Recently I got hold of a new e-bike drive system to test out on my cargo and kid carrying Surly Big Dummy.
The motivation is that for myself and many out there using cargo/sports utes, we sometimes have big loads strapped to our bikes, and in a place like Chapel Hill, big hills to climb with them.
That taxes the standard electric bike hub motor system. Some can handle it, but constantly pushing their limits may ultimately lead to failure. ( the same can be said for one’s legs – which is why I use a an electric assist on my cargo bike).
One solution to this problem has been the Stokemonkey. Instead of a hub motor, it uses the bike’s existing drivetrain – and gears. So, when you’re climbing a hill with it and you shift into a lower gear to give your legs a break, you’re giving the motor a break too. This increases overall system efficiency, and motor/battery system longevity.
But there have been two limitations to the Stokemonkey: limited supply (it is produced in small batches by our supplier in Portland, Or), and it only fits on Xtracycle-style cargo bikes.
A few brave designers have tried to crack this same nut with a system that doesn’t require an Xtracycle style frame.
The first was the Cyclone. I don’t have any experience with that system, but have heard certain things that have put me off from trying it – mainly that the installation is very involved.
Now comes the Electric Mountain Drive from the folks at Ecospeed (also from Oregon!).
It is another electric assist system that uses the bike’s own drivetrain, benefiting from the gearing on the bike to reduce motor strain and increase climbing ability.
I’ve been using it for about two weeks now, so this review is only preliminary.
Here are some benefits of the system:
- Because it uses the bike’s drivetrain, it can handle steep hills without strain (if I shift into the right gear)
- It mounted to the frame in a relatively straightforward manner
- It uses a standard electric bike brushless motor controller, so when the first one died (a note on that later), I was able to swap in an Infineon controller we had in the shop
- Using only a 36 Volt battery with a controller consuming 20 amps, the bike can achieve powered speeds of up to 25mph+ (depending on headwind and hills). Most of the hub motors I’ve tested – even the high speed ones – can’t do this on only 36V 20A system. For me those would top out around 22mph on the flats, pulling maximum amps.
- Its installation wasn’t too difficult, and the instructions were very detailed.
For certain kinds of applications such as steep hills to climb on a cargo bike without a spot to put a Stokemonkey, this appears to be THE solution.
But it does have a few drawbacks to be aware of:
- It is somewhat noisy. It is not louder than the cars on the road – but not a lot quieter, either. I like to operate in “stealth” mode on my local bike path so as to not get any of the other users upset that I’m using electric assist. It is hard to do with the EMD, unless I just entirely leave the electric off. That’s fine… except for that I’m usually in a hurry (note: I never, ever use the electric assist to exceed 20 mph on the bike path, and I always slow down for other users – doing otherwise would not only be rude, but would likely land me in trouble). Also, the way it mounts on the bike makes it more obvious that the bike has some kind of motor attached.
- I found the overall system efficiency to be disappointing – which means that I can’t travel as far on a single battery charge. When I used the eZee hub motor, I typically got 18 watt hours per mile or better (at 36V). That meant I could do a 20 mile roundtrip with my 10 amp hour battery. With the EMD system, I’m getting at best 24 watt hours per mile, reducing the range to around 15 miles. I think there are three factors causing this: a) It uses a chain/gear system with a oneway clutch that may loose energy; b) Some energy may be lost in my Nuvinci continuous variable transmission; c) it is easy to go too fast with the system, which always sucks down juice very fast (any speed over 20mph on an e-bike is usually quite inefficient). I’ve tried to keep the speed low, and still had poor efficiency. At some point, I’ll try it out on a bike with a regular rear transmission using cassette and derailleur, to see whether that makes any difference.
- The first controller fried within only 1/2 hour of operation. It turns out that the motor and controller are made by BMC. BMC makes decent motors… but their controllers have a not so good reputation for reliability (we won’t sell them anymore after a failure rate of over 50%). We replaced it with an Infineon, which has worked well so far (an is in general a very reliable controller). To their credit, Ecospeed did send us a new controller right away, and it is a different design. But it is still made by BMC. I think I’ll keep the Infineon for now.
- It requires a bike with a circular downtube – the tube from the handlebars down to the pedals (many bikes these days have ovalized downtubes). And, once installed, it does protrude down a bit.
