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 All,
For those of you who will be checking your WTC for its water tight integrity using a vacuum pump, please find attached a useful document that may help you distinguish a true vacuum leak from an outgassing induced vacuum loss.
Regards,
Tom C AVD
RateofRise Curves-Diagnostic Tool.pdf
Hi All,
It looks like I have identified the source of the vacuum leak in my Battery Compartment WTC vacuum test setup.
As I stated previously I had purchased a cutoff ball valve that was specifically designed for compressor/vacuum systems. I used the new ball valve to replace my existing universal cutoff ball valve in the vacuum test setup. After pumping down the WTC to 550 mm Hg I closed the cutoff valve and waited half an hour before checking the vacuum gauge which had stayed at 550 mm Hg.
So far so good. So I opened the cutoff valve after starting the vacuum pump and the vacuum gauge did not move off the 550 mm Hg mark. So I waited for an hour this time and then checked the vacuum gauge which again had not moved off of the 550 mm Hg mark. So it looks like it was the original universal cutoff ball valve that was leaking air back into the WTC after the pump down.
Now I can move on to completing the assembly of the Battery Compartment WTC and then move on to the Navigation Controller WTC assembly.
More to come.
Regards,
Tom C AVD
Wew! Well that is a relief! Glad your potted fittings seem to be well sealed. I would be interested in learning more about the pump and other fittings you've settled on for your test. I may need them when I get to that point in my build.
Hi bigkahuna,
Your test setup can be on the low cost side like mine or more high end like Blue Robotics.
My setup uses the following components:
vacuum pump: http://www.amazon.com/gp/product/B00DYA21PU?psc=1&redirect=true...
vacuum gauge: http://www.harborfreight.com/fuel-pump-and-vacuum-tester-93547.html
cutoff ball valve: http://www.homedepot.com/p/Husky-1-4-in-Full-Port-Ball-Valve-HDA701...
Plus 1/4" ID diameter vinyl tubing and an assortment of 1/4" barbed brass adapters and threaded brass "T" blocks that you can get at Home Depot in either the plumbing or air tool isles.
Blue Robotics used these more expensive components:
vacuum pump similar to this one: http://www.amazon.com/1-Stage-Vacuum-Pump-Rotary-R410a/dp/B00CDL9OG...
vacuum gauge: http://www.mcmaster.com/#38545k5/=zfqdyn
cutoff ball valve: http://www.mcmaster.com/#4112t13/=zfqe9f
vinyl tubing: http://www.mcmaster.com/#5393k31/=zfqgzs
Plus an assortment of fittings similar to mine to get the components hooked together.
Regards,
Tom C AVD
Hi Tom. Do you have any photo's you can post? I've seen the photo's you have posted in this thread to date but any updates would be great. I can see the bits but not sure how your putting everything together - even if its partially done I'd love to see any updated photo's you have.
Thanks, Grant.
Hi Grant,
Are you referring to the vacuum test setup or the ROV?
In any case I will provide a picture of the vacuum test setup shortly.
Regards,
Tom C AVD
Thanks, time to go shopping.
By the way, I used a HVAC pump like what Rusty is using for vacuum bagging composites. Got mine for $25 used from a HVAC repair shop. Worked like a champ.
Hi bigkahuna,
During my G mail conversations with Rusty, he informed me that they tried different cable potting techniques where in one case they carefully potted the cable in the cable penetrator and then another case where the potting was sloppily applied as someone in a rush or an inexperienced builder might do and they still found the cable/potting seal to be vacuum leak proof.
However, one thing that must be kept in mind is to insure that there are no nicks/cuts in the cable jacket that can expose the inner wires to the outside environment. If a cable has a nick or cut, do not attempt to pot it especially if it is an ESC power/signal or Thruster motor cable.
Based on my testing, I would say that Blue Robotics cable potting process, if conducted per their tutorial, will be leak proof as long as the cable has not been compromised with a nick or cut in the cable jacket.
Regards,
Tom C AVD
Hi All,
Rusty and I are still troubleshooting the 20 mm Hg/hour vacuum leak that I am experiencing with my Battery Compartment WTC.
Today I went to Home Depot and purchased an air compressor cutoff ball valve and used it to replace my present universal cutoff ball valve to see if the leak is being caused by the ball valve.
I presently believe that the leak is not in the WTC and needs to be isolated to a component /connection in the vacuum test setup.
More to come.
Regards,
Tom C AVD
Hi Tom,
I've designed and begun building a mini ROV using Blue Robotics components. You can follow my progress here:
http://marinesimulation.com/?page_id=1571
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