What do you think?

Discussion in 'Electric Bicycles' started by Rob Mcgregor, Aug 12, 2007.

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  1. Rob Mcgregor

    Rob Mcgregor Guest

    Hi Folks,

    I'm new to your site and have been very intrigued by your electric bikes. I recently tried an electric Schwinn World GSE and was very impressed. It looked really clean and rode well but I did notice some room for improvement. It cuts off the assist at 18 mph. I had forgotten how fast 18 mph was on a bike since I hadn't rode that fast since I was a kid. At that speed, I could feel every bump and it struck me that a bike like this needs a full suspension and fatter tires. I also craved more speed but I couldn't go any faster than 18 mph because the assist completely shuts off above 18 mph. Also, at these speeds or higher, it seems a bike like this needs the best brakes possible.

    So I did some research and I've come up with an idea for a bike from components and I wanted to bounce the idea off you guys. Please feel free to mention all the ups and downs of these components.

    -Mongoose XR-200 $170 A full suspension aluminum bike with front disc brakes.
    -Crystalyte 406 rear motor w/ 7 speed cassette. 8 pounds less than the 5000 series.
    -35 amp or 40 amp controller running at 72 volts.
    -Four Dewalt 36V nano-phosphate batteries running series/parallel 72V 5 amp hours for a total of 360 watt hours.
    -Two Dewalt 36Vchargers to charge each pair of parallel batteries.
    -A seat post rack to mount the batteries on such as:
    -Or a full suspension rack such as:
    -A lockable box to mount on the rack for the controller and batteries such as:

    If my calculations are right, this should go around 37 mph at 77% efficiency. What do you guys think of this idea. Anything wrong with this configuration? What do you think can be improved upon? Thanks so much in advance for the dialogue.

    Thanks so much,
    Rob McGregor

  2. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Hi Rob,
    ya might want to introduce yourself in the "new guy" forum first.(protocol)

    years ago, the manufacturers had a helluva time stuffing their rear hub motor AND the multiple gears. i installed my CRYSTALYTE hub up front.

  3. Rob Mcgregor

    Rob Mcgregor Guest


    Hi 5-7Heaven and all,

    Woops, don't want to break protocol. Done deal.

    I was hoping to put the motor on the rear to be more stealth and have more solidity for the torque. In this configuration, the motor would put out more than 1700 watts which seems like a lot for front suspension forks, or at least that's what I've heard. The Mongoose also has a steel suspended rear section which I thought might be ideal for a powerful rear motor. Maybe I should put it on the front. It does seem it would be balanced better in the front. What do you think?

    Thanks so much for the dialogue,
    Rob McGregor
  4. gone_fishin

    gone_fishin Guest

    hi...this is only my non-owner's opinion, but i've been dying to get an e-wheel because i really want to feel that front-wheel-drive "pull"...i bet it's a heckuva ride on a balanced bicycle. i've also considered that front drive would allow for a more balanced load with the batteries in rear-bags.
  5. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Rob, on my CRYSTALYTE hub install, i ran 72v/16ah and had no problems with the front fork. when you file the dropouts for clearance, make sure that the axle bearing retainers are a perfect fit into the dropouts, and fabricate torque arms out of cheap coaster brake levers.
    just one bikerider noticed the hub, and declared it was a drum brake. the front hub is invisible to the average Joe.
    on my gas engine, more than one third of the people who see my bike remark about the "weedwhacker" engine, and that's with the engine off.
  6. Rob Mcgregor

    Rob Mcgregor Guest

    Hi and thanks to Myron, Augidog and all,

    How many volts and amps is your controller? What kind of batteries are you running? How fast does it go? Which Crystalyte motor?

    Do remember that the nano phosphate batteries can supply the full 35 or 40 amps easily because of low internal resistance, actually over 100 amps. Also, the 406 motor can put out over 1700 watts at 72V with a 35 amp controller(peaks at 38 mph on 26" wheel) unlike some of the other motors. I might be wrong, but I think this configuration is going to put an enormous amount of stress on the frame/fork, front or back. I'm also worried about aluminum and fork's propensity to break rather than bend like steel. Might get some warning before a catastrophe on the rear steel portion of the frame.

    Thanks again to Myron, Augidog and all for the help.

    Thanks soooo much,
  7. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Rob, i used the dual-speed 4000-series motor and controller. it was cool, because it acted like a manually shifted 2-speed automatic trans! fortunately, the controller was very versatile, allowed deadstop starts, and worked on 36-72vdc with no problems.it was a sweet setup, 50-mile+ range, speeds up to 25mph, and the hub and controller never got hotter to the touch than warm cocoa. recently, i realized that using the motor from a deadstop was the most taxing and demanding to the fork's dropouts. however, if the fork would've failed, the torque arms would've saved the day. if you make it a point to fab torque arms/axle retainers and ALWAYS pedal off from a stop, you should have no problems with your fork.
    sadly, the biggest drawback were the 80+pounds of batteries. lead batteries were much cheaper then NiMh or LiIon batteries. i wasn't sure how long i'd be interested in the hobby, so i didn't want to spend over $1K just for batteries. the lighter batteries might cost $350/pack, but to get the 72vdc AND the ah/hour for range, i'd be pay $1400 for the juice!
    besides that, i just got tired of breaking the bike down to carry it up a 2-story walkup. it was a brand new girlie bike, and sometimes i could feel the aluminum frame twist just a bit.
  8. Rob Mcgregor

    Rob Mcgregor Guest

    Hi Myron and everybody,

    Will I be able to retain the disc brakes if I install the motor on the front? A front disc brake is important to me for a bike with this much power. Can I fit a torque bar on each side of the front motor? What about two torque bars on the rear?

