Soft Copper Pipe for a Propel Tank?

[warpatroller]

I am wanting to construct my own tiny copper propel tank to go inside a tiny ballast tank. I found a local source of 3/8" OD 1ft long SOFT copper pipe (they also even have 1/4" OD). The smallest diameter HARD copper pipe I could find is 1/2" diameter and larger than I want. When I say it is the "soft" kind, it is a straight piece and it takes a fair amount of force to bend it slightly.

My question is, would this soft pipe be ok to solder the appropriate sized hard copper end caps onto and use for a propel tank? You should be able to solder SOFT copper as well as the HARD copper, I would think.. Again this is not the kind of soft pipe that is rolled, it comes in straight pieces. Even at a depth of say 15 feet, I don't think the water pressure would deform this soft copper pipe..as it really isn't THAT soft. Any comments?

Steve

[wingtip]

i would silver solder and

i would silver solder and not soft solder just for safety.

[warpatroller]

I think I might have

I think I might have found a source for the smaller hard copper pipe, instead of the soft pipe.

Wingtip,

I don't understand your comment about using silver solder versus soft solder. What do you mean by "soft solder"? I thought all soldering on copper piping was done with silver solder..

Steve

[ramius-ii]

Hi Steve!
First question would be

Hi Steve!
First question would be why copper pipe and not brass? Brass comes in different wall thickness from .014 and up. How much pressure are you working with? Propel is typically around 85 PSI. When it comes to solder, there are several types. There is still lead-tin solder (soft solder) used in electronics, there is lead free solder used in plumbing and, of course, silver solder. What is important to notice is what type of flux is used. Some people use acid flux and this can be in the core of the solder. Most use a petroleum based flux. The big concern with acid core or acid type flux is that it will eat the metal if not completely cleaned off the surfaces or joins. Brass and copper are okay to join together without any fear of electrolysys and is a common practice. Hope this is of some value to you.

Best, Ed

[JWLaRue]

The hard temper copper plumbing

The hard temper copper plumbing (pipe, end caps) that one finds in the local home project store is strong enough for r/c sub use as long as you follow some simple rules.

Even if you use the so-called 'low pressure' version, the pipe is good to something like 3-400psi....well beyond what will normally be generated by Propel. The one exception being that if the tank is filled completely (as in with no air space), then it is possible to fracture the tank due to the minimal (?) expansion of the liquid itself when it warms up. I've yet to see this failure with a copper tank and Propel, but I have seen it happen with CO2. (ouch!) As an aside, that's why CO2 tanks are required to have a burst disk....to prevent the tank itself from fracturing and essentially becoming a grenade.

So simple rule #1 - always provide a means for an over pressure condition to be relieved without structural failure of the tank. My preferred choice is to use a safety valve. It'll 'burp' once or twice and that's it. An alternative is to use a sacrificial hose connecting the tank to the blow valve. In this case, when there is an over pressure condition, the plastic hose bursts..and not the copper tank. Of course if the hose method is used, you've just lost all of your Propel....that's why I like the safety valve.

Simple rule #2 - place the copper tank inside the ballast tank. In the unlikely event of a rupture (tank or hose), the ballast tank will serve to contain and re-direct the force of the eruption downwards.

As to the solder question, I *think* that the dive modules sold today with copper tanks are soldered with some form of rosin core solder....but regardless, when building your own tank going the extra step and minor cost for silver solder provides that much stronger of a solder joint.

-Jeff

p.s. rule-of-thumb: the pressure of Propel within a tank is *roughly* the same as the outside temperature (in Fahrenheit degrees). 72 degrees outside....the pressure is about 72psi.

[theo]

Propel Tank properties of metals

It has been my experience that if you use thin wall tubing and regular solder, you will be OK. Jeff's comments are correct. The pressure will be as the ambient temperature in where the tank is located. I have tested Brass tubing up to 110 degrees temperature and no problems. I use Brass because I didn't want to have weight problems with my sub. I tested up to 100 degrees because I wanted a safety factor. The good news is that I would have to be a masochist to be out in 110 degree heat to play with my sub.

Jack

[JWLaRue]

Re: Propel Tank properties of metals

I tested up to 100 degrees because I wanted a safety factor. The good news is that I would have to be a masochist to be out in 110 degree heat to play with my sub.Jack

Same here! However, I have seen instances where a sub exposed to the direct sunlight got hotter than that. Those black hulls are quite a heat sink after all. If you do leave your sub out in the sun, please make sure that the Propel tank is emptied.

Please keep that in mind!

-Jeff

[warpatroller]

Ed,

Let me answer some of

Ed,

Let me answer some of your questions. I was looking at copper pipe because that is all I saw available locally. What would be the advantage of using brass pipe, other than perhaps it weighs less? I will be using the typical stuff in the tank, either airbrush propellant or the canned duster stuff that has been mentioned on this forum before. So my presssure will be low, around 72 to 115PSI (I say 115 PSI if I was to be crazy enough to try and run a sub on a day that it gets as hot as 115 F, i'm in Phoenix so it gets this hot often in the summer).

Jeff, what exactly is this "safety valve" you speak of, and are they expensive? Would a Schrader valve (attached to the tank) release before the tank exploded during an over pressure situation? I was thinking of using a hose to connect the tank to my blow valve setup. My tank will be so small, that even if the hose burst and I lost all the propel, it wouldn't amount to much of a loss anyway.

I just want something that works and is available without shelling out a lot of money, so whether it is Brass or Copper I really don't care. But, if anybody can state a reason to use Brass over Copper besides the Brass being lighter weight, I'd like to hear it.

