Thanks for the interesting real life data points. Is your 4th gear a "straight-through" gear?
--- "Jon \"Sheer\" Pullen" <[EMAIL PROTECTED]> 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 > > > __________________________________________________ Yahoo! - We Remember 9-11: A tribute to the more than 3,000 lives lost http://dir.remember.yahoo.com/tribute
