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Working in my virtual shop: My next big project

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  • Working in my virtual shop: My next big project

    Last year I built a prototype electric bicycle and found out a lot about electric power and light vehicles. This year I am going to build version 2 which will incorporate what I learnt and will be a much more practical vehicle suitable for trips to town in nice weather.

    The new vehicle is a tricycle design with much more power and greater range. It will also be able to accommodate most any bicycle as a bolt on with no permanent modification to the bike. Pedal drive is maintained but only as a legal requirement and backup for limited operation in the event of a drive failure or flat battery.

    The main unit is a separate two wheel power and cargo system. The bike, minus the rear wheel, bolts on using the original wheel slots and a pair of stabilizers to the seat post. A longer chain is fitted with a single high numerical ratio for pedalling.

    The power unit will use a rewound treadmill motor designed to operate on 48 volts with a power output at maximum of around 2 kilowatts. Suspension will be single axle with two trailing links and sprung shock absorbers. Unsprung weight will be at a minimum. The chassis is designed for very light weight and simple construction and the aerodynamic shell will be of composite construction. Plenty of cargo space under lock and key will be available.

    Possible options will include solar charging for battery top up and a gasoline or alcohol fuelled engine/alternator battery assist hybrid unit.

    Preliminary design was done in Google SketchUp. All images here are rendered directly in SketchUp.

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  • #2
    Evan, Very impressive, how long did it take you to learn Sketchup ?

    Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.


    • #3
      That's incredible --- Only would a virtual shop stay so clean, shouldn't there be a couple of oil spots on the ground from your PT cruiser?

      Your a Wiz-Kid...


      • #4
        Pretty cool - think a sway bar might be a good idea? I'm also trying to visualize the effects of the motor torque on the suspension when accelerating and decelerating, and braking forces, of course. Putting some angle on the sprung shocks will improve the ride and dynamic range of loads you can carry while keeping it off the stops. As a former Harley Softtail owner/rider, staying off the stops is sometimes challenging. Rubber bumper cones help.


        • #5

          I have been messing about with Sketchup for a couple of months but very quickly ran into the limits of my old computer. It is only since I built the new computer that I have enough power to make it practical to use for complex designs. SketchUp is extremely powerful but a lot of that power is hidden. This especially applies to the real CAD functionality. It's in there but figuring out how to make the program stick to precise coordinates, lengths, snapping, etc, etc, is not at all obvious. Much of what are explicit features in other programs are concealed as automatic functions of the drawing interpreter. The trick is figuring out how to make the drawing interpreter behave properly since it will just as easily allow you to slop everything together with no concern for accuracy, alignment or precision.

          Once you have it under control you can whip out complex drawings in 3D in little time. The free version has the ability to read all the usual formats and there is a plugin available that will export to the standard OBJ format making it possible to export to other CAD software. Sketchup is fully parametric once the appropriate plugin modules are installed.

          While I prefer to figure out how things work for myself I would recommend for most people to take advantage of the numerous tutorials that are available.
          Free software for calculating bolt circles and similar: Click Here


          • #6

            That is just the basics of the design. It will have rubber snubbers and the exact placement of the shocks may vary. I am hoping to use a pair of planetary gearboxes back to back as both reduction and differential at the same time. I may however simplify that to a friction plate that allows for differential motion under load and just drive one side of the axle. I also havent shown the rear brake which will be a single disk on the axle. If possible the disk brake will use a caliper to clamp on the drive sprocket.

            As for a sway bar I am leaning toward using a reverse Watt's Linkage as is used on the PT Cruiser. It's a simple system that prevents body roll relative to a live axle and constrains the axle laterally at the same time.
            Free software for calculating bolt circles and similar: Click Here


            • #7

              You may want to consider using a multi-speed hub in the wheel, and driving that wheel via either the pedals or the motor or both... humans are pretty constant speed devices as power sources, and the motor can be lighter and smaller if it doesn't need to provide large amounts of low-end torque. The brushless hub motors get around this somewhat, but it's still noticeable when you examine the efficiency curves.

              You may find the following useful:

              These guys are up your way, and quite knowledgeable. Note in particular the simulator...

              - Bart
              Bart Smaalders


              • #8
                That's impressive well done I can't use these programmes still I've never really tried .Alistair
                Please excuse my typing as I have a form of parkinsons disease


                • #9

                  The plan is to use a pair of multi speed bike hubs as the differential. By using a bored aluminum shaft section I might be able to even change gears on them magnetically...
                  Free software for calculating bolt circles and similar: Click Here


                  • #10
                    May I suggest something like the NuVinci hub.


                    A friend of mine has one on an old mountain bike frame with a small Honda motor on it, off idle it is not possible to hold back the bike, that hub is very rugged, but not cheap.
                    James Kilroy


                    • #11
                      I will be building this from recycled bike parts. That has become a habit for me as nearly everything I build has recycled content. There is a very dedicated bike shop in this town where I beg and borrow and even buy what I need much of the time. These guys are not salesmen, they are gonzo mountain bikers. If I need it it is probably in their scrap pile behind the shop for the asking.

                      These guys sell bikes that cost 4K on sale. They have high quality scrap.

                      Free software for calculating bolt circles and similar: Click Here


                      • #12
                        For simplicity, have you considered a sprag clutch on one rear wheel rather than a differential?

                        You don't need reverse so it should work if you put the brake on the correct side.

                        Location: Newtown, CT USA


                        • #13
                          A sprag clutch would only act as a differential when turning to one side but not the other.
                          Free software for calculating bolt circles and similar: Click Here


                          • #14
                            Would your trike benefit from a little suspension travel in the front? Perhaps your mountain bike shop has some springer forks which could be adapted.

                            [edit] removed thread hijacking photo of Harley.
                            Last edited by aostling; 06-10-2009, 11:16 PM.
                            Allan Ostling

                            Phoenix, Arizona


                            • #15
                              I don't think there is much advantage to front suspension for paved on road use. The front forks already have some flex and the larger 26" wheel makes it less affected by road irregularities. Also, I discovered even the slightest extra slop in the front end makes a noticable difference to handling. Also, it would allow for greater weight transfer to the front wheel during braking, something I want to avoid. I am using a mountain bike frame as it is of much heavier construction than a road bike and will take the extra weight and twisting moment. I picked up a really nice mountain bike a few weeks ago at a yard sale in excellent condition for $10.
                              Free software for calculating bolt circles and similar: Click Here