This is a big post that will review a wide range of design choices on Morph 4.
First up is the design for the "lift system" - the gas spring and any other elements that make the Morph...well... morph. Here we see a design that uses a single long-stroke gas spring that fits in between the dual arms of the upper and lower link arms. This spring would be rated at about 500 lbs of force. It is an off-the shelf shock from McMaster Carr:
Details on the single shock. Click here
to see the gas spring online.
Morph 2 (and its modified version, Morph 2.5) uses two gas springs. We're debating right now which is better. With two gas springs, we can have more force, and the place the springs closer to the hinge point. This means a smaller shock, and maybe a neater look.
Side view animation. Gee, the single gas spring seems like it's hanging out in low rider mode. Is that cool? Or wrong? Note the "extension" that holds it to the upper morphing arm. This member is only in tension. It is like the vertical cables on a suspension bridge.
Rear view animation. Note that the big shock "pokes up" in Morph 4, but in Morph 2/2.5, the gas springs protrude downward and are handled by an extension from the axle tube.
Note the two thin extensions welded to the axle tube. These welds actually failed on Morph 2 because there is about 250 lbs of force acting at a distance on these extensions. But they do serve to allow a longer gas spring to fit into the system. I believe we could use a similar approach on Morph 4.
We decided to look into this some more, and scheduled another online meeting for Tuesday, Feb 2, 2010. Or calls uses www.yuuguu.com
for screen visuals, and we are in Bath, Maine, Cambridge, MA, Somerville, MA, and Santee, CA.
Adjustable Lift System
Let's say you weigh 170 lbs, and the gas shock is sized just for you. You want to show a guy who's 200 lbs exactly how cool the Morph is. Well, it won't work that well, because the 200 lb person is 30 pounds over the design weight. This means that he will sink down fast to low rider mode, and will need to work a bit to get up. He won't have that wonderful "float" that makes the Morph so amazing.
We would like to have a fast, easy way to adjust the lift system. One idea is to have the gas spring handle part of the weight, and have an adjustable elastomer system handle the rest. Those are the red cords in the picture above.
You can see the elastomer cord bisecting the "diamond" of the frame, and then going inside the main tube, then emerging to a hook. What hook you set it on determines how much supplemental force you get for the lift system. Want to change it? just move the hook when you are in high rider mode and the cord is slack.
This is one proposed supplemental lift system. Just hook it to get the lift you want. We're still working on other ideas. The silver item below the cord is the coupler that lets the front and back of the bike come apart for getting the Morph in a car.
We're debating aesthetics vs ease of construction. Here is an upper link arm with straight tubes. Much easier to make, but will it have that "cool" look that gets people excited? Other arm has the cuts/and welds shown.
Aye, she's a beauty, but oh, the work to make this part. Cuts, welds, and precision machining for the bearing races that mate at either end.
This design avoids having to seat bearings at each end. Uses ball joints. Hmmm.
Here's another way to complete the tube. A machine insert that is welded on. We're also thinking about teardrop tubes which would look much better than rectangular.
In the previous post, we had an issue with seat clearance to the main tube. The new design moves the cross-member further forward, so the horizontal supports can straddle the main tube.
A look at an assembled version using ball joints. I like the ball joints for the little seat adjusters. Not sure they're great for the main morphing joints.
Here is the e-Drawings file for the SolidWorks model: You'll need the free e-Drawings Viewer (for Mac or PC)