Quite true. This is the "trucker paradox" as I call it. It is obviously more expensive for them to drive faster (higher fuel cost, more tire wear, more maintenance), but it nets them more money in the end.BB said:Wages for the driver, costs of capital, repairs, breaks, etc.--alll of those are also important too... (example, driving faster uses more fuel, but less wages and can transport more cargo for the same time, or for farther distances before manidtory breaks)... Hence folks willing to pay for airplane flights instead of taking the bus, and paying for next day air shippment for their packages.
You'll certainly get no argument from me on that! I was only discussing the situation where fuel economy from an ICE vehicle with a gearbox is NOT going to necessarily correspond with speed in a logical way. Didn't mean to imply that the gearbox was there ONLY to screw with that graph.winny said:Darell,
Yes, you are indeed correct but I would just like to add that fuel efficiency is not the only reason why you have a gearbox. Unless you have a massive amount of torque (read electric engine), you need a gearbox to impedance match the engine against the load
And you'll get no argument from me on this either (I must be getting soft, or you're making sense. )It is the added drag, complexity, weight and expense that makes gearboxes on EVs a losing proposition (as Mr. Idle points out so well above). If a cheap, lightweight, lossless VARIABLE transmission were incorporated, EVs could have BETTER acceleration (up to the limits of traction!) and more efficient cruising all from the same battery/motor combination. Finding parity with these factors has not yet happened, and EV builders (even the guys who WANT to build EVs) typically skip the transmission. One important thing to note: Dr. Andy Frank at UCD, and made a 99%+ efficient constantly variable transmission that he's using on his plug-in hybrids to achieve astonishing torque gains from the E traction motors. If this thing gets into production we may see something spectacular. He says efficiency is so good that they typically safely ignore the transmission loss in their calculations. For my money, the constantly variable trans is the answer - not the antique "gear box" of yester year.Hmm, back to the impedance matching. Although I haven't read that comment here, I'd like to take the opportunity to straighten out the issue with electric cars and gearboxes once and for all. It's often said that due to the flat torque-rotation speed frequency curve of most electric engines they don't need gearboxes and that they will accelerate just as good without one. Not true, at least if we disregard the weight added by the gearbox itself. They will accelerate very good but they would have done better with a gearbox in most cases.
Ah. I can tell from these comments that you have not yet had the pleasure of driving an EV???winny said:However, if I would have had a normal four seated electric car, I would like to have at least some gears to keep the noise down during normal cruising (although very little from an electric motor, lower frequencies are more pleasant) and the performance up when climbing hills at low speed or pulling a trailer from standstill.
No question that it has limited practicality in the real world. Was just pointing how how different driving techniques in different cars can give wildly different results. And it surprises most folks that the "pulse and glide" can work on just about ANY ICE to increase mileage if there were no real-world practical limits to doing so. It is just easier in the Prius since you can "turn it off" by just using your right foot.gadget_lover said:Regarding the "punch it and coast" technique in the Prius....
Many have reported great results with this technique, yet I find it difficult to do consistantly. It has a downside in that people behind you are not always happy when you coast below the speed limit.
It can, yes. But that's a really poor use of it. The cogging can be totally eliminated through electronics, and the gearing can then be chosen for practicality, not the brute-force method of eliminating cogging.The use of gearing allows some benefits with the electric motor. It can reduce the "cogging" effect.
Ha. Only up to the limits of traction The X1 would accelerate no faster with more torque. It reaches the tire limits WAY before it runs out of torque. It would have better quarter mile time if it had a taller gear though. It reaches the 112 mph limiter well before the quater mile.It can make accelleration even faster
This one isn't even in the running. Electric motors last for freaking ever. I have yet to hear of a single failed AC motor in the production cars (at least not a failure caused simply by usage). The EV1 motors were tested well beyond 1,000,000 miles of sythesized driving. I wouldn't spend an extra penny in an attempt to prolong electric motor life. No return on that investment when they already outlast any resonable vehicle in which they'd be used.or it can reduce the motor's RPM to a range that ensures long life.
Right on the money as far as I understand it.Is it a coincidence that 100 kph is the limit in many countries and that Darell's Civic is most fuel efficient at 62 MPH? 100kph = 62 mph. I think not. That was one of the arguements against the national 55MPH speed limit. People argued that cars were designed to go 65 and therfore most efficient at that speed. Cars built in the 70's and 80s were designed to be most efficient at 55.
I'm pretty sure that we were all talking about a changeable "gearbox" known as a traditional transmission. Certainly most EVs need to gear the output shaft to keep the motor in a prescribed safe RPM range. But this is fixed gearing - different than a standard/variable transmission.cobb said:Excuse me guys, but all EVs have gears.
Certainly not. In smaller applications like circular saws, and maybe even wheel chairs, this might be the case. And that's probably pretty close to what happens in a traditional/variable transmission. Not the case for a well-designed full-size EV with single-ratio gearing, however. There are losses in the gearing, of course, but nothing like 10%.Its my understanding any gearing takes at least 10% from the power in frictional losses.
?? You realize that all the production EVs have brushless AC motors, yes? Super efficient and drop-dead reliable. That they're expensive is really the only draw-back.Needless to say, the brushless motors were nothing but problems, over heat quicklyand did not give the performance vs efficiency they were suppsoed to.
....
or that brushless thing improves.
Attention is cheap! I sure haven't won the lotter, and this stuff is about all *I* think about (maybe that was obvious?)Man, if I win the lottery, I am giving this my undivded attention.
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or it can reduce the motor's RPM to a range that ensures long life.
This one isn't even in the running. Electric motors last for freaking ever. I have yet to hear of a single failed AC motor in the production cars (at least not a failure caused simply by usage). The EV1 motors were tested well beyond 1,000,000 miles of sythesized driving. I wouldn't spend an extra penny in an attempt to prolong electric motor life. No return on that investment when they already outlast any resonable vehicle in which they'd be used.
Ah! In that case then gearing is of course MANDATORY!gadget_lover said:I was probably not clear. It's possible for spinning parts to be over stressed when they spin too fast. Windings de-laminate, bearings overheat, etc. Gearing allows parts to spin faster or slower than the motor.
Daniel
There are not buts to more tire smoke...Darell said:Yes, it has the potential of making the whole system more efficient, and could allow for the use of a smaller motor, and will allow for even MORE tire smoke... But...