Electric cars are a pipe dream

Discussion in 'General Science & Technology' started by Syzygys, May 20, 2010.

  1. billvon Valued Senior Member

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    Not too practical. I have an electric bike and even to maintain 35-38mph on the bike (which weighs about 70 lbs) takes about 1200 watts; your typical human is good for about 250. But it would give you something to do and would be good exercise.
     
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  3. Grumpy Curmudgeon of Lucidity Valued Senior Member

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    Billy T

    The pedals are connected to the rear wheel with near standard derailleur bicycle chains or gear hubs. Bicycle chain drives are in the high 90s for efficient mechanical energy transfer. Many of these "Velomobiles" have electric hub motors to boost speed and for easy pedaling and acceleration. They usually have a 25-50 mile range on motor alone which can be extended more or less depending on how good a pedaler you are, how many hills you climb, how fast you drive and whether or not you have regenerative braking(or you could get a bigger battery). Direct electrical generation from the pedals is not quite as efficient, but would have advantages of stationary generation, simpler installation and uniform cadence with no need to shift gears.

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    This motor puts out 25 HP(20kw)on 96 volts DC. In a Velomobile it would give a top speed of over 70 mph, easily.

    Grumpy

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  5. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    I had a co-worker who was a bike nut - would think nothing of going off to Ohio for week end to participate in a 500 mile race, etc. His ~1500 dollar back then, bike was custom made of titanium I think, and weighed very little. He too said it was great exercise.

    One day as a joke, which he did not appreciate, I gave him a present in a cardboard box and told him with it and his bike he could get the same exercise near his home in only an hour or so of riding. In box were two bricks tied together with short piece of rope and on the sheet "user´s manual" instruction sheet it said: "Wrap rope around handle bar of bike until each brick is secure on a different side." Judging by his reaction: some people have no sense of humor, but at least he did not find an immediate use for the bricks to my injury.
     
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  7. billvon Valued Senior Member

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    . . . at least until it burned out.

    That is a Rolf Strecker motor intended for RC aviation applications. (Short duty cycles, lots of air cooling.) In a car the waste heat would quickly melt it down.

    Choosing a good motor for an EV is a difficult task, and most newer EV conversion people go through a phase where they see ever-smaller and lighter motors (intended for RC/Sunraycer/servo applications) and say "WOW this thing is great! It solves all my problems!" Then they try it and discover they must average low speeds or install insane cooling systems. One guy from an EV conversion board used a similar motor and ended up with a forced air cooling system that was 10x the size and 4x the weight of the motor - and ended up clogging the motor with all sorts of airborne debris. So he added an air filter. Which got clogged by bugs. The motor burned out anyway.
     
  8. X-Man2 We're under no illusions. Registered Senior Member

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    Stephen Mosca a Velomobile Dealer in NJ made a decent You Tube video familiarizing curious ones about the Mango Velomobile.A very popular Velomobile across seas is the Quest.And Win Schermer a Velomobile professional along with a handful of others are working on a Velomobile called the Velotilt.The Velomobile is big in certain parts of the World such as the Netherlands,Germany etc.But slowly growing all over.

    http://wimschermer.blogspot.com/2012/09/introductie-velotilt.html


    http://www.youtube.com/watch?v=cAcy7EVRpXc&feature=player_embedded
     
  9. Grumpy Curmudgeon of Lucidity Valued Senior Member

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    billvon

    Your buddies experience is not the norm for the outrunner motors I have had. Yes, if you run it above it's continuous rating all the time you will have problems with heat, but in normal use we don't run them that way. And a simple centrifugal fan on the motor allows even higher power. In the extreme, water cooled stators can be used, allowing over 200% higher amperage in the same motor(the boat guys do it all the time). In outrunners it is not the windings that are the limiting factor, it is the magnets. High temperature neodium magnets now will withstand over 200C(they used to be limited to 80C). Don't put these motors down just because they are used on RC aircraft, being on the nose of an aircraft in no way offers any special cooling ability through the motor than a good fan would do. If your buddies cooling setup weighted several times what the motor itself did that says more about the lack of technical ability in your buddy than it says about a limitation in the motor itself. Besides, just what do you think the hub motor on a bicycle is? It is either an outrunner directly connected to the wheel, or it is an outrunner geared to the wheel. Either way, it is no more robust, nor does it cool any better than any outrunner that comes from the RC hobby.

    Here's a geared one...

