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Electric bicycle project update with video

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  • Electric bicycle project update with video

    I have been making good progress (although slow) with my electric bike. I have been trying out various permutations on the drive system and have come up with something a bit off the wall that works great. I have one major requirement and that is hill climbing ability. That is also the biggest weakness of most electric bikes. I would like to be able to ride this bike to town and that means a 1000 ft altitude gain in only a mile or so going in and on the way back a 1400 ft gain over three miles.

    I determined that I will need at least a 40 to one gear ratio to keep the motor in an efficient operating range. That normally means planetary gearing or other similarly complex compound arrangement. While I can make such a system I found a much better solution that is also very efficient with minimal wasted power.

    This is what I came up with. It's effectively a 24" rim sized serpentine belt pulley that is fastened to the rim with flush screws on the inside of the rim to 10 tabs on the perimeter of the pulley. I bent the pulley from flat stock using a simple cobbled together ring roller on my bender. It doesn't have any grooves and they don't seem to be necessary. Belt tracking is excellent. The belt is a 69 1/2 " six rib belt that I split in half to make two 3 rib belts.



    This is still a test rig but the drive design is finalized. A HTD belt drive from the motor has a 3 to 1 ratio to a jack shaft. The jack shaft carries a hub freewheel with a serpentine belt pulley that drives the main drive belt. It's all on ball bearings with a ball bearing tension adjuster that also helps retain the belt in the pulley grooves and keeps it from slipping too much. Some slip is desirable as I don't yet have a speed controller so the power is either on or off. Total drive ratio is about 45 to 1.




    The motor is a modified lawn tractor starter motor from a 15 hp Briggs. I have a spare MTD lawn tractor with a dead ring gear so I robbed the starter from it. It pull starts just fine anyway. I modified the motor by machining ventilation holes in the normal shaft end cap and mount bracket and made a new aluminum cap for the other end. I extended the shaft on that end as I had to drive from that end to get the right rotation. Even though this is a 4 pole permanent magnet DC motor it is designed for one way rotation. The extended shaft runs in a ball bearing now instead of the steel on steel bearing that was original.

    I also clamped on some heat sinks after turning the housing just enough to to clean it up and make a good contact surface. On the regular end of the shaft I have put a high efficiency centrifugal fan that I CNCed from a block of Delrin. It blows a gale through the motor. So far in testing the motor barely becomes warm and puts out gobs of torque. Best guess based on amp draw is that the motor is about 1 hp. That actually puts it above the 500 watt legal limit here for licence free e-bikes but who is going to measure that?




    Next is the construction of a proper lightweight aluminum chassis for the drive system that will also support a good sized cargo box. and some new batteries. The batteries are a pair of thin profile gel cells with 18 amp hour capacity each. The motor draws about 30 to 40 amps in level running at a top speed of around 25 kilometers per hour. That could be a lot higher if I put in a 2 speed automatic high gear system that I have already designed but the hill climbing ability is more important than speed. I haven't measured the hill climbing amps yet but expect it to be near 100. I have tried it on our hill here and it pulls me (about 190 lbs) up the 12% grade just fine at about 10 mph.





    Next items are the new chassis, a disk brake, an onboard quick charger with constant current and full charge sensing, a PWM speed controller, an instrument panel with amp and volts display and some LED lighting.

    Here is a short video showing the performance of the bike.

    2.7MB
    http://www3.telus.net/metalshopborealis/biketest.wmv
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  • #2
    Originally posted by Evan
    Here is a short video showing the performance of the bike.
    Good one, Evan! That gave a chuckle.

    One of the web sites I host is run by a friend who is a Triumph motorcycle fan and tinkerer. He built this bicycle using a tub engine from a washing machine and parts laying around. http://triumphchoppers.com/gallery/album48

    The rest of the photo gallery is interesting too for anyone with soft spot for those great old British twins.

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    • #3
      Love the burnout, now you just need to work on your circle wheelies.

      ME

      ADD: Saw an electric bike in Machine Design magazine, thought you might find it interesting.

      http://e-ms.us/
      Last edited by Michael Edwards; 06-19-2008, 11:38 AM.

