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Old 09-15-09, 02:40 PM   #1
cgattny
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Crank Motor vs Hub Motor

Hi All,

Help! I am a newbie and I am looking at several ebikes.

One is the R11 model sold by R. Martin in Austin, TX. I emailed Mr martin and he replied that the R11 has a 200 W brushless crank motor instead of a hub motor. He claims the crank motor is better than the hub motor because it allows the bike to get more climbing power with lower battery usage His website also states the crank motor allows the gears to be used with the motor. The bikes look good and I am wondering if anyone with experience/knowledge of this can say if the crank motor on an ebike is really an advantage over the hub motor.

Thanks.

Curt
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Old 09-16-09, 07:09 AM   #2
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Just about any motor coupled to the bike's gears will perform better than a hub motor of equal, or perhaps greater, power output. The mechanical advantage offered by gears should not be underestimated.

That said, chain drive systems tend to be more noisy, usually a whining sound. They are generally not very stealthy if you live in a bike-police state.

If I mostly rode where it's flat to moderate hills, I'd go with a hub motor. If there were lots of hills to climb, I'd consider a chain drive. Or do what I'm doing, use both, chain drive on the back, hub on the front
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Old 09-16-09, 11:17 AM   #3
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I installed the Currie conversion kit on my mountain bike this summer. The Currie kit has a non-hub, chain-drive motor on the rear wheel. One of the big pros of this system for me was the great torque. I'm currently living west of Glacier National Park in an extremely large national forest; there are very few flat areas to ride here. I wasn't riding my bike much at all before I added the kit because most hills here are steep and my knees were killing me. The Currie motor is a trooper and I've been having a ball riding the unimproved, gravel forest roads, many of which have quite steep grades.

There are users who love hub motors who claim great torque, but then they're generally using the high-end, expensive and powerful hub motors that will run you close to $1000. I think many of the hub motors that come standard with most generic Chinese-manufactured bicycles may not have enough torque to perform well in mountainous areas since they tend to be lower-powered motors to comply with e-bike restrictions imposed by the EU.

As for noise on a chain-driven, non-hub motor, I think it's over-exaggerated. I only use my motor for power assist and rarely have the throttle depressed fully. The wildlife out in the forest may look up as I pass, but I don't make enough noise that they bolt. In fact, I still have problems with the wild turkey who tend to cross the roads in number.
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Old 09-16-09, 12:28 PM   #4
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Thumbs up Crank motor vs Hub motor

Thanks for the reply. Very good information for me to consider. I do not have a lot of steep hills in my area, so i may go with the hub motor.

Curt
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Old 09-16-09, 12:30 PM   #5
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Thanks, MTBK. I appreciate the information you provided. I do not have lot of hills to climb in my area and may go with the hub.

Curt
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Old 09-16-09, 08:53 PM   #6
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Originally Posted by nwmtnbkr View Post
As for noise on a chain-driven, non-hub motor, I think it's over-exaggerated. I only use my motor for power assist and rarely have the throttle depressed fully. The wildlife out in the forest may look up as I pass, but I don't make enough noise that they bolt. In fact, I still have problems with the wild turkey who tend to cross the roads in number.
To each, his or her own of course; the difference between noise and silence in this case is deafening, metaphorically.
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Old 09-16-09, 09:11 PM   #7
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LOL, well given the deer and elk in the forest don't bolt when I've gone past them using power assist, I don't think the "noise" of my motor is deafening. They're definitely impartial judges. I have much more noise to deal with once I've reached the peak of a hill and am going down it (clearly with no power assist). Speed-generated wind is definitely noisy.
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Old 10-02-09, 05:47 AM   #8
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For hills and hubs you are looking at a 1000w kit at 48v. It has to be gearless and brushless. Anything less for most hills is going to be hard on your AH.
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Old 10-06-09, 02:07 PM   #9
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You can't beat a crank motor for going up steep hills. The problem with hub motors is that they develop peak efficiency at around 90% of their maximum speed. When you get to 50% of their maximum speed, the effieciency falls off a cliff so the motor is burning a lot of electricity, but not producing much power at the wheels.



What happens is that if your hub motor is designed for peak effiency at 18 mph so your 500 watt motor produces about 450 watts of real power to the wheel. When you go up a hill at 10 mph the 500 watt motor is only 50% efficient, so you only have 250 watts to get up the hill even though the motor is burning 500 watts of electricity. The steeper the hill gets, the less power you have to get up the hill. It is a vicious circle, you need more power for a steeper hill, but you get less power.



With a crank motor, the motor speed is directly related to your pedaling speed. If your crank motor hits peak efficiency with your pedals spinning at 70 rpm, then you can go up any hill spinning your pedals at 70 rpm by using your gears. The motor will be working at peak efficiency the whole time. This improves your hill climbing and range.