Steve

[wingtip]

steve,

the rods we use

steve,

the rods we use here at work to make copper manifolds for air and water high pressures are the silver rods with pink flux... there are others here but thats the main one we use and works well but you need to clean the joint up after soldering as that flux can actually eat at the joint...

as for the schrader valve it doesnt work automatically or when a pressure reaches a certain point... its just like on your bicycle, it will only relieve pressure when pressed by your finger or by some sort of other force, in our cases, a servo and some sort of arm... I'll try to get a pic up.
here is a pic of a basic rcab setup i made a few years back just to screw around.. have a much smaller unit now.. but you can see the servo arm and in one position it will hit the schrader valve and let the air out or hit the servo switch to activate the pump when i want...

[JWLaRue]

Ed,

I'm using a relief valve

Ed,

I'm using a relief valve (more properly called a "poppet check valve") made by Nupro (a subsidiary of Swaglok). It's part number B-4CPA2-50. The pressure at which it releases is adjustable between 50 and 150 psig. The price for a single piece was something like $18.00 about 8 years ago.

Here's the link to the specific part:

http://www.swagelok.com/search/product_detail.aspx?part=B-4CPA2-50

Here is a photo of the valve itself][/url]

To install it, I used a simple brass cap that is screwed onto the top of the valve. Two holes are drilled in the cap and hose barbs soldered into place, one to connect to the Propel tank and the other to connect to the blow valve.



And here is a photo of the finished unit][/url]

Enjoy,

-Jeff

[steve k.]

have a look at some

have a look at some other valves available, go to www.mcmaster.com and search for "pop-safety valves"

-steve

[Guest]

If you want the least

If you want the least hassle and inexpensive system look into a pump system.It is a very easy to make and the parts are readily available,and the thing is not dangerouse!

For me to have modified a large sub such as the U-32 from a dynamic diver to a static one cost less than 70.00$.

A windshield washer pump used in Volvos or Benzes even Porches has all the properties that are needed to fill and empty a ballast tank of any size since the tank is not presurized as are other pump systems that was a drawback.
The system I use simply vents out the air and water when the tank is full ,at the top and running the entire lenth of the tank is a vent tube with slits cut every 1/2 inch or so this tube goes out of the pressure hull and to the sail or directly out of the sub.

The pump is connected to the midle of the tank at the bottom and has no valves what so ever.

So what happens when its time to serface, the pump is reversed and the water removed leaving a vacume.This vacume is relieved by the air that is in the pressure hull via a normaly closed solinoid valve wired to be activated when the pump is reversed,again nothing fancy just microswitches ca to a micro servo,very small and cheap and efective.
Well now you wonder how do you get the vacume out of the pressure hull.By now the sub has serfaced and another solinoid valve at your comand will open and relieve the pressure,while at the same time removing any dangerouse gasses produced from the baterries,totaly safe.

Also when serfaceing the vacume can be used to siphon up any water that might have entered the pressure hull.The vacume is not that great since the volume of water is far less than the air volume in the pressure hull and it acts like a secoundary lock to maintain hull integrity.

These pumps are realy good very efecient and well made gear pumps that dont leak alot hence no valve needed.I get mine off of Ebay motors as seen in the picture.Usualy 25 bucks new,and has a built in noise surpressor.Oh and by the way this pump can be made to operate in the free flood saving you space in the WTC.

The realy neat thing about this system is that you can peciesly control your depth to a hover! Or pump it emty and have alot of freeboard.Also the tank has baffles as I highly recomend them no mater what size sub,and they are installed with no glue ,thats right ,a unique construction process that I will post later is good for very small to very big tanks and is also easy to make from whats available at the plumbing store.And they will never crack or leak nor get punsured as a bladder would.
The real subs do it the same basic way in there trim tanks.Then compressed air blows out the water of the main tanks,no I ran out of gas.

Why buy gasses that ultimatly polute in there use and fill the landfills,and your just getting someone ritcher.
Well its my opinion any way and it works with 4 subs and a 5 on its way.
If you had a large sub such as the 5 ft Alfa a compressor bassed system that also uses the above as trim is quite close to the real thing that I developed a long time ago and its sweet!
Also you dont have to get your sub out of the water to charge the propel or Co2 tank.
I know you are building a small sub and you are on a budget,believe me this is the cheapest short of going dynamic and as safe.
Dave Amur Ship Yard



More pics of inside U-32 are at SCR Deep South section Devils Den fun run

[JWLaRue]

Dave,

To each his own.

I actually

Dave,

To each his own.

I actually prefer to use a different ballast system in each new sub I build. There are pluses and minuses for every system. No one ballast system type is perfect.

-Jeff

[warpatroller]

Dave,

That is interesting, but the

Dave,

That is interesting, but the pumps your talking about will only fit in large boats. I'm going to make a guess that your U32 is the 1:40 Robbe U212 model.. Car windshield washer pumps won't fit inside little models like this thread initially referred to. A water pump for my boat would need to be VERY small. I am talking a 1:72 scale XXIII, you can't get much smaller than that. It is very rare to see an RC boat on this forum that is any smaller. If I am wrong feel free to show me a link on here that shows a completed, functioning model that is as small or smaller(I'm not talking about the RTR micro toy subs you can buy to run in fish tanks). Petn7's 1:200 Alfa is close, but I think his hull is a little bit wider.

In closing, after reading several of your posts, I have to say, your spelling is, well, not very good at all. Not that I'm trying to insult you, but after seeing so many misspelled words I find it hard not to say something about it. I'd recommend visiting hotforwords.com and watching a few of Marina's lessons. I think you'll find them worthwile, even if you don't care too much about your spelling.

Steve

[chuck chesney]

USE SPELLCHECK ON WINDOWS OS

USE SPELLCHECK ON WINDOWS OS COMPUTERS. PROBLEM SOLVED.