Saturday, July 26, 2014


Pot those motors right
Set them overnight

We decided to pull the motors off and do some work on them to better seal them against current leakage. The site had some other groups post about a method they used to pot the motors for saltwater use, so in the interest of a robust solution as well as the idea of possibly doing a saltwater flight someday, we got to work.

Here we go!

As you can see above, we pulled the brushless motors apart, and then wrapped them up in painter's tape, to make them into epoxy holding little buckets.  We filled the propeller holes with wax to keep those clear, and then Danny made a super high tech funnel out of tin foil in which we mixed and poured the 2-ton epoxy.

Goop Dreams

This was trickier than it looks, it really was.  The goal is to let that epoxy fill in every single gap around the wiring, but you have to take pains to keep this super viscous substance from dripping into the bearings (and all over yourself and your workbench for that matter.  Something I failed at.  My workbench is a minefield of epoxy drippings from this project now.)

Set time is 24-48 hours on the epoxy, and we did this on Thursday, so on Sunday I'm going to pull the tape and take a look.  The next step will be to bust the dremel out and smooth the epoxy down so that the motors fit back together again.  We've seen mention of folks on the OpenROV forums making new custom bushings for this process - this may be a direction we eventually have to take, I'm not sure yet.

Settle down, you.

We're really in the nitty-gritty of making the thing work now.  It's an interesting process to do a project like this - the excitement and anticipation of all the cool things we'll do with it gets run up against the reality that making something like this go is actually some hard work.  I've used computers and electronics my entire life, and have worked on computers professionally for a decade now, but only after building this thing have I truly gained a perspective of awe and appreciation for the electrical engineers in this world that make all the wonderful things in our lives just work.  And that's another thing I've loved about this project, and about doing science in general - I've learned things and gained perspective on things just by doing.  It gives me great hope for the future of this project and I am really excited to continue working on this ROV.  We hope to be back in the water soon, and the fun will really begin.  Until the next post, cheers and thanks for reading!

But first, lemme take a selfie

Wednesday, July 9, 2014

One does not simply dive into mordor...

The ROV ran into some problems during the test dive that we didn't encounter at home. As James hinted, there were some electrical shorts that we didn't previously notice or check for. Things had been going pretty well up to this point and it is only now that we realize the vast amount of effort required to make this thing go.

First, we discovered that the motors leak power into the water on all leads. Maybe some level is okay but we think that our readings were too high.

The water testing tank, donated from a different project
James happened to have a perfect water test tank. It was a 5 gallon bucket from a project that had holes cut in the side. These holes allowed us to bring the ROV connector outside of the bucket for poking and prodding.

See that tiny brown mark next to the motor? 
One of the wires in the harness was routed incorrectly. This put it too close to the motor bell and caused it to get sliced up. We think this might be wicking water into the battery tube causing the moisture that we observed. Hopefully we can fix that with a solder, hotglue and heatshrink (SHH) fixture.

James confirming the burned wire
In hindsight we could (should) have tested our motors submerged in water before potting the harness into the main tube. This way we could have tried a few times and made sure the wires were all sealed and long enough after being cut several times.

In any case it needs to come all the way apart and fortunately there is a small loop of extra wire for the entire harness. That will give us some slack to try fixing the seals on the motor solder joins. All nine motor wires need to be repaired, we think. The only external wires that passed the continuity test go into the IMU, indicating maybe the motors are the problem and not the SHH joints.

Tuesday, July 8, 2014

Mama didn't raise no pool

Hey everybody!

So after Danny's solo work on the ROV, the team decided it was time to do a water test.  Most of the team was able to get together the day after Independence Day at the home of some lovely friends of ours (thanks Hatches!) and test in their pool.

Perching peacefully before plunging into the clear blue

We booted her up and tested the camera, lights, motors - everything worked.  She's on and ready to go.  Check it out!

View of the pool from the onboard cam.  

We've got live video from the ROV and everything is in working order.  So here it is.  The moment we have all been waiting for.

The ROV is going under for her maiden voyage.  


Thar she blows

Woo!  We have live underwater video of the pool from the ROV!
I can tell you, the team was pretty excited.  We cheered and Danny flew her around the pool.  Awesome! But first thing we all noticed - the buoyancy wasn't quite right - she rose straight up, nose up, immediately after dunking.  It's important to balance the buoyancy of the ROV - flying up and down can burn through our battery needlessly, so we talked about ways to balance it out.

Pulled her back up - let's fix this buoyancy

And Richard contributed an interesting way of zeroing out that buoyancy:

Science can ball on a budget too.  Why not tape some rocks to the battery tubes?

So we taped the ROV down with some rocks to even it out and tried it again.

We toss it in and - Ruh Oh.  


Just kidding.  Did I scare you?  No, the rocks didn't crash our ROV.  They worked out eventually, although it took a few tries to get it right.  No - the latency we first noticed has now become much more pronounced, and motor control commands are either going sporadically or not at all.  The ROV DID fly around a bit, but never for long before shorting out.

We pulled the ROV out and checked for leaks, and saw none.  Although there was a slight bit of condensation inside one of the battery tubes, it was slight enough that we weren't convinced it was the problem.  

So sadly, we had to call an end to the test to come back and lab the ROV again to see what was up.

Next post, Danny will be explaining some problems we found with the ROV and what we need to do to fix them - check back soon for that story, more pics, and as always thanks for reading the blog!