Yesterday I've tried to register power consumption on the stretch of I84 and I205, and can tell that it's not possible- there is no flat portion of either highway long enough to get steady results on two different gears to compare.
So I must disregard my previous results (which are just looking at kW number displayed) and wait 'till I get a chance to use better test area. Naturally I expect to see the same trend Jon sees. Victor Rod Hower wrote: > > 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 > >> > > > > > >
