Electric Motorcycle & Scooter News/Updates

Discussion in 'Electric Motorcycles' started by voltsxamps, Jun 18, 2016.

  1. ctromley

    ctromley Long timer

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    No, it would not. The myth that low cg benefits the handling of single-track vehicles is just that, a myth, but it simply refuses to die. Low cg benefits vehicles that are inherently stable, like cars. Motorcycles are inherently unstable, meaning that without constant input from the rider they will fall over. The two situations could not be more different, so vehicle characteristics to optimize handling need to be different too.

    To conceptually oversimplify an incredibly complex system, you basically trade responsiveness for stability. There is a sweet spot for cg height (and more importantly the polar moment of inertia that is affected with it), depending on your use of the bike. A Bonneville streamliner has different needs from a trials bike.

    To see this for yourself, go to your toolbox and grab a hammer. Hold it vertically, head high, and put the handle on the tip of your finger. Now let go and balance the hammer upright on your fingertip. Easy, right? Now turn the handle over and try it again. No cheating, no cupping the head in your hand, just fingertip contact. Let go and balance it again. How long did you last? Stability vs. response.

    For road motorcycles the sweet spot is generally somewhere just a little below the level of your kneecaps as you sit on the bike. Not sure, but dirt bikes are probably in the same ballpark. So on the Super73 that puts the battery pack and any other heavy components where all that air is in the middle. Totally different look. This is a new type of product and manufacturers are hooking buyers by offering products that seem familiar enough. Get too weird and it won't sell. Of course at the low speeds these things travel, handling isn't that big an issue. Looks are a big issue.

    Where performance matters, you'll find things looking different. That sub-kneecap-level cg sweet spot that works for ICE motorcycles may not be ideal when EMs start leaning in the direction of heavy-duty bicycles with substantially lower overall weight. But as it always has been and always will be, low cg is not the goal - the proper balance of stability vs. response is.

    Can we please kill the low cg myth?
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  2. Cat0020

    Cat0020 El cheapo

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    "Just below the knee-cap"... that seems significantly lower than waist height as pictured... myth?
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  3. ctromley

    ctromley Long timer

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    Yes, lower than pictured, but not as low as the layout proposed by HD, for example, for their similar product (non-pedal, seen here: https://advrider.com/f/threads/elec...er-news-updates.1154248/page-53#post-39167934 ), where motor and battery are around footpeg level. Low cg is not the goal. Correct cg height is the goal. That's one of those subtle-but-critical distinctions that many people miss, but make all the difference.
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  4. WDG

    WDG Not entirely domesticated

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    I’ve noticed something like this on a demo ride of a Honda CTX 1300. When sitting still, it’s clear this bike carries its weight somewhat high.

    What I noticed in the test ride is that it’s mass seems to be located fairly closely to the roll axis. It allowed this bike to maneuver much better than I had expected.
  5. ctromley

    ctromley Long timer

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    That is a nicely-worded layman's way of describing a low polar moment of inertia about the roll axis. Generally speaking, low polar moment is more important than cg height, but few people understand it or talk about it. The roll axis is defined by a horizontal line running fore-aft through the cg. "Low cg" says nothing about how stuff is placed around it. Two bikes can have the same cg and widely different polar moments of inertia. Guess which one handles better? The market-speak for low polar moment of inertia is "mass centralization." Honda has been working on that and promoting it for decades.
  6. snowjob

    snowjob Thinking about bikes....

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    I've had my dual sport packed out for week long ADV trips a number of times. Usually a dry bag on the tail and a tank bag up front. Once I even added saddle bags and a tail bag along with a fender tool kit. On each trip, the bike was much worse to ride with all the weight up top. Cg is a real thing and it changes dramatically once you add in the load of rider & gear. The biggest impact while on single track was all the added weight and the location of it was less of a concern. Though now that I think of it, riding rock/boulder trails was also much worse due to the weight up high. Not technically single track, but definitely challenging. We rode a couple days as a loop without gear and it was easy in comparison. Where the top-heavy setup really hurt was faster, sliding turns on gravel roads. High Cg can make it very easy for the wheels to slide out from under you at speed around corners.