The important thing to remember is that an electric motor's efficiency depends on its speed. Generally speaking, the electric motors used for bicyles are fairly efficient from 70%-95% of their maximum speed. If their speed drops below 75%, then you start burning lots of electricity and losing power at the same time. This kills your hill climbing and range. If the hills in your area are steep enough that the electic motor cannot carry you up it at about 13 mph (assuming peak efficiency at 18mph), then switching to crank based motors would be beneficial.
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Old 10-06-09, 06:56 PM   #10
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Right on., crock. Therein lies my one complaint about crank systems which is noise. It's just not easy to keep a high speed motor quiet, plus the chain is always in use under power. Chains make noise as they serpentine sprockets, derailleurs and Teflon chain tunes (recumbents). The eerie silence of a hub motor has it's rightful place, IMO.
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Old 10-07-09, 09:45 PM   #11
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Good debate. Lots of good info here.
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Old 10-07-09, 09:57 PM   #12
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I have put around 10 miles on 4 different hub motors and around 100 miles on a cyclone 500 24 volt recumbent. On one of the hub motors I climbed a little hill. On the cyclone I have gone up hills of all kinds. Even though the hub motors were all 36 volt I know the cyclone 24 volt has much more climbing power. Since my hearing is not that good the noise of the cyclone does not bother me. Also with the cyclone on long rides I turn off the electricity on flats and extend the range many times. Even though my experience is limited with the hub motors I believe the cyclone will be my choice when I build my own ebike.
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Old 10-13-09, 06:10 PM   #13
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Where can I find a crank motor?

I'm sold on the advantages. Chief among them being, I can shift gears for the motor as well as for my legs. This can keep the motor turning at fairly high speed when going up some of the hills around here, thus keeping it in its most efficient range. Even when neither the motor nor I have the oomph to go 20 or 30 mph up that long, pretty steep hill.

If I lived in a completely flat area, I'd probably go with a hub motor. Since I'm in a hilly area, though, I'd MUCH rather have one of these "crank motors".

Anyone know where I can find one?
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Old 10-13-09, 08:24 PM   #14
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Where can I find a crank motor?

I'm sold on the advantages. Chief among them being, I can shift gears for the motor as well as for my legs. This can keep the motor turning at fairly high speed when going up some of the hills around here, thus keeping it in its most efficient range. Even when neither the motor nor I have the oomph to go 20 or 30 mph up that long, pretty steep hill.

If I lived in a completely flat area, I'd probably go with a hub motor. Since I'm in a hilly area, though, I'd MUCH rather have one of these "crank motors".

Anyone know where I can find one?
If you want a ready-made kit to install on a bicycle you already own, you might look at the one produced by cyclone. Here's a link.

http://www.cyclone-usa.com/store.php?crn=199
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Old 10-14-09, 11:16 AM   #15
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nwmtnbkr, great reference! Thank you!
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Old 10-15-09, 03:21 PM   #16
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Little-Acorn

Here are some other "crank drives"

I think elation is best, don't have one yet. It has a better mount, freewheel and allows 3 chainrings and a front derailer. It uses the Headline motor like cyclone

http://www.elationebikes.com.au/

epac similar to elation but same motor as eZip.

http://www.epacpower.com.au/Epac_Home.html

cyclone taiwan offers a lot more choice than taiwan-us

http://www.cyclone-tw.com/index.html
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Old 10-26-09, 05:32 AM   #17
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The thing about hub motors is there is nothing to fix ever pretty much. No noise, no moving parts and above all things no police bothering you when you ride. I have a friend with a cyclone kit. We hit the open space trails all of the time. He gets bothered by park rangers and police constantly. Most of the time because they hear him coming. I ride all over NYC and most of NJ on and off the road and have never even seen a police officer look at my bike because I have a hub motor and carry my battery in a nice backpack. I have never had to fix my setup. My friends kit requires constant upkeep of his chian and shifter. He goes through rear bearings alot as well. I have over 2k miles on my hub and the only thing I have done is true the wheel 2 times. Think about it before you buy.
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Old 10-26-09, 01:37 PM   #18
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One thing I hadn't thought about before: With a crank motor, if you use power, your pedals are ALWAYS turning. You cannot coast and let the motor push the bike for you.

I suppose you could put some foot pegs on the bike somewhere, high on the down tube I guess to keep your legs and feet out of the way of the pedals, but riding that would be a little awkward.

With a hub motor, you can coast with your feet resting on the pedals, and the pedals not turning, and let the motor push the bike for you, on level ground at least.

For those of you who regard e-bikes as pedal-assist power, you won't mind the pedals turning whenever you're using electric power.

