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  1. #1
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    Effective motor power to wheel

    Hay guys,

    Just wondering does anybody know how to calculate the effective power which is being delivered to the wheel. A 1000 Watt motor say with a chain drive will not deliver 1000 watts to the wheel, because of Efficiency. Do you guys reckon the way to work out wheel power is just to subtract the estimated efficiency from the engine power rating. E.g. 25 % for Motor, 5 % for controller, 25% for gears and chain, to equal a wheel power of 550 effective watts. Thoughts would be welcomed

    Currynut
    Last edited by Currynut; 02-14-10 at 09:43 PM.

  2. #2
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    I ride an electric bike, and I'm in Melbourne.

    Unfortunately, the max power rating of 200W is the rated power at the drive shaft of the motor itself, and doesn't relate (for the purposes of applying the relevant law) to the power at the road. In other words, there's no allowance for loss of power through the drive train. A 600W motor is illegal for public road or bike path use in all Australian states.

    If you're unlucky enough to be caught by the police riding a 600W electric bike, you'll actually be charged with operating an unregistered vehicle on a public road.

    Maybe sell the 600W to a cocky?

    Cheers.

  3. #3
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    thanks,

    have u ever been pulled over?

    currynut

  4. #4
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    I was looking at some chain driven motors like the one you were looking at, Currynut, on youtube. And someone in comments said he built an e-bike with a 200w motor and it was too weak for what he wanted so he upgraded to a 1000w motor. Attach as much value as you want to this but you probably will be happy if you go straight for the 1000w motor. I don' t live in Australia so you might find out how often they enforce it. If you can't go with a 1000w motor, it's not going to be as much fun. I think if I lived in Australia and I found out they were enforcing the e-bike law, then I'd just buy a motorcycle and get licensed. Here in USA, I ride around and my e-bike hits over 1500w peaks all the time and I've gotten it up to 37 mph and I've never had a cop bother me at all and I'm going on over 1 year of riding my e-bike.

  5. #5
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    Hi

    I am quite happy to ride at cycle speeds (15mph), with a cycle that might not comply with UK law 100%.
    But if I was travelling at over 30mph, I would want to be legal, for my own safety, and others. One year not being stopped by the police, does not mean its ok. Come back again after 2 years, hopefully you will be accident and no court appearance.

    S

  6. #6
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    Legal in my state is 25 mph on an electric bike so 30 mph isn't all that much higher.

  7. #7
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    My bike has only the Aussie legal 200W motor, and I don't really have any negative issues with that relatively low power output. I live near the coast, so it's pretty flat around most suburbs around me. I guess if you lived in a regularly hilly or mountainous locale, then 200W ain't gonna make it.

    It's surprising how fast you can go on a downgrade with pedalling + motor. I can top 40 km/h without a head wind.

    If I see cops nearby, I always "mock" pedal anyway, just so I don't attract unwarranted interest.

  8. #8
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    Here is an app that might do what you want. It has a bunch of hub motors on it and it has a selection for "custom" and rear/front sprocket so maybe you can put in the variables and graph it and figure out if it does what you want. The author of the app says to take off 10 % of it if you are working with chain driven motors because of the chain friction or something like that. So take off 10 % from the speed and acceleration and stuff if you are going to do chain driven motor.
    I found this on endless-sphere....all you do is extract it and then double click the ebikecalc2.jar file. Then maximize it so you can see it all.. It's a big application. Then you can graph velocity and acceleration. it will tell you what you are max speed is likely to be. It's pretty cool.
    http://www.mediafire.com/?lgj4zy2mz44

    found it here:
    http://www.endless-sphere.com/forums...119810#p119810

  9. #9
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    I've been fooling around with this. I went to the "Prediction" part and it is dead on accurate. I can't believe how accurate it is for my hub motor. I put in my voltage and my amps and it predicted my top speed completely right. Don't forget your total weight including you on the bike.

  10. #10
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    I want to buy an electrical bike, but I am confused... How many miles can I ride it without charge it?