    ....oh, and short legs, they definitely like lower Cg.

    Hancock Pass
    IMG_20170710_104104856.jpg

    Michigan (proof I actually did ride single-track fully loaded)
    IMG00188-20110529-1011.jpg

    About to remove all gear to get up the hill
    Michigan.jpg
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  7. Yinzer Moto

    Yinzer Moto Sloppy 300 rider Supporter

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    You bring up some interesting points and I agree with most of it as it pertains to road going bikes. Where I disagree is with dual sport and dirtbikes. Where the bike is getting thrown off balance and the rider is constantly having to correct it. If the weight is up high, it takes more work to bring the bike back into balance.

    Roll axis is very important too, Yamaha has been making what they call “reverse” engines in order to put more weight in the center of the bike.

    On a recent trip to Mexico, we were worried about the availability of fuel. So we all carried 1 gallon on our rear racks for about 10 days. Then one day we rode 30 miles down a dirt road, ate lunch. While eating and studying the maps, we decided we need to go back on that exact same dirt road. We also decided that we were going to be close to fuel for the remainder of the trip. So we dumped the gas in our tanks. Moving that weight from the rear rack to the tank made a night and day difference. We were now drifting the corners on the dirt roads with way more control than we had before. I had to stop and ask my buddies if they were experiencing the same thing and they were.
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  8. ctromley

    ctromley Long timer

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    What I'm seeing here is that these myths continue because people attempt to apply simple rules of thumb to a complex issue they don't understand. For example, roll axis is not disconnected from cg. Whether pitch, roll, or yaw, any axis is defined by the cg, because they all go through it. And saying low cg is not a proper goal is not the same thing as saying high cg is good. Too low or too high are both incorrect, and handling will suffer. And if you take a bike and change nothing but add gear to it, you haven't just raised the cg, but you've also greatly increased the polar moment of inertia about any axis, which is frequently the much bigger issue, but few mention that at all. A 'reverse' engine improves polar moment about the pitch and yaw axes. A gas can on the rear rack is a BIG change in polar moment of inertia, which is why taking it off makes such a difference. Improved drifting in corners shows a reduction in polar moment of inertia about the yaw and roll axes. Overall improvement in control means improved polar moment (to varying degrees) in all three axes.

    (BTW, be very careful how you pack. A friend on a Gold Wing land yacht very nearly died because a gas can behind one of his bags caused a tank-slapper on a high speed sweeper and launched him into a forest. Yes it was the gas can, because others in his group with the same setup complained of handling issues, which disappeared when the cans were removed. And this is on 800 lb. Gold Wings! ALL additional weight needs to be close to center. If that's not possible, only light stuff goes out at the extremes. Because, physics!)

    Since few are getting this, it would be foolish to bring up how it all changes when the rider partially de-couples his mass from the mass of the bike. For example, all the talk of weighting the pegs or bars is really just a more understandable way of getting you to shift your body's cg around relative to the bike's.

    We're not even in the right forum to be dissecting this, so I'm out. I'll leave you with this: Be very wary of pat rules of thumb applied to complex situations. At best you get gibberish that will lead you in the wrong direction because it's incomplete and/or misguided. At worst it can get people hurt. Anyone wishing to really understand would be well-served by hanging around https://motochassis.com/ . It's probably best to do a brain dump before you do, or you will find yourself having to unlearn some of what you thought you knew. It's a good place for the layman to learn, though many will need a refresher in basic physics. A good place to start that is thoroughly understanding the concept of polar moment of inertia as it applies to rotational motion. (One key point: It increases with the square of the distance of the mass from its axis. Think of doing a pirouette with a 40 lb. pack on your back, then doing it with your head through the middle of a 40 lb. ladder balanced on your shoulders.) If you want to go deeper, the SAE has some meaty publications too.
  9. Yinzer Moto

