Model Boat Mayhem

Please login or register.

Login with username, password and session length.
Pages: [1] 2   Go Down

Author Topic: An easy to build WTC for r/c model submarines.  (Read 16866 times)

das boot

  • Guest
An easy to build WTC for r/c model submarines.
« on: November 09, 2008, 09:53:31 AM »

Having looked at the prices of the commercially available WTC’s for my Steve Neill Blueback, I decided to try and build my own. Having asked plenty of questions and looked at hundreds of images of both commercial and home brewed designs, I came up with the following design….it utilises a length of transparent acrylic tube (bought from ebay) two plastic screw on lids from the large sized instant coffee jars from the local supermarket, a length of grey plastic water down pipe and a strip of either plastic or aluminium to install the internal equipment upon. All the parts are easily available and all of them are easy to work with using just basic hand tools ( I don’t have the luxury of a fully fitted workshop any longer, my first wife and her lawyers saw to that….) and all the materials are easily glued together with either superglue, plastic solvent or epoxy glues.

Having bought the acrylic tube of the correct diameter (depends on your personal needs) I used 80mm for the Blueback as the coffee jar lids fitted nicely, cut it to whatever length you need for your particular boat, sand off the cut edges perfectly smooth with a sanding block, and place to one side. Take the length of grey plastic water down pipe (easily available from plumbers merchants, DIY shops or even builder’s rubbish skips) it needs to be as close as you can get to the next (internal) size down to your acrylic tube, so it sits well inside the tube. Cut it to the same size as the outer tube, then mark off and cut it into a U section approx 1/3rd of the outer tube’s diameter….this will depend upon your needs for internal fitting out with your equipment and how and where you place the servos/rx/batteries/pumps/etc. Having cut the tube, sand all the edges perfectly smooth and level, take your time over this and get everything level. Be prepared to make a mess during this stage, sanding this stuff leaves a thick layer of shavings everywhere, so keep the hoover close at hand if you value your domestic arrangements….

Once sanded level, take the strip of either plastic or aluminium, whichever you prefer, and cut it to fit the top edge of the plastic water pipe…once trimmed level, you can either fit the internal equipment now and then glue the strip to the plastic water pipe, or glue it together first and then install your internal pumps/servos/batteries/etc, the choice here is purely personal as to which way round you complete this stage.
You can either cut out the strip to sit your equipment into, or attach everything to the top, again it’s a personal choice. I used a combination of both ways for mine, which left me with a handy space under the tray to slide the main battery pack into, tuck wiring away neatly, etc…it all depends on how you set out the internal equipment layout.

Next, the coffee jar lids have to be slightly modified….it’s a very simple job, all you need to do is to sand off the internal screw threads where the lid screws onto the glass jar, and that’s it. Being plastic, you can glue items such as rubber bellows or plastic water/air pipe with epoxy glues, providing you rough up the areas to be glued first with sandpaper. I added an thick internal plastic disc to the stern end cap on my WTC, just to give the lid some support as I attached the main drive motor directly to the lid. You can also make up a couple of different lids set up ready for single motors/dual motors, and if you have worked out your internal equipment layout about right, you can then simply just swap end caps and use the WTC in two or three different boats, as long as it fits the boat. And if you make a mistake or decide you need to change any internal layout, spare lids are very easy to get hold of, so it’s no great disaster if you do something wrong.

All outlets such as water inlet/outlet pipes, control surface push rods, the extension to the radio on/off switch, and any external wiring are fed through rubber bellows, which are filled with waterproof grease. The main drive motor shaft exits through a brass bush with small ‘O’ rings either side to keep water ingress to an absolute minimum, so far it hasn’t leaked a drop of water during submerged trials in my indoor test tank, aka the bath.

You can use different diameter tubing and different sized lids to suit your personal applications, but the basic principal is the same whatever sized tubing you need. Just make sure the coffee jar lids fit tightly over the acrylic tube, if you are at all worried about the fit, just wind a few turns of plastic insulating tape over the join to make a perfect seal. I filled mine with several heavy tools…files, drill chucks, spanners, etc and dropped it into a bath of water overnight….in the morning the tube was as dry as it was before I dropped it in.

And there you are…a cheap and easy way to build a WTC for any submarine model. My coffee jars came from Somerfields, their own brand of coffee, but I’ve no doubt that other supermarkets jars can be pressed into service. If you don’t drink coffee, have a look around your local recycling centre. Most people don’t bother to take the lids off their clear glass jars when they drop them into the bins, so just have a quick look around….but don’t cut your fingers when poking about in glass recycling bins.



