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  1. J

    48 - 265V 500 Lumen $1 eBike light from hardware store parts

    I tested about a dozen different LED bulbs, 5 brands from 3 hardware stores, to see over what voltage range they would function. LED bulbs have a built in PWM step-down voltage to current converter that is set to different voltages for different bulbs. Many of these voltage converters are...
  2. J

    Help suggest low cogging outrunner for Univ robotics project

    We bought a high pole count motor with LCM in mind, but in practice we found that the Quantum 4008 (24t 22p) cogs about as much as the Turnigy 5208 (12t 14p), despite the latter being much bigger. So stator and magnetic pole count is only one factor. Geometry of the magnetic paths and field...
  3. J

    Help suggest low cogging outrunner for Univ robotics project

    We have a haptic robotics project at school. It involves designing and making a force reflective robot wrist. The application is in tele-robotics, where a human moves one motorized arm, and those motions are replicated by an identical robot arm at a remote site. Here is an example picture and...
  4. J

    Split-crank Electric Tricycle

    Is the purpose of the drive just for aiding with propulsion? Or does it specifically have to drive both the left and right chain and cranks (as you suggest with the proposed application of two GNG drives), e.g. for rehabilitation of a person with lower body disability? If you tell us a bit more...
  5. J

    recumbent build with homemade triple stator AF motor

    I'm amazed and impressed what you can do with basic tools and materials! (My own attempts tend to have +-0.5mm error and assembled results end up distorted :( I have a recumbent with a similar jackshaft and chainring setup under the seat. One problem I have is that the jackshaft flexes a bit...
  6. J

    what is a safe limit for battery temperature during use?

    Hi dh, Thanks for your good advice. I would like to ask what you consider "charge too fast" at low temp to be? To be more specific, I have a 16s pack of 20Ah A123 on my eBike. For overnight charging I use a small 1.8A charger in the garage. Is charging with c/10 all right at -20C? How about...
  7. J

    Help me find a job in the Bay Area!

    You tried both big (Sandia) and small (your own business). How about medium? Startups or small companies with 5-25 people are less bogged down by administrators and lawyers. Usually high creativity = high reward, but can be high stress. Another alternative is to be a lab tech for a university...
  8. J

    Aosom bike trailer

    I agree with the previous poster that you should pester both the company and Amazon to actually support their product. If you bought with a credit card you could also see if it has an extended warranty or the CC company will do anything else. While these efforts may not succeed, at least the...
  9. J

    Worlds Worst Dyno - Version 2

    I'm certainly no expert in the design and analysis of electromagnetic machinery. However it seems to me that significant hysteresis and eddy current losses are caused whenever there is rapid change in magnetic field strength, independent of if commutation or PWM is the source. Commutation causes...
  10. J

    Worlds Worst Dyno - Version 2

    Hi Adrian, Hats off to you for one of the most informative threads on ES recently! Excellent job. The expectation (e.g. as quoted above) that higher PWM frequency should give smoother current and therefore smaller losses is clearly contradicted by Adrian's data in previous posts. Fechter's...
  11. J

    DC residents: Is this plan crazy? *update* No it's not

    Absolutely do it! When your packed bike arrives at the luggage belt, choose a prominent space in the arrivals area and assemble the bike there. Guaranteed you will get a lot of lookers. Teach them something!! When I've done the same I'd had no trouble with officials. (People assembling and...
  12. J

    Worlds Worst Dyno - Version 2

    Thanks for the testing. Maybe one shouldn't expect better from an ebike controller. I wonder what regen efficiency is in say a car where engineers might have put more thought into that part? For overall generation efficiency (including mechanical and iron losses) I get 60-65%. Worse than a car...
  13. J

    Worlds Worst Dyno - Version 2

    Hi Adrian, I'll second Miles comment: Great setup. I'd be curious about the efficiency of the regen part of it, and how it varies with rpm and regen current. I don't think real world regen efficiency has been tested/posted for these types of controllers and motors. Probably motor/controller...
  14. J

    Lightweight folder - build thread

    Hi Jeremy, For those of us building small folders it would be interesting to hear more about how you compare the Cute and Tonxin/Keyde motors. I'm building a Brompton so would be using the 82mm version of one of these. Your initial impression of the Tonxin was that it was weak uphill, but...
  15. J

    Aptera is gone for good. :'(

    To bad to see a visionary company close. But not unexpected. If it was easy to start auto manufacturing we would have seen more new companies grow in the past 50 years, and less dominance by the old big ones. If there was an "experimental" class for cars, just like for planes, then maybe new...
  16. J

    Heavy cargo hauler project

    Hi Tom, I love that classic cargo bike and don't want to dissuade you from the build. However a 25km daily commute may not be ideal on it. After a while you'll probably long for a bike that is lighter, faster and more agile at swerving around pedestrians, bikes and cars. Think about it: How...
  17. J

    Good Deal? Or Rip Off?

    Edit: Added some cost estimates in text below You can always try to post with a specific title like "Help with ebike wanted in Toronto, ON area, Canada". Or you could just ask if some nearby ES members would like to meet up and try out each others rides. It is not clear to me if the best...
  18. J

    Any College drop outs on ES? Care to narrate?

    KF's story tops my list of best ever ES post (2nd one is LFP's encounter with Mustang and Camaro guy from some years ago). I had plenty of experiences like KF's with narrow minded types. In one early assignment we were to design a garage floor engine crane. I did my design so there were no...
  19. J

    Good Deal? Or Rip Off?

    I also think your old bike has a lot going for it: http://www.green-cruiser.com/bay-street-angel-2.html A geared Bafang hub in a 20" wheel is going to be better on your hilly route than a similar hub motor in a 26" wheel. You get 30% more torque (26/20=1.3). Also a Direct Drive hub (such as...
  20. J

    Edit: solved! HK screwing me on Nanotech order. What do?

    Success at last. After 1 month of wrangling, 10 or so emails, HK finally agreed to fill missing/out of stock pieces in the order I had paid for a month ago with the next better parts and get it shipped. I'm hoping it ships in the next couple of days so I'll have the gear next week.
  21. J

    Occupy REI!

    http://www.economist.com/node/21534759
  22. J

    Hobbyking Customer Service.

    I have a similar problem with Hobbyking. (Reported in a separate ES thread) I think your plan sounds good: Report to Paypal. Racking up a bad record with Paypal is not going to be a good thing for them. Still, you might have to continue following their instructions, however ridiculous, so you...
  23. J

    Edit: solved! HK screwing me on Nanotech order. What do?

    Had they bothered to check actual stock and tell me right away I would have probably just paid. After being jerks and stringing me along with BS for nearly a month, I'm reluctant to have them get away by skinning me for $50 more. If there's no comparable source I guess I'm kind of stuck though...
  24. J

    Edit: solved! HK screwing me on Nanotech order. What do?

    Battery packs weigh the same, but they hiked the nominal shipping weight for the new 5.0. If they were honest they should be wrapping them in 200g more of protective covering. Otherwise they are just pocketing the difference. I thought the 25-45C was substantially worse than the 45-50. (packs...
  25. J

    Edit: solved! HK screwing me on Nanotech order. What do?

    Edit: After nearly a month of wrangling and customer support emails it's now finally solved. They will ship similar batteries with a different part number at no extra cost. See last post. Hobbyking customer service is giving me a runaround with an order of 45-90C Nanotech LiPo. I ordered...
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