r/rov

Any Rov pilot out there using a 3 finger claw on a schilling titan 4? I'm having a lot of issues working with the stock jaw. Is it worth it to swap to a 3 finger jaw? For context it is for uxo dredging jobs.

Hi, for my next DIY ROV, I am trying to design bi-directional ducted thruster propellers (which would have equal thrust forward and backward), and I've been using OpenProp and it's recent reimplementation PythonProp to iterate over various designs to try and find the most efficient one within my constrains.

I need some help / guidance with this.

My constrains are:

Thruster hub => 32mm in diameter to fit small BLDC motors.

Duct diameter <= 70mm (it's a very small ROV)

Motors - I can choose from 950kv A2212 (proven choice in the past) or 350kv F2838. Not many other motors in between.

I wrote an OpenProp script that keeps the torque (Q) of the motor constant to give prop designs a fair comparison, assuming I would be running motors at or near their maximum torque capacity. From datasheets, I calculated it to be ~0.1 Nm@10000 RPM for A2212, and 0.2 Nm@3000 RPM for F2838.

First, disregarding these two motors, for a baseline, at 0.15 Nm torque I swept through the RPM range from 3000 to 10000, noting efficiency and thrust:

Q	Z	RPM	D	T	EFFY
0.150	2	3000	0.070	18.782	0.398
0.150	2	4000	0.070	23.532	0.374
0.150	2	5000	0.070	27.520	0.351
0.150	2	6000	0.070	31.060	0.329
0.150	2	7000	0.070	33.844	0.308
0.150	2	8000	0.070	36.113	0.288
0.150	2	9000	0.070	38.042	0.268
0.150	2	10000	0.070	38.960	0.248
0.150	3	3000	0.070	18.669	0.396
0.150	3	4000	0.070	23.189	0.368
0.150	3	5000	0.070	26.788	0.342
0.150	3	6000	0.070	29.925	0.316
0.150	3	7000	0.070	31.907	0.291
0.150	3	8000	0.070	33.286	0.265
0.150	3	9000	0.070	33.804	0.239
0.150	3	10000	0.070	33.361	0.213

As you can see, efficiency clearly drops with higher RPM, suggesting I should stick with low kv motors. Difference between 2 and 3 blade props is minor. This holds true for all D values. I also played around with various blade chord scaling factors, but surprisingly, even making blade 2x larger doesn't seem to affect numbers much.

So, sticking with 0.2Nm@3000RPM, all I'm left to play with is prop diameter and blade count:

Q	Z	RPM	D	T	EFFY
0.200	2	3000	0.070	22.869	0.363
0.200	2	3000	0.065	20.900	0.333
0.200	3	3000	0.070	22.827	0.363
0.200	3	3000	0.065	20.991	0.334
0.200	3	3000	0.060	18.559	0.296

And from here it is obvious that larger diameter is better, both for thrust and efficiency. Blade count is once again (surprisingly) inconsequential.

I also checked hub diameter influence on the results, and it's clear that smaller hub always wins, so I'm skipping that table.

So, with my "best" design, Dhub=32mm, Z=2, D=70mm, I get 22.86 N of thrust (which is enough), but only 36.3% efficiency, which is terrible.

This was all done using this blade chord profile:

https://preview.redd.it/hx73bfk0lq0h1.png?width=901&format=png&auto=webp&s=24f3d7fdfb5510a55f34d816180027ff0786b78e

And section profile used parabolic meanline and elliptical shape. After exporting the section curves to 3D, they look like this:

https://preview.redd.it/f8q745i7lq0h1.png?width=1443&format=png&auto=webp&s=65e920b7e04496899e5d61831b9da29cb4517461

Also confirmed by 2D blade image from OpenProp:

https://preview.redd.it/il1ywi5ilq0h1.png?width=1247&format=png&auto=webp&s=8692333ab357c3ca3c7ecdea94ef9809cd6e9692

Now, I don't know much about propellers, but something tells me that such a small radius of curvature at the tip of the blade (black section) is really bad. No way the flow can be expected to follow such a tight curve without detachment.

But the only way I can find to solve this is either increasing blade count (helps a little), increasing prop diameter (which I can't do due to my constrains), or decreasing torque/thrust (which won't utilize my motor to the max).

Can anyone experienced with propeller design help out a newbie? Is there something I'm doing wrong here, or is this the best I can expect with my constrains? Is there any way I can achieve higher efficiency without losing thrust or increasing prop diameter? And how do I get rid of that "hook" at the tip of the blade?

I would really appreciate any comments. This is my 3rd attempt at getting help with prop design over various subreddits, and no one seems to be answering :(

Hi everyone,

I’m working on a low-budget underwater lake surveying project using a FIFISH V-EVO ROV, and I’m trying to figure out the best practical architecture for large-area coverage.

My original goal was underwater 3D reconstruction / photogrammetry of entire lakes, but after researching more, I realized the real challenge is not just imaging, it’s trajectory consistency and localization underwater where GPS doesn’t work.

Current idea:

• Use the FIFISH V-EVO mainly as a stable sensing platform
• Add an external IoT payload with:
  • pH
  • temperature
  • turbidity
  • TDS
  • dissolved oxygen
  • ORP
  • depth sensor
  • IMU
• Create environmental + bathymetric maps instead of full photorealistic reconstruction initially

Main problems I’m facing:

1. How to generate repeatable survey paths over large lakes?
2. How to semi-automate the survey process with a FIFISH V-EVO (which doesn’t seem to support waypoint missions)?
3. How accurate would a surface GPS float/buoy system be?

One idea I had:

• Attach a floating buoy above the ROV using a short tether/rod
• Put GPS + telemetry on the float
• Use the float trajectory as approximate underwater positioning
• Possibly combine this with depth + IMU data

Questions:

• Has anyone here attempted large-area lake surveying with a tethered consumer ROV?
• Is surface-GPS-assisted surveying a reasonable approach?
• Would an autonomous surface boat towing/guiding the ROV make more sense?
• Any recommendations for low-cost bathymetry methods?
• Has anyone used RealityCapture / RealityScan / Gaussian Splatting underwater?
• Would stereo cameras help underwater in low-visibility lakes, or is sonar the only realistic route long term?
• Any advice for maintaining repeatable grid/lawnmower survey paths underwater?

Budget for the additional system is around ₹30k INR (~$350 USD), so professional USBL/DVL systems are unfortunately out of reach.

I’d really appreciate practical engineering advice from people who’ve actually worked with ROVs, hydrography, photogrammetry, or environmental surveying.

Thanks!

Hi everyone. By trade I’m an elevator service guy but I’m looking to start a side business using ROVs and Drones. During covid I cleaned hulls and I really enjoyed the job just didn’t pay enough. I’ve been in contract with a couple yacht brokers and am trying to brainstorm more ideas for the ROV side of the business. Small scale, anyone have any ideas? Hulk inspections and dock inspection are about all I’ve got so far.

Hi everyone, I’m just wondering what pathway we all took to get into rov work. I’m 19 and thinking of working my way towards it. My number 1 right now is getting into the Navy as an engineer. Any advice and your thoughts on the job would be appreciated aswell.