Pressure Testing Results!


#1

Hey Guys, After an Etube end cap failed on an expedition in Lake Shasta, we decided to conduct an experiment on end cap assembly and methods which we believe might negatively affect the integrity and therefore fail at a lower PSI than expected.


We lost many end caps and Etubes in the process, but we came out of it more knowledgeable about our product!
https://forum.openrov.com/uploads/openrov/3413/7e2b637f8cff6f07.jpg
https://forum.openrov.com//uploads/openrov/3414/cb0bad43ef475d95.jpg

  • End Cap 1: Acrylic cement was applied and while curing, it was shifted or twisted and shifted back. Done by JR
  • End Cap 2: Acrylic cement was applied and while curing, the two acrylic pieces were taken apart and placed back together. A moderate amount of acrylic cement was added for support. Done by JR
  • End Cap 3: Similar to End Cap 2 except no acrylic cement was added afterwards. Done by JR
  • End Cap 4: Acrylic pieces were placed together and acrylic cement was added along the edges and spread as much as possible through capillary effect. Done by JR
  • End Cap 5: The faces of the acrylic parts being cemented together were first breathed on adding a layer of moisture onto the surface before being moderately acrylic cemented on. Done by Zack
  • End Cap 6: Similar to End Cap 1 except it was twisted immediately after acrylic cement was applied. Done by Brian
  • End Cap 7: Acrylic cemented together with the center hole not being concentric. The inner 1/8in piece and inner 1/4in piece are concentric due to the syringe but all other pieces outside of that are off center. Done by Brian
  • End Cap 8: The end cap parts were first dropped on the floor to collect dust / dog hair. Then we acrylic cemented the pieces together with the dust / hair in between the pieces. Done by JR
  • End Cap 9: This end cap was built quickly with moderate amount of acrylic cement. Done by Brian
  • End Cap 10: This end cap was built “production level” by Zack. “production level” refers to the quality we build the ROV end caps here in house for assembled units. Applied a generous amount of acrylic cement between the pieces and once placed together, spread throughout majority of the surface with minimal air gaps.
  • End Cap 11: Production level by Brian
  • End Cap 12: Production level by JR

Conclusion

You can make a reliable and sturdy end cap if made correctly. A crylic pieces need to be generously given acrylic cement all along the surface so that the pieces adhere completely to one another. A good sign of complete adherence is being able to see clearly through the two pieces without having any circles of bubbles or gaps of any kind. If built properly, the end caps will be reliable at 100m depth and even deeper.
E Tubes
It came about that when we were testing different end cap construction methods, we reached a problem that the acrylic main tubes would collapse before our target PSI. This led us to take a random sample of the tubes and place them in the pressure chamber for testing. We tested each to fail and recorded the pressure (relative) at which each of the tubes failed. The strongest tubes failed at around 145psi (which would be 101.9 meters fresh or 98.9 meters salt if adjusted to absolute pressure) and our weakest at around 110psi (77.3 meters fresh or 75.1 meters salt). The average was 132.5psi relative. This corresponds to 93.2 meters in fresh water and 90.4 meters in salt water. Previously we stated we have a maximum depth of 100 meters, but now with our modern tubes it has become a maximum depth range of 75 - 100 meters. To ensure no implosion on your E Chassis, prevent from diving beyond 75 meters.

We will continue to find ways to push the limit and explore beyond 100 meters and will keep you guys updated on any discoveries.

Don’t let this happen to your Etube!!

https://forum.openrov.com/blogs/1-1000/37-IMG_20141015_144008887.jpg


[solved] Endcap does not have complete coverage with cement between layers, is that a problem?
#2

Great information. Don't ya just love destructive testing... Expensive, yes.... But FUN and oh so necessary.


#3

Nice info's

The dog bowls are for testing baby OpenROV's ???


#4

Sounds like there is a lot of variation possible in the end cap assembly that can adversely affect depth rating. It would be helpful if you could provide before photos to indicate what a non-production level cap would look like. There is a bit of a nack to putting them together and we only get one chance as kit owners.