APRIL 7, 2007: A BOUNCING FOUR-BAR CRACKS A WELD

During this test, there was no locking mechanism in the down position. (Although the Morph 2 design includes an up and and a down locking mechanism. We only built the up lock, which is safer to operate.) 

With almost 200 pounds of upward force coming from the gas springs when you are in the low rider position, we figured the down lock had to be perfect. If it ever released, you’d get quite a shock as the unweighted Morph sprang to the upright position.

So we left off the down lock and rode without it. This had the fun effect of allowing me to bounce while riding, somewhere in between up and down.
But take a look at the side view of the mechanism. There is a very large mechanical advantage applied to the gas spring. I think that both of them total 600 pounds for a 180 lb rider.

This means as you bounce along, your long lever arm over the attach point of the gas spring means you can apply a huge force to the to of the member. And that’s just where it cracked!
Crack in upper morphing arm.
Bill Warner on the Morph 2 prototype.
The final version of Morph 2 included some serious extra welding at the area of high stress. We haven't seen any problems so far. Nevertheless, the high forces here are something to keep in mind.