heeding advices from boating players for my FYP project

[^ZEd^]

I'm currently doing a FYP project on RC submarine. After designing the submarine, i have got concerns over water leaking into the gearbox and motor chamber through the propelling shaft.

In my design, what i could think of was just to use rubber-sealed bearings which might not be sufficient to stop water from seeping in. The submarine is suppose to go under water abt 10m, so the water pressure is pretty high. Anyone here have the expertise in this field, or has got ideas or concepts in designing the propelling drive-train of submarines to solve this problem?

Thanks in advance~~~=)

[ammo]

10 meters is a very considerable depth for r/c subs.

Even the popular thunder tiger sb-1 has a structural LIMIT of 10m.



Rubber sealed bearings will not stop leakages at all.
Maybe, you'll need a rubber seal in the form of multiple O-rings, etc.
SB-1 uses a preformed seal.

[Adrianli]

I am not sure the size of ur sub and the speed u want it to move. I suggest :

1) The use of lots lots of grease + rubber seal.

2) The use of magnetic driven props.



Otherwise if u have access to cnc machine, take a look at pump's mechanical seal. These are wear and tear items that are changed on regular basis.

[^ZEd^]

thanks for all the valuable advices. seem like mechanical seal is a great option.

sorry, may i know how do i put rubber seals on the shaft to prevent water from going into the gearbox? jus stuck it together with the shaft close to the gearbox opening?

[Akula]

At 10m your water needs to be pretty clean!!!

Sea water wont pass any singal
River water probly 5-6M (if you can see it)
Pool - depends on chlorine levels

Seals - orings are obviously simplest but not that good. specialist seals (and other stuff) can be found here

http://www.mikessubworks.com/page1.html

The push rod seals and 380 drive seal can both be used for roatating or linear shafts. postage isnt that bad and they are very reliable to deal with

For the drive train you might want to look at their 380 Drive system, combined with the 380 seal.

What ballast system??? I am experimenting with a RCABS (recirculating air ballast system) which is very simple yet effective.

OK now i've started here is a simple shopping list of things to build a WTC for a reliable static sub, using attached website

all numbers in USD
380 drive system - $37 - You could use a standard motor but maybe it will be too fast and you will also need to create a 1/8" output shaft (YMMV)
380 Seal - $8
Pushrod seals $16.95 (this is a pack of four and you only need 2 [rudder servo and elevator servo] on simple sub so you have 2 spare.
Bladder $16-24 dependant on size of sub (might be able to find something locally (they are out of blood pressure measuring machines, its the cuff that tightens around your arm)
Air pump $47.5 - expensive, some other places have them for <$20, but then u need two lots of postage. maybe can find locally
Sub safe 2 $27.5 - u really need this.

Useful to have but can make yourself
3" od x 12" $58 - yeah pricey, and really want to be a bit longer. The end caps cost the money also the tubing is Lexan (which i cant find here and ive tried hard - if you find some let me know).


Other things you need inside the tube
RX - obviously
ESC - preferably reversible
Servos x3
Schrader Tire valve !!!
micro switch


Simple RCABS WTC
So the motor drive unit gets installed in one end cap, with seal on outside.
Then you need to mount two servo's to the end cap and have them with push rods going out through two of your pushrod seals - this controls the up and down dive planes. A forth hole through the end cap should have small brass pipe, the outside of which connects to your bladder and the inside has a T piece.

make a small shelf to fit inside the tube, on this you mount your other stuff.
Machine away, or cut or file the shrader valve so that the pin is exposed! you then mount the thrid servo so that in one direction it pushes the micro switch (which you connect to the airpump). in the other direction the servo pushes the pin on your schrader valve!!! . Not connect your schrader valve and airpump to the T piece. still with me?. Lastly the fail safe should be in series with the third servo.

you need 4 channells BTW.

