Nautilus Drydocks ALVIN (3D printed)

[gboxwood]

It was time for the first water trials:

Senza titolo by Giacomo Bosso, su Flickr

Senza titolo by Giacomo Bosso, su Flickr

And this is were the learning process started...

[gboxwood]

Mistake #1

Initially it was impossible to pressurize the tanks above 1 bar without the solenoid valves to open "automatically" (they are normally closed). One bar could work (1 liter of air) but I was looking for more capacity.

I then thought about the connections into into the valves and I realized that by accident (read "not thinking about it") I connected the high pressure inputs to the wrong inlet of the valve, i.e., the inlet parallel to the spring.

ALVIN-032 by Giacomo Bosso, su Flickr

ALVIN-033 by Giacomo Bosso, su Flickr

I managed to consistently plug them in all wrong and as soon as I swapped the inlet's, I was able to pressurize the system to 3 bars (3 liters).
I could do more but then I need a new valve design which is a tight fit in the available volume of the cylinder and I think this will do for the time being.

[gboxwood]

Mistake #2

Well, the equipment cylinder took some water as I was testing it and I was 100% sure it was not the endcap seals as I pressurized the ballast tank cylinder with up to 5 bars with no leaks at all.

This left me with the dryseal and I became very skeptical about the design I have at the moment.

Eventually, it turned out the mistake was even simpler, i.e., I left one of the 2 waterproof connectors (the 4-pins one) unplugged for the test and that's what let the water in.

Senza titolo by Giacomo Bosso, su Flickr

[gboxwood]

Mistake #3

Regardless, and before I figured out it was the unplugged connector, I realized the dryseal strategy was not going to work on the long term for a principle flaw in the design.

Right now, the motor sits on the equipment tray and the dry seal is in the bulkhead: there will always be a degree of misalignment between the two and there is only so much you can do with cardans and/or flex couplings. This will result in a radial pressure on one side of the seal and at the very least, higher wear on the seals and/or more torque required from the motor.

I therefore decided to abandon this setup and design a new arrangement where the motor is attached directly to the endcap:

ALVIN-034 by Giacomo Bosso, su Flickr

ALVIN-035 by Giacomo Bosso, su Flickr

I have the dryseal assembly as a separate part with some play around it: I will glue it to the endcap with the driveshaft fitted so that the alignment will be as good as possible while the bonding happens.

I will keep you posted, enough for the moment.