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  1. #1

    Multiple, inline electric motors?

    Anyone out there (OEM's, wink wink, nudge nudge) ever thought of maybe putting 2 electric motors together inline with the drivetrain instead of just one?

    The basic arrangement of many of today's popular hybrid cars is simple: a basic gasoline engine, coupled at the flywheel with big electric motor, then the clutch, then the tranny, then the wheels.

    Anyone thought of maybe sacrificing a cylinder for another electric motor? I don't know a lot of the details on the motors themselves, except that they generate massive foot-tons of torque...ok, maybe not quite that much, but that's what they're known for.

    If another motor were coupled inline, wouldn't that multiply the RPM's delivered to the clutch and tranny?

    If this is possible, it would eat electrical power like mad, but more battery could be added because of the added power and efficency...right? Or no? And would this affect the top speed and acceleration?

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  3. #2

    Multiple, inline electric motors?

    i've noticed with my honda hybrid civic that i seldom reach the low battery mark. this may mean that ~ for the driving i do ~ i have more battery then really needed? or the electric is used less then what i can get away with?

    this may tie in with your comment for a second motor - or simply bigger motor. it might be achieved with no extra battery needs.

    i've only reached the low bettery mark when driving to las vegas where thru the desert we can get LONG stretches of slow up hill rides. some 15 to 20 miles long steady uphill on 5% grades.

    for me that's a rare drive.

    maybe they can create a switch to swap between city style driving to desert driving, to other significant driving styles.

    the concept of piggie backing motors might be useful in design. they can use one standard motor and add one for each larger size vehicle. and is there something sacred about even number cyclinders in a car? we're used to even numbers, but some mechanical systems work better with odd numbers like windmill blades (three blades).

    maybe there's a motor style that today lends itself to hybrids nicely? recall the old mazda wankle rotary engine?

    any motor heads out there reading these posts?

    see ya

  4. #3

    Multiple, inline electric motors?

    Tim, you're describing the Honda IMA system. The Prius system (as well as Ford's) is completely different, and it does use two "motor generators" in the design.

    There are some excellent resources on line that describe in great detail how the motors interact with the ICE via the planetary gear "power split device" and a google search should bring them up quickly. They tell the story in much more detail than I can here.

  5. #4

    Multiple, inline electric motors?

    I read up a bit a while back on the technology, and I might be a little misguided, but to me the definition of an electric motor is a part that receives an electric current, and a magnetic part that reacts to the electric current.

    And I think that all the hybrid-power engines I've seen in current production cars use (in addition to the standard ICE) a single stage stator that receives the current from the batteries, and a single, permanent-magnet rotor that reacts with the stator to produce motion. I'm not too sure on the internal specifics of Honda's IMA system, but if I'm not mistaken, it's still a singile-stator, single-rotor electric motor. How interesting would it be to put more than one electric motor inline with the rest of the drivetrain?

    Am I mistaken on the number of stages in the electric portion of Honda's engine?

    AND!! to answer the question about even numbers of cylinders!!! I think I know this one...

    There is a certain geometry and trigonometry to the crankshaft, camshaft, and valvetrain of an ICE which is designed to make sure (among many other things) that the time between piston firings is the same for all cylinders. I believe (and I can't prove this because I dont' have the numbers, but an ICE engineer might be able to conform this) that the geometry of using an even number of cylinders is MUCH easier than that of using an odd number of cylinders. Aside from that tidbit that I can't really prove, the vibration aspect always comes into play as well. Even-numerated engines always have a cylinder to counter the vibration created by another piston's detonation. This is what led to the parallel bank arrangement of today's modern engines.

    All that crap said, I know for certain that one of Volvo's sportier type cars actually has a 5-cylinder engine (turbo, I think, too) but I don't know which model, I'm sure you could find that out on volvo's website. And if Volvo did it, I'm sure one of the German manufacturers have at least tried it. I've heard of ultra-fuel efficient ultra-low-power cars having 3-cyl engines, but never actually investigated it (Geo Metro maybe, possibly some of the older VW Beetles)

  6. #5

    Multiple, inline electric motors?

    I wish to clarify my previous post about multiple electric motors. The knowledge I have of how hybrid engines work is that the electric portion and the gasoline portion work together to generate the total power given to the tranny.

    I admit, I have not looked at ford's powertrain, so I don't know much about it.

    I do however know a LOT about how the Insight's powertrain works, and I think I might have confused ppl as to what I meant.

