Electric Bikes - Anyone know the Kettler Obra? Compare to Kalkhoff?
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03-20-12, 05:47 PM
It looks a lot more expensive than the Kettler Twin, a website for a store in San Francisco says as the difference:
powerful hydraulic rim brakes and a larger range Nexus 8-speed hub
I'm not very knowledgeable, but how important are the hydraulic brakes for Bay area biking--and I live atop a STEEP, BIG, hill? Are the Twin's brakes good enough?
And anyone know how the Kettlers compare to the Kalkhoffs?
The biggest advantage in brakes over the rim brakes both companies offer would be disc brakes like those offered by Ohm which that shop also sells apparently.
Both the Kettler and the Kalkoff bikes use the Panasonic mid drive system which due to their EU regulated motors you have already been informed would be hardpressed to make it to the top of your hill without some hard pedaling. The Ohm that shop sells uses a Bion X system which also would be hardpressed to make your hill without some real effort to the pedals.
The reason I know this is that I own and have used both systems and tried them on steeper grades. They do fine in rolling terrain but lack the torque to do the steeps because they are less than 500w and here in the US you can have twice that which will get you up there.
Still think you should go see the other shop mentioned that adapts kit motors to the bike of your choice as they will be able to provide you with the power you need and also advise you on the brake system that best suits it.
03-21-12, 11:11 AM
Mabman, thanks, yes I am going to try and test ride this weekend.
I hear what you say about the European restrictions on wattage, but AllenG and others seem to think that the Panasonic inline motor is really powerful enough. Also Sarahlou of a few months ago loves her Kalkhoff and feels like it is a dream going up hills.
Obviously the test drive will be the proof. I am coming to the idea that the BionX is NOT powerful enough--but then again, why would a local, specialized, SF e-bike store sell something that won't make it up SF hills? So I need to see for myself and I'll report back.
Going up hills is not about horsepower (watts), it's about torque.
My Panasonic is a 350 watt drive. Put my internal gear hub in a low gear and it will out pull my 500 watt Heinzmann hub motor I have on my Baria. There is no contest. Hub motors have a 1:1 drive, that's it. Run that through a hub one can gear down and what you get in return is torque. Lots of it; so much so that on my Panasonic I cracked a few hubs because I was out torquing them (disclaimer--my Panasonic is attached to an Xtracycle and I out torqued the hubs when loaded with over a hundred pounds of cargo).
Difference between torque and horsepower (http://www.straightdope.com/columns/read/2215/whats-the-difference-between-horsepower-and-torque).
Torque refers to the amount of work a motor can do.
Horsepower refers to how quickly an motor can perform.
My Acura has a 200 horsepower engine. My Massy Furgson tractor has a 35 horsepower engine. My tractor can quite literarily drag stumps out of the ground. The Acura has nowhere near that pulling force. The Acura can go faster, but can't pull a load anywhere near what my tractor can. Bring your car to a full stop on a steep hill, put it in its top gear and let the clutch out. It'll stall because it has insufficient torque to move forward. Put it in first and let the clutch out and up the hill you go. You haven't increased the horsepower by gearing it down, you have increased the torque.
Oh, I spoke to SaraLou via email the other day. So far she has not had any issues with her Klakhoff. The only maintenance so far has been pumping up the tires and putting the bike on its charger. You are going to find that Kettlers have similar performance. Both companies use high quality components. Panasonic will not license their motors to companies that use lower quality parts.
i agree with everything that Allen says in theory but the reality is that in CA you are allowed to have a 1000w motor. As I said I have a Panasonic, and a Yamaha, mid drive and they do take good advantage of the bikes gearing but my 48v 1000w hub motor will outdo either of them on steep terrain yet stays within my states restrictions on top speed (20 mph) because it is wound for torque not speed which in a 1:1 situation you get to choose one or the other. If Panasonic made a higher wattage motor it would be great but they probably never will just for the US market.
I also prefer a throttle over a pedal assist system and still pedal all the time because I like to pedal. I find that I can find a better cadence relationship to the motor that way and like it better for stops and starts. Try both and you will be able to decide for yourself.
The difference there is you are sacrificing range. It takes almost three times the juice to run a 1000 watt motor than it does a 350 watt motor. If you want to go fast, more watts will get you there quicker. If you want to pull a load then what you need is gearing.
The upside to inline motors is they utilize the bike's gears. The downside to Panasonic's system is that the frame has to be specially built to accommodate the motor. Hub motors can be fit to nearly any bike that has wheels. The downside is they have limited gearing.
Not necessarily as far as the range issue goes according to the way I ride. My 48v LifePo4 battery is 12ah and the BMS shuts it down at 9.36ah. Over hill and dale I can get close to 40 miles of range out of it using mostly WOT pedaling in gearing on top of the motor. This is a while averaging 18 mph. With my mid drives and Bion X bikes I am lucky to get 25 miles out of them averaging 13 mph in the same terrain in PAS mode. YMMV of course but that is how it works out for me.
This is the mid drive system that I would like to try out: http://www.bosch-ebike.de/media/ebike/dokumente/englisch/Flyer_eBike_Speed_eng_final.pdf It is a step in the right direction as far as a bit more wattage.
What batteries do you have on your other bikes?
04-18-12, 04:13 AM
So OP, did you go for your test ride? Thoughts?
So OP, did you go for your test ride? Thoughts?
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