Nine dragon shells


How rugged are the nine dragon shells? Has anyone broke their’s at all?


I can’t attest to the new ones, but I have heard about the Delrin ones cracking.


That’s what scares me. I have some cool tricks I really want to try with it but I’m not sure how much stress they can take. Anyone know how much just the shells will cost?


in general the Delrin is much more elastic than polycarbonate instead is an absolutely rigid polymer and with little deformation capacity … so, personally I suggest you choose a version with shells Delrin to prevent likely cracking.


Wasn’t the point of the polycarbonate was that it was stronger (as well as lighter)?


The polycarbonate is much more durable.

$5 a pair for polycarbonate.

If you have a Delrin pair enter the trick contest in and score a set for $0. If you have broken a Delrin psi and want to enter the contest follow the instructions to get a set sent to you.

There will be a different spinning part also released later this month compatible with ninedragons too.


Only $5! That’s pretty cheap in my book! Thanks! :slight_smile:
May I ask what you mean by other spinning parts? Like the metal inner body or bearings?


The polycarbonate is more durable? At what? Not to shocks. Perhaps it is harder, but it is not absolutely elastic and this makes it very prone to breaking when it is subject to a force.
These two yoyo not have never hit anything , are new, the aluminum ring was installed by creating a force that compresses the material around, the Delrin has absorbed this force with its elasticity but not the polycarbonate and it is breaking … . just remember the YYF Northstar!!! In the event of a ground collision happens the same. Now choose your favorite shells.


Will we be able to buy both Pom shells and polycarbonate shells? I’m totally up for a stress test!


Pressing a ring into a rim results in a constant high level of stress in the material. Delrin, with higher elasticity, deforms more than polycarbonate, if the interference fit of the ring is the same. Also, the resultant constant internal stresses in the Delrin after the press would be lower lower than in the polycarbonate, that’s just physics. Impact physics are different than the pressed ring example, as the force of impact is localized, vary rapid, and does not result in any long term internal stresses in the material, unless some of the mechanical interfaces change, such as axles bending, bearing posts/seats/systems becoming bent or dislodged, etc. The stress wave the moves through the material upon impact travel through the material at a speed that is based on the Modulus of Elasticity and the density of the material, if the stress is in the elastic range of the material. Once the energy of impact has been fully absorbed and dissipated in the material, the impact event is complete, and there are no residual stresses left in the material. If the impact stresses are high enough, the material may locally experience plastic deformation, and even failure (fracture). Depending on the amount of deformation and/or material failure, there may be residual internal stresses in the material.

The fun part is when you look at an already pre-stressed yoyo, such as one with a press fit ring, and have an impact event…The additional propagated impact stresses add to the already existing “high” internal stresses and may result in some problems…



I believe as the manufacturer of the product in question that yyfben2 knows more than a little bit about what he is talking about here.


excuse, explain to me, because I did not understand, how it differs the breaking strength of a material subjected to:

  • a compressive force, constant (entered for intrusion ring)
  • more compressive forces but not continuous (repeated shocks).
    Thank you!


For the purpose of existing in this form on the nine dragons the polycarbonate is stronger, lighter and superior in almost every way.

For fun, not science


That’s science enough for me ;D


All that proves is you’ve got a weak left foot Ben… More science!


Made my day!


And what does that probe?
How did you fall on the polycarbonate shell with middle heel and placing the tiptoe!
Why do not send also two to me and I do the test !!!
Absolutely ridiculous! Today we discovered that the polycarbonate is more than titanium :
Falling, neither shell is broken and … What is the test.

P.s. Satisfy my curiosity, why for the first run of sales of nine dragon it has chosen the Delrin (more expensive to work) when you could be more fragile?


If you would look back on his post he says very clearly “For fun, not science”

Also, Delrin is machined, so the short term cost is relatively low so that if the 9 dragons didn’t do well they could cut their losses and move on. But seeing as it is popular they could invest in a mold for injection molded polycarbonate that is more expensive upfront and less expensive in the long run.

But I really don’t see the point in hassling poor Ben, its a miracle he has an account on here in the first place.


Game over…