Logged

Roger in France

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #1 on: November 09, 2008, 11:45:39 AM »

Looks very good. Great description and illustrations.

How well does it work?

Roger in France
Logged

das boot

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #2 on: November 09, 2008, 11:54:04 AM »

Still awaiting the esc, failsafe and the new main drive motor Roger, but in bath tests it didn't leak a drop...which is the main objective! The air pump runs perfectly and fills the bladder very rapidly, so I'm keeping all digits firmly crossed for future success!

Stand by for further developments as and when the remainder of the bits arrive....

Rich
Logged

Roger in France

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #3 on: November 09, 2008, 01:14:41 PM »

Great, look forward to your reports on progress.

I have always felt that WTC's were over complicated by some and overpriced by others!

Roger in France.
Logged

Sub driver

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 605
Re: An easy to build WTC for r/c model submarines.
« Reply #4 on: November 09, 2008, 06:35:09 PM »

Interesting..

Have you tried it under pressure ??

Regards SUb.
Logged

Sandy Calder

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #5 on: November 09, 2008, 06:57:10 PM »

Hi Rich.
I think I can make out a pump but how do you make the sub go up and down if it is enclosed?
Sandy
Logged

Martin [Admin]

  • Administrator
  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 19,285
  • Location: Peterborough, UK
    • Model Boat Mayhem
Re: An easy to build WTC for r/c model submarines.
« Reply #6 on: November 09, 2008, 07:55:33 PM »


"Under pressure?" Do you mean the 'Mrs' find's out how much modelling really costs?!  %)
Logged
"This is my firm opinion, but what do I know?!"    -   Mayhem FaceBook Group!

das boot

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #7 on: November 10, 2008, 09:57:24 AM »

Interesting..

Have you tried it under pressure ??

Regards SUb.

Sub, if you mean did I pressurise the WTC, then yes (in a manner of speaking)...all I did was to blow into the air pipe before I submerged it to check for air bubbles escaping. None emerged....

Hi Rich.
I think I can make out a pump but how do you make the sub go up and down if it is enclosed?
Sandy

Sandy, the air pump you can see is a SubTech AP01, it draws air from the WTC cylinder and inflates an external bladder which is simply velcroed to the top of the cylinder externally, this displaces enough water to surface the boat. To submerge, there is a one way valve attached to the plate on top of the forward facing servo you can see, this releases the air in the bladder and lets it back into the cylinder, allowing water to replace the area taken up by the inflated bladder and  thus submerging the boat. I guess it's an updated version of the old John Darnell system?

Once the hull comes back from Ramesh (he's carrying out emergency surgery on it for me) I can then get things installed properly and just jury rigged, and then see what happens.

Cheers,

Rich




"Under pressure?" Do you mean the 'Mrs' find's out how much modelling really costs?!  %)

Don't have that problem any longer Martin....  :-))
Logged

Sandy Calder

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #8 on: November 10, 2008, 10:12:06 AM »

Hi Rich.
Thanks very much for that one paragraph explanation.Your addressing someone whos eyes glaze when submarine articles mention static ballast and I think you've just covered everything I want to know.

I'm about to start a sub and I think my mind is now made up on the water tight compartment idea.I'm going to give your idea a go.

Regards
Sandy Calder
Logged

das boot

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #9 on: November 10, 2008, 10:37:13 AM »

Good Sandy, I'm glad you're starting a sub, that's what I like to hear. If you get any problems, then by all means shout me and I'll try and help you out if I can. The WTC does work, maybe not as well as the $200+ commercially available ones, but it works. If you get the odd air bubble escaping around the seal between the coffee jar lids and the cylinder, then just put a wrap of waterproof insulating tape around it, that cures it. Fill all your rubber bellows with grease, that's another leak source cured.

If you use 80mm acrylic tubing, then go for the 200g size coffee jar, as in the attached image (hope I'm not breaking any advertising rules and regulations here Martin?)...that's what I used in this one. I'll post up the ebay links to the acrylic tube and the bellows later if you wish?

Good luck mate...

Rich
Logged

Sandy Calder

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #10 on: November 10, 2008, 11:20:16 AM »

oh crap!
Now you tell us. {-)

Did the avatar of me with pipe and the untrimmed beard spook you for a moment?
Sorry if it did.
Logged

das boot

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #11 on: November 10, 2008, 11:52:02 AM »

Hope the attached diagrams may help you…top one shows the bladder inflated, water displaced from the hull and the boat in surface trim. One way valve is closed preventing air from leaking back into the cylinder.

