones, or ride diagonally through ditches that send the wheels going up and down all over the place like a spider doing leg stretches.
ah! here we go - http://thekneeslider.com/wesll...
Yeah, try to drive one of those in the sort of lava fields we have here, it'd bottom out before it even gets started. ;) Even on less extreme terrain, its clearance looks like a pretty big flaw - it can hardly drive on a flat slope without nearly bottoming out, let alone uneven terrain. They could raise the center, but then they'd also be raising the CG because not on the driver but the batteries are in that center bit, and on an offroader you really want a low CG.
Seems to me the solution is to put the batteries next to the hub motors. Something right next to the hub should never bottom out, and as they're low so the CG will stay low. It also allows you to reduce or eliminate your in-arm power wiring (esp. good given all of the bending that goes on in those swing arms), thus reducing wire mass, wire cost, and wire resistance. If you fully eliminate the in-arm power wiring you'd have to charge the packs individually, but even if you retain it you could reduce it to smaller wires that only need to be able to handle charging currents and inter-pack charge balancing, not peak discharge currents. Having the batteries next to the hub motors, you could upgrade them to pretty much whatever power level you wanted.
Another problem I see is with the use of hub motors. Everyone loves them until they start messing around with them and then the problems start to become clear. One, they're unsprung mass, which reduces your ride quality. Two, they're harder to cool, which limits performance. And three, you shake them to bits even on normal roads, let alone offroad. I'd prefer each wheel being hooked up to a small high power motor, connected to the wheels via a stubby CV joint (which should lose only a fraction of a percent of the energy transmitted). That way you keep your unsprung mass low, your motors are easy to cool, and they're not shaken to bits.
This thing is underpowered, but with some proper design choices there's really no limit to how high powered it could become.
The last issue I see is, if you're making an offroader, do you really want motors and wiring connections somewhere that they're going to get wet? Do you want to have your wheel drop into a deep puddle and suddenly short out? It seems to be that they really should have the motors (and as per above, battery packs) protected by a cowling. For transmitting the power to outside of the cowling I see two options. One is to use a waterproof rotary joint, like submarines use, although those are somewhat lossy. A better option might be to have the rotor simply penetrate the cowling (with only a small clearance around it) and use your pack / battery air-cooling system to maintain sufficient positive pressure inside to resist water influx - around 5-10 PSI should be enough for unbridged river crossings, while only 1-2PSI would be needed if you only want to be able to handle the occasional puddle. The air ingress to the cooling system would need to be located as high as possible, of course, whatever design one chooses.
(Yeah, this is something I've been thinking about for quite a while, I'd love to build my own go-anywhere electric vehicle some day ;) )
I'll never forget the last thing grandma said to me before she died: "What are you doing in here with that knife?!?"
This vehicle is going to be Detroit's answer to the deferred highway maintenance problem.
Spider car, spider car,
Goes wherever that spiders are.
Climbs terrain, any type,
At least that's what they say in the hype,
Look out!
Here comes the spider car.
File under 'M' for 'Manic ranting'