Another attribute I noted that is neither plus nor minus is that to optimally use this motor, I had to get in the habit of shifting the bike appropriately. This requires letting off the throttle a bit, doing a rapid shift, then getting back on the throttle. At first it was a bit clunky for me – but just like learning to drive with a clutch and gearshift, once I picked it up, it worked well. I have come to enjoy the challenge of shifting properly through an acceleration cycle to get up to speed.
Bottom line: The EMD will be a perfect solution for people who have big/long hills to climb, and provides a worthwhile alternative to the Stokemonkey, especially if the latter isn’t available or if it won’t fit on your bike.
My assessment is that hub motors will be better for the person who has moderate hills, long distances, or is concerned about noise. Since I fall in several of the latter categories, I’m likely to return back to a hub motor system at some point.
Cycle 9, I’m guessing this was written by Morgan, but if not, thank you to the author so much for posting initial impressions and experiences with the EMD system. There is so precious little posted on ecospeed kits on the net. It’s great to be hearing real world experiences from an experienced electric assist cyclist and scientist. I see this kit, and the people who make it, as very progressive. They are trying to give the cyclist the best of everything: lighter weight, more torque for a given power level, unmatchable hill climbing and highspeed for the size, weight and power of the motor, and system quality – which should translate to owner satisfaction and the best levels of reliability over the lifetime of the kit.
From a physics standpoint, I don’t see how a hub system without the “through the gears” advantage can be as efficient, let alone more efficient. Simply because the speed of rotation of the motor is the single largest variable for efficiency, all else being equal. Although a hub and EMD can theoretically be equally efficient, this would only be in the ride envelope where the motors were turning the same speed and producing the same power. In practice this is only happening at around the 12-17 mph area. An important area because most riding time should be spent there for aerodynamic resistance reasons. BUT, everywhere else, slower and faster, the efficiency stays pretty much the same for EMD while the hub efficiency drastically falls off. And on hills, if you aren’t in the optimum motor speed range with a hub motor you are REALLY inefficient while the EMD is again at optimal efficiency because with the through the gears transmission the motor speed can allows be kept in its optimal range.
Ecospeed explains this nicely with graphs on these pages:
http://ecospeed.com/emddet.html
http://ecospeed.com/motdet.html
So, as you suggest in your post, I think it would be GREAT if you can do some comparative testing for us. Ecospeed should be doing this but they don’t seem inclined which is understandable but in my opinion leaves a, valuable for them, demonstration of the superiority of their kit against hubs undemostrated. If someone would equip two identical bikes with identical loads, batteries, and rider inputs, where one is a hub motor of similar continuous and peak power rating and the other an EMD, we could at last see what is what in performance, usability, and efficiency. Showing real time data from their “Cycle Analysts” side by side they go up a moderate hill, side by side they go up a steep hill, flat riding at various speeds, and coasting efficiency i.e. what if any drag the systems produce when coasting, motor off.
From a physics standpoint the hub motor could approach the EMD in only one area of the performance envelope. That would be constant speed at the hub motor’s optimal motor speed for power and efficiency. Everywhere else the EMD should drastically outperform any hub of similar power rating in both performance and efficiency. On hills and at high speed and acceleration, the EMD should leave the hub systems far behind. And in comparison to any hub motor of sufficient power to match the EMD on the hills and at low and high speeds, that hub system would be drastically less efficient and suck the battery down at several times the rate of the EMD in those extreme areas of the riding envelope.
The EMD can do the entire envelope of required functioning without restriction. And this isn’t because hub motors are inferior, but simply because the EMD’s motor output is transferred to the wheel through variable gears. This requires extra expense, complexity and noise (for a lightweight motor). Those are the admitted trade-offs. But for the cyclist looking for a system that can do it all and do it with the highest efficiency, nothing other than the Optibike can match the ecospeed systems for performance, lightweight, and longevity (unreliable controllers aside, smile ). The other current through the gears systems simply don’t have the quality, and the stokemonkey by design does not allow for motor use with the rider not peddling. I.E. when the stokemonkey motor is on, the cranks are turning and the rider must peddle along if only to keep their feet on the pedals. This is a point that stokemonkey admits freely to their credit but didn’t come up in this post. The EMD can run with peddle only, motor and peddle, and motor only cranks stationary, as the rider prefers. Complete flexibility for the rider, no compromises. And the EMD’s motor is a lot lighter and smaller. Reliability, longevity, performance comparisons are unknown to me.
