bigdummy27

I just picked up my cetma cargo bike with a bionx rear hub motor. If anybody has any questions about the setup feel free to ask.

I also got a question for anyone who had a similar experience. Everytime the bike goes over 17 mph the front wheel, which is a 20", will wobble violently. The front box isn't loaded so i think it might be the bike lifting slightly off the ground just enough to cause the wobble. Any info is appreciated.

powell

What BIONX electric kit you have installed on that bike?
I cannot imagine front wheel would lift due to power applied ESPECIALLY on such heavy front ebike like yours.
BIONX has quite weak torque to lift front on any MTB bike , it is computerized intelligent system , throttle rump up , no jerking like cheap CHINA analog drives.

15rms

I would be interested in knowing what system it is and what kind of range you are getting? Also is level one or two giving you enough boost so you could enjoy a long extended ride?

bigdummy27

Powell, the kit is a Bionx PL350 36V with the 10AH battery pack mounted on a rear rack mount. We biked yesterday from Manhattan to Queens, a 12.7 mile trip and I didn't notice the problem. The bike was not loaded when I first brought it home when I noticed the wobbling. On the trip to Queens I had both my daughters, one is 6 years old and the other is 2.5 years old, in the box, so I estimate thats around 80 lbs in the box. Although, I'm not sure yet, because I rarely got a chance to go over 17 mph for any extended period of time except on the 59th Street bridge coming down. I did hit speeds exceeding 17mph, but I was testing the regenerative brakes and wasn't really looking for the wobbling. I will look for it when I ride back to Manhattan today.

You are right, the acceleration is very gradual and smooth, but still quite satisfying.

fietsbob

Steering geometry, is what it is, ... If its fine at 15 MPH? then don't exceed that speed..


IDK, You use the motor Build in the front wheel?

bigdummy27

you can see what system I have by reading the other post in this thread. As for the range of the system, I regularly ride with cargo so it is always lower than the rated range. During yesterday's ride I was carrying around 50lbs of cargo and started with a fully charged battery and ended my ride at around 20 miles with one bar left. If it remains this way, than I will be satisfied.

I don't think level 1 or 2 will be sufficient for my needs since I use the bike to commute between manhattan and the other boros and the route is not very level. The commute averages around 10 miles one way. But this is just me and I am still getting use to the system.

bigdummy27

I might have found the problem with the wobbly front wheel. I was talking to the owner of Hudson Bikes in lower Manhattan and he tells me that he notices the same occurrence among the other box bikes he has ridden and it goes away , although not completely, if he loosens his ride on the handle bar and just let the ride find its own line. I tried it afterwards and he was right. Is there anyone who can explain this please let me know. I'm very interested in why this happens.

bigdummy27

No, the motor is in the read wheel.

fietsbob

Overdriving the Keyboard .. Looks a little slow for the typing ( proofreading ) too..

Carry on .. keep the speed down ..

cerewa

The wobble probably has something to do with the geometry of the bike. If that's true there isn't much you can do beyond what you already know-- relax your hold on the handlebars if that works... and/or keep the speed below 15mph

croppera

This is an old thread, but I just found it and felt that it was worth saying that my Cetma cargo -Largo does not have a front wheel wobble. I have had it up to about 25 mph and never felt a wobble with or without cargo weight on it. Ok, not totally a clear answer - it is never without weight completely as the stoke monkey e-assist, battery and box add 35 or so lbs. to the base of headtube area. I don't tend to let it roll faster than that as I am not comfortable with the speed and precious cargo.

I don't know what could cause your wobble, but I would hate for folks to assume that it is inherent in the general design and all cetmas wobble.

Also, would love to hear an update on your bionx and how much power you tend to use with it. Do you know how many watts you average per mile with general use? I roll with three kids in the box - a current total of 109 kid lbs and growing. I seem to be averaging 16 watts/mile with my local rolling hills. I keep hoping fitness will bring the watt/mile down, but I am not sure that my fitness will grow faster than the kids.

Cheers.

nliang

I don't know anything about front wheel wobble on a Cetma Cargo but I do have a 48v BionX 350 kit installed in my HP Velotechnik Scorpion trike which weight in at about 72 lb. I have put almost 3,000 miles in my trike and the power consumption is around 5.2 watts per miles if I keep the average speed to around 15 mph.