Lower one shows the bladder deflated, water takes the place of the air in the bladder in the hull, boat is now in submerged trim. One way valve is open, allowing air back into the cylinder.

The aquarium valve on top of the cylinder is just for topping up the air in the cylinder, if the air seems to run low for any reason, open the valve, blow into the air line attached to the valve to top up the air inside and close the valve. You can get the valve from most aquarium shops, I believe the manufacturers name is ALGARDE, or very similar to that.

Ballast/trim out your boat so that with the air bladder deflated you still have slight positive buoyancy…ie, the boat should be JUST about afloat. Slight forward motion and a touch of down on the dive vanes will be enough to submerge the boat. When you inflate the bladder, the water will be displaced by the inflating bladder and the boat will surface.


Good luck with your project, enjoy it!!

Regards,

Rich

Logged

Sandy Calder

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #12 on: November 10, 2008, 02:27:00 PM »

Hi Rich.
Thanks very much for that one paragraph explanation.Your addressing someone whos eyes glaze when submarine articles mention static ballast and I think you've just covered everything I want to know.

I'm about to start a sub and I think my mind is now made up on the water tight compartment idea.I'm going to give your idea a go.

Regards
Sandy Calder

http://www.modelboats.co.uk/forum/forummessages.asp?chklast=1&URN=6&UTN=1112&source=forumnot&&
Mike Caswell's post.  8) 8) 8)  Triple glazed I am at that.
Regards
Sandy Calder
Logged

Sub driver

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 605
Re: An easy to build WTC for r/c model submarines.
« Reply #13 on: November 10, 2008, 03:19:26 PM »

U-33

So are you pre inflating the bladder with air in order to suck it out and store it in the WTC

OR

Are you relying on the air in the WTC to inflate the bladder ??

From the diag it appears the latter

Regards Sub.
Logged

das boot

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #14 on: November 10, 2008, 03:26:46 PM »

I blow a couple of lungfuls of air into the WTC prior to setting sail, that way there is sufficient air to fill the bladder via the pump, Sub..although bear in mind that this is only a prototype, although I used the same method in my Darnell P class (converted into HMCS Onondaga) and it worked fine. It's just a updated Darnell system really.

Rich
Logged

Mankster

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 770
  • Wheelerdealer
  • Location: London, UK
    • RC Model Submarines
Re: An easy to build WTC for r/c model submarines.
« Reply #15 on: November 10, 2008, 03:54:16 PM »

I wouldn't blow into the WTC if i were you ok2, Firstly your are  running an RCABs system so you are relying on creating a vaccume in your WTC when you inflate your ballast bag. If you over pressurise your WTC by blowing into it, then you may not create enough of a vacuume to deflate the ballast bag when you want to dive (the bag does not a have second airpump to assist with deflation). Secondly you are liable to blow out or unseat you pressure fit endcaps.

Personaly those presure fit endcaps have me worried. If you have to go this way, I'd seal them in with silicone sealent and fit something like a plastic bottle top as a quick access vent/ battery charge  point. Hopefully you wont need to get into the WTC for a season or 2, and if for some reson you do, just slice the silcone with a blade and reseal when done.

Sub driver

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 605
Re: An easy to build WTC for r/c model submarines.
« Reply #16 on: November 10, 2008, 04:45:17 PM »

U-33

Thought so,

I agree with Mankster,

I think it would be prudent to have bought some acrylic sheet where you got the tube from and made some proper end caps with an O ring seal, then used the vaccuum in the WTC to help seal the end caps in, also don't forget that air will expand when warm and an increase in pressure will occure.

The cost of some sheet would be minimal, even a partial failure of your set up will loose the sub.

Just my opinion.

Regards Sub.
Logged

das boot

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #17 on: November 11, 2008, 07:39:26 AM »

Ramesh and Sub, I thank you for your comments, and I’ve duly taken them onboard, to the extent that I will be ordering some M5 studding to run the length of the cylinder to hold the two end caps in place and have removed the aquarium valve, so I’ll now rely on the air that is present in the tank to fill the bladder.

Ramesh, I’m also going to use your idea of the plastic bottle neck/lid to provide access to the charging sockets and the radio on/off switch.

Like I said, this is only a prototype cylinder, based upon a method which has been in use of several of my previous boats, although not with the higher pressure air pump. I’d always used the old Darnell USE steam engine as an air pump, which obviously works at considerably lower pressure than the SubTech one does, and I didn’t take that into consideration. Model submarines have moved on so much since I last built one, I'll have to do some rapid catching up....

I thank you again for your comments and your fears guys….much appreciated.


