Electric Bikes - I need some help and advice
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06-19-08, 06:30 PM
I recently converted my old sears bike to electric with a Chrystalite 408 motor, and 36 volt setup with SLA batteries from www.itselectric.ca (http://www.itselectric.ca) in Calgary.
Since May 14 I have been commuting to work 5 km each way to work, with a steep hill 5% grade on the return trip. Then once a week, I go up the opposite hill of the valley up a 6.5% grade for 3.5 km to a radio tower I look after, then roll back down into the valley, across the river, then back up the opposite hill to return home. That one-way trip is 11.5 km.
Rolling to work, the battery takes only about 45 minutes to charge, the return home trip, its about 3 hrs to charge. The once a week long trip the battery takes nearly 5 and half hours to charge.
Everything seems to be working fine, except that I get a vibration or a resonatant frequency from the motor when it is under load, when it first takes off, and right around 18 km/hr. This vibration will come right thru the frame of the bike, and can make my hands feel like they are going numb.
Is this normal??
I can simulate the whole thing with the bike on a stand so the motor is freewheeling, and it will still cause that vibration.
The people at itselectric were going to send me a new controller, but I am not sure that is the problem. I had gotten a wrong controller to begin with. I got one for a regular twist throttle, but mine is the one with the indicator lights. I used the wrong one until the new one arrived, and it did the vibration on that both of them
I have taken some video's of the vibration, but need someone to tell me how to post them somewhere so others can see them. I basicly just held the camera on the handlebars and it will vibrate thru it. Once its at the full speed of 27 to 30 km/hr its fine.
I checked that the spokes are tight, I checked the hall sensors by putting in 12 volts on the input and reading about 6 volts out on each line at 8 different spots when the wheel is rotated. The bike is a heavy old Sears 18 speed, and I put on fenders, saddlebags etc. The bike with all that crap and the conversion is 92 lbs, and I am one more cookie under 195 lbs, but it pulls me along fine on the flats and with regular effort on the hills. When I biked the hills before the conversion, it was way more than regular effort for me on those hills!!
The hub motor is in the front, the batteries on the rear rack.
If I just push my bike without the power on, I can faintly feel that vibration, which I am assuming that is the magnets passing the coils in the motor.
Can anyone help!!!!!!!!!!!!!!!!!
It almost sounds like the axle on your hub motor is slightly bent, and the motor is causing it. Give that a check! Good luck.
06-19-08, 08:09 PM
Please correct me if I'm wrong, I'm still just learning about these kits, but isn't the number the model controler you're using (eg. 3620, 4820, 3625, 4825, 3640 and 4840)? I've only seen the motors listed by names (Sparrow, Roadrunner, Brute, Cruiser Racer). And if your controller starts with 48 then it's meant to be run on 48V not 36V like you said you're running. I don't see how this could cause the vibration you're describing but it could be bad for the controller.
Also, the vibration happens when the motor isn't powered. If the coils aren't powered the magnets moving over them induce a minor current but it shouldn't be enough for you to really feel the reistance.
What's the frequency of the vibration? It possible the wheel is off-balance?
The video would probably be helpful. You could create a youtube account:
06-19-08, 09:46 PM
The bent axle theory sounds possible. When the kit was delivered the plastic protector on one side of the axle was broken, and a mark in the cardboard box.
At the time I didn't think anything of it. How would I check it is bent?
The controller was matched up by the company I bought the kit from. I think the 408 motor is the same as the Roadrunner. The motor will run on 24 to 48 volts I believe. And the controller is the Crystalyte 36 volt 20 amp immediate start controller.
I had thought about finding something that can measure the frequency of the vibrations, and have a buddy who is a machinist I will talk to.
Thanks for the link to YouTube.
While I am writing this I am uploading the video's and will post the links shortly
Keep the ideas coming!
Tell me about how it should be when the motor is running, what happens if you don't pedal on a hill, does it just stall out or what?
06-19-08, 09:54 PM
First video is the wheel freewheeling.
The second one is the camera sitting on the handlebar the metal part.
The buzzing starts around 14 km/hr, then at top speed settles right out again.
