We are heading towards a "Reference Design" for Morph 4, which we hope will the the configuration that we build six prototypes. This SolidWorks model shows a colored model of a wood model that we will use to finalize the design. The finished bike will not be made of flat sections like this!
This model is deceptive, because it looks so simple. But in fact, it encapsulates almost a year of work to figure out how to get everything we want in the Morph to all be possible in a single design:
- A good, very low rider height in the Low Rider Position
- A full High Rider position
- Self-adjusting seat bottom so you don't tilt too far forward when you morph up.
- Self-adjusting seat back to you are comfortable in both positions. (looks a little vertical in the high mode here, but its adjustable.
- Narrow, bike-like frame
- Single gas spring (not shown). It will be mounted between the arms. This will be nice and strong.
- Slug seat bottom and seat back. (Not shown, but the room is there to do it.)
- Capability for main tube to have a coupler so you can break the bike apart for travel by car, plane, etc.
- Light weight
- Simplified construction
- Proper steering trail in high and low modes (not easy to get right!)
- Easy to build. (ie simple parts, no fancy construction needed.) (after all, this one will be made out of wood as a scale model)
High mode. Back is a bit vertical, but we can adjust based on length of the green and yellow arms.
Low mode. Note that the dowels are not shown. These will hold the wood model together and let it morph.
High mode.Notice that the seat is tilted more towards the blue tube now. This corrects the tilt that occurs when you morph up.
High Mode Isometric for wood model.
High mode iso. Remember, this is a wood model. Next step is to decide on materials, and on other items, like foot rests, locking mechanisms.
Here is the list of what remains to be figured out after this reference model and wood model:
1. Main tube materials selection - chrome molly steel most likely for main tube. (Coupler not possible in aluminum.)
2. Other members materials - probably many will be aluminum.
3. Design for the morphing joints - how to make it light, strong, reliable, easy to build, easy to repair.
4. Slung seat bottom.
5. Seat bottom adjust mechanism - we show the mechanics, but not the design itself.
6. Slung seat back
7. Seat back adjust mechanism - again, we have the mechanics, not the design.
8. Bike component selections
9. Foot rest design (this always gets too little attention!)
10. How to lock in high and low mode. (and with high reliability! Our current latch design has had its reliability issues.)
11. Desired: a way to lock the bike in intermediate positions and even ride in that mode. (Harder than it sounds!)
And then some things that may seem like minor add-ons, but they matter:
12. How to hold crutches, and make it fast and easy to get them on and off.
13. Storage space - how do you carry groceries, for example?
14. Water bottles
Additional design issues:
15. How to make it easy to get on and off. This relates to how often people will use it.
16. Design care to be sure the high mode stays short and turning radius is good.
17. Design of pedals so rider can (ideally) turn 90 degrees in high mode)
18. Design of foot rests so rider can turn as sharply as possible in low mode. (ie avoid footrests hitting ground, or maybe they have movement)
Input to Alan for finalizing the wood model:
1. Look at verticality of seat back in high mode. Seems too vertical. Fix before we cut wood!
2. Make the steering work. (Right now its fixed.) Key design issues relate to turning at the steerer tube.
Otherwise, look good to go to wood. The nice thing is that it's very inexpensive to make a wooden model with the technique you've worked out.
Here is the e-Drawings file for the SolidWorks model: You'll need the free e-Drawings Viewer (for Mac or PC)
(Note: this model is a little tricky because it is set to a small scale. But if you're careful you can get the views that I showed.)