    Some hybrid engines do come with more than one electric motor, technically. But, I'm fairly sure that Honda's IMA only has 1 gas engine and 1 electric motor that is designed to give the car motion. (It DOES have a conventional starter motor and battery to start the ICE in case there isn't enough juice in the "big" battery and "big" motor, but these are not used to move the car, just to bring it to life.) The power split technology mentioned earlier in the post is designed to balance out the amount of boost that the electric motor gives to the ICE.

    GM has introduced 2 different kinds of parallel hybrid engines. They are the flywheel-assembly engine (FAS) and the belt-assembly engine (BAS). For those not familiar, the FAS is the more traditional hybrid-style used in the Prius and the Insight, with a big-honkin' electric motor coupled between the ICE and the tranny. BAS is more of a glorified alternator, which doubles as a starter, and when current is applied to it, it acts like a motor, transferring rotational motion through a belt system to the crankshaft of the engine. (Not a very good system in my opinion, because I don't trust a belt to do the job of a steel shaft, but thats just my opinion) Now, I dont' think they are designed to be installed at the same time, although I dont' see why they couldn't be. That would be more along the lines of my original idea...more than one electric motor. The only problem is that 1) you're still depending, at least partially, on a belt to do the job that a solid steel shaft does in teh case of the flywheel assembly, and 2) the power isn't multiplied, its only additive.

    What I'm really trying to find out is why there isn't a way to couple 2, or 3, or 5, or any number of stages of electric motors to each other in a flywheel-assembly-style hybrid engine. If this could be done, the number of RPM's could be multiplied with each successive stage of stator/rotor assembly.

    whew, that was a mouthful.

  7. #6

    Multiple, inline electric motors?

    well, a basic flywheel spinning thru most of the cars' drive would be handy i suppose. years back (82?) they were part of the technology used then. using a clutch to engage or disengage was a way of getting some extra acceleration power from dead stop - without a motor.

    i wonder why they dropped that aspect aside from extra parts being used?

    and is there some extra inherent stability from having a flywheel spinning? i would think so?

    see ya

  8. #7

    Multiple, inline electric motors?

    The Prius and Escape (which are essentially similar) do NOT utilize a flywheel in the hybrid drive system. The entire concept (which was apparently developed by TRW in the 1970s) revolves around a planetary gear called the "power split device". If you are familiar with how a planetary gear works, there are three rotating components, the center or "sun" gear, the "planetary carrier" which contains a number of gears that rotate around the "sun" gear, and an outer "ring" gear which engages the outer part of the planet gears. This provides three rotating shafts (the sun gear, the carrier which is connected to the axes of the planet gears, and the ring gear). In the Prius and Escape, the gas engine is connected to the planet gear carrier, one electric motor/generator is connected to the sun gear, and the drive train and the second electric motor is connected to the ring gear.

    The advantage to this system is that by varying the speed or load on the sun gear (motor/generator) you can also vary the RPM at which the planetary gears (gas engine) has to turn to provide a given RPM at the ring gear (drivetrain). Furthermore, you can actually have the gas engine using the motor/generator to produce electrical power which can also be used to either run the second electric motor, recharge the battery, or both. This is important because gas engines are most efficient near their peak power output. So if you are going to run the engine you may as well take advantage of the maximum efficiency when you can.

    The Lexus 400h and Highlander hybrid are supposed to add an additional electric motor in the rear to provide AWD. The Escape uses a conventional transfer case and an electronic clutch based control to provide power to the rear wheels when needed.

  9. #8

    Multiple, inline electric motors?

    Oooh, wow, so maybe I invented a new system...hehehe!

    Apparently, I have been corrected on the operation of the Prius and the Escape engines. I think one of the advantages of the Honda IMA system (and again, there may be room for me to be mistaken) is that there is no planetary-sun-ring gear system to transfer power, so that reduces the weight of the car. Instead, where a flywheel might be located, there is a big "stator" portion of an electric motor. Of course, there will be a "rotor" portion as well, but keep in mind that the stator is not really stationary; since it's mounted directly to the crank of the ICE, its moving at the same rpm as the ICE. However, when electric power is applied to the stator, the rotor is pushed through electromagnetic power (basic operation of an electric motor). It sort of works like the hydraulic part of a torque converter, only instead of the LOSING a little bit of the RPM's in the torque conversion, the engine is actually ADDING torque.

    OK, enough with the hybrid engine lesson.

