Quote:
Originally Posted by pete c
Ken, thanks for the link.Ii did find it and your excellent site.
At first, i was thinking that the suspension fairing was a bit clumsy looking, but, as i watched the video, i decided that it is a beautiful car.
I kind of agree with Frank about direct ICE drive, but, understand your reasoning.
Perhaps there is a way to have both a series and parallel hybrid.
My idea is mount the ICE in the rear so it can have the generator hanging off one side and a clutch out the other side to a direct chain drive to the rear wheel.
Such a system could run just as you have designed and engage the clutch for constant highway cruising. It should add little complexity, weight or cost. I think it would give you a considerable gain in highway cruising mileage.
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Excellent suggestion re the direct drive. Although the electric drive is in the front in the production version, the engine is in the rear, so lends itself to driving the rear wheel, and a single speed would be adequate, because the clutch would only be engaged in cruise. I'd planned this for the X Prize, (prior to pulling out) because it would indeed improve efficiency, by almost 20%, under a specific cruise condition. On the other hand, under any condition other than that specific cruise condition (at which the engine is operating at its efficiency peak) the gain diminishes and then disappears when not too far away from that condition (because BSFC goes up with lighter load).
Had I continued in the X Prize, I would have put this arrangement into play. But for a production vehicle, is is very hard to cost-justify (and oddly enough carries a negative connotation for a large segment of my market: many people were disappointed to find that the Chevy Volt can drive its wheels mechanically from the engine in a power split not unlike the Prius*.) There is a larger financial incentive for Chevy, because the mileage on gas would otherwise be even lower than it is... and even 37 doesn't look good in comparison to a Prius. But with the Zing, many people will essentially never use the engine, with it just giving them the security of knowing they can always get where they want to go. And it uses so little gas anyway that it becomes harder to justify refinements. Even in the condition where you've forgotten to charge and drive to work on the engine, the clutch would be unlikely to be used, because it is a rare commute in which you can spend a significant amount of time in high speed cruise.
The deal breaker for the production vehicle is cost/benefit, largely because the Zing already gets 100 mpg. 115 mpg under that specific cruise condition does not reduce gas costs enough to warrant the hardware costs alone, let alone the development and test costs. For a competition it makes sense, and for a one-off vehicle it makes sense, but for a production vehicle, I could not cost justify it.
The same kind of thing happened with a diesel. Given the higher cost of diesel fuel, and the already high mpg, the large increment in engine cost could not be recouped in any reasonable amount of time. The average user will spend $80 per year on electricity to fuel the Zing. People who do a lot of driving might spend an additional $200 on gas or $180 on diesel in a year. $1000 additional for a diesel just doesn't make sense -- it would take 50 years to break even.
Your system could also be used for a performance (acceleration) boost -- and in fact, that boost could be big. Both the engine and generator (which is a motor) could supply power in addition to the front wheel drive, and it would only be a matter of using the same clutch and some electric controls. For competition, this could be cool, but for production, complicated.
The overriding goal has been to keep it as simple as possible, while still providing 100 mpg on gas, and 10 miles per kilowatt-hour on electricity. Another overriding goal is to make the business scaleable, to avoid the go-big-or-go-home syndrome that Aptera got caught up in. I'd rather give up a few mpg to gain some simplicity, less engineering time, etc. Some things that are not too costly to do in high volume can be killers at low volume. I must have fifty $100 bushings on the Zing. I knock them out on the lathe, easy but time consuming. If I had to pay someone these little things become expensive.
Very good idea though, and it is neat to see people thinking about this stuff. And yes, it would work exactly as you described.
Thanks, Ken
* Dunno if you followed this, but it seemed pretty strange to my engineering brain. If you like the Volt, and if this improves its efficiency, then shouldn't you like the direct drive? But many people thought it made the Volt less an electric car. If you wanna drive it only on electricity you still can at exactly the same efficiency level... the direct drive just means you will use less fuel, if you need to run on gas. How can that be bad?
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