Sunday, July 5, 2009

The inspiration for this project was diverse, but I guess first off, it’s simply the stuff of childhood imaginings (we used to really want bikes with motors when we were kids) Now that I mention it, how about oil slick dispensers!? Or re-spawning handlebars! Err- anyways, the "awesome/radical" factor is somewhat self-explanatory.

A few months ago my sister and I were discussing a local library/grocery store/pub travel paradox when the same topic came up again: how useful a motorized bike of some kind would be for short trips to the shops... However, my sister wanted something that:

A) had the option of pedal power (and)

B) something that wasn’t super loud or “scary” to use

I started to sketch out a few ideas… Immediately, I thought of something like this and these types of traditional motorized bikes. Similarly, I’ve seen quite a few people retrofit small gasoline engines onto their bikes for a similar sort of project, like this:



However, both share the same traditional drawbacks of being A) pretty loud, and B) a somewhat environmentally un-friendly replacement for a traditional bike… But what about electricity?

While commercially available electric bikes do exist, they come at a cost. Around here, Canadian Tire and Walmart already sell a few different models but virtually all of them start at around seven hundred bucks, and many are around nine hundred! While an electric bike could be a fun or even helpful thing for some people, it's clear they need to become way more accessible... There’s no reason someone should have to pay nine hundred dollars for an electric bike. It even sounds wrong… nine hundred dollars…Harumph! Alternately, some online bike shops offer their own models as well, but often only sell the very best of the best (like expensive hub motor designs) which are indeed awesome, but also very expensive... So while not everyone can afford new hub motors, or commercially made electric bikes, a simple chain and free-wheel setup – aka – a DIY electric bike - can be assembled for far less (under $300) and is accessible to almost anyone who already has a regular bike… so let’s build a totally homemade electric bike!

Required Parts and What to Look For:

Motor:



People have used all kinds of motors for electric bikes and in fact, when it comes down to it, you could effectively use whatever motor you wanted, as long as it was powerful enough (and in this case I figure 250 Watts is your absolute minimum). Here are a few things you’ll want to bear in mind if you want your motor (and bike!) to last. Firstly, try to get a “brushless” motor if you can, it’s by no means a necessity, but it’ll last longer than a conventional (brushed) motor, and if you want to be able to pedal your bike as well (pedal assist) as (I hope we’ll be able to do) with our design, then you’ll want to make sure you get a motor with the proper gear reduction… Lucky for us, relatively inexpensive bicycle motors with the proper gear reduction ratio are available from online vendors such as electricscooterparts.com and monsterscooterparts.com… Away we go!

Battery:



Generally, most electric bikes can range from 24V, 250W all the way up to the 48V, 1000W + range… For the most part, whether you choose an SLA, AGM, NiCad, NimH or even the – mythical LifePo – battery… it’s likely you’ll mostly (though not always) find the kind of batteries we want in units of 12V. So…if you decide to go with say, a 24V motor, you’ll need two 12V batteries for your bike. Alternately, if you decide to use a 36V motor, you could use three 12V batteries (or two 18V!) etc etc.

While LiFePO4 (Lithium Iron Phosphate) batteries are all the rage these days, they’re way too expensive for our purposes… Similarly, a lithium-ion battery is probably ideal but also often very expensive… One way around this is to use the Lithium Ion batteries found in rechargeable tools by companies like Dewalt and Bosch. Though their disassembly can be tricky, some (such as some of the users at the Endless Sphere forums) have successfully linked multiple packs together with really good results…

Because I want to build the most affordable (yet functional) electric bike possible, I think I’ll be going with an AGM (absorbed glass mat) battery for my bike which is basically a fancy SLA battery… Sure, they’re sorta dirty… and may not last as long as Lithium ion, but they’re cheap and should last at least a few years if cared for properly. These SLA and AGM batteries are very close to what you’d find in a golf cart (or in other EV’s like motorized scooters, or the infamous Hoveround!) so there are many places that may carry them… I mention this as shipping is brutal these batteries (owing to their weight). Make sure you check around locally before resorting to ordering them online…


If all goes well, I’ll have a finalized parts list for the next post (as well as a basic wiring diagram for how to put the electronics together) but in the meantime, I still need to get some parts...

Stay tuned!


Labels: ,

posted by Marcus at 8:58 PM | 1 comments
Epic Disclaimer: Certain projects are inherently dangerous, and even the most simple tool can cause serious injury or death if not used properly. Always read and follow instruction manuals and safety warnings. You must be particularly careful when dealing with electricity - always use common sense. Any advice, guidance or other information provided on the Robot Party! website or within any of its publications cannot completely anticipate your situation. If you are at all unsure about completing any aspect of any projects, consult a qualified professional or contractor to advise or perform the service(s) for you. Always follow electrical code requirements specific to your area, and before undertaking project that involves electricity, contact your local electrical authority and your insurance company to ensure that you comply with all policies, warranties, regulations and authorities concerning this work. You expressly agree to hold Robot Party! and its contributing authors, harmless for any property damage, personal injury and/or death, or any other loss or damage that may result from your use of the information provided. No advice or information obtained by you from us shall create any warranty not expressly made herein. Reader agrees to assume all risk resulting from the application of any of the information provided by Robot Party!. By using this web site, including any applets, software and content referenced therein, the visitor agrees that the use of this web site and its information product is entirely at his/her own risk. RobotParty! does not take any responsibility for the information presented. Information offered through Robot Party! is in no way guaranteed. Due to the nature of the internet, technology and the DIY movement some articles may discuss topics which may be illegal in some locations. Said information is provided for educational purposes only and is to be used at the reader's own discretion. Robot Party! and its contributing authors do not condone or endorse any illegal activity. All contents copyright © 2010, Robot-Party! All Rights Reserved.