I thought I would contribute to the forum on one possible solution (you can do it however you want) for mounting the BlueRobotics OpenROV Compatible Kit to a v2.7.
As you can see from the attached pictures, I deviated from the posted tutorial and mounted my horizontal thrusters to the top of the ROV frame instead of on the sides. I was concerned with “rolling” the ROV if they were mounted on the side walls. Luckily the v2.7 allows one to do this, not the v2.6.
I started by positioning one thruster at a time using just the back screw hole. I also used calipers to ensure both thrusters were placed the same by making light etchings in the frame.
After I was satisfied, I drilled one hole for the back screw and mounted each thruster. I then installed the inner frame and checked to see if the thruster was straight adjusting as necessary and then marking the remaining three holes for each thruster.
As you can see, I got very good results and I am confident the thrusters are mounted straight even if they were “eyeballed” in.
Thanks so much for posting your progress. This looks excellent. I really like the idea of mounting the thrusters to the top. I’m not too familiar with the v2.7 kit but it looks like this is the way to go.
Please keep us up-to-date on the rest of your build! Do you mind if we include some of these images in our tutorial?
Of course! Let me know if you need any more shots and I can work backwards the best I can. It mounts very easy and I have no problem taking it apart.
The vertical thruster is going to need some work so it doesn’t hit the E-tube, but I have some ideas. I only need to raise the propeller a few millimeters and it should clear it.
I just bought OpenROV Compatible Kit (#OROV-KIT-R1) for my 2.7, I expect to have to some modifications. are these thrusters different than the ones you showed??
The attached picture is everything I got in my kit: 2 Standard T-100’s, 1 M-100, Propeller and assorted mounting hardware.
I actually finished work on my 2.7 yesterday and everything works perfectly. After I get my endcap replacement set (yes, I messed one up), I’ll put up some pictures. I haven’t water tested it, but I know it is going to be stern heavy so I’m looking at flotation options.
The only other major modification is to find a new place for the IMU as it won’t fit on the top anymore due to the thruster cowlings. I’m going to make up something for it and mount it on one of the old motor mounts.
Thanks for the excellent information, I am wondering if I could create a platform for IMU protruding off the back. Let me know if the larger motors and magnetic field interfere with the compass. My ROV had her maiden run this morning and she was already a bit tail heavy. I am interested in installing a GoPro topside. Have you heard or seen anyone doing this? I was thinking I would add an addition vertical threaded rod forward to bring the bow down. Please let me know what you do.
Just a thought… I like the idea of the thrusters mounting to the top, but the original thrusters are mounted much lower. I am assuming they need to be mounted close to the center of gravity in order to maintain level forward travel. I am thinking that with the thrusters mounted so high, it may tend to force it down while moving forward. Perhaps a small spacer to drop the thruster down lower closer to the CG would help? This would also help clear the preferred IMU mounting location. I could be way off base with this. Please let me know if anyone has any knowledge of the subject.
You should be good to add the IMU off the back, but you just want to be careful you don’t knock it off in transit. And I think the magnetic compass was disabled on the current software release. I think it’s Inertial only right now.
For the GoPro, my friend Scott added one like this to the bottom. He uses it for making up wreck mosaics, but it can certainly be turned forwards. I think slinging it to the bottom is the best way as it adds a sort of “keel” to the ROV to balance it out.
Harry,
I was thinking about the thruster placement as well and I went into my copy of The ROV Manual to check to see if there was anything on the subject and there is not for how high or low thrusters should be placed on the frame. Center of Gravity (CG) is not the only factor in ROVs, there is also a Center of Buoyancy (CB), which I am taking into consideration.
I have a thought going that the closer to the CB the thrusters are, the more stable it will be. Is it true, I don’t know, I haven’t done the math, but I keep looking at the larger ROVs and all their horizontal thrusters are placed pretty high on the frame and very close to the floatation. The most I can do is try it!
As promised, attached are a few of my completed shots of my OpenROV.
You will notice that I made a little platform for the IMU that simply screws into the starboard motor mounting holes.
The functions and water integrity tests were SAT. I still have to go about adding buoyancy to the stern as it was pretty back heavy with the new thrusters.
