diy elec bike assist

I guess I need to explain that I'm an old guy with a bad ticker. I also have some big time balance issues. I needed to get a little more active and work on my balance, so I bought a bike. The bike is about a million year old cruiser, so I had some work to do before I even took off on it. I cleaned and repacked everything. Then I switched out some parts to make it more comfortable. I replaced the sprocket drive set on the 26 inch bike with one from a 20 inch to make the peddles easier for me to reach. I also used the smaller drive sprocket. That might not have been such a good idea as I have to peddle more to get the same distance. I had intended from the start to install a helper motor so the pedal thing isnt really a big deal. I designed it this way. Motor: 24volt 250 watts from a kids scooter toy. drive: friction with a wheel that sits on the rear tire. Now the motor and mount I have worked out just fine. I'm waiting for everything to arrive so I can begin work. My question is about the power source. I really do not want the power source to ever run the bike. I simply want it to assist me climbing hills. I dont want to run out of oxygen (fuel) as is happening now. So this is my planned power set up, please tell me any flaws you see in it. One twelve volt battery 12ah complete with momentary on off switch. Push the button when I need a little assist climbing a slight grade. A completely secondary battery probably 7ah with its own momentary switch just to kick in on top of the first battery. When both are on, It should make a 24volt system for steeper inclines for just a few minutes at a time. What problems do you foresee. Any advice would be helpful. Did I mention I like to tinker with stuff. I found over the years when you buy something you learn to write a check. When you build something you learn lessons that are transferable to all problem solving. And my wife made sure I knew how to write a check early on.

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CameronSS10 years ago
We currently have two electric bikes. The one pictured is my dad's, a BikeE recumbent with a hub motor in the front wheel, 36V system. The other one is mine, though I don't have a picture. It uses an 18aH 12V battery and a friction drive motor on the front wheel. I well tell you this: There's a reason that friction drive is oftentimes called "scuff drive." It eats tires. At least make sure you have smooth road tires on first, as knobs aren't particularly good with scuff drive.
Bike on Courier.jpg
retrophoto (author)  CameronSS10 years ago
I might have posted this already but thanks for the information. How does your assist scrubber work does it help you with the hill climbing
i see a problem with normal riding, because of the drag caused by the motor, so if you could find a way to disengage it it would be a good idear.
The motor does not cause drag unless it's connected to something that will make it work as a generator. when you take out the throttle, the controller essentially disconnects the motor, and there is very little additional resistance.
NachoMahma10 years ago
. Sounds like it ought to work. Just make sure your switch can handle the current. . Instead of running large wires to the switch, it might look better if you used interposing relays and smaller wire to the switch. . Since you like to tinker, why not an electronic controller with some kind of continuous adjustment near your thumb?
retrophoto (author)  NachoMahma10 years ago
To be honest I wanted to start with the simplest construction and switching possible. Something that was so simple it would not intimidate anyone. Also something to save the battery charge. I wanted to work off one 12 volt battery full throttle and pulse it. Then a second battery that could be brought onto line to kick the power up for steeper inclines otherwise to save as an equal backup when the first battery dies. I have a lot of experimenting to do first I'm sure. I have some push button switches on order ,if they are too small there is a plan b... I just checked with advance auto while I was picking up some small bungee cords. They have the old push button horn switch for a direct circuit from the auto battery current directly to the horn. That cuts out the horn relay so it should work fine, if the hong kong ones dont that is. I wanted to build something anyone can do in their shop with no special tools. I would like to make a set of simple plans available to anyone who is interested. Plans using inexpensive parts easily available. It's what I did with the polaroid conversion to film plans. Of course I may have to go with the throttle controller type mechanism yet. I hope not.
. KISS is nearly always the best policy. ;)
lemonie10 years ago
What about a nice 2-stroke engine instead? I've seen old bikes power-assisted in this way, and you get a better power to weight ratio.

CameronSS lemonie10 years ago
It also requires mixing two-stroke fuel (pain in the neck), it stinks (pollution! pollution!), and it makes an obnoxious, rattly whine that I would NOT want to have sitting on my bike. Electric motor requires plugging it in when you get home, has zero emissions, and is whisper-quiet. SO much more pleasant.
Zero emissions at the point of use. But if the power to charge it comes from a power plant burning coal, weeeeeell ;-)
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