Tostino's Custom BMC build

[tostino]

Hi all, i've been working on my bike for about 5 months now, and I just got it ridable this past weekend. Sadly, my chain popped off my rear sprockets, and ripped the derailur right off. I ordered another and am waiting on it coming in to continue my testing. However, I am taking advantage of this down time to get some of the finishing things on my bike done (like wiring).

My bike is based on a Schwinn S60 DSX from target, and uses a BMC motor (non hub) from powerpack motors, 6 milwaukee v28's in 1s6p, and a shenzen controller (not the new infinion). The controller has a 28 amp limit, and I am running 28 volts. So my peak power out should be around 780 watts. I reached 20 mph without any pedal assist, and 25 mph was very easy to reach with minimal pedal assist (measured with an atv driving next to me). I ran the whole day on a single charge, a lot of it offroad, and then I made probably a 14 mile on road ride before the batteries died.

My drive train is not exactly ideal, but is the path I chose to take. I have my motor mounted on the botom of the frame, with a jackshaft on the top, offers dual gear reduction, bringing the motor rpm down from 3000 to about 100. From the jackshaft, we go to sprocket mounted on the left hand pedal. So when using the motor, it turns the pedals. Like i said, not ideal, but it worked well from what i've seen so far.

I will update this post with pictures as soon as I get home and I have access to my camera.

 

[tostino]

Here are some images of the bike!

Any comments, questions, or suggestions would be appreciated.

 

[swbluto]

That looks craaaazy. I take it the pedals go chop-off-your-legs fast when that motor's pushing the bike at 50 mph?

(I've been wondering what a "jackshaft" looked like.)

 

[tostino]

That looks craaaazy. I take it the pedals go chop-off-your-legs fast when that motor's pushing the bike at 50 mph?

(I've been wondering what a "jackshaft" looked like.)

lol it's not geared to go over 25 for now. I will be making the pedals quick detachable, and putting foot pegs on the rear swing arm so my feet have a place to rest. That jackshaft does a great job of a 23 to 1 gear reduction , so my motor can spin fast without your feet going insanely fast.

It's limited to 780 watts at the moment, and is only running 28 volts, so there is plenty of room for more speed. I just need an infinion controller before I am able to do that.

 

[tostino]

Hrmm, interesting. I just hooked up an ammeter to test the amps it pulls, and it's not going above 18 with full throttle and at a dead stop. I guess my motor needs a little more voltage before i'm able to get max power out of it.

 

[swbluto]

I don't know much about the motor, but I'd assume its internal resistance is less than .5 ohms. 27/.5 = 54; Perhaps the controller's amp limit is a bit low? Or perhaps it starts PWM-ing the battery's current at a lower current?

And, also, make sure you account for the amm-meter's internal resistance. It seems my amm-meter has an effective series resistance of ~.5 ohms, which would affect a circuit working off .2 ohms.

 

[Fumesucker]

Nice shade-tree build.. Ingenious..

How's your hill climbing ability?

What gears did you end up using under power?

 

[tostino]

Nice shade-tree build.. Ingenious..

How's your hill climbing ability?

What gears did you end up using under power?

I took off the cable for the front chain ring, and have it locked into the highest one, and on the rear, I use anywhere from 2-7. I normally start out in 3rd, and pedal along while I shift up every 2-3 seconds until i'm at top speed.

I am not sure about hill climbing, I live in florida, so I will need to find some man made hills to test it out on. I know of a bike overpass I could try.

And thanks .

 

[AussieJester]

You could always fit a freewheel crank set to the bike so the pedals dont HAVE to spin with the motor, this would keep it 'Legal" rather than taking the pedals off and fitting foot pegs...nice ride anywayz matey well done

 

[cargo]

.

 

[AussieJester]

You could always fit a freewheel crank set to the bike so the pedals dont HAVE to spin with the motor, this would keep it 'Legal" rather than taking the pedals off and fitting foot pegs...nice ride anywayz matey well done

This would only work if the motor was driving the right side crank.

Would work either side if you made the freewheel crank yourself and not a store bought

 

[Miles]

Would work either side if you made the freewheel crank yourself and not a store bought

That would definitely be a non-trivial task

You would need a dual concentric bottom-bracket axle....

Simply not worth thinking about, as you can drive the right-side, without driving the BB axle....

Haven't we been here before...?

 

[tostino]

There is no easy solution to making the bike move without the pedals going without completely re-designing the bike. In my next build, I will go for a setup that works like that, but for now I will just live with it how it is. From the couple days I have got to ride it so far, it hasn't been an issue.

 

[tostino]

I just got back from a little ride on our local bike trail, and there was an overpass over a two lane road that is probably a 40 foot climb. I had my grandpa take a video of me going up it on my bike. This wasn't quite as fast as it can go, because I can only use the 32 tooth front chain ring on the drive side of my bike, so that limits my speed to 20mph top. I think I was going about 16-17mph up it without pedaling, and 20mph with.

The video is attached and placed in a rar file.

Let me know what you think, and how comparable this is to other bikes.

P.S. I don't have a CA yet, so I don't know my amp draw, it was probably peaking at 28 though.

 

[pwbset]

Mirror for rar-challenged people:

http://justev.info/ebike.mp4

 

[tostino]

Mirror for rar-challenged people:

http://justev.info/ebike.mp4

Lol I didn't even think of that ... Sorry for the crappy quality, I used my cellphone. Next time I will at least use a real camera.

 

[tostino]

Oh, I wanted to update you all on how it's working as well... I took a 10 mile motor only trip yesterday, and the motor was completely cool to the touch. It was 10 miles, WOT the whole way non stop. The phase wires were cool too, as were the battery wires. It was probably 70f out yesterday, so not too cold that it just sucked all the heat out, it just wasn't generating much.