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
A turns counter is a useful addition, but on a battery powered micro ROV where your source of power is limited I think a disconnect is still the better way to handle this... although an even better solution would be to have both. :)
John,
That's a great idea and I'm sure we can integrate that into the software.
-Rusty
Hi All,
I have attached the ROV end cable penetrator to the neutral buoyancy Tether as shown in the picture below. Since the Tether is 75 meters long I stripped approximately one foot of insulation off of the ROV end of the tether to give me a sufficient length of twisted pairs for connections within the Navigation Controller WTC.
Cable Penetrator on ROV end of Neutral Buoyancy Tether
Since the Tether cable will eventually be wound around a cable drum that will include slip rings, I will hold off making any permanent connections to the Topside end of Tether cable.
The path forward now will be to electrically connect the Topside Interface Board to the ROV-side Interface Board through the Tether cable and then attempt to communicate with the ROV-side BBBMINI Navigation Controller from the Topside laptop running QGC. To that end I have fabricated a bi-directional level shifter to convert the 5 vdc serial output of the ROV-Side Interface Board to the 3.3 vdc input of the BBBMINI telemetry connection. The level shifter is a Sparkfun standard bi-directional level shifter available here. There is no need for a Topside level shifter as the communication between the laptop and the Topside Interface Board is done through a USB interface.
Once the Topside QGC has been setup to work with a gamepad controller Linus and I will attempt to communicate with the ROV-side BBBMINI running an alpha version of ArduSub.
More to come.
Regards,
Tom C AVD
Tom,
Looks good so far! I know it's a bit late in the game with the tether connection already being epoxied in place, but have you considered using wet-connectors for a quick disconnect for the tether?
I have had great success using them on my OpenROV based vehicles, and I find having a detachable tether quite convenient when toting around the vehicle and tether reel. I typically have 100m, but I will be adding another 100m extension. I have been using the SeaCon ones available from Amron.
http://www.amronintl.com/seacon-mcil8m-micro-wet-con-inline-connect...
A bit on the expensive side, but you get what you pay for and having a detachable tether is now a requirement for me.
Kevin
Hi Kevin,
Thanks for the kudos, much appreciated.
I will take a look at the SeaCon connectors and see what I might be able to do even though the cable penetrator has already been installed.
Regards,
Tom C AVD
I'm with Kevin, I highly recommend a disconnect fitting at both ends of your tether. If you don't you'll wish you had. My Deep Trekker didn't have one and it was a PITA to have to spin the ROV around to take out all the twists at the end of every dive.
Rusty's also correct. You will want to make sure that the strain on the tether goes directly to the ROV's frame. Lots of ways to do it, take a look at some of the commercial ROV's to get ideas.
Tom,
If you do end up using a connector, make sure you place it between the enclosure and the thimble so that the tether still maintains it's pull strength. The Seacon connectors don't have any way to attach the Kevlar strength fibers from the tether.
-Rusty
Hi Tom / Rusty,
I guess you are talking tether strain relief, you could also use a prussick knot setup with a small dia dyneema rope & bridle to the frame.
regards
John
Looks good, Tom! I'm excited to see this move forward.
-Rusty
Hi Rusty,
Yes, we are now making progress again:-)
Could you provide a picture or diagram on how the ROV end of the Tether cable should be oriented in the Thimbles and where the Thimbles should be attached to the ROV Chassis?
Regards,
Tom C AVD
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