    In the case of the prius and the escape hev (since they use separate, self-contained electric motors) what do you think the effect would be of adding more electric motors to the planetary-sun-ring gearing system (effectively putting 2 or more electric motors in the system with the ICE instead of just one)?

    In the case of the Honda IMA system, since the elec. motor is inline with the ICE, this is what I mean when I say more than one inline electric motor. Would the torque multiply? Would acceleration increase? Would we be able to keep up with a 'vette or a 'stang? Or would we get 1000 foot-tons of torque, getting us to 30 mph in half a second, and then still depending on the ICE and its pathetic torque to get us the rest of the way to 60?

    I would think that if you added another electric motor to the prius/escape, it would add torque, so you'd see a LOT of low-end accel., but in the mid-range and high-end, you'd still be depending on the ICE. In the case of the Honda IMA system, that's where I'd be interested to see "just what happens" because the RPM's, and therefore the torque, would be MULTIPLIED. Am I wrong?

  10. #9

    Multiple, inline electric motors?

    The planetary gear assembly is about the size of a 12-ounce soda can. It's not that heavy (certainly it's lighter than the conventional transmission it replaces).

    The AWD system Toyota will be using in the Lexus 400h and the Highlander Hybrid will use an additional electric motor, which will be used as the exclusive source of power for the rear wheels. It will be very interesting to see how effectively they can implement this concept.

    Ford was much more conservative with the Escape Hybrid, the hybrid drive system is connected to a conventional AWD system.

  11. #10

    Multiple, inline electric motors?

    I've been trying to get someone to take a look at these ideas for some time. In one scale or another everyone of these systems have been proven.

    Like to produce a vehicle that can burn rubber on takeoff on all four wheels and get 90+ mpg?

    What I would like to see the automakers working on would have:

    A turbocharged, two cylinder opposed, 2-cycle, air-cooled diesel directly
    driving a generator. (It would not be running most of the time.) A 111 volt Lithium-Ion Polymer battery pack. Nothing but wires going from the
    controller to every wheel, except for the necessary additional friction
    brakes (of course). An added advantage of this would be the ability to recharge from the electrical grid while at home, saving even more on fuel.

    Each wheel, depending on the feedback to the controller from wheel speed sensors would drive with just the right power depending on the accelerator position. You would get recharging from deceleration just as you do in today's hybrids. You would also use this feedback to stop the wheel from skidding.

    Each wheel would have a stationary stator and a series of fixed magnets
    closely adjacent all around the inside of the wheel. In a sense it would
    operate each wheel in a very similar fashion that the mag-lev trains use,
    except the motion would be circular, of course. Something very different
    about this type of motor is that the stators are fixed to the axles and the
    magnets are driven around them. This gives a significant increase in
    mechanical advantage. That's like turning an ordinary electric motor inside out.

    There would be no need for ordinary electric motor brushes. In fact, many electric motors operating today are brushless.

    Such motors already exist in the model airplane field and their efficiently
    is amazing - approaching 90%. I've got a couple and doubt that I would ever buy any other type.

    It's possible to hang the model on the prop right out in front of you and
    accelerate straight up, like a rocket, with this type motor

    In the vehicle the motor/generator would not turn on to recharge the
    batteries until they needed it. There are already experimental Lithium-Ion
    driven cars that can get in excess of 200 miles before they have to be
    recharged by plugging them in.

    Lithium -Ion battery technology is so new that I doubt that very many
    automotive engineers have even heard of them, much less thought to use them in this manner. Their energy density exceeds that of any other form of rechargeable energy storage.

    The Lithium Ion battery is the most efficient battery available right now. So is the outer rotor electric motor the most efficient motor.

    Build an SUV right and it will weight less and have simpler, easier to repair/replace modules.

    Lets see what we can eliminate while improving performance and efficiency.

    Transmission - None

    Ignition system - None

    Liquid cooling - None

    Valves and valve train - None

    Use bio-oil/fuels for both fuel and lubrication.

    Feel free to pass this along to anyone you know in the Transportation business. I suffer from no delusion that any of them have the imagination to be able to see how something like this could jump them ahead of the competition.

    I bought a Honda Civic Hybrid last summer. I enjoy it more than any vehicle I've ever owned. I will Never buy another vehicle that isn't a Hybrid and doesn't get at least 50 mpg.

    As far as I can tell, Detroit isn't even thinking the same way I and the vast majority of it's potential customers are.

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