Hi All,
I am sure that many of you have heard of the OpenROV Project which involves building your own ROV from a kit. I am an experienced model builder with plenty of experience and a reasonably equipped workshop, but I was a little taken aback at the complexity of assembling the OpenROV from their kit of parts. It seemed to me to be a high school to college level project requiring a small team of experienced modelers to successfully put the OpenROV together though I could be wrong.
It appeared to me that there were a number of critical assembly requirements that had to be performed spot on as there was no going back to realign or reseal once the assembly was completed. Therefore I have been looking around to see if there might be an easier way to design and build a ROV similar to the OpenROV without having to perform some of the critical assemblies required to complete the OpenROV.
One area of the OpenROV design that I took exception to was the thrusters. They were not going to last very long when immersed in seawater due to the exposed bearings and stator/armature. To me this was a kind of deal breaker as to the questionable lifespan of these thrusters. I know that commercial thrusters are not cheap (think Seabotics or CrustCrawler) and the OpenROV project was just trying to overcome the high price of commercial thrusters with their homebrew design. Still the unknown lifespan of the OpenROV design did not leave me with a warm feeling to say the least.
Then came along Blue Robotics and their T100 Thruster KickStarter Project Link. Their design approach looks good and they have actually tested and characterized prototypes of the thrusters they will deliver to the pledgers. With the addition of the in-thruster water cooled ESC this design becomes very attractive in that it reduces the number of wire penetrations in the Water Tight Compartment (WTC).
Great! Now we have a source of reasonably priced thrusters so what is next? Well, that is where you, the ArduBoat members, come in.
Let's start thinking about the WTC, navigation controller, communication, power, ballast, buoyancy, etc. and attempt to come up with a reasonably priced ROV that the average ArduBoat member might want to consider building.
Regards,
TCIII AVD
Replies
Hi Rusty,
Without the batteries, the ROV Chassis was about only 75 percent submerged.
The batteries weigh about 2.2 pounds which will help with some negative buoyancy, but the Navigation Controller board will not add much in the way of negative buoyancy.
HDPE is about as close to neutral buoyancy as a material can get and the two 4" diameter WTCs are adding quite a bit of positive buoyancy.
Ok, maybe I will start with two 5 pound PVC tubes of bbs (0.5 ft X 1.5" in diameter) and see how close I can come to neutral buoyancy. PVC pipe is cheap and I can always buy more to make the pipes longer if necessary.
Regards,
Tom C AVD
#9 lead shot would get my vote. Very little air space or epoxy space between the shot. You have to buy a 25# bag unless you have a friend with some. It's a winner as far as density goes but pricey. We use it in model sailboat keels. About $2 a pound I think at Bass Pro Shops
Regards
David R. Boulanger
Hi David,
Thanks for the suggestion, much appreciated, but for the amount of ballast I think that I will need, the bbs are still the most cost effective.
Regards,
Tom C AVD
I just happen to have several tins of lead air gun pellets that I will likely use on my build. If I didn't already have them I probably wouldn't consider using them as I'm sure there are cheaper sources for lead out there.
Don't forget to leave some ballast for trimming the ROV fore/aft and port/starboard as well as adjusting for fresh/salt water and tooling changes.
Hi All,
For those of you with a GoPro HD/2 or GoPro 3/3+/4 and would like to use your GoPro on your ROV, you might want to checkout the GoPro watertight housings offered by Eye of Mine.
These housings have a SD composite video connection to the back of the camera housing and are good down to 200 feet. The SD composite video cable is 5 mm in diameter and will easily fit into a BR cable penetrator. The SD composite video can then be brought into the WTC through the cable penetrator and then connected to the ROV Tether. The nice thing about this housing is that the camera can be positioned anywhere on the ROV chassis and the GoPro can record HD video on the removable SD card, for later review, while streaming the live SD composite video topside.
Regards,
Tom C AVD
Tom,
Once again thanks for the heads up on interesting stuff. I have a Hero 2 and a 3+Black. These small housing are prone to fogging up though. They sell small packets of some material to insert in them to help with the condensation. I suppose the water temperature you are in has a lot to do with it. But again, good find.
Regards,
David R. Boulanger
Hi David,
Maybe the waterproof case could be baked out in an oven at a moderate temperature and then the camera installed and the case sealed up?
Regards,
Tom C AVD
Tom,
Even sealing it up in an air conditioned car might help with the high humidity environment we live in. Never tried the moisture strips or packets though.
Regards,
David R. Boulanger
Hi All,
Since I cannot move forward with the Battery and Navigation Controller portion of the Project until additional components arrive, I thought that I would test the buoyancy and trim of the chassis today.
With an assist from my son-in-law we took the ROV chassis down to the Association swimming pool and gently slipped it into the pool water. In all honesty I was expecting the chassis to start to sink to the bottom of the pool, but much to my surprise it actually floated at a slight angle with about 25 percent of the chassis above water.
I suspect that the Thruster ESC cables, being connected to the WTCs in the rear of the WTCs, is causing the chassis to list slightly towards the stern. So it looks like I am going to have to add some ballast to the chassis even after I add the batteries and the navigation controller to their respect WTCs. However I suspect that not much ballast will be required to reach neutral buoyancy and to trim out the chassis.
Since I plan to add a gripper and lights to the chassis, I think that I will need even less ballast in the long run.
I plan to run a ballast and trim test as I add the additional components, like the batteries, navigation controller, and lights to the chassis and adjust as necessary.
More to come.
Regards,
Tom C AVD
Hi All,
Today I ordered two Turnigy-nano tech 5000mah 3S 35C LiPo batteries from Hobby King, one EC5 Battery Parallel Y-Harness, and two sets of E-Flite EC5 Device/Battery connectors to change the LiPo battery 4mm connectors to the E-Flite EC5 battery connectors and one EC5 device connector for the input cable for the Battery Junction Board.
As soon as these components arrive I will change out the battery connectors with the EC5 connectors, size the length of the Battery Junction Board input cable, and then install a EC5 device connector on the input cable. At this time I will also size the Velcro strap that I will use to hold the two LiPo batteries to the battery sub tray to keep them from shifting around when the ROV chassis rolls.
Now I will be ready to attach the ESC power cables coming from the cable penetrators to the power cables attached to the Battery Junction Board.
As far as the Navigation Controller goes, I am still waiting on the custom Tether that I have on order and I am also considering looking into collaborating with a local electronics developer to design and build inexpensive ROV top side and bottom side navigation control and video boards for hobbyists. I plan to use these in place of my original simple two board ROV control system.
More to come.
Regards,
Tom C AVD
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