1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

Next electric bike - illegal DIY!?

Discussion in 'Electric Bicycles' started by fabola, Apr 8, 2008.

  1.  
    fabola

    fabola Just Joined

    Joined:
    Jul 21, 2007
    Messages:
    2
    Hello,
    Today I own an Salisbury LPX (as the only e-bike experience). It is ok, but too slow and not strong enough (because it's legal!). Maximum speed is 22kmh (13.7mph) on flat. 22kmh is not fast, and if I want to increase speed by pedaling, it feel like the motor "steal" all the power from pedals!

    So my next bike should be an illegal DIY built on an MTB with discbrakes and full suspension. If motor is to slow and weak it should have freewheel. Otherwise its not nessesary.

    I thinking of a cyclone kit (see cyclone-tw.com), the new 500W with double freewheels, because it will be have good balance, easy to install/remove and I can use the old LPX-battery.

    The other alternative is a 350W front wheel with regenerative braking from www.goldenmotor.com.

    What do you think about this? Other options?
  2.  
    Jeremy

    Jeremy Just Joined

    Joined:
    Oct 25, 2007
    Messages:
    1,010
    Location:
    Salisbury
    I thought about the "illegal" ebike option, in fact I went so far as to try it with the big Crystalyte motor on my 'bent, but concluded that bicycle frames just aren't really designed to take three or four times the power that a rider can deliver.

    I have started another electric vehicle project (although keeping my Tongxin powered 'bent) but have decided that it must be completely legal. I have purchased a small motorcycle (actually categorised as a moped) rolling frame and have ordered a motor and controller to convert it to electric (the combined cost of the motor and controller was about £400, comparable to an ebike kit).

    I believe that if the electric motor power is kept below 4kW, then it will remain in the moped category (the original engine in this bike was only about 4 or 5hp). I haven't had confirmation of this from the DoT though (despite asking them the question a week or so).

    The advantage of doing it this way, apart from remaining legal, is that the frame and rolling gear is working within it's original design limits, which means that the brakes, tyres, frame etc are all up to dealing with the power safely.

    Jeremy
  3.  
    joab

    joab Just Joined

    Joined:
    Feb 1, 2008
    Messages:
    113
    Location:
    Serskamp, Belgium
  4.  
    flecc

    flecc Member

    Joined:
    Oct 25, 2006
    Messages:
    27,671
    Not because it's legal! It's because it's the lowest powered legal bike, that's all.

    There's plenty of faster legal machines out there, and many a far better bet than Cyclone or Goldenmotor products. I know of two people who are satisfied at the point of receipt of a Cyclone, but have known of many who are unhappy after owning one for a while, plus dealers in the USA who refuse to supply them any more.

    We've had two members buy Goldenmotor, both failed on or straight after receipt and no resolution of the problems ever posted here.

    So I've warned, but it's up to you of course. If you do want the illegal route, why not Crystalyte or the Puma motor, both with better records here and UK supply and support?
    .
  5.  
    john

    john Just Joined

    Joined:
    Nov 1, 2007
    Messages:
    531
    Location:
    Manchester
    I wonder why you concluded that. A competitive cyclist can put out 400+W and travel up to 70mph on a flimsy lightweight frame. A good mountain bike (and rider) can drop 6 feet and more without damage.

    BTW, keep meaning to ask you; did you think of limiting your crystalyte with an in-line resistor from the throttle. I have one on my setup so I can switch between legal/performance modes.
  6.  
    Jeremy

    Jeremy Just Joined

    Joined:
    Oct 25, 2007
    Messages:
    1,010
    Location:
    Salisbury
    That's a bit like comparing a formula one car with a family saloon, isn't it? How durable would that light weight bike be if ridden every day, in all weathers, over normal roads at that sort of power and speed, I wonder.

    Are bike brakes really up to reliably stopping a bike from high speeds (30mph plus), at full weight, in all weathers, on a daily basis?

    I suspect that there are some bikes that will take this, like the beefy downhill mountain bikes, for example, but they have frames, wheels, tyres, brakes and suspension that are similar to mopeds in many ways.

    The Crystalyte 405 I have runs at around 1100 watts max, nearly three times the power of a really good athlete. It also adds a lot of weight, my 20" front wheel alone weighs about 7kg.

    The increase in weight is significant, particularly the added inertia in the wheel. This latter effect seriously upset the handling of the 'bent, which was one of the reasons I switched to the much lighter Tongxin.

    Several people on the Endless Sphere forum have run ebikes at well over 30mph, but quite a few have reported that they get scary at very high speeds. It seems more sensible to me to use a base vehicle that is designed to be safe at these speeds and weight.

