"Crank drive" or internal hub? Which to choose

6 replies [Last post]
VishnuTensleep
VishnuTensleep's picture
Offline
Joined: 06/15/2008
Points: 8

I am new to this game and would like some advice. I live in Seattle, which has significant hills, and lots of rain. I weigh about 210, and am an avid human-powered cyclist. I don't mind pedaling, but my goal is to replace some 10-15 mile cargo-hauling errand trips for which I currently use my car - e.g. the awkward 4 bags of groceries and a can of paint. My criteria are a range of 15 miles with an average speed of 10 mph with a bike trailer.

I've been looking at the various options for converting a std bike to partial battery power, and the options seem to fall into two camps: internal hub motors (e.g. Crystalyte) and "crank drives" (e.g. Cyclone). Based on the info I can find, there doesn't seem to be a significant difference in performance - seems like I can spend maybe $500-700 for either a setup like a 48V Crystalyte RoadRunner or a Cyclone 500W kit, and get approximately the same performance.

The main advantages / disadvantages of each I can see are that the internal hub gives more protection for motor to everpresent spray of wet oily road grit on winter Seattle streets, but involves the whole rear wheel and so if the rim gets wiped out there's more work to getting the bike back up and running. Converse for crank drive.

What am I missing?

VishnuTensleep

------------

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.
reikiman
reikiman's picture
Offline
Joined: 11/19/2006
Points: 8454
Re: "Crank drive" or internal hub? Which to choose

One thing you might be missing is the mechanical advantage of having the motor connecting to the gearing rather than being inside the wheel.

__________________

- David Herron, Green Transportation Examiner, Green Transportation Info, The Long Tail Pipe, Electric Race News, davidherron.com, 7gen.com, What is Reiki
- Charger bike (rebuilt), Electrified Electra Townie, 1971 Karmann Ghia

dogman
dogman's picture
Offline
Joined: 04/29/2008
Points: 830
Re: "Crank drive" or internal hub? Which to choose

Exactly, the crank drive lets you use the bikes gears to get up hills. That's real good for huge loads. Most of us running 48v hub motors fly up hills like superman though. I really like my schwinn trike for grocery runs under 8 miles, see dogmans bikes in the WE section for pics. But for 15 miles out and 15 miles back, no charging, that takes a more efficient bike and a really expensive battery. Anything very far, like 20 miles round trip, I still use the subaru. My commuter bike goes about 20 miles, but I don't like to ride it much further than 15 to keep the battery happy.

__________________

Be the pack leader.
36 volt sla schwinn beach cruiser
36 volt lifepo4 mongoose mtb
24 volt sla + nicad EV Global

spinningmagnets
Offline
Joined: 12/12/2007
Points: 295
Re: "Crank drive" or internal hub? Which to choose

Disclaimer: I dont have one yet...

I vote for the cyclone crank drive. The two benefits are that by using the stock gearsets you can easily trade some speed for hill-climbing torque without overheating the motor or controller.

The other benefit is that you will get more miles from your battery pack. Or, conversely, the same miles while dipping less into the batteries Ah capacity, which can lead to longer battery life (for lead/acid). Charging deeply discharged lead/acid batteries will cause erosion of the plates. So, using twice as much battery can last 4 times longer before replacement rquired.

When using lithium or NiMH, I'm told you can use 90% of Ah without damage.

deronmoped
Offline
Joined: 12/25/2007
Points: 342
Re: "Crank drive" or internal hub? Which to choose

I have a Giant LaFree, a crank drive. What these guys say about the added hill climbing is right on. Today I went off road for the first time, I came upon some dirt hills that were almost impossible to climb on my regular mountain bike, I just put it in low gear and zipped right up them. What impressed me even more was whenever I tried to climb them with a human powered mountain bike, I would almost always lose traction, sometimes forcing me to put my feet down. With the Pedelec traction was not a problem, do not what the different is, but the not losing traction makes a big differance.

Deron.

tropmonky
Offline
Joined: 07/02/2008
Points: 25
Re: "Crank drive" or internal hub? Which to choose

Deron, The difference is that without having to pedal you are able to keep steady pressure on the bike allowing for greater traction. Try climbing up the hill with the power on and then hopping your body up and down like you are peddling hard, I bet it will loose traction.

I've been looking at starting a new EV bike and am having a hard time figuring out how to start, or rather what to start with. I do think that the crank drive 1000w system with a really nice downhill MTN bike would be Sweet, however just the MTN bike is a little too expensive for me to start with right now. I was thinking of starting with the Mongoose CX200, even though it's not a crank drive it looks like a good starting point.

My thought would be to see if it's possible to use a 7spd internal gear hub with the motor side...

Kyle

spinningmagnets
Offline
Joined: 12/12/2007
Points: 295
Re: "Crank drive" or internal hub? Which to choose

As I'm sure you know...

In the cyclone kit, the crankset must be a part of the frame (instead of part of a rear swingarm), and also have room between the frame front and the front wheel (Hmmm, may also be possible to mount motor in triangle space with longer chain?).

When pondering the Cyclone, I noticed that my current (non-EV) cheap-used MTB bike has the crank-set as part of the the rear suspension arm. I am in the market for a more substantial bike anyways, so I was glad to notice I want a frame-mount crank to ensure the Cyclone option.

http://endless-sphere.com/forums/viewtopic.php?f=1&t=3921

If a friend wasn't very mechanically inclined, and lived in a fairly flat area, I think a 408 hub-motor would still be a great option for him.

Front drive is apparently good in slippery weather, results in 2WD when pedalling, and balances the weight of a rear battery pack.

Rear-drive makes having a front disc brake easy (also easier to remove front wheel if transporting in a car rack)

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.
Customize This