My daughter kept asking me to go bike riding with her and week after week I kept giving her excuses when the truth was I had grown bored and tired of it, we we're always looking for a place to go, hoping the scenery would somehow transform the experience it never did. Our bikes mostly sit.
The last time my daughter asked me to take her bike riding an intense feeling of guilt took over me and I decided to look at a real way to make it fun. My default is speed, it is the one experience that never seems to get old. Making the bike faster has been done the problem is feeling the sensation at lower speeds.
The solution is simple in theory and difficult to execute properly: Lower the ride height dramatically. The first thing I did was search to find one, after months of literally nothing I designed my own.
Reciprocating to rotary. I started my design wanting the rider to sit as low as possible, this meant that the classic rotary pedal crank wouldn't work. Nothing like that was on the market, and after months I actually had a mechanism that work profoundly well, the problem was it was going to be very expensive. I went back to rotary by asking myself the simple question, would I pay the extra 40% simply for that feature?
Steering. The original method used an aircraft like joystick in the center with a grab handle on the sides. This turned out to be a failure, the joystick was supposed give a different sensation and slim the profile making it easy to store and transport, (two pet peeves of mine), instead it made it very difficult to ride since much of the riding balance is obtained through holding on the handlebar. Then there are the linkages to make the joystick work, two u joints, 5 bearings, a lot of precision machining and massive amounts of time to assemble + check functionality of each one. In the end I compromised with a collapsible handlebar, a straight bar and just one linkage. Needless to say I'm going to pass the cost savings directly to the customer.
My design made it impossible to use a chain. The fact that my design has a long distance between the pedals and rear wheel, meant that I would need the chain to slink around multiple idlers just to get it to work. Add in fold-ability and it's a straightforward choice to go with a shaft drive. As with everything on this thing gears are expensive! Worse, I was not able to find or adapt anything to work, I've had experience with gear design and manufacturing with my car, supercharger and with my first turbojet engine, so i knew that gears are a time consuming ordeal to do correctly! The shelf items are way too cheap to last and I had to make my own custom sets. There is one great advantage to making your own parts: you get exactly what you want! In my case it was two sets of very stable gears that are to my dimension, very strong and light, (cheap gears deflect and or break), In my application the gears themselves are expensive due to size constraints and subsequent strength required from the smaller size gears. I asked a local machine shop to custom make them, delaying the project by weeks but I was able to get one offs for each of the designs for a fraction of what they should have cost. I will say having experience designing gears and related housings made it so I didn't need to go through more multiples of prototype gears, in fact it only took three tries to get them working and in proper ratios.
Seat I can't buy: Designing a seating position with back support brings out a huge challenges: You can push harder on the pedal using your back support as a restraint. This means the seat has to be able to handle both your body weight on the seat and potentially more force on the back support. Put simply nothing exists that would do that for anywhere near my price, size or weight, I need to make my own..here we go again $. On some of the tests i used a springed seat base but comfort levels were low and I was set on the most comfortable seat. The result is something you can stay on for long periods.
The decision that transformed the experience.
Housing the drivetrain internally. This one is truly a undertaking, its everything that engineering nightmares are made of complete with constant failures in quasi dimensional forms that have to be worked out to perfection and perform flawlessly in a folding bike. It's an experience all its own. having done it the big advantage is the ability to carry store, transport and ride without cumbersome intrusion of parts prodding into your body, your clothes and everywhere you take or store this bike, No oil is present anywhere externally making it closet friendly. On top of that it makes this bike completely separable into two halves which detach from each other by removing one bolt! Making it foldable was a must do for my bike which is long making it a challenge to fit into most cars, its slender profile means that it can be compacted to fit into the smallest of spaces but..making it foldable is not just a matter of a hinge, everything had to work and hold in the most stable way, it had to feel like a single structure, I have been on many folding bikes and all of them feel as two different structures as your riding. My bike feels rock stiff.