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Hi,
I had a question about your motor here (http://www.launchpnt.com/capabilities/electric-motor-design.html)
Do you guys have any plans for releasing and electric bicycle version of this motor?
I am part of an online electric bicycle community ( http://endless-sphere.com/forums/ ) and the shape,
and power to weight ratio just sound excellent for an electric bike hub motor application.
Thank you for your time, and any info or ideas would be awesome!
-Max
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Max,
Electric bikes is one of the potential markets we’ve been investigating for the motor.
Presently we are focused mainly on electric aircraft applications as the business drivers make more sense for that application. Initial production of the motor will obviously be expensive, so we need to pursue a market that can afford a more expensive motor, and aircraft have a much higher $/lb that almost any vehicle except a spacecraft, so the weight savings are worth more.
The motor technology is great and we’re really excited about it, right now we’re mainly held back by business (read: “dollarsâ€Â) considerations. We are close to getting a contract to develop a larger version of the motor, which will get us a lot further along the development process.
I did some quick scanning through your forums and it looks like there’s a lot of interesting stuff going on. I noticed some discussions of a “group buy†of motors… Our problem to date has been that most of the people we contact want one motor, and we can’t possibly tool up for them and deliver a motor at a reasonable cost. We’re a small company, and thus quite flexible in our dealings as long as we can somehow not lose money doing it. Someday we might be able to consider doing an e-bike version if a group of hobbyists could get together, decide on a common spec, and order a larger quantity.
At the present, unless you’re really avid about it and want to spend money experimenting, it would probably be premature.
We have run our prototype as a generator up to about 6600 RPM, making > 6 N*m of torque. At this operating point it was somewhat above 90% efficient, creating about 4 kW of real power and about 4.5 KVA of apparent power. (Our load bank had some inductance and thus drew some reactive power from the generator.) From this data we know that the basic design works wellâ€â€it will operate as a motor almost exactly the same as it operates in generator mode (assuming we have a good sinusoidal driveâ€â€trapezoidal drive will reduce efficiency by about 8%).
However, there are still a lot of details that need to be refinedâ€â€mechanics of the hub, the holding of the stator disk, etc. etc.â€â€that could make the motor fail prematurely in real-world use. This prevents us from wanting to make additional copies that go beyond lab testing until we’ve gotten the money and time to really “beat up†the motor in real world conditions and do a few design iterations on the things that will inevitably fail in HALT testing.
If you have any ideas on what you guys think an ideal e-bike motor spec would be, I’d like to hear it. We’ve done some research into the market, so we have some ideas; but I wouldn’t mind hearing your opinion. Things like continuous torque, peak torque, and stall torque requirements as well as speed requirements would be interesting to know. Also, there are serious trade-offs between direct drive versus gearedâ€â€in general gearing make the motor much smaller and lighter, and the reduction in motor weight is much more than the weight of the gearsâ€â€so if you are going for lowest weight solution a gearbox is almost essential. From the analysis I’ve done, direct drive only makes sense if you are going for very high efficiency during ‘cruise†mode i.e. >95% electric->mechanical energy conversion while running at full speed. (At 0 speed efficiency is always “0â€Â, and the lightest way to get high starting torque will always be with a gearbox…)
Other applications for direct drive might be extremely long life applications where the gearbox can not be kept lubricated; but I doubt that this applies to e-bikes.
I’ve also considered making a brushed version of this motorâ€â€industry has gone heavily into the brushless motors because they have almost no wearing components and have no brushes to wear out. But machines in industry must run 1000’s of hours and maintenance is expensive. I believe the e-bike industry probably fits better into the consumer world, where brushed motors still reign supreme. (Ever worried about the brushed in the motor in your electric drill wearing out? I didn’t think so….) Any guesses how many hours someone (normal e-bike customer, not RAAM rider) might reasonably put on an e-bike?
Anyway, I appreciate your interest, you can pass on any thoughts your forum group has to me and we’ll take it into consideration. Check back in a couple of months and we can give you an update on how our development work under contract is going. What we learn doing that project should put us closer to being able to confidently manufacture a _product_ instead of a lab demo, at which point we can entertain low volume orders from customers such as yourself.
Best regards,
Michael Ricci, P.E.
VP Engineering
Launchpoint Technologies
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Above email posted with permission of Michael Ricci.
Up for discussion...