cheapo electric bike assist system

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
Building the simplest electric bike possible.....

First thing you have to understand is that when I say simple I mean simple. This is an electric bike for those of us mechanically challenged.

I began with the desire to build a bike that would allow me to pedal most of the time but help me up that hills that kicks my butt on even a good day. So I started with the premise that I just needed some help not a full blown motor scooter. It would be a bike with an electric assist not an electric scooter with pedals for emergencies.

From all I could find there was a great deal of math and mechanical knowledge needed for gear ratios ect. Not so with the friction drive assist. What I read told me that friction drive was the most logical for me. Mostly because it was the easiest.

So now I had decided what kind of drive. I then needed to know what kind of motor. I went looking around not really for the best possible motor but the easiest and cheapest one that would do. I stumbled onto a man on ebay who had a bunch of schwinn scooter motors for sale.
The first one I bought was 250 amps for about 20bucks. When it came it had a sprocket on the drive.

Okay I had the engine and I needed a drive wheel. I messed and messed wasted time and money till I came up with the easiest of all drive mechanisms. Below is the one that works.

My neighbor has a welder and loves to play with it. What I did was get a few 5/16 bolts of different lengths. I also got three nuts. I put all three nuts on one of the bolts and made sure they were lined up so that all could be taken off at once. Then my neighbor welded them together. He did a great job for me.

Then he welded the three nut package to the sprocket. As close to the center as possible. I ran a long 1/4 in bolt with washers through the sprocket (after it was off the motor or course) and then through the three nut package. I lined them up centered as much as i could and Mike welded them.

So to make the drive wheel I just bolt any kind of wheel to the nut package on the sprocket which I put back on the motor. I have used caster wheels and they work fine, i have made wheels from pvc water pipe joints of varying size. Those work just as well.

Okay at this point you have the motor and the drive wheel. Now you have to attach it to the bike somehow. This is where your ingenuity comes in. I have used a hinge on a flat bar then bolted the flat bar to the bike right behind the seat. Usually where there is a cross bar at the junction of the two rods that hold the wheel on....

Okay now you have the motor, the drive wheel, and you have it on the bike.

Next you need a power source. If you want the bike to be self contained you need small batteries. Sealed lead acid are the least expensive. I ran 8amp hour.

The way that is supposed to work is, your engine is rated in watts. To get the amp draw of the engine at full throttle, the only way i run mine, You divide the watt rating of the engine by the voltage required to run it. Mine was 250 amps divided by 24 volts equals about ten amps.

So you are looking at something under an hour of battery life. If your bike averages 15mph which isn't too far off. On a new full charged battery on fairly level ground you should bet about ten miles. However it never worked that way for me. I would guess more like half that amount due to hills ect.

If you don't mind lugging your power source on a trailer behind you, and I don't. You can get a little more bang for your buck with flooded cell batteries. Ie marine or auto batteries. Marine would be best.

Okay so now you have a motor, an attachment plan, a drive wheel, and a power source. How about all those fancy controls you hear about. Well yeah you can get an electric throttle, and a controller to help control the motor. I chose not to go that route. If you have a motor with brushes, which all mine are so they are not hard to find, and you are looking for an economical, and easy to find switch, which I was, It's home depot for a house switch. I use 15amp on the 250 watt motor and 30 amp on the 350 watt motor. I don't have any that are bigger.

Now you wire it up as the diagram below shows. It give me an on off switch which I use like a pulse jet engine. Flip it on when I need an assist and off when I no longer need it. If you want, you can use it all the time but it will eat up your batteries. I have done it both ways.

So here is how you wire it.


Okay Norm here is my contribution this is my 24 volt system
 

Norman

LORD VADER Moderator
Jan 16, 2008
2,605
2
38
68
pampa texas
Have you tried a dimmer switch as a throttle? You would need to rig it up to the twist grip by the throttle cable and have a spring return I don't know if this would work. The dimmer might smoke I don't know. There's another experiment to try.
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
The one i had didn't work but it was old so I just put the on off on there and that did what I wanted.

In my case i thought it might be because the dimmer is set up for 115 volts and im running 24, but I expect the new low voltage light dimmers might work very well.
 

sparky

New Member
Aug 2, 2008
4
0
0
I know this is an old thread, but those chaps you see in old war movies pedalling generators for the secret radio set, does anyone know, using "current" tech, how much power a human can comfortably generate? and how effective can hub-centre dynamos be? Thanks in advance for any replies.
 

Dan

Staff
May 25, 2008
12,775
107
48
56
Moosylvania
The one i had didn't work but it was old so I just put the on off on there and that did what I wanted.

In my case i thought it might be because the dimmer is set up for 115 volts and I'm running 24, but I expect the new low voltage light dimmers might work very well.

Did you ever get the dimmer switch to work? I am looking at controllers and throttles and they are big bucks.
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
I went to a controller and throttle instead. You are right seems it was bout fifty bucks and now they are on a shelf in my workshop. Make me an even unreasonable offer. lol.

You would need a brushed motor of 24 volts it might do more but I know it will work on 24volts. I have both the throttle and matching controller. Also a couple of 24volt scooter motors. One even had a friction wheel. They both might have them I don't remember.