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    And this one is direct drive...

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    And THIS is a monster...

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    "Specifications:
    Model: 120-70-15
    Resistance: 4.8ohm
    ESC Required: 250A
    Input Voltage : 30~70V
    Kv : 150 rpm/V
    Weight: 2550g
    Shaft: 10mm
    Non Load Current: 17A
    Dimensions: 168x140x118mm (Including Mount)
    Equivalent: 100cc Twin Gas Engine
    Price: 299.99"

    Let's see 70V times 250 amps=over 17kw(about 22hp) max power, probably around half that continuous with a centrifugal fan.

    Grumpy

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  10. billvon Valued Senior Member

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    I think that's the issue. Automotive motors are typically run at high powers for a long time (hours in some cases.) A friend of mine who converted a Kewet overheated her 12kW motor several times before she finally dumped it and got a 25kw AC motor - and even then she has to be careful about long times at near-highway speeds. And you're probably not going to find a smaller, lighter highway legal two seater than the Kewet.

    Excellent example! My current motor is a very efficient 3 phase 12 pole brushless DC that runs at about 1.2kW for in some cases an hour at a time. It gets quite warm even though it's exposed to that 35mph airflow directly.

    It cools much, much better! My current hub motor is roughly 10 inches across and is flat. That's about 160 square inches of heat sink with good airflow. How much surface area does that 20kW motor have?

    That looks a lot like the Ezee hub, which is definitely a good one. It's rated at 400 watts. People have pushed it to 700-800 watts, and it gets very hot, but it works OK at those power levels. Again, if you went to 20 times that power, I wouldn't expect it to survive.
     
  11. elte Valued Senior Member

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    That video was very good. Very nice velomobile.
     
  12. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Car Sharing:
     
  13. universaldistress Extravagantly Introverted ... Valued Senior Member

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  14. Syzygys As a mother, I am telling you Valued Senior Member

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    The order was placed in 2009, finally they delivered it.

    http://imgur.com/a/hxLTw

    Well, if it takes 3 years to satisfy costumers, how far are we from real mass production?
     
  15. Syzygys As a mother, I am telling you Valued Senior Member

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    the consol's view:

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  16. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Government to end "free loading" EV etc. that avoid road taxes in gasoline:
    Many if not most new cars have GPS and lots of computers built in, so trivial to have annual inspection station read out of how much they were used - I.e. you must be a good computer hacker to cheat - not just have reversible electric drill to turn the odometer backwards as in the "good old days" when getting ready to sell or trade in your car.

    Hidden Plan? Just like printer makers get a lot of product (or in this case hybrids & EVs) sold by reducing the initial cost, and then collect forever - In printer case by high cost ink cartridges.
     
  17. billvon Valued Senior Member

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    Or be able to tape a piece of aluminum foil over your GPS antenna.
     
  18. KilljoyKlown Whatever Valued Senior Member

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    GPS antenna? I couldn't tell you where it is on my phone, let alone on my car. Also what makes you think aluminum foil would interfere with the antenna? Do you have any documentation to verify that this can be done and that it works?
     
  19. billvon Valued Senior Member

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    It's pretty easy to google. And it's easy to test; turn on your navigation system and see if it can get a fix.

    It's GPS; that's 1575MHz. Metals block those frequencies quite well. Also GPS receivers need very high sensitivities; you need at _least_ -150dBW sensitivity in your receiver, which means it won't take much to block it.
     
  20. KilljoyKlown Whatever Valued Senior Member

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    Maybe, but finding it and then being able to get to it in your car could be harder than most people are willing put up with. My car is a 2006 Kia Optima and it doesn't have a built in GPS, but I did install a Lo Jack on it. The installer said it was best if I didn't know where it was for the obvious reasons. But I'm sure a car thief would be happy to block GPS signals to it if he could find it.

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  21. gmilam Valued Senior Member

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    We already pay a flat annual fee... it's called a license plate.
     
  22. billvon Valued Senior Member

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    That's fine. Up to them.
     
  23. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    Don´t most states charge the same license fees, but some charge (less I think) for small cars.

    In Brazil, back when it imported almost all its car fuel to reduce FX losses, the military government forced conversion to home grown (sugar cane) based fuel, and I think cars with 1000cc or less engines still get lower sales tax at time of purchase. It would be easy to make EVs pay different license fees from those that will be paying the "road taxes" in gasoline.
     

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