When you move the 3rd servo so it hits the switch the air pump turns on and pumps the bladder full of air, making your sub bouyant. when you move servo to hit the pin, it releases the valve and the air flows back into the WTC and your sub sinks.

If you go too deep and lose signal the Sub safe will move the servo so that the pump starts.


Make sense?????

[Akula]

further to earlier heres some photos to make it clearer.

Dive module right to left
RX
ESC
Airpump
just in front of it - schrader valve
third servo
micro switch
above the micro is my home made brass t piece

there are two circuit boards under the micro, one is the sub safe the other is a leveller (nice to have but not 100% required)

End Cap
I use "Engel" motor, mount and bellows on this one, but same principal

Ta Daa
Shows the whole lot complete with battery under the shelf. Overall length is 305mm and 75mm dia.

[Akula]

sorry 350mm long

[^ZEd^]

At 10m your water needs to be pretty clean!!!

Sea water wont pass any singal
River water probly 5-6M (if you can see it)
Pool - depends on chlorine levels

Seals - orings are obviously simplest but not that good. specialist seals (and other stuff) can be found here

http://www.mikessubworks.com/page1.html

The push rod seals and 380 drive seal can both be used for roatating or linear shafts. postage isnt that bad and they are very reliable to deal with

For the drive train you might want to look at their 380 Drive system, combined with the 380 seal.

What ballast system??? I am experimenting with a RCABS (recirculating air ballast system) which is very simple yet effective.

OK now i've started here is a simple shopping list of things to build a WTC for a reliable static sub, using attached website

all numbers in USD
380 drive system - $37 - You could use a standard motor but maybe it will be too fast and you will also need to create a 1/8" output shaft (YMMV)
380 Seal - $8
Pushrod seals $16.95 (this is a pack of four and you only need 2 [rudder servo and elevator servo] on simple sub so you have 2 spare.
Bladder $16-24 dependant on size of sub (might be able to find something locally (they are out of blood pressure measuring machines, its the cuff that tightens around your arm)
Air pump $47.5 - expensive, some other places have them for <$20, but then u need two lots of postage. maybe can find locally
Sub safe 2 $27.5 - u really need this.

Useful to have but can make yourself
3" od x 12" $58 - yeah pricey, and really want to be a bit longer. The end caps cost the money also the tubing is Lexan (which i cant find here and ive tried hard - if you find some let me know).


Other things you need inside the tube
RX - obviously
ESC - preferably reversible
Servos x3
Schrader Tire valve !!!
micro switch


Simple RCABS WTC
So the motor drive unit gets installed in one end cap, with seal on outside.
Then you need to mount two servo's to the end cap and have them with push rods going out through two of your pushrod seals - this controls the up and down dive planes. A forth hole through the end cap should have small brass pipe, the outside of which connects to your bladder and the inside has a T piece.

make a small shelf to fit inside the tube, on this you mount your other stuff.
Machine away, or cut or file the shrader valve so that the pin is exposed! you then mount the thrid servo so that in one direction it pushes the micro switch (which you connect to the airpump). in the other direction the servo pushes the pin on your schrader valve!!! . Not connect your schrader valve and airpump to the T piece. still with me?. Lastly the fail safe should be in series with the third servo.

you need 4 channells BTW.

When you move the 3rd servo so it hits the switch the air pump turns on and pumps the bladder full of air, making your sub bouyant. when you move servo to hit the pin, it releases the valve and the air flows back into the WTC and your sub sinks.

If you go too deep and lose signal the Sub safe will move the servo so that the pump starts.


Make sense?????

Thanks for the great help, Akula.

THe sub u built is very well-done, have u tried it so far? though i'm currently working on one that is abt 1.5m in length, but i'm interested in building one like yours too... if u're playing it any days, can let me know? i'd like to check out ya sub and see it in action!!!

[WoW]

What an interesting FYP!!

Hey ^ZEd^!! What an interesting FYP you have got.
Which school are you from.