String climb
The diabolo walks up the string on its own, driven by the friction of its own axle. A fixed axle can do it and a bearing axle cannot, which makes this the trick that decides which diabolo you want.
The string climb is the trick that explains the axle. The diabolo grips the string, and because it is spinning it drives itself upward along it, hand over hand, with you doing almost nothing. It looks like a trick about skill. It is mostly a trick about friction.
Why the axle decides this
A fixed axle is a solid bar. The string grips it, so the spinning axle pulls itself along the string. That grip is the entire mechanism of the climb.
A bearing axle spins inside a bearing precisely so the string does not drag on it. That is what lets a bearing diabolo spin for minutes on one throw, and it is also why it cannot climb: there is nothing for the string to grip. This is not a matter of technique or a better bearing. The climb needs the friction that a bearing exists to remove.
So if the climb is what you want, you want a fixed axle. If long spin times and vertical play are what you want, you want a bearing, and the climb is not part of that road.
The climb
- Get into a trapeze, and get the diabolo fast. The climb costs a lot of spin, and it will stall halfway up if you start slow.
- Hold the string vertical, the diabolo at the bottom, both strands close but not pinching.
- Feed string upward with small alternating pulls of each hand. Not one big pull. Small ones, quickly.
- The diabolo takes over. Once it grips it will climb faster than you are feeding, and your job becomes keeping the string straight in front of it.
Keep the string vertical. A string that leans lets the diabolo climb off the side of the axle and drop.
What goes wrong
It will not grip at all. Check the axle. If it spins freely when you turn a cup by hand, it is a bearing axle and the climb is not available on it.
It climbs and stalls. Not enough spin. The climb is expensive. Accelerate longer before you start.
It climbs crooked and falls off. The string was not vertical, or the two strands were at different tensions.
It grips and stops. You pinched the strands together and clamped the axle. Keep them apart.
It climbs beautifully and you cannot get down. Stop feeding and let it run out of grip, then drop it back onto flat string and catch. Coming down is its own trick and can wait.
When it is working
The diabolo climbs the full length of the string, under its own power, and you bring it back onto flat string without a rescue. At that point you own the fixed-axle half of diabolo, and the trick has told you more about what gear you want than any spec sheet will.