Brushless motor

[KR2_Diving]

Sounds like a good idea!
Steve has done a very good test using a varity of different props, and found that the Robb 50mm seemed to be the most effecient.

I would reccomend cornwallmodelboats.co.uk (or something like that).

They stock most of the props that Robb produces. The trick with those props is mounting them. I reccomend drilling out the brass insert and using a prop adapter similar to the ones used on model aircraft.

Sorry I can't post links, as I'm mobile at the moment...

Ryan
"KR2_Diving"

[ngkb]

It's alright! Because my project is going to be due-ed in 2 weeks time. Man i'm struggling with the props. now, thus i have to get it locally. I stay in Singapore, so yea, i have to get it here. However i know where I could get the props., just to make sure what diameter i should get.

Thanks for the recommendations though, i will get a 50mm diameter prop. to put in place and try it out!

[bikerbones1968]

Sounds like your doing everything right. 50 to 55mm diameter props on 750K to 950K brushless motors will produce quite a bit of torque and thrust. Depending on your ROV design and how hydrodynamic it is should push 10 to 12 kG very well. Just as a foot note to really examine your ESC specifications. Most "boat ESC's only operate at about 25% of max rpm when in reverse. Some car ESC's will only run at 75%. There are others that through calibatration or within setup menus will operate 100% in both directions.

[ngkb]

Erm biker, what do you mean by hydrostatic? Due to time constraint, my group decided to change the casing where all the batteries and ESC will be stored was changed to a squarish shape. I think it will weight lesser than 8 kg. so will my combination of 50-55mm propeller + motor still work?

About my boat ESC, I am able to make my motor move in reverse but I don't know about the efficiency. I wonder if I should change it to a car ESC or just stick with it since I had already bought 1. A boat ESC seems to be costly since it was already waterproofed.

[bikerbones1968]

Not Hydrostatic , Hydrodynamic. Hydrodynamic is to water as Aerodynamic is to air. General Physics dealing with the mechanical properties of fluids and pertaining to forces of motion in liquids. A flat faced box like structure moves less efficient through water than does a torpedo.

[leeinmt]

This is my first post here , but I have been lurking for a long time but with nothing constructive to contribute.
I am building my 2nd ROV but this time using the better technology that has come in the past couple years. The 1st was a miniature that worked ok, but was mostly a learning experience. This one is serious to look for a missing payroll treasure deep in Flathead Lake.
My thrusters are brushless outrunners 975 kv controlled by ESC's that have reverse capability. The motors are installed in oil filled containers and are connected to the thrusters via brass flex cables. The thruster props are mounted inside PVC housings with brass screen at each end to prevent snagging on fishing lines, etc. The ESC's are in the main body of the ROV which is kept at normal atmospheric pressure. I have two side thrusters which provide forward / reverse / lateral motion, and two verticals which give me forward and back up and down.
The teather (tether?) is an 8 conductor phone wire that transmits the command signals from a JR radio that I learned about on this forum. Bench tested, it works great.\
The main body of the ROV is a big piece of 6 inch PVC from Home Depot called a 'riser' - $8 something plus sales tax (we don't have sales tax here). Schedule 40, looks pretty tough.
Video is twin GoPro cameras to render stereo imaging for close ups.

Lee

[rossrov]

Welcome Lee. Sounds good, especially the oil-filled and flex-shaft thrusters. Have been thinking of using flex-shafts myself. This is a new way to do submersible ROV thrusters, as far as I know. Are you using this approach to get better flow through the shroud - unobstructed by motor housing?

Ross

[ngkb]

Oh ya, I managed to mix and match the mix menu and I managed to make it move forward/reverse/left/right!
Apart from mixing mix 1 and 2, i also went to mix in mix 3 and that made it work! (for my controller FS-T6)
THANKS Biker!

[leeinmt]

The flex cable allows for motor movement and bearing misalignment. Two motors are mounted at each end of a 5 " long oil-filled container (clear 2 1/2" OD acrylic tubing with a o-ring grooved end piece) and connected via a short flex cable to a short 3/16 brass shaft that exits the container at the other end through a stainless bearing and soft silicone grommet seal. This exit shaft then connects to the thrust propeller with a much longer length of flex shaft.
I originally had all 4 motors in one 3" oil container, but I shattered it on the lathe trying to trim the end shorter. Not wanting to buy an 8 foot length of 3", I am using two 2 1/2" tubes that I have a good supply of, with 2 motors each.
The flex cable is .098 diam (2.5 mm or 3/32") and is made by Octura, or at least it was when I acquired it at a Spokane hobby store several years ago - about $1 per foot. Amazingly flexible and can be silver soldered to brass tubing.
The propeller housing is thin walled 3" pvc drain pipe just long enough to house the prop and it's brass bearing supports. Two mounted midway on the side of the pressure vessel and one at each end mounted vertically. Stock tank test showed much better (anc cleaner) flow through the prop housings with the flex cable compared to a motor mounted inside the housings with the prop.
Thanks to Biker for how to wire my JR 75mgz rc transmitter to the receiver via the trainer cable.

Lee

[rossrov]

Cheers Lee. The flex rod to overcome bearing/motor alignment a good solution - suitable commercially-made couplings few and far between.