A PVC pipe ROV

Waterproof Housing, Frames, and Buoyancy Methods.
RonGinger
Posts: 6
Joined: Feb 1st, 2015, 8:32 pm

A PVC pipe ROV

Post by RonGinger »

A friend in town built an ROV a couple years ago that got me started thinking about building one as well. It seems like a perfect project for me- it requires a lot of building which I can use my CNC equipment for, and it will require some electronics and programming for control. And when its done it will be useful from my small Ranger 21 tugboat.

I found the http://openrov.com OpenROV.com web site and spent a lot of time looking at it. I almost bought the kit several times, but I was just not happy with the way they mounted the motors out in the open water. That might work in fresh water, but I will use my ROV in salt water.

I guess some other guys did not like the open motors because they started a kickstarter project to design and build a self contained thruster, the http://bluerobotics.com T100. I bought into the kickstarter for 2 thrusters. I thought I would do my vertical control with a ballast tank.

When the Thrusters arrived about the end of November I decided it was time to get serious. I spent a lot of time browsing the web and a few forums on home built ROVs and began to generate design ideas. I spent several hours in the plumbing departments of Home depot and Lowes trying to find PVC pipe fittings that would work.

I will use a piece of 4" PVC for the main hull. Since this will contain the electronics it must be watertight, but it also must be easy to open to make changes and charge the batteries. My fist attempt at an end cap was to make a disk with a flange that would slip into the pipe with an O ring seal. I made the disk from some scraps of a PVC house trim material a friend was using on a project. As I was making the disk I measured the inside of the pipe and discovered it was way out of round, and had several lumps that ran down the length of the pipe. Clearly this would never make an O ring seal.

Next I got a threaded plug fitting and tried to modify it to make it easier to remove, but still a tight seal. Eventually it became clear this was not going to work either, there was not enough material in the pipe end to make the shoulder for the O ring.

I finally settled on a simple flat plate with an O ring and a circle of bolts. To make the end of the pipe thick enough for the o ring groove and the bolt circle I added a pipe coupling which made the wall thickness about 1/2" inch.

Here is the coupling being stuck to the mill table with double sided carpet tape, then having the bolt circle drilled.

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Next I used the CNC mill to make the end plate with a 12 hole bolt circle. I made one of the solid grey PVC and the other of clear acrylic for the video camera.

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I gave up on the idea of a ballast tank for verticle control. I do not think it will give me the response I need to follow along the bottom looking for treasure ! So I ordered a third T100 truster.

My first design used a flat sheet of PVC as a wing like structure with the main tube under it. I used some 1" pipe to be the landing gear, but when it was all assembled I didn't like the look, it seemed to be to spindly.

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I cut the landing gear down and moved the main tube to the top. Once it was assembled I temporarily added the thrusters to see what it will look like. I think I am happy with this design and can now turn to the electronics and control.

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KR2_Diving
Posts: 391
Joined: Aug 30th, 2012, 11:43 am
Location: Currently: NW Suburbs of Chicago. Originally: NE Wisconsin

Re: A PVC pipe ROV

Post by KR2_Diving »

Awesome! Great to see the BlueRobotics Thrusters in action! Cant wait to see how you bring this all together!

Have you had a chance to test the water tight seal of your bulkheads? I like the idea of drilling right into the PVC. (I was looking into a more "external approach with slip rings and external hardware... but seeing what you did... i would be very interested in hearing about the seal and the performance of that method!)
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theinlinaung
Posts: 58
Joined: Jun 22nd, 2014, 7:48 am

Re: A PVC pipe ROV

Post by theinlinaung »

I look forward to your test results and how the seals hold up. Nice choice with bluerobitics thrusters.

IMO, your vertical thruster is blocked by PVC pipe and bottom plate. It could hinder and reduce the downward thrust which lifts the vehicle but the experiments will tell if that's the case.
RonGinger
Posts: 6
Joined: Feb 1st, 2015, 8:32 pm

Re: A PVC pipe ROV

Post by RonGinger »

No testing of anything yet, I live in Maine and right now I could not get to my dock or boat with a bulldozer- we have had about 6 FEET of snow this month.

The end cap idea is not mine, I saw it on a forum, here I think. To get a thick enough wall to hold the holes and O ring groove I glued a coupling on the pipe, then machined it flat and cut the grove. I have 12 10-32 SS screws to hold it on, and the O ring grove is sized to fit a .090 dia ring.

I am also concerned about the vertical thruster, but I just did not want to spend the money to get a 4th one to balance them off the pipe. The OpenROV has its vertical thruster more obscured than mine, so I guess I have to wait for some sea trials to tell. A nice thing about PVC pipe is its cheap- I dont think I have $50 in this yet, even counting the false starts and junked parts. If it turns out bad Ill make another one, and maybe buy that 4th t100. I am retired so have the time to do this.
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rusty
Posts: 6
Joined: Aug 5th, 2014, 12:43 pm

Re: A PVC pipe ROV

Post by rusty »

Ron,

I'm curious to see how the vertical thruster works as well. I can tell you that when we place objects (like hands) an inch or two in front of the thruster it makes almost no difference in the amount of thrust. For gentle maneuvering I think you'll be fine. For heavy lifting it might be a problem.

-Rusty
RonGinger
Posts: 6
Joined: Feb 1st, 2015, 8:32 pm

Re: A PVC pipe ROV

Post by RonGinger »

Since I expect to trim the ROV to be neutrally buoyant the vertical thruster should have little work to do. I do not expect to be lifting anything else.

I got my camera today, and I think I have the code written for the two arduinos. Ill post here when I get that working. Now I just have to wait for spring.
perfo
Posts: 151
Joined: Jan 27th, 2015, 12:05 am

Re: A PVC pipe ROV

Post by perfo »

I'm going through the same stage at the moment trying to find a compromise on looks , cost , ease of stripping down and water tightness. I suppose water tightness should have been the first in the list :).
Those look huge thrusters so I don't think you'll have any problems with a near neutrally buoyant ROV..
RonGinger
Posts: 6
Joined: Feb 1st, 2015, 8:32 pm

Re: A PVC pipe ROV

Post by RonGinger »

I thought a lot about how to get the wires to the thrusters out of the main tube and finally settled on using some
commercial watertight connectors. I tapped the hull tube for these and will seal them in with silicone.

At this point I have basically completed the hull and thrusters.

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Next I turned to making the tether. For this I bought a chap braided poly rope that is supposed to float. I found
some without a center strand, so I pushed the cat5 wire through the center. I hope this combination of floating
rope and wire will be about neutrally bouyant. It sounds crazy to push 100 feet
of wire through the center of a rope, but it actually worked easier than I thought it would. It did take a couple
hours and resulted in a small blister on my hand, but I now have what looks like a great tether.

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At the ends I split out the wire so I can have the rope tied to the ROV and to the boat and have the wire run
out to the control. I will make a stand to hold this reel and have a crank on it to rewind the tether.
a_shorething
Posts: 289
Joined: Sep 10th, 2013, 5:26 pm
Location: New Jersey Shore

Re: A PVC pipe ROV

Post by a_shorething »

Cool. That's exactly the tether configuration I plan to use. I'll be watching to see how well it works!
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theinlinaung
Posts: 58
Joined: Jun 22nd, 2014, 7:48 am

Re: A PVC pipe ROV

Post by theinlinaung »

Have you thought out the electronics and control system? And a camera?
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