Jon, Your power estimates seem to be more expected than Victors. I would really like to see more data on this subject with different configurations. Most of the motor curves I have seen showing torque/speed/efficiency seem to correspond with your data. I would think that cruising around town at 35mph could find an efficiency sweet spot in one gear while cruising at 65 on the highway could use a different gear with another efficiency sweet spot. Yout data would seem to support this theory. Rod
Jon \"Sheer\" Pullen wrote: > My experiences are somewhat different from Victor's. They are also somewhat > different from the projected results I announced several months ago, and are > somewhere between interesting and unexplicable. > > [NOTE: All values below are approximate. Please don't plan your life around > them.. they're just to give you the 'gesalt' of my experiments in this > arena] > > I use 1st, 2nd, 3rd, and 4th. > > For highway cruising on level ground: > > 65 in 1st is not a option > 65 in 2nd uses 10kW > 65 in 3rd uses 9kW > 65 in 4th uses 7.5-8kW > > I may have worn bearings in my transmission.. it is pretty noisy.. but > still, these results are reliable - that is, they happen every time. > > OTOH, 0-60 remaining in 3rd is 12s, 0-60 going 1st, then 2nd is 9s. [times > are approximate] so there is definately a acceleration advantage to using a > multispeed transmission. > > I would say that at least for my transmission, one should not discount > 'windage' loss as it is not negligable. > > For highway cruising with my gen-trailer, by the way, to demonstrate why I > am doing a aero workover of it: > > 45 in 2nd uses 8kW > 45 in 3rd uses 7.5kW > 45 in 4th uses 7kW > > 50 in 2nd uses 12kW > 50 in 3rd uses 11kW > 50 in 4th uses 10kW > > 55 in 2nd uses 16kW > 55 in 3rd uses 15kW > 55 in 4th uses 14kW > > 65 2nd = 22kW > 65 3rd = 20kW > 65 4th = 18kW > > > ----- Original Message ----- > From: "Victor Tikhonov" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Tuesday, September 10, 2002 1:45 PM > Subject: Re: AC drive trains (was Re: [EVDL]Re: Volume build proposed for > high performing EVs) > > > >>"VanDerWal, Peter MSgt" wrote: >> >> >>>At any rate it's still pretty damn quick. I don't see where having a >> > second > >>>gear with a ratio higher than 11:1 would help any, especially since, as >> > you > >>>point out, the tires probably couldn't get any more torque to the road. >> > If > >>>you spent a lot of time driving at 5mph it might improve your efficiency >>>some, I guess. >>> >>> >>>>It's my opinion that AC is only rarely flexible enough to do the job. >>>>And for now I am keeping that opinion. I have never driven an EV-1. I >>>>live in the northeast, so I probably never will. I sat in the Impact >>>>once, but that didn't tell me much. >>> >>>I agree you are completely entitled to your own opinion. I'm just >> > curious > >>>which AC powered vehicles you have driven that you've developed this >> > opinion > >>>from? >>> >>>P.S. I'll grant you that the Siemens motors would need a ratio closer >> > to > >>>8.5:1 if you wanted a top speed of 80 mph; but I still don't think that >> > an > >>>even higher ratio would help efficiency or torque much, certainly not >> > enough > >>>to make it worth the extra hassle, weight, and complexity. And you >> > could > >>>always solve that by deciding to have a top speed of 65-70mph, going >> > faster > >>>than that is just a waste of energy anyway. >>> >> >>I have some expertise in this area and can chime in with some >>hard data. >> >>Peter is right that switching gears within normal AC motor range >>does not impact efficiency or it's very minimal. >>But the ratios must be lower than 8.5:1 for "normal" >>RPM range (3000-6000). >> >>Take my ACRX: >> >>1st gear ratio is 3.25:1 >>2nd is 1.65:1 >>3rd is 1.033:1 >>Final diff is 2.954:1 >> >>So total reduction on the second gear is only 4.87:1 and >>on the third - 3.05:1. >> >>Now, I drive on the second gear all the time. >>ACRX goes 65 mph at exactly 5000 RPM and consumes about 12 kW >>to do that. I have a battery power monitor (part of inverter's >>software) and can watch the power value as I drive. If I switch >>to the third, the RPM becomes exactly 3000. Acceleration is not >>as quick anymore because the torque at the wheels is lower >>but the torque the motor puts out is the same at 3000 and >>5000 RPM (the case for my voltage). However, power consumption >>is identical - still 12 kW because main contributor at that >>speed is aero drag loss, not motor efficiency. The motor >>current on the third is proportionally 1.7 times higher >>than on the second so its losses may be few watts more, >>but nothing compared to 12 kW overall. Switching to the first >>gear in my case is not possible for highway use - the motor >>would need to make 9800 rpm. It can do that, but there will >>be little useable motor torque there - even multiplied by >>1st gear high ratio I suspect I will have less torque >>at the wheels than on the second gear. Not to mention >>the motor efficiency at near 10,000 rpm is lower - about 75% >>(http://www.metricmind.com/line_art/efficiency.gif) >>and the gear box will be very hot (more watts wasted to that). >> >>Victor >> > > >