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      • #4
        Dear Poppa Wheely,

        More duck tape on that seat will help the overall efficiency.

        Yours truly,

        J. Hob.

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        • #5
          I have one of those motors in a box in pieces. I also put it on a bicycle back in the seventies but nothing as cool as the one in your friends pics. That sounds like another fun project. Here you don't need a licence or insurance for anything under 50cc displacement.
          Free software for calculating bolt circles and similar: Click Here

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          • #6
            Originally posted by Evan
            ..... I would like to be able to ride this bike to town and that means a 1000 ft altitude gain in only a mile or so going in and on the way back a 1400 ft gain over three miles.
            ............
            [/URL]

            Are you saying your trip to/from town is uphill both ways?


            I like that bike. ...I want one!

            Have you figured your miles/kw yet?

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            • #7
              I am at about 2600 feet. The bottom of our hill is about 2350 and the top of the ridge I have to go over is around 3300. Town is in the next valley at 1850ft. So I have to climb out of the valley and then can coast all the way into town. It won't take that much power since all the bike has to do is the 1 mile climb and the rest is down hill. Coming back is a bit different as the hill up isn't as steep but much longer. The efficiency will play a much bigger part there. So, it is uphill (and downhill) both ways.

              I haven't yet done any real trials. I need to finish the mounting frame and install the gel cells for that sort of testing.
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              • #8
                Very interesting, like the drive system.

                I'm a regular bicycle rider, and do a lot of long rides.
                I'm working on a motorized trailer so I can hook it up to whichever bike I want to ride at the time. Thinking that with the trailer I can add extra batteries for longer range, or leave it home when I just want to cruise around.
                Started hauling the trailer, because for some reason when I'm out on the bike I run into TONS of garage sales, and find great stuff when I don't have a way to carry it. Ever try to carry an 8" scope (luckily no base or tripod) on a bicycle for 12 miles?

                Ken.

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                • #9
                  Neat,how about regenerative braking?Boost up the batteries on the downhills
                  I just need one more tool,just one!

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                  • #10
                    I will be mounting the gel cells on each side, saddle bag style. That will leave room on top for me to throw in a spare battery if needed for range. I have to depend on the bike running on electric power because if it dies halfway up the hill the only way I can go is back down. I don't have enough stamina to do otherwise and heavy exercise only makes my condition worse.

                    Darin,

                    Regenerative braking is in the cards. The easiest way to do it is with a seperate motor that is an efficient generator. I have a magnetic clutch that I was going to use and will use it to clutch the generator in and out. Thats why there is a sprocket on the free wheel. It's driven by the belt pulley full time.
                    Last edited by Evan; 06-19-2008, 02:33 PM.
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                    • #11
                      Evan your a goofball
                      I said it before and i'll state it again, i like how that seat has a separate place to put your nads.

                      Im really surprised how well a starter motor does as I would think it would cook its guts out as their not designed for it, also would think they would be inefficient as all hell?

                      I like your ingenuity.

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                      • #12
                        It isn't the same as most automotive starter motors. They are usually series wound 2 pole motors with no magnets and inefficient as all getout plus they will suck an almost unlimited amount of current if stalled. This motor is a four pole magnet motor designed to start Joe Public's lawn tractor every time even though his 29 dollar POS battery hasn't been charged since last fall.

                        I am surprised at how cool it runs though. That tells me it must be fairly efficient and my cooling tricks are doing the job. Too bad it isn't brushless.
                        Last edited by Evan; 06-19-2008, 04:21 PM.
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                        • #13
                          Nice Ideas, also... How did you train that bear to ride it in your video clip?

                          Tom M.

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                          • #14
                            "How did you train that bear to ride it in your video clip?"

                            Drugs.
                            Free software for calculating bolt circles and similar: Click Here

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                            • #15
                              Evan good tip take the old nuts and bolts out of your pockets when riding it as you've knackered the saddle with your shenanigen's boyo.Alistair
                              Please excuse my typing as I have a form of parkinsons disease

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