    The battery configuration I spoke of will cost around $440. Over 2000 cycles to dod, 1 hour recharge capability, 140 amp at 72V in this configuration. That's over 9000 watts. The electric drag motorcycle Killacycle is using these exact batteries to get an 8.13 sec 155 mph quarter mile. The packs mentioned above (36V 3.3Ah) weigh 2.5 pounds in plastic pack and bms, 1.5 each without. Highest tech available right now.

    Thanks again and keep the dialogue flowin',
  9. Rob Mcgregor

    Rob Mcgregor Guest

    Woops, that's 36V 2.3Ah, not 3.3Ah. Some might mention it's more like 33V after a peak of 36V.

    Take care,
  10. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Rob, i apologize if i might be way off-base, but you'll need FOURTEEN(!) of those 2.3ah battery packs to add up to 72v/16.1AH capacity.(i've tried my hub motor with 36v/18ah...ho hum @15mph.)
    lemme see...$440 X 14 battery packs = $6160 for batteries?

    keeping your front disc brake is a question for your vendor. back then, it was a no-fit. today...maybe they made the hub to accomodate the disc brake.

    dual torque arms can be fabricated cheaply from coaster brake levers, and i vaguely recall a recent website offering torque arms for $17 each.

    on rear hub installs, you could probably fabricate tiny axle retainers(torque arms), using axle nut retainers such as on DAHON front forks and many other bicycle makers. basically they lock-tab on the axle nut, then another of its tabs is secured in a small hole nearby, in the dropout.(rear dropouts have much more meat than most front forks.)
  11. Rob Mcgregor

    Rob Mcgregor Guest

    Hi Myron and all,

    The batteries I spoke of are actually about $110 each. $440 price was for 4 of them. For 4 of them, that's 72V 4.6Ah 330 Wh and as low as 8 pounds. Not a lot, but I'm trying to build the lightest high power bike possible. I assume I'll be using it mostly in the 15-20 mph range most of the time and the higher range for thrills. At 15 mph, I should be able to get around 30 miles without pedaling. At 20 mph, about 20 miles. At top speed of 38 mph, about 7 miles. This seems fine to me for starters since I live downtown and I could always add 2 more for a 50% increase of these numbers.

    If I just wanted the top speed at the lightest configuration, I could just use 2 batteries equaling 5 pounds to get the same top speed.

    I'm staying away from lead acid mainly because I hate to throw away batteries and the high weight. A friend of mine maintains golf carts and complains about how the batteries last less than a year with vigilant maintenance and much much less with less than vigilant maintenance. The phosphate bats last over 10 years and over 2000 cycles with no maintenance. This alone counteracts the higher initial investment. The weight of lead acid seems counterproductive on a bicycle. The 72V 16Ah lead acid pack must have weighed quite a bit.

    I feel a little guilty building an electric bike being a avid biker for years. I'm getting older and the weather is getting much hotter with global warming and I'd prefer to ween myself of my car and eventually get rid of it. It was over 105 degrees heat index most of the last week here in Gainesville, FL. Unfortunately, I dread riding my bike in this heat. Electric I think would cure this problem for the most part.

    Lots of love and thanks,
    Last edited by a moderator: Aug 15, 2007
  12. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Cool, Rob. keep us informed of your progreds.

  13. jerryt

    jerryt Guest

  14. azbill

    azbill Active Member

    there is a very nice how-to here somewhere on crafting your own torque arm
    I believe the author was blaze
  15. Rob Mcgregor

    Rob Mcgregor Guest

    Hey thanks Myron, Jerry, and Bill,

    Yeah, I'll definitely want to put a torque arm on the wheel. Can I put an arm on each side of one wheel? Seems a bit more balanced for the frame. I plan to have 72V 40A running. Do you think that is too much for the 406 or 407 motors? According to hub simulations, this will have an output of over 1700 watts.

    Thanks for the heads up on the disc on rear. This must make the drop out even wider, huh? Here's a question for you. I can't seem to find the difference in drop out spacing for 1 gear, 3 gear, 5 gear, 7 gear, and with disc brake.

    Thanks so much and lots of love,
  16. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:Hey Rob. one torque arm would suffice. after all, there is only one coaster brake lever per bike, right?
    i ran 72v/16ah on my cruiser. my motor and controller never overheated, never smelled or made strange noises. with the correct controller, 72v is safe.
    are you referring to 72v/40amps, or 40amp/hour?
  17. Rob Mcgregor

    Rob Mcgregor Guest

    Hi Myron,

    40A refers to current draw.

    I've been hearing stories about how the torque of 72V 40A has broken forks and frames before so I was thinking about how to distribute the torque more evenly. That said, I'm sure one arm would do.

    Most batteries can't supply that much current and voltage even if you have a 40A controller. These batteries can supply 3 times that current so every amp the controller can handle will be supplied. More than most people are asking of their bike frame I'm guessing. These same batteries are being used on the drag bike that does an 8 second 155 mph quarter mile. Of course I'm only talking about using 40 to 60 of them instead of 990.


    Thanks again and take care,
    Last edited by a moderator: Aug 23, 2007
  18. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:keep us in the loop, Rob.
  19. turkeyssr

    turkeyssr Guest

    Where did you buy your batteries? I went to the A123 website and I didn't notice a reference. How about your controller?

    Thanks! - John
  20. Rob Mcgregor

    Rob Mcgregor Guest