This last one, the first couple of noises you hear was the tire rubbing on a tool box beside it, then the vibration, then again clearing at full speed
Let me know what you think
First thing I would do which wont take long, is take off the tire and do the same thing. If the noise is gone, its just a badly aligned tire on the rim. If it still does it, then you know its the hub.
06-24-08, 10:35 PM
I just did the thing about removing the tire and trying it. Same thing.
The bike is on a jack stand, the front wheel free to spin off the ground.
Still have the vibration. I cannot feel the vibration at the axle nut, but just above it on the forks all the way up.
I am still trying to get my hands on test gear that can measure the RPM and the frequency of the vibration, but so far no luck.
I am thinking maybe on the weekend to even mount the wheel into a entirely different bike frame to see if its a sort of resonant frequency of my bike frame.
If anyone has more suggestions, pass them along, and I will try things as I get time and get back with what I find
06-24-08, 10:37 PM
One more thing, as I have never really rode an electrified bike before, what noise or vibration do other people get from their bikes, and what happens when it is under load up a hill.
If you don't pedal will it stop, does it do it quietly, or what noise does it make??
I guess WORST case scenario, there is some hairline cracks in the fork or frame that is causing the vibration.
07-02-08, 10:18 AM
Well, so far I have changed the wheel to a different bike, with the same result.
I am now awaiting a new controller from the dealer, and if that doesn't work, then the wheel itself
will be changed.
The theory is that the controller does not always know what position the motor is in, so it is
"Hunting" trying to find the position, thus the vibration.
However it turns out, I will post on the board.
Thanks for the replies to date to everyone!!
07-02-08, 12:01 PM
I have a front hub motor (thread here: http://www.bikeforums.net/showthread.php?t=434383).
When going up a steep hill or from a standstill with no pedalling, the hub makes more of a noise. To reduce this noise, I increase my pedal effort until the bike is rolling along before giving it full throttle.
07-02-08, 12:55 PM
Thanks for the reply puppypligrim, That is the same as mine.
However, it does the same thing when the bike is freewheeling with the motor off the ground.
I kind of expected some noise when it is under load, but it will do it without a load, and the noise will
vibrate through the frame to the point where it makes my hands numb.
But, like yours if I pedal more, or reduce the throttle, it goes away. At full speed, it is gone too
07-02-08, 01:17 PM
I saw your video on Youtube. Mine doesn't behave that way so I think something else is out of order. Best wishes in getting your problem fixed.
07-05-08, 12:05 AM
I talked to the dealer the other day, and he sent me out a new controller.
I got it this afternoon, and have just finished trying it out. It is the same thing.
It appears to be all in the motor. So I guess that will be the next thing.
Its a bit frustrating having the dealer 1000 km away, if it was local I could spin down there with the bike, and they would say "Oh Ya, its this....."
But the dealer seems really patient, and I am sure it will get resolved.
I want to learn how everything operates, so that troubles can be diagnosed easier because of the distance.
But then again, its my choice to live here, and it has served me well for the last 36 working years, so one must learn patience to survive!! At least I am still able to use if for my daily commute. I am getting so I do not want to drive at all, and am looking to build or buy a pull behind trailer to haul, groceries etc
I will keep the thread posted as I go through this.
08-24-08, 12:36 AM
I got the answer to this problem, and it has nothing to do with the controller, or motor. The folks at ItsElectric in Calgary have been very good in resolving this issue. They replaced the controller, and even the motor. They even put my components on a bike and rode it over 10km.
But the issue is the bicycle that I have it installed on. Specifically the front forks. This is about a 20 yr old Sears special. They had a exact same trouble arrive at their shop and they found it to be the front fork.
I finally see how that makes sense. The hub motor by its nature "Pulses" at a varying frequency. The frequency of the motor, and the fork I am using, at certain RPM will resonate thru the forks into the frame.
Its not in the budget to replace the bike right now, and I will have to see if I can
change the front fork to something entirely different. I tried a different fork, from pretty well the same brand and vintage of bicycle and got the same result.
I think with the days getting shorter I will ride it as is, and work on it thru the winter months.
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