But for me, lazy cuss that I am, I've changed my mind. I'm going for a hub motor. I'll pedal to start the bike off, and for going up hills, but for the rest of the time I'm happy to let the motor do the routine work, while I sit there (with feet still) and watch the scenery go by.
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Old 10-26-09, 02:19 PM   #19
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Quoting Crock...

You can't beat a crank motor for going up steep hills. The problem with hub motors is that they develop peak efficiency at around 90% of their maximum speed. When you get to 50% of their maximum speed, the effieciency falls off a cliff so the motor is burning a lot of electricity, but not producing much power at the wheels.


Crock, this is generally true as you stated...

I have a brushed geared motor which I have found to be quite efficient at all speeds, with oodles of torque compared to my Crystalyte 406 brushless direct drive. The brushed motor has the disadvantage of having to change the brushes every couple of years, but is effectively "start immediate" without the hassle of hall sensors which I have found to be problematic in wet environments like here on the BC West coast. Using a sensorless controller on those brushless motors to get around the Hall issues, they tend to run rougher with more cogging torque. So at the moment, I prefer the brushed motor to the brushless - not sure why brushed has almost died out - apparently the brushed geared types are about as efficient in general as direct drive non-geared (around 90%) but these efficiencies are obtained at low speeds as well as high speeds. And you get the torque bonus off the line, with good freewheeling. It seems that changing the brushes is the only disadvantage. You also get a considerable saving in weight. Unfortunately, I haven't been able to identify my motor - I aquired 3 of them from a failed business. The controllers are really cheap too, around 24 US plus shipping from ecrazyman on ebay, very easy to set up.
I've got mine on a Giant Revive comfort bike, and totally love the motor overvolted to 48 from the original 24. The gears are holding up well so far after about 300 miles. I generally pedal as well, considerably. I'm pushing close to 900 watts through that little 8 pound motor, top speed around 25 mph at 48 volt Ping 15Ahr battery. It really hauls me up the hills too. So these might be worth checking out if you can find other brushed geared types..


Here is my bike and its motor...

http://endless-sphere.com/forums/vie...hp?f=6&t=13255

Last edited by chvid; 10-26-09 at 02:25 PM.
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Old 10-26-09, 05:03 PM   #20
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Just to throw in my 2c...I'm hub motors all the way.

I may be biased by my TidalForce that I bought in 2004. It's gone 7,000 miles without touching it, and in utter, complete silence. It climbs very steep grades even with the heavy grocery and laundry ladened trailer attached.

Just got a new Chrystalite 4840 Racer a while back that I've been pushing me and a heavy custom built trike (550 lbs together) around with. No lack of power but that's close to 2,000 watts. It does make that buzzing "errerrerr" sound though.
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Old 10-26-09, 05:24 PM   #21
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"One thing I hadn't thought about before: With a crank motor, if you use power, your pedals are ALWAYS turning. You cannot coast and let the motor push the bike for you."

Not so; my Ecospeed freewheels. I can pedal, use power or both, independently. Can't speak to other crank systems.
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Old 10-28-09, 07:43 AM   #22
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Like the one guy said - chains and sprockets are a hassle. When you start delivering considerable power through 'em they wear much faster. Lube, adjustments - messy and noisy!

A lot of the downside about hub motors is because manufacturers have offered too small of motor. If you get into hub motors that can handle 2k watts or more - Crystalyte 5000 series for example - the comparisons change dramatically. Sure, compare cheap Chinese hub motors to geared setups and there's no comparison but those are designed by salesmen - not engineers. Get a hefty BLDC hub motor going and you'll have much less maintenance (other than spokes, lol...) than even the best chain system and a very stealth and simple installation that, in many cases, can be transfered to other bikes rather easily.

They each have their advantages and disadvantages - I have run both for years and I've learned that if I have a big enough hub motor and no extreme grades the hub motor is much less trouble while delivering practical performance for commuting.
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Old 10-30-09, 04:37 PM   #23
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while I sit there (with feet still) and watch the scenery go by.
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Old 10-30-09, 04:56 PM   #24
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BroadwayJoe is right I believe. Where I ride though, I'll stick with my cranker. I tried walking up that hill, once...
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Old 10-30-09, 10:05 PM   #25
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hub motor all the way. the multi gear setting is overrated. In theory, it makes for a good debate, but in practice, it's a waste of time. Chain drives make a little of noise, but not a lot. hubs are nearly silent. the only time that chains would have an advantage would be with very steep hills, above 15% grade. I have a cheapo wilderness system, and get up hills fairly easily with a little assist.

I come from using multiple chained gas systems, and while all were faster than my current electric, none were as simplistic. I leave my bike in the rain ffs, and it's not an issue. I do keep the controller very well shielded from the elements.
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