Back at it again

[m-zed]

Nine years ago I created an account here, because I meant to build an ebike for my final engineering project.

This was inspired by the fact that I saw the proliferation of ebikes in the rest of the world, I thought they were awesome, and I couldn't get the parts needed to make one, because Venezuela.

So I set out to make something using only locally sourced materials, and this is what I came up with.



The batteries were small AGM lead-acid batteries, meant as starter batteries for motorcycles.

The motor came from a broken down submerged arc welding machine - I chose it because it included a built in 90degree turn and speed reduction stage at the motor output, and because it was a small brushed DC motor with some ridiculous power (I think it was rated for over 1000W but I'm not really sure as I didnt have any specs for it - other than the machine it came from and it being rated for 100Vdc in normal operation).

I used a simple PWM circuit made out of a few op-amps to control the motor. The circuit is so crude (and actually wrong, like, I put components in the wrong places) that I'm a bit ashamed to share it (though its part of published research).

I short circuited a few versions, and learnt about the importance of "fail safe" when these faults caused my bike to go into full power mode with no way to stop it (the final version had a big red button to avoid this).

It's kind of a miracle that it worked, but work it did. I recon I was probably reaching around 30km/h peak (though I had no way to measure it), and it had enough power to get me from home to the university and back (with some to spare), so I considered it a huge success.

Soon after I presented my research, I had to move away and my mom asked for her bike back so I took everything apart, and since then I've been longing to get a new one... and yesterday, I finally did

Got a little BB02 + battery kit, converted my new bike, and got to experience what a "professional" made system drives like - and it's great!



This reminded me about this place, so I decided to come check it out again and was surprised to find that my account was still around - so, I figured I'd just tell yall about my ebikes and how excited I am to be back on them

 

[Comrade]

Congrats. Judging by the fact that your white wall now has baseboards, welcome to capitalist USA? :lol:

 

[m-zed]

lol. Thanks. We had baseboards in Venezuela alright - the other pic was just taken in a garage. What's different here in the USA is how easy it was to get everything.

 

[fechter]

The first bike looked great. Reminds me of Naeem in Pakistan. Similar parts sourcing problem.

Check out his bike:
https://endless-sphere.com/forums/viewtopic.php?f=6&t=3983

 

[m-zed]

Oh wow, that's a really cool design!

His drivetrain looks far more complex than mine, probably sturdier too - I was using a regular ratchet soldered into the center of the pedal sprocket to allow the sproket to rotate without moving the pedals.

Unfortunately, the ratchets didn't take the soldering too well, and at some point one left me hanging (the pedals just became fully lose so I had - efectively - an e-motorbike ). His design seems to not have this issue.

I REALLY love the electric control system though - just using relays to change the battery connection to control speed? Genius.

It reminds me of this photo I saw recently, allegedly of a young Howard Hughes with his "motorcycle" (which I pointed out was actually electric!)



The control system here is even simpler, just a knife-switch between the motor and batteries - which I figured is about the simplest "control" you can make. Naeem's method is definitely a big step up from this without needing to bother with electronics

 

[amberwolf]

His drivetrain looks far more complex than mine, probably sturdier too - I was using a regular ratchet soldered into the center of the pedal sprocket to allow the sproket to rotate without moving the pedals.

Unfortunately, the ratchets didn't take the soldering too well, and at some point one left me hanging (the pedals just became fully lose so I had - efectively - an e-motorbike ). His design seems to not have this issue.

I used a very similar motor, though a somewhat different chainline on CrazyBike2's middrive version (before I went to hubmotors because the torque from the powerchair motor in the chainline would twist the frame and derail the chain and destroy things).

https://endless-sphere.com/forums/viewtopic.php?f=2&t=12500
https://endless-sphere.com/forums/download/file.php?id=26906

https://endless-sphere.com/forums/download/file.php?id=275043

https://endless-sphere.com/forums/download/file.php?id=275044

 

[m-zed]

Lol, CrazyBike seems fitting :lol: I hadn't considered that the torque could be so bad! Thanks for pointing it out. I've definitely felt it when riding, and I keep reading more and more people talk about it. Oh well, I hope my chain lasts

 

[amberwolf]

The gearbox in those powerchair motors is pretty hefty, and if they're run on higher voltage than original, it'll be even higher. (I was running a 24v motor on 36v, and later on 48v....)

If the motor is mounted so it won't move on the frame, then the next thing to pull on depends on the chainline and gearing, etc.

In my case, the line from motor to pedal input sprocket was pretty straight, but not perfectly, and I trashed some chainrings on there before I got it right--instant taco once problem occured.

The pedal output sprocket to the wheel was also trashed from the torque, whenever misalignment occured--usually at low gearing (high torque) and high load like startup, as the frame would be pulled more on that side than the other and twist in that direction; the very long frame was pretty flexible, which was nicer for riding given the lack of suspension, but bad for a chain drive that could do this.

One of the last times things were destroyed was when the rear wheel axle was pulled so hard by the chain wrapping itself around the tacoed pedal-ouptut sprocket on that side that it damaged the wheel, pulling spokes partway thru the rim, etc.


Eventually I stiffened the frame enough it probably wouldn't do any of this, but by that time I was using hubmotors, and though I'd like to go middrive again to make wheel-fixes (mostly tires) simpler, I never have.