Topic: Snort help (Read 13457 times)

bbdave · « **on:** May 01, 2012, 10:00:38 pm »

I am planning a simple snort can i just run this by you for clarity

If i make a cylinder with holes in the bottom then an outlet tube in the top through the pump up to the snorkel in the tower so as i pump air out water comes in the bottom taking the sub to just positive buoyancy reverse the pump air pushes water out the holes boat comes up.

Or do i have to have a servo operated valve in the tank to release the air if so where can i get one.

Dave

Bob K · « **Reply #1 on:** May 01, 2012, 11:32:06 pm »

I would recommend the Caswell Snort Pump system, which costs from US$44 including the small controller board that solders across the pump terminals. The controller PCB has a servo-type lead that connects direct to your receiver.
http://www.caswellplating.com/rc-modeling/air-and-water-pumps/mini-pump-controller.html

As you say, the water ballast compartment has a hole in the bottom. The pump is mounted in the dry section, with one pipe going into the water compartment and the other going to a snort tube at the top of the sail. Very little current is required. As long as your snort is above water you can surface or dive to periscope depth as often as you like. Going below this depth you would need an alternative method of surfacing, such as a gas valve.

Subculture · « **Reply #2 on:** May 02, 2012, 10:50:10 am »

Diaphragm air pumps aren't bidrectional. If you want to pump air in and out, you will require two air pumps, otherwise you need to use an air valve on top of the tank as you suggested.

You can switch the pumps using various methods. A pair of forwards only ESC's, or servo actuated microswitches are two methods that spring to mind.

Something else you could consider is the using a geared water pump with a vent to the surface, and use that with a reversible speed controller, that will work in the same fashion as a snort system with twin pumps.

bbdave · « **Reply #3 on:** May 02, 2012, 04:11:26 pm »

What is the control circuit for is it just a switch or does it allow forwards and reverse?

Whats best for a servo operated valve?

I'm only going to use it in a swimming pool and boating lakes so no dramas if it does a long dive

Dave

Subculture · « **Reply #4 on:** May 02, 2012, 06:18:22 pm »

Are you referring to the Caswell device? That's just a solid state on/off switch. It doesn't matter which way your run these pumps, they will still only pump in one direction.

What's best for a valve? Well the ones on the Caswell cylinders are a custom design that I haven't seen elsewhere, it seals tighter as the cylinder is pressurized- probably more important if using gas to blow the tank.

You can modify a tyre valve to do the job.

bbdave · « **Reply #5 on:** May 02, 2012, 09:23:37 pm »

Ok i see now, seems expensive for a switch though. Hadn't thought of using a tyre valve is that just a case of using a servo to push the pin in?

Dave

Subculture · « **Reply #6 on:** May 02, 2012, 09:39:28 pm »

Yes that's it. A tyre valve set up that way is not self sealing against pressure, but these diaphragm pumps only make between 5-15 psi depending on the model, and they don't flow well at higher pressures either, so it's unlikely to be a problem. What is important is to make sure the valve is right at the top of the tank, to enable it to vent fully.

bbdave · « **Reply #7 on:** May 05, 2012, 12:33:07 am »

How come it doesn't seal against pressure is it not doing that on a tyre? would a steam valve do the job as i could get a positive linkage to one of them as opposed to trying to hit a small pin.

Like one of these
http://www.steamfittings.co.uk/asp/d-no.asp?ProductID=268&Process=1

Dave

Subculture · « **Reply #8 on:** May 05, 2012, 10:56:56 am »

Depends which way around you mount it. To actuate it easily from inside the cylinder, a tyre valve needs to be spun around 180 degrees, so the pin points downwards. With that configuration any pressure inside the cylinder will push the valve open.

If you put the valve the other way around, you will need a cantilever arrangementto actuate it, which is feasible but more fiddly. The drain cock looks like a ball valve to me, should be okay, may get leaky with wear.

bbdave · « **Reply #9 on:** May 05, 2012, 12:04:18 pm »

My valve will have to be external as it will vent water once the tank is full so i'll need to think of ways of not making the linkage to complicated, i'm looking for some pictures of schrader valves in subs to rob some ideas

Dave

Subculture · « **Reply #10 on:** May 05, 2012, 12:42:43 pm »

What boat is this for, and what are you using for a tank- e.g. cylindrical or a box?

bbdave · « **Reply #11 on:** May 05, 2012, 01:06:14 pm »

It is for a welman i have just started building the hull and planning the WTC at the moment i am looking to make it from acrylic tube, i was considering a small engel tank but think a snort will be cheaper and more suitable as it is going to be used in the swimming pool at work.

I have been looking for some detailed drawings of a snort system but only found descriptions up till now. My plan is to have radio motor pump etc. in a rear section a central tank and a battery section fwds so three seperate tubes. The central tank will have a valve on top with free flood holes in the bottom some baffles inside air inlet from the pump in the bottom. so

1- Open valve water fills tank sub to periscope depth or just tower on welman.
2- shut valve switch pump on tank fills with air pushing water out sub floats
OK?

So once the sub and all the gear is ready i can test float and calculate the size of ballast tank needed.

Dave

upscope · « **Reply #12 on:** May 05, 2012, 02:04:40 pm »

My Darnell Biber uses this method -

I pump water into the fully vented tank, until was just over decks awash or up to halfway up the tower, i would then on another channel flick a switch that would move a servo to close a valve on the airline out of the tank whcih went to the periscope, from there i can fully dive but the air is under pressure, stop pumping and she comes back to the same position, open the valve i can then dry the tank using the air to come back in.

The valve was one made by a model boat steam guy in my club, but you could use solenoid valves or as Andy says a car tyre valve that servo pushes in the shrader valve, they hold 40- 50psi back so no problem really.