By the way, ecospeed’s new fully digital controller is now available. They claim unmatched efficiency, adjustability, and performance. Maybe you can get a hold of one of those to test. I’m not aware of ANY posted independent testing on that controller.
Stick with the EMD. You may get used to the noise and find that as the miles pile up the reliability, efficiency, range, and just plain do anything that rises before you bike strengths will win you over. If not, I’d be so grateful for the stories and insights. It’s a system I am very interested in and I appreciate and will appreciate all the testing and posting you can do. Your efforts towards educating us prospective electric riders is rare and very much appreciated by myself and I’m sure countless others.
If you can talk Optibike at optibike.com into a bike lend and review for us, that would be GREAT !!! smile. You could pull a trailer with a “tub” bolted on for the kids. It would be great to hear your reviews for trailers from: http://www.bikesatwork.com/ and http://www.tonystrailers.com/.
Thank you,
Floyd
Hi Flloyd,
Thanks for your great comment.
I have removed the EMD and moved onto testing a Nine Continent hub motor.
Honestly (and this is just personal preference), I like the hub motor better. There are people for whom the EMD will be perfectly suited, but that wasn’t the case for me.
My hills are such that I can maintain that “sweet spot” speed range that is perfect for a hub motor. Only a few hills around here are so steep that I get into the < 10mph inefficiency range, where the EMD would really shine.
But I've found that, for my regular cruising speeds (17-22 mph), the NineContinent is a bit more efficient, and definitely more quiet.
I agree with you and the designers that hub motors have a limited range of efficiency.
But I believe that for a motor like the nine continent, IF you're within that range (15-20 mph at 36V for the standard wound motor), then the efficiency is very high – as much as 85-90%.
My experience indicates that the EMD efficiency is never that high, though it maintains its efficiency over a broader range of speeds.
So for people who are grunting up long steep hills, the EMD will shine. Maybe if/when I move to the mountains, I'll get a chance to test it under those conditions.
But for rolling hills with occasional steeps (we do have some hills ~25% grade, but they only last for a few hundred yards), I'm pleased with the hub motor silence and efficiency.
Thanks again for your note!
(and ps – your idea of me testing the Optibike is a great one! We're going to start doing more in depth testing of some motors soon)
Hi Morgan,
Just read your response to my post. Thank you for sharing additional insights and thoughts. Interesting and enjoyed. I have to agree that most of our riding with an electric assist CAN be done in its “sweet spot”. If 90% + of a rider’s routes are mostly level or just short hills done near the optimal speed for the hub motor’s powere and efficiency than the trade off against an EMD is minimal. I completely agree. And like you, I am VERY much attracted to the quieter nature of the slower turning hub motors. So your points are very well taken. And fact is my riding routes ARE 90% flat 90% of the time. A quality hub motor would do the job for me without a doubt.
There remain many performance advantages to the EMD as you agree. The lighter weight, the less stress on the motor when working hard, superior acceleration and hill climbing. But at the end of the day, most of us are just cruising, some faster, some slower, and the hubs do the job. AND, by nature I’m very much an easy does it cyclist. I like to go slow and “smell the roses” as I cycle. A gentle assist is all I’m looking for. Something to spare my legs and leave me feeling strong at the end of my “getting from A to B” rides. At 50 I don’t have endless reserves for all the riding I enjoy doing. I’m looking for the assist to give me the same speeds I do now, 8-10 mph, with half the effort. That ratio would keep me refreshed day to day.
Money no object, we’d all have several bikes. Each set-up for the particular type of riding we plan on doing that ride. Enjoyable pedal only bikes, an optibike or EMD for “adventurer” and high performance riding, and cargo rides for shopping and kids transport, smile. Your assisted cargo bike set up IS the do anything combo in one machine.
Again, thank you so much for taking the time and sharing your experienced cyclist, real world experiences with me and others. I intensely look forward to the day when my finances improve and I can finally choose with confidence the system that will work best for me. The insights you share are invaluable.
I will enjoy your every posting and further system reviews.
Regards,
Floyd