Rich
Logged

jinks8

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #18 on: November 15, 2008, 02:25:48 AM »

If i could ??? ;)I would lick to give that a go . Just one thing wear did you get the one way valve from
Logged

das boot

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #19 on: November 15, 2008, 05:45:02 AM »

It came from my odds box, which is where it now is again, I've completely revamped the WTC and gone back to using my old faithful water ballast system. Bit more stuff inside the cylinder, but it's fitted somehow.

I have no idea where it came from, but you can use Clippard valves which are designed to do this very job. I've no doubt that Andy will provide a web link....he's good like that.


Rich
Logged

boatmadman

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 2,719
  • Location: South Cumbria
Re: An easy to build WTC for r/c model submarines.
« Reply #20 on: November 15, 2008, 08:30:41 AM »

This is all very interesting.

As a submarine numpty I have to ask, wouldnt it be better/safer to have the 'default' ballast condition such that the bladder is empty and the sub has full bouyancy, and fill the bladder with water to make it submerge? Then maybe include a failsafe of some type to empty the bladder on loss of signal?

Ian
Logged
if at first you dont succeed.....have a beer.....

Mankster

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 770
  • Wheelerdealer
  • Location: London, UK
    • RC Model Submarines
Re: An easy to build WTC for r/c model submarines.
« Reply #21 on: November 15, 2008, 09:25:41 AM »

If i could ??? ;)I would lick to give that a go . Just one thing wear did you get the one way valve from

You dont need to have a one way valve as the Subtech air pump is effectively a 1 way valve and will only pump in one direction and will not allow air back down it. To release the air from the ballast bag you need to introduce a Y connector (aqaurium shop or Halfords winscreen washer fitting) into the air line to/from the ballast bag. Off the Y you connect a bit of tubing or pipe to a Schrader valve (Car trie/bicycle valve). To empty the bag you hook up a servo to operate the valve by depressing it to allow air back into the WTC. An electronic solution to using the servo and Schrader valve is to use a solonoid air valve like the Clippard one (which is not a one way valve and is available from SubTech).

das boot

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #22 on: November 15, 2008, 10:06:23 AM »

Thanks Ramesh, that's explained it in far greater detail than I could have done.  :-))

Rich
Logged

jinks8

  • Guest
Re: An easy to build WTC for r/c model submarines.
« Reply #23 on: November 15, 2008, 10:15:21 AM »

thanks for that this is my first time at sud work and all inofo welcome
Logged

Mankster

  • Full Mayhemer
  • *****
  • Offline Offline
  • Posts: 770
  • Wheelerdealer
  • Location: London, UK
    • RC Model Submarines
Re: An easy to build WTC for r/c model submarines.
« Reply #24 on: November 15, 2008, 10:32:09 AM »

This is all very interesting.

As a submarine numpty I have to ask, wouldnt it be better/safer to have the 'default' ballast condition such that the bladder is empty and the sub has full bouyancy, and fill the bladder with water to make it submerge? Then maybe include a failsafe of some type to empty the bladder on loss of signal?

Ian

Ian, your describing a water pump based system rather than an compressor based system.  There are 3 main water pump systems. 1) pumping water into a sealed ballast tank (which is what I think Rich is going to do). Here the air within the sealed ballast tank is compressed to sufficient amount to be able to empty the tank of water when desired. 2) pumping water into a ballast tank that is vented into the WTC (so the increase in pressure isn’t as great as air is introduced into the much larger WTC. There is a small increase in pressure within the WTC but not normally sufficient to empty the ballast tank, especially if the sub is at any sort of depth. So the water pump will need to be able to pump in reverse to empty the ballast tank. 3) In this system the ballast tank is vented to surface via a tube to the highest point in the sub. The advantage of this method over the previous 2 is that there is no free water surface within the ballast tank to slosh about and upset trim. The down side is that the to of the vent has to be kept above the surface of the pond if your to be able to pump out water by switch the pump in reverse. (this last one is what you have in that submersible ship)

There is a refinement to the Air compressor system that will allow the sub to be on the surface in the neutral state. Here you store compressed air via that same air pump in a sealed air container (modified aerosol can / Robart air can).  Once the container is full  you close up the WTC. Now the compressed air is used to inflate the bag (the neutral state) and the pump is used to pump air from the bag back into the air container when you want to dive. Advantages are if you have a power or pump failure, you wont be able to dive but the sub will be on the surface and there is no change in pressure with the WTC to introduce leaks (only the air container experiences pressure differences). The down side is you need a larger WTC to accommodate the air container.
Pages: [1] 2   Go Up