Paul

Subculture · « **Reply #13 on:** May 05, 2012, 02:22:10 pm »

I've seen a variation on that theme from some modellers in Australia.

Same principle as your Biber, but instead of using a servo controlled valve, they used a float which capped off the air vent as the water level rose, thereafter creating a sealed pressurized system.

The servo valve has a big advantage though- assuming you're using a reversible pump, you could still clear your tank fully in an emergency by keeping the vent shut and pulling a vacuum in the tank.

bbdave · « **Reply #14 on:** May 05, 2012, 05:10:59 pm »

Is there a reversible snort pump? as i could pump air in and out.

Dave

Subculture · « **Reply #15 on:** May 05, 2012, 05:16:29 pm »

As I said in the first post, you can't reverse a diaphragm pump, the valves see to that. You can fit two though (they are quite small usually). But you can use a water pump instead, which is reversible (gear type).

With a servo controlled valve arrangement, it's possible to have one air pump suck air out or push it in, but that increases complexity, and would I think require a scratchbuilt valve.

bbdave · « **Reply #16 on:** May 05, 2012, 05:33:25 pm »

Ok so a pump and a steam valve is my simplest action or a schrader if i can figure a simple linkage

Dave

Subculture · « **Reply #17 on:** May 05, 2012, 06:42:09 pm »

Just use a servo actuated cam. Crude paintbrush image, shows the principle. Small length of copper pipe soft soldered or epoxied onto a schraeder valve. Epoxy that into the top of tank, ensuring that the pipe is perfectly flush with the inside of the tank to prevent trapped air bubbles, Makes sense to site this at the back of the tank, as boats tend to dive slightly nose first if they're trimmed right. Then use a cam or eccentric disc (can be fashioned from metal, plastic etc.) to open/depress the needle for the valve, thus allowing the air to escape. The control shaft for the cam should pass through a watertight gland into the rear pressure hull (not illustrated) onto the servo. Same servo can operate a micro switch to switch on the pump. Simple, cheap.

bbdave · « **Reply #18 on:** May 05, 2012, 08:12:11 pm »

Excellent thanks i have a little way to go before building the WTC but it's handy to get things clear in my head before hand

Dave

Subculture · « **Reply #19 on:** May 05, 2012, 08:27:02 pm »

Good. Couple of other things to add, try to get the tank as low in the hull as you can, and make sure you have nice big flood holes in the bottom of the tank, Dave Merriman typically uses 1" diameter holes, and the tank floos easily through those once you open the valve.

If you choose to use two pumps, then you can get away with smaller flood holes, as you pulling vacuum which helps draw the water in.

bbdave · « **Reply #20 on:** May 05, 2012, 09:31:04 pm »

I think i'll go for one pump to keep it simple to keep the waterline shown on the plan i can use a 70mm WTC max to keep it below waterline but it is shown just above mid point on the plan which does seem low compared to photos i have and other midget subs but info is very limited.

Any suggestions for pumps the caswell one is a possibility with just a microswitch instead of their pcb.

Dave

Subculture · « **Reply #21 on:** May 05, 2012, 10:01:00 pm »

Apart from Caswell, there is the RC submarine workshop on ebay, they sell a couple of different models. Thomas pumps are really nice, and come on ebay from time to time, although some are wicked prices, caveat.

Lloyds the Chemist sell blood pressure monitors quite cheaply, and they have little pumps inside. Sparkfun do a good pump for larger models (sold as a vacuum pump) too big for a 70mm cylinder though.

This is for the Welman project I take it? Have you considered using a bag and peristaltic waterpump for that boat- low freeboard means you won't need a lot of volume, so the slow pumping speed won't be an issue. All you need is a pump, switcher board (TT Neptune boards can be had new for about £13 on ebay) pressure switch and a suitable bag.

bbdave · « **Reply #22 on:** May 05, 2012, 10:47:51 pm »

Yes for the welman if i go a little above the plan W.L. i can use a 90mm WTC. Are you talking about these boards?

http://www.ebay.co.uk/itm/Thunder-Tiger-Power-Distribution-Board-Neptune-TTRPJ6175-/160789169754?pt=Radio_Control_Parts_Accessories&hash=item256fc8065a

I presume you mean a pump and bladder system? Again i need to source parts for this it is a possibility if it's cheap all i need is diagrams etc and i'm sure i can get it together and as you say i wont need much volume

I have just seen Rc submarine workshop on ebay and this could do the job.

http://www.ebay.co.uk/itm/RC-Sub-SUB-ES2-Electronic-Switch-DC4v-12v-Free-MICRO-AIR-PUMP-DC-3v-7-2v-/280864372887?pt=Radio_Control_Vehicles&hash=item4164d23897

All worth thinking about

Dave

Subculture · « **Reply #23 on:** May 06, 2012, 10:58:10 am »

No you don't need this board.

This is the one- http://www.ebay.co.uk/itm/Thunder-Tiger-Control-PCB-Neptune-TTRPJ6174-/360452874449?pt=Radio_Control_Parts_Accessories&hash=item53ecaa60d1

The board from RC sub workshop would also work, but I would fit a pressure switch or a mechanical safety valve- peristaltics are capable of very high pressures.

They do peristaltic pumps and bags too e.g. http://www.ebay.co.uk/itm/RC-Sub-Rolling-Pump-Type-GM-B-DC6v-24v-Best-Static-Diving-Do-Not-Need-Valve-/270952191448?pt=Radio_Control_Vehicles&hash=item3f160255d8

bbdave · « **Reply #24 on:** May 06, 2012, 04:36:03 pm »

Thanks i was thinking of just using an air bag in a free flood tube pumping the air to and from the WTC is that acceptable?. Does the TT board do the same job as the other ebay one?

Dave

News:

Author Topic: Snort help (Read 13457 times)