Your Help Needed designing affordable electric bike! - Page 1
Forum section: electronics / beginners

author: Kedar264
author_rank: Regular Contributor
timestamp: February 18, 2018, 03:24:03 pm
content: Hello guysSo I am designing my own electric bike but my goal is to very cheapest price but still high performanceSo as a motor I was thinking to use an angle grinder which is used in any old common metal Works, and since it is very commonly used and mass produced it's really cheap to get almost everywhereSo after doing some experiments I was able to successfully mount to my bike I wired my angle grinders coil in series configuration so now if I provide 240 vdc it works really good but the real problem occurs when I disconnect the motor extremely big arcs are produced at the switch terminalsNow if I Connect the angle grinders coils parallel it works on 120 volts and produce relatively manageable arcs but now the motor produces half number of rpms (150)and twice amount of torque , now my bike is just able to go about 10 km per hour which is slow as Turtle...., I'll be satisfied if my bike will take me 40 to 50 km per hour.by the way gear ratio of my bike wheel as 10:1 so if the motor rotates 10 time wheel rotates one time, that gear needs 10-20kg/cm torque, if I don't use that gear combination I will need to use very high torque motor with low RPMI also had 1 blower motor lying around (600 watts 30000+ rpm) but upon testing this motor I found torque is very low and this Universal Motors are hard to operate on dc battery power, I might need clever arc suppression circuitry.So what I am looking for is the system of motor and controller and the required specifications are below#Motor1.Rpm- 500-6002.Power - around 1kw3.Torque - 10-30kg/cm4.DC or Ac5.Voltage - within spec's of controller6.Price - less than 50$without gears here are motor requirements# Motor1.Rpm- 50-702.Power - around 1kw3.Torque - 100-300kg/cm4.DC or Ac5.Voltage - within spec's of controller6.Price - less than 50$# controllerany speed adjustable electronic circuit for motor aboveSo guys it will be really helpful suggest me a motor and Controller configuration around the specifications ,I'm really investing my time in this project so your help is really appreciated so I can give benefits to our community.Please excuse my typos...

author: Jwillis
author_rank: Super Contributor
timestamp: February 18, 2018, 05:03:29 pm
content: Maybe a starter from an auto salvage.

author: max_torque
author_rank: Super Contributor
timestamp: February 18, 2018, 05:09:15 pm
content: Good, cheap, powerful. Pick any two.....The simple answer is you can't do "cheap" and still be much good. If cheap comes in front of "good" then i'd be looking for some 24v truck fan motors, which can run over 500w, and use a cheap ebay motor controller to drive it, with a couple of 12v small lead acid batteries in series for the energy storage.Any HV AC motor is going to be a pain to drive, and not to mention a significant safety risk on a bike (which gets wet, gets dropped, generally isn't very well looked after etc)

author: cowana
author_rank: Frequent Contributor
timestamp: February 18, 2018, 05:33:23 pm
content: One specification you don't mention is duty cycle (how long it can run for before having to cool down). A cheap angle grinder motor is likely rated for around 10-20% duty, meaning after 5 minutes of continuous use it could need a further 20 minutes to cool down, otherwise risk overheating.

author: Jwillis
author_rank: Super Contributor
timestamp: February 18, 2018, 05:59:40 pm
content: wait a sec. 300kg/cm ?I'm old school and that's like 20000 foot pounds ! That's 5 Chevy's!

author: rstofer
author_rank: Super Contributor
timestamp: February 18, 2018, 06:09:58 pm
content: Quote from: Jwillis on February 18, 2018, 05:59:40 pmI think you're off by 3 orders of magnitude:https://www.convertunits.com/from/kg-cm/to/foot-pound+forceIt's around 22 foot-pounds.

author: rstofer
author_rank: Super Contributor
timestamp: February 18, 2018, 06:10:59 pm
content: Most of these projects tend to start with treadmill motors:http://www.ebay.com/bhp/treadmill-motor-dc

author: Jwillis
author_rank: Super Contributor
timestamp: February 18, 2018, 06:33:21 pm
content: Quote from: rstofer on February 18, 2018, 06:09:58 pmNot my bad .http://www.endmemo.com/convert/linear%20mass%20density.php?q=Gram/centimetereven the google converter is out. but you are correct.