    Jeremy
  7.  
    john

    john Just Joined

    Joined:
    Nov 1, 2007
    Messages:
    531
    Location:
    Manchester
    I'm not trying to put you off Jeremy. I only mentioned the frame because I have been surprised at how much punishment a quality frame can take.

    I think that making an EV that can do 30 mph and is legal would be a big plus. I hope that you can get acceptance from the DoT. The 15mph limit puts a lot of people off e-bikes as many can easily exceed this speed without a motor.

    Will it have pedals? Do you have a target spec yet range/weight etc?
  8.  
    Jeremy

    Jeremy Just Joined

    Joined:
    Oct 25, 2007
    Messages:
    1,010
    Location:
    Salisbury
    To be honest, it's taken a lot of digging around to get the definitive interpretation of the law, but I think I have it straight now. The motorcycle in question is an old Yamaha RD50MX, which is legally a moped. The frame is relatively light (I'm guessing that it's around 35 to 40kg minus engine etc) and is already registered.

    Apparently, as long as I only change the engine and transmission to an electric motor, it doesn't need to go through any form of special approval process. All I need to do is apply to get the engine type and number, plus fuel type, changed on the registration document. I've been warned that I may be asked to show that the motor power is limited to 4kW maximum and that a speed limiter is fitted.

    The motor I have purchased (a Mars ME0709) and the controller (a 200 amp Kelly KD48201) is easily capable of delivering up to about 9.6kW maximum, but the controller is software programmable from a PC, so it can be limited to the 4kW legal maximum. The original engine fitted to this little bike was only a few hp, perhaps 4 or 5, so 4kW should be plenty.

    I will probably add a speed limiter to keep the maximum speed down, but this is not quite clear from the regulations. They state that the "design speed" should meet the limit, not that it should be enforced by any device.

    Range will be dependent on the depth of my pockets when buying batteries. The frame will take around 60 or 70 Ah of LiFePO4 at 48V, which, if my estimate of Wh per mile is reasonable, should give a useful range of around 40 to 50 miles at 30mph. I will probably only fit about 30 to 40 Ah at first, as I can't see that I will need a range of more than about 20 miles.

    If I were to choose to remove the current limit and run the controller at maximum, then the acceleration would probably be quite interesting. Top speed will be limited by the maximum motor rpm, rather than the power available, and is gearing-limited to about 50mph at the moment (13t motor sprocket, 37t rear sprocket). With the controller current limit adjusted down, then the power can be reduced to set the "design speed" to a legal figure.

    I am in the process of getting all the frame parts shot blasted and primed, prior to building up the rolling chassis, ready to install the motor. I have a lot of work to do, as I need to make a new seat pan and dummy fuel tank to house the batteries, plus install some hefty cabling, a contactor (to kill the power easily) and a big power fuse.

    It doesn't need to have pedals, as it will remain classified as a moped. It can be ridden on an ordinary full car licence (no need for a motorcycle licence), is exempt from road tax and I've been advised that it should be relatively cheap to insure.

    Jeremy
    Last edited: Apr 8, 2008
  9.  
    frank9755

    frank9755 Just Joined

    Joined:
    May 19, 2007
    Messages:
    1,223
    Location:
    London
    I agree with Jeremy that it is not wise to take a bike beyond its engineering limitations. Some of the more extreme creations on Endless Sphere with high powered motors and vast batteries to give them any sort of range have ceased being bikes and I would not want one of those.

    However I think there is scope to extend the performance of electric bikes a little, in the direction of the limits that John suggests. Often this involves configurations that would be legal in other countries, such as the US, where 20mph is a typical speed limit or even Australia, where the limit is not on speed but only on average power output. The tongxin kit I attached to my hybrid bike was this sort of modification. As it was capable of speeds of up to 22mph it went beyond the laws in this country, but the bike, its brakes and wheels could cope with that sort of speed (which is not an unusual speed for a non-electric bike), and the very modest weight addition.

    Unfortunately that Tongxin kit didn't work! If I were going to do another one now, I would either get a Tongxin with Hall sensors and a controller from someone else (eg a crystallite from ebikes.ca), or one of the tried and tested Sufou Bafang motors & controllers, from ecrazyman on ebay - which are pretty light and are giving excellent performance in (illegally fast) Ezee and Wisper bikes.

    Frank
    Last edited: Apr 8, 2008
  10.  
    fabola

    fabola Just Joined

    Joined:
    Jul 21, 2007
    Messages:
    2
    Well, the legal limit is 25kmh, so 22kmh is not so far below. Of course it could be more powerful. I have measured it to maximum 242Watt from battery (uphill and when starting). With 90 percent effiency it means 220Watts to the wheel. The legal limit here is 250 watts continous power. On flat at 22kmh it was 115 Watts from battery.

Share This Page