Thanks for the excellent photos and info. My thrusters arrived today and I thinking of installing the main thrusters on spacers made of a material with positive bouancy to offset the weight. I am also hoping the spacer will allow clearance of the installed IMU. I am thinking of a PVC cap filled with bouyant material… I will post and share what I try.
I used 4 nylon bolts as spacers to allow the thrusters to clear the IMU with no issues. The main thrusters went in without any issues, make sure you leave about 12 inches of cable to allow you to disassemble the frame from the main ROV body. I had more difficulty with the vertical thruster. I made a motor mount out of surplus acrylic and glued it to frame. The motor mount plate is strengthened when the motor hardware runs thru it and is installed to the motor. I had purchase longer M3 stainless screws of varying lengths to accommodate the spacers on the main thrusters and some small spacers I made to accommodate the different lengths of the screws thru my homemade vertical thruster mounting plate.
My next step was to work on a buoyancy solution to make up for the heavier thruster in the stern. I used different sizes and lengths of PVC pipe figuring I could cut to length depending on the correct buoyancy. The larger PVC sections installed above and below served as unintended control surfaces and really had a negative impact on the control of the ROV. I found 2 lengths 3/4 of PVC pipe cut 15" running along the top and with the direction of travel worked well and the bouancy was pretty close.
Looks great Dave! I can also see you had some fun with this!
I took your advice and moved the thrusters down so that they are now inline with the old motor mount holes and it runs perfectly straight.
I also had it out in the ocean this weekend and it ran great even if it did get beat up with the current a bit. We were just drifting in about 200 ft of water.
It was like a 2x2 foot piece of Foamular XPS foam I picked up at Home Depot. I’m not sure on the density. It’s pretty rigid but will probably get crushed at about 20-30 feet, but it works well for testing in shallow water.
Let me know what you find. I’m on the hunt for some good stuff that will work down to 300 ft. So far, I would have to custom order a pretty large piece from General Plastics.
Kevin - What was your reason for initially mounting to the top of the outer shell, rather than the side. If I can’t come up with another solution for buoyancy, I will need some foam as well. Perhaps a few of us could split a piece to help keep costs down. How much better are these thrusters performing over the original OPENROV thrusters? I have not had a chance to work on this, but I m starting to wonder if it is worth the effort.
My experience with the Blue Robtics thrusters has been very good initially and well worth the modifications. I plan to use my ROV in salt and fresh water. I also fly RC planes and the Turnigy motors are at the bottom of the food chain and should be fine for occasional use but I would suspect frequency salt water use could be problematic. It is a very good choice in terms of an entry level motor and perfect for new users.
I would be interested in sharing notes and costs of a foam order. I was thinking of covering foam with fiberglass resin for water proofing. I am thinking of making a couple of horse shoe pieces of foam covering with fiberglass resin to account for saltwater, freshwater and different payloads. I am thinking of installing lengths of surgical tubing to allow stainless bolts to pass thru for installation.
Craft stores sell foam used for artificial plants that is easier shaped and cut which might be a good foam candidate.
I was just pointed to some fishing net floats, which come in hard plastic and hard foam varieties. These might work great and I’m sure they are more pressure resistant than the XPS insulation foam. The four blocks that Kevin is using are probably providing about 1.4 oz (40 g) of buoyancy each. You could replace those with four of these foam floats or plastic floats.
They are definitely a little larger for their buoyancy than the insulation foam.
We’d be happy to place a bulk order on foam if you guys can agree on a size. Kevin and I talked about the General Plastics R-3300, which is pretty well priced in quantity.
I originally mounted them to the top because that is where the shell is the most rigid and would still allow the installation of the poly-fin. I’m fine with the changes and the extra holes on top. Lesson learned.
Before we dive into the R-3300, let me try some of those foam floats Rusty found. Cutting one of the “hot dog” looking ones in half might work out pretty well and be more “off the shelf”.
I ordered 2 of each of the suggested net buoys from Memphis Net, I want to have a set for fresh water and another for salt. Depending on how the net buoys work out and if I mess it up I would be interested in getting in on an order with General Plastics. I am looking to shoot a grouper spawning event which happens every full moon. We plan to dive, place and tether the ROV on a ship wreck at approx 160 feet and wait for sunset. 100’s of Grouper are known to appear but it has never been recorded.