    Yinzer Moto Sloppy 300 rider Supporter

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    Great description. We could use more people like you writing articles for the front page of this site instead of all the click bait that is up there right now. You mentioned standing and that is something I really try to describe to people. Standing really helps the way a bike handles. Motorcycles are not really designed to be sat on. I would be interested in if you decide to write a dedicated thread on bike packing, cog, and weighting the pegs.
  10. outbacktm

    outbacktm Bullrun Bison Supporter

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    Yes please do a write up
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  11. outbacktm

    outbacktm Bullrun Bison Supporter

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    One of the most illuminating posts in along time, please continue and post here where I can find it
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  12. Crash217

    Crash217 The short guy with a beard

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    It’s the largest manufacturer of motorcycles in the world if I remember correctly.
  13. outbacktm

    outbacktm Bullrun Bison Supporter

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    I read the basics Tony Foale shared on the website, Very interesting stuff definitely influencing how I you look at the bike as far as weight and input goes.
    We need some more dialogue on the subject, especially as it applies to the AVD and Dualsport Bikes and gear, I am definitely not an engineer but the principles are straightforward to apply.
    Will buy his book
    Another big rabbit hole
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  14. MUDHWY

    MUDHWY Simple Math

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    Anyone know from riding one what the ergos are like on these models? Are they large/tall rider friendly? I'm 6'2" with a 34 inch inseam. Interested.
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  15. voltsxamps

    voltsxamps Advolturer

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    Barcelona-based electric motorcycle manufacturer Pursang preps for its first production batch of electric motorcycles

    Micah Toll - Feb. 18th 2020 7:50 am ET

    Pursang is currently offering two different models, the Pursang E-Track and the Pursang E-Street.

    upload_2020-2-18_9-46-53.jpeg

    Both the Pursang E-Track and E-Street feature tubular chromoly frames, inverted front forks, rear monoshock suspension, JJuan floating caliper hydraulic disc brakes, Morad wheels, and Pirelli Scorpion tires.

    [​IMG]
    Pursang E-Track electric motorcycle

    The E-Track packs in an 11 kW (14.75 hp) continuous-rated mid-drive electric motor with primary belt drive and a final chain drive. The motorcycle has a range of 160 km (100 miles) from three non-removable 2.4 kWh batteries (7.2 kWh total) and a top speed of 120 km/h (75 mph).

    Pursang expects to have the first 60 units of the Spanish-made electric motorcycle on the market by May 2020, retailing for €13,700 ($14,800). The first 60 units will receive unique features including carbon fiber body panels, making them akin to Founder’s Edition bikes.

    [​IMG]
    Pursang E-Street electric motorcycle

    The slightly less powerful E-Street will offer a smaller 8 kW motor, is powered by two removable 2.4 kWh batteries (4.8 kWh total), and receives a range rating of 100 km (62 miles). Its top speed is rated at 100 km/h (62 mph) and the bike will retail for €8,700 (approximately US$9,400).

    The tail and subframe of the Pursang E-Street is actually hinged at the top and lifts up using a gas cylinder. Once lifted, the removable batteries can be slid out from the rear of the motorcycle, where they can then be charged off the bike.


    source: https://electrek.co/2020/02/18/pursang-e-track-e-street-electric-motorcycle-beginning-production/
  16. MUDHWY

    MUDHWY Simple Math

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    Why do they have to cost so much?
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  17. Cat0020

    Cat0020 El cheapo

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    and no compartment to hold stuff...
  18. davenowherejones

    davenowherejones short old guy

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    Hey, go away and ride your 36 inch seat height KTM. Like I never could with a 27 inch inseam, well I could but I have to learn gymnastics.

    They look small.
  19. MUDHWY

    MUDHWY Simple Math

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    Nope. I gave up on KTM after owning a couple of crappy ones. :lol3

    They do look small, don't they? Thus, my question.
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  20. RedRocket

    RedRocket Yeah! I want Cheesy Poofs

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    Looks good.