The 350 watt motor stepped out pretty good but the batteries just wouldn't hold up for more than five miles. I even have a rear scooter wheel and chain that i was using as a friction drive wheel. It worked pretty well but again it was battery problems.
 

Dan

Staff
May 25, 2008
12,775
107
48
56
Moosylvania
I would definitely be interested! What make and model?

Is a tuff time right now with holidays and the Baby's Mama's birthday comin' up.

Build I am exploring is a small engine/ alternator/ battery/ motor/ wheel. I was hoping to get away with 12 volts and no reduction. Just buy the $15 throttle. If this works, would have the option to go "run silent. Run deep" with Option of engine. Like a diesel/electric train. Another build I am doing will need a home made gear box. So might make it 2, dunno.

You have to see this! Vid of UBER Ebike.. ElectricRider - Dave's Bike Outrageous!! (^) Below and to the left of first pic is 2 vids. I might have to go sparky.
 
Last edited:

Dan

Staff
May 25, 2008
12,775
107
48
56
Moosylvania
Well, just lemme know what you want for it. Am getting into this elec stuff. Did you see the vid? Not that I want to do 50 on a MB, but lovn the power.

Wanted to ask you Deacon, do you think the fancy, big cash batteries are any better? I am going to use an old truck bat for this build. Is just an experiment at this point.
They are getting $300+ for lil nothing motors for these things. Gotta be some thing to 'em.
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
I used two 8ah sla batteries at first. Then I moved to two garden tractor batteries. I still have three of those. Pulled them in a trailer behind the bike.

I found them both to be less than satisfactory. Two to three miles tops on the sla batteries. On the garden tractor it was about 5 miles.

Dan I have no use for this stuff what parts do you want. If you really want to part with the money, I'll make you a deal. I expect I can get a lot of it into one of those priority mail boxes with the fixed rate shipping.

Tell me what you need and I'll do you a real deal.
 

deacon

minor bike philosopher
Jan 15, 2008
8,117
3
0
north carolina
You know i learned about the front wheel drive advantage after I moved on to gasoline. An electric motor on the front fork might be better. Also I know now about weight so an alum road bike might be the answer. The battery in a small light trailer behind and you could rock it out.

The problem is the weight power ratio on all those bikes. The hub wheel is probably the best at that for now. The nano motor just doesn't seem that it would pull hard enough to transport a decent battery system but who knows some of the guys were using power tool batteries with some success I heard.
 

Dan

Staff
May 25, 2008
12,775
107
48
56
Moosylvania
You know i learned about the front wheel drive advantage after I moved on to gasoline. An electric motor on the front fork might be better. Also I know now about weight so an alum road bike might be the answer. The battery in a small light trailer behind and you could rock it out.

The problem is the weight power ratio on all those bikes. The hub wheel is probably the best at that for now. The nano motor just doesn't seem that it would pull hard enough to transport a decent battery system but who knows some of the guys were using power tool batteries with some success I heard.
Been thinking about this a lot. (hi, I'm dan. I'm an addict) thunking heavy batteries used like a pendulum weights to hold motor against the wheel aided by springs. the pivot point would be the axle. the bracket holding them would be an "L" shape with batteries between the axle and the down tube. Clutch would pull bottom of the pendulum up and towards the bike and move motor away from tire. From an extended (from the bottom of the fork) But would have to be a heavy cruiser with all that weight forward and handle even close to well. (have to rethink the clutch) But would be able to carry more energy. (after rereading, would work better on rear wheel, hmmm. Clutch would definitely be better)

I think I just want a front wheel drive and a cheapo ebike (pronounced CHA'IBICK ((is too a word. It's right there on the interweb)) and am trying to marry them together. rotfl

My plan for a front wheel drive up till now was a motored pump in the "V" and pump minus the motor that turns a solid axle turning the front wheel. Could be done, but is silly and project list is long (like this post, hehe) and cash is short.

OK, I am turning off the coffee pot and cracking a beer.
 
Last edited:

Dan

Staff
May 25, 2008
12,775
107
48
56
Moosylvania
There are no cheapo bikes lol they start out that way but they grow like a cancer

rotfl, Oh good God yea. I went to look at the felt bike "Heritage" today. Is $500! Not really worth it and I am getting it. (Really is a sharp bike and made to need an engine) No shops had it but will order it for me w/ a non-refundable deposit of $30. Last bike I bought was 100 at wally world. The really sad part is I build these things and have every intention that they are an investment that I plan to sell. When done, I find a reason why I can't.

PS; BlueSkyCycling.com - 2008 Niterider Minewt X2 Dual Beam Bike Light $200 for bicycle lights. We are in the wrong biz
 
Last edited:

Egor

New Member
Jan 30, 2008
714
0
0
Hurricane Utah
One way to have speeds it to change voltage. One some of the electric golf cars they use a series of solenoids that as you change the position of the throttle they activate the solenoids to increase the voltage. I starts out on one battery at say 12v. then as the throttle is moved it changes the alignment of the solenoids till the voltage is increased by adding another battery. As you can see you need more than one battery. Only one thing you always start on the same battery, so it gets the most use and looses power first. I guess then you just get to the second speed sooner. I have not thought about this for a long time, so if you need a schematic it will take me a while to get it together, it is not too complex. Have fun, Dave