First build

Discussion in 'Photos & Bicycle Builds' started by Weihenstephaner, Dec 14, 2015.

  1. Weihenstephaner

    Weihenstephaner New Member

    Built my first motorized bicycle a couple weeks ago. Some posts from these forums helped me along the way so I thought I'd join up and share what I've learned. I'll post details of build and photos in the appropriate forum though. I'm planning on doing some extensive electronics work on my bike, hoping to keep a 6 volt sealed lead acid battery charged using the white wire and some diodes, and power an arduino based cyclocomputer as well as lights and blinkers from it. Until then just introducing myself, so greetings from north Texas.

  2. bluegoatwoods

    bluegoatwoods Well-Known Member

    Welcome aboard. It sounds like an interesting build.

    Don't keep us waiting on those pics, eh? We can't get enough of that sort of thing.
  3. Weihenstephaner

    Weihenstephaner New Member

    So this is it so far, but I'm afraid it doesn't have any terribly interesting features yet. The only changes so far are the tensioner and that to get the engine to mount a little higher I 3d printed that spacer you can see in the second photo. I was a bit worried about it not holding up to heat but so far it's been good. We'll see if it gets soft in the summer. The tensioner is sold by a guy on ebay (not me). Over all it works ok (much better than the one that the kit came with) but it can't take up very much slack so you have to get it really close before you use it. I couldn't get both chains right so I gave up and used the stock tensioner on the bike chain side. It looks a bit goofy having a tensioner on each chain but it's been working well so I'm leaving it.



    I got a six volt sealed lead acid battery and I am going to try to keep it charged off the white wire. I actually should be pretty qualified in this sort of thing but the wiring on this still confused me. It looks like to get it to work I have to use a positive ground system and a single diode to half wave rectify. Apparently other people need to use negative ground, depending on the bike. Once that's done I have some leds I'm going to make 3d printed fixtures for for the lights and blinkers, and a dollar store door alarm out of which I'm taking the reed sensor to use for cyclocomputer sensor. That will feed to an arduino powered off the sla that will also look for the pulses out of the mag, that should give me speed and rpms. My current plan is to display those on little steam gauge things I made with RC servos, but I think that might draw too much electricity. If it does I'll go back to the backup plan of having a super boring lcd display. I figure this whole thing will take a few more weeks at least possibly a few more months before it's really "done". In the mean time I'm just driving it around in it's unfinished state. I'll post links to circuit diagrams and firmware as I go, so anyone else who wants to do something similar can use them.
    bidardian likes this.
  4. Kirk

    Kirk New Member

    Can't wait to see the arduino stuff. A touch screen shield on the arduino wouldn't be boring. Let us know how well you can count pulses off the magneto.
  5. Weihenstephaner

    Weihenstephaner New Member

    OK, I'm gonna make a new thread in the projects and builds section. For now though I have been experimenting with the arduino rpm measurement. It's sort of working but I don't think it's very accurate. There is mad emi coming off the engine and I think I'm counting stray pulses. My bike is positive ground, so I have the positive SLA terminal going to ground (one of the engine studs), and the negative going to the white wire through an N4001 diode. There is a second N4001 diode that goes to pin 2 of the arduino, which is tied to interrupt on the falling edge and increments a counter when it is pulled low. The internal pullup (~5k ohms) holds the pin high otherwise. Theory is when the engine volts goes low enough to charge the battery it will also pull that pin low. I think this may not be the best way to do it though since I have the two diodes in parallel they have to match pretty precisely to work right. When I first hooked this up I was reading 7000 rpm at idle, which is obviously wrong. I put a 100 nF capacitor from pin 2 to ground and then it dropped to about 2900. That sounds closer, but still high. Any idea what these things usually idle at? It's a 80cc two stroke. Anyway it might be good enough I just wanted a rough indication. I'll start working on the speedometer next then the lights and controls. I'll start a new thread once I have photos.