OpenROV & the RC Submarine, crossover of technology


#1

Hi all,

I really dislike it when we 'reinvent the wheel', but I'm a firm believer in 'necessity is the mother of invention',

As a fully fledged & experienced Engineer Diver, I'm always looking for the easiest method to achieve any given task, 'KISS (Keep It Simple Stupid)'.

Due to the very nature that we are all human and therefore inquisitive and individual, our individual OpenROV's are very likely to be 'personalized', from the simple to the complex, and through that, we will all learn from each other.

I believe in the concept of 'Openness', that's how come we have evolved, we've shared idea's and developed them further, and in such a short time, IMHO.

With that said, has anyone looked into the crossover of technology between mini/micro ROV's and the RC Submarine industries? we're working in the same environment..... underwater, whether it be fresh or salt water. There is a lot of good technological information to be gained as well as a off the shelf parts, from sealing prop shafts to buoyancy control, to control systems, & we're working within the same voltage range, although OpenROV's will work deeper, it's just a case of stepping up the engineering for greater depth.

Let me start the ball rolling with this link.

Regards to all

James


#2

I completely agree with you on taking what works from existing established technologies / spaces, but my take on where the RC submarine technology falls short is that they dive nowhere near depths that the OpenROV is hoping to achieve (100M). So, their shaft seals, hull designs, etc might only have a tolerance to a 1 to 5M. I'm no RC submarine expert but from very cursory l googling "how deep can a RC submarine dive", those are numbers that I came up with.

Also, RC submarines use radio frequency, not tethers (that I'm aware of). So I think this is a major limiting factor to the community which thus means their physical designs only have to work to a much shorter depth.

Pressure calculator tool:

http://www.calctool.org/CALC/other/games/depth_press

Depth ATM Psi

10M 1.99 29.27

15M 2.48 36.56

25M 3.48 51.14

50M 5.96 87.59

75M 8.44 124.03

100M 10.92 160.48

Just my $.02


#3

Hi Marcus,

Thanks for the reply,

I wasn't inferring that we can use the current RC Sub technology directly, it would quite obviously need modification to fit in with the greater depths that ROV's attain.

The link I sent was merely for those that wish to explore, adapt and consider alternative solutions to the ROV project. E.g. I have seen enquiries on this project regarding ballast, trim, recovery and alternative methods of testing.

For someone wishing to 'test' an ROV, RC will work! to a limited depth (<=10m) i.e. bath, pool, pond etc.

Regarding 'shaft seals' it is literally a case of 'tolerance' & the number & composition of 'O' rings used. I personally work in the 25m - 100m range, and not a single piece of LSE (Life Support Equipment) I use in my work has more than 3 inline 'O' rings, in fact, I regularly use a CCR (Closed Circuit Rebreather) and most if it's components only have one 'O' ring, it's all down to the composition and tolerances of those 'O' rings.

Adaption of a standard RC Controllers to use an umbilical (my apologies I'm an engineer diver, and use the term 'umbilical' seeing as it supplies (think - unborn baby), as apposed to a tether, which restrains (think - animal)), is a very reasonable option while you learn, understand, build & test the umbilical & comms system, I believe Eric did this & we do it in our company.

Thanks for the Pressure calculation tool link, however, there is a difference in water salinity and composition i.e. Fresh Water, Brackish water, Sea Water & the industrial chemical properties contained within it and the effect of high and low pressure weather systems & altitude above sea level, all of which is quite difficult to calculate at a given time and location.

In our company we use the following algorithms for calculating depth:

Fresh Water Applications
Because most fresh water applications are shallow, and high precision in depth not too critical,
we use a very simple approximation to calculate depth:

depth (meters) = pressure (decibars) * 1.019716

For Seawater Applications
We use the formula in UNESCO Technical Papers in Marine Science No. 44. This is an empirical formula that takes compressibility (that is, density) into account. An ocean water column at 0 °C (t = 0) and 35 PSU (s = 35) is assumed.

The gravity variation with latitude and pressure is computed as:

g (m/sec2) = 9.780318 * [ 1.0 + ( 5.2788x10 -3 + 2.36x10 -5 * x) * x ] + 1.092x10 -6 * p

where
x = [sin (latitude / 57.29578) ] 2
p = pressure (decibars)

Then, depth is calculated from pressure:

depth (meters) = [(((-1.82x10 -15 * p + 2.279x10 -10 ) * p - 2.2512x10 -5 ) * p + 9.72659) * p] / g

where
p = pressure (decibars)
g = gravity (m/sec2)

This has proven to be as accurate as needed for Human Exploration of the Subsea environment and is therefore greater than that needed for ROV exploration.

I do hope this clears up any misunderstanding, I'm only trying to offer and give others idea's.

regards

James