  11. #11
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    Quote Originally Posted by philiboy View Post
    I want to buy an electrical bike, but I am confused... How many miles can I ride it without charge it?
    It depends on what kind of batteries you get and how big they are. I get 30 mile max range on my electric bike. That's going about 25 mph the whole way. The faster you go, the less range you get. Is 30 miles enough for you? If you get lithium batteries, you get lots of range. Lithium has come down in price in the last few months. In another thread in this forum, I made a post about a 36v20AH for $312 so you might check that out. Those are the cheapest lifepo4 that I have found on the internet. That's what I'm using on my bike.

    Also, if you build your own bike, you'll likely get better range and faster speed for your money. The commercial bikes are usually pretty weak. My bike is pretty fast. It goes 35 mph on 48v. I love it. hahaha. Most commercial bikes only go 20 mph. My bike goes as fast as a moped and I don't have to insure it or register it.

  12. #12
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    Quote Originally Posted by philiboy View Post
    I want to buy an electrical bike, but I am confused... How many miles can I ride it without charge it?
    A few more things. With Electric bikes, it's really all about the battery. You really need to build your bike around the battery because the battery pretty much dictates how fast and how far you will go. For example, if you buy a 48v20AH lifepo4 battery, and it has a max continuous amp rating of only 25 amps, then you need to get a controller that is max 20 amps continuous and nothing more or you will destroy your battery. So lets say you got a lifepo4 battery that has a max continous amp rating of 40 amps, then you could get a 35 amp controller for it since it's well under the 40 amp rating.

    You have two different types of motors: hub motors and chain driven motors. I have a 5303 crystalyte hub motor. It's a front hub motor. And I have a 24 - 72v 35amp controller for it so I had to get a lifepo4 battery that had a 2C rating ....2C rating ona 48v20AH battery means that 20AH * 2C = 40 amp continous max rating so I needed that kind of battery to work with my motor and controller or the controller would fry a weaker battery. Hope I'm making sense. It's called the "C " rating. I'm just assuming you haven't read this, that's why I'm telling you thiis. Sometimes manufacturers will give the "C" rating and sometimes they'll just say 30 max continuous amp rating for that battery....both say the same thing.

    Anyway, you got these hub motors to choose from:
    crystalyte
    Ezee
    Nine continent
    BMC
    Aotema
    Heinzemann
    Golden Motor
    Bafang
    Bionx

    Those are some of the well-known hub motors. Anyway, hope this gets you started. Beware of crappy e-bay lifepo4 batteries and crappy e-bay motor kits. I bought my motor and controller from http://ebikes.ca ....that's a good place to start and you can e-mail a guy named Justin if you have some questions and he'll answer them. I think he's the owner of ebikes.ca . He's a pretty good guy. That company has been around a while. They do good work.

  13. #13
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    one thing to remember with politicians and laws is that they don't give a rats a** about how much force is being transferred to the wheel. if you have a motor that has a higher watt rating than the law says is allowed there is no way you are gonna win your case in court. if you want more speed or torque just get a 200W chain drive or something. either that or do what some guy on youtube did with his motor. he lives in the UK and bought a 500w or 1000w cyclone, i can't remember which, and had some fake stickers made up on that metal foil material they use for manufactured parts. basically it just says his watt rating is 200w so if he gets stopped he's still "within the scope of the law". I doubt a police officer is going to impound your bike and have a specialist run tests just to make sure you are in compliance.
    DISCLAIMER: I cannot be held responsible for any offense taken. Should you have taken offense to my comment my lawers will be in touch. Said lawers are most often seen flying disk shaped vehicles accompanied by men in tin foil hats. Should this DISCLAIMER offend you, you are hereby declared a lost cause and the men in tin foil hats will be in touch.

  14. #14
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    Quote Originally Posted by morph999 View Post
    Legal in my state is 25 mph on an electric bike so 30 mph isn't all that much higher.
    I have never seen any state in the US that allows e bikes to go 25, only the 20 mph that follows Federal regs.

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