Material selection: water tanks, fuel, coolant, A/C and brakes

[Ndmker]

I am in the process of building my car from scratch and I would like to hear your opinion on metal selection for different applicarions.

1. Water tanks. They are usually made of stainless steel because it is very resistant to water and minerals in it. No oxidation or deterioration, that's why it is widely used in food companies. But what about aluminium? Sometimes it does get some nasty looking oxidation (from salty water) but is it only cosmetic or maybe also dangerous? I would prefer to make a water tank (washing water, not potable) of aluminium due to the very low price and weight.

2. I've seen fuel tanks made of aluminium so probably it is OK, but I just wanted to mention that a fuel tank is also in my plans.

3. I am planning to use PVC tubes to route coolant to different parts of the truck. The PVC tubes which are used to run water in homes are a good choice: cheap, lighter than a reinforced rubber hose and easy to assemble (I have that special heater to connect PVC elements). I hope that coolant will not eat thorugh PVC

4. I have to reroute the air condition lines and they are made of aluminium. Obviously finding aluminium tubes and welding them precisely will be much more complicated than using copper lines and soldering it. Can it be done? I have a short distance to cover so the weight of copper will not be an issue, but the flexibility of copper will let me bend the tube to fit right where I want. But will A/C fluid (R134a) eath through the soldering points or react with copper?

5. With brakes I have no doubt as anyone who replaces corroded lines uses copper tubes.


Any feedback will be highly welcome.

[Scoutn79]

For water why not polyethylene? Used in RV's and other campers for potable water. Light weight and cheaper than stainless. Aluminum needs a coating on the inside. You can have them custom made and are lighter than stainless.
Aluminum for a fuel tank is just fine.
Coolant and PVC? I am not sure how the PVC will handle the heat from the engine..House water should be no more than 140...engine coolant can be as high as 260 when the engine gets really hot just before it overheats but you don't want the PVC to rupture and add insult to injury.
For the A/C will copper of the correct size withstand the 400+ psi the system works under? I am not sure what the working pressure of copper is.
Copper for brake lines? Not in this country. Just buy the correct brake line tubing at any auto parts store.
Darrell

[dzzz]

I agree with Scoutn79 that there no need to make this overly complicated. Use standard parts unless you have a very good reason to vary. Marine supply has high quality heater hose to route coolant.

[FellowTraveler]

You might consider EVANS waterless coolant w/large aluminum radiator.

Fuel tanks should be built by those who can certify them as roadworthy for application.

Water storage should be down low and within vehicles center of gravity (CG).

Diesel fuel while more costly here in the USA is much safer than other fuels and can be stored for a very long time it still beats out other fuels for mpg's in med and HD vehicles, on occasion I've used 20+ year old diesel w/o any issues and because of its high sulfur content it works better to lube fuel system. Alternate fuels such as VO/bio-diesel blends, and diesel made from algae will be the norm w/HHO becoming more popular IMHO.

[chasespeed]

A/C line are copper(with the exception of ammonia systems). In a vehicle, they are aluminum, because, copper will "work harden". With all the vibration, it will get brittle, and crack/break.

3/8 coiled ACR, at 200*F, is 800PSI internal pressure. IF, you were to go with copper, that is what you would use. My recommendation, get the proper sized aluminum, and go from there. Also, try calling Vintage Air, or one of them, and they will most likely make you lines. You can also try NAPA believe it or not, certain stores have the proper hose and fittings on site, and the proper tubing, to make what you need.

No, copper is not used for repairing brake lines. Its either stainless steel(best choice, though expensive), or steel lines.

PVC and coolant. No, coolant itself shouldnt pose a problem. BUT, the heat WILL. I would look into PEX, find something that has a temp rating of 250+ @ 20-30 PSI. I wouldnt run PVC at those temps. I am not even aware of PEX that will be okay at those temps, but, that doesnt mean it isnt there. PLUS, PEX is pliable....and can be run around things....

Aluminum tank... no reason for non-potable water. Just keep it treated(bromine solution), to prevent/inhibit bacteria/algae growth in the tank.

Chase

[Doctor W]

The best tubing for brake lines is annealed tinned (or aluminized) steel rated and approved for that particular use.......Copper brake lines are a big no-no!

PVC leaches toxins into water and food and is thus not suitable.....HDPE - high density polyethylene is a better choice.

[Ndmker]

Thanks for the replies. Maybe I got some things wrong, so here is the update:

1. Water tank cannot be made of any kind of plastic because it has to be custom fitted between frame rails, driveshaft and other stuff. So it will really have lots of bends. Building the tanks from aluminium will only be the cost of materials and this is much cheaper than even buying a plastic water tank, not to mention making a custom-fit one. I am planning to have an ultraviolet lamp installed inside in order to prevent bacteria growth.

2. The fuel tank stuff is obvious. There are lots made of alu so no problem with that.

3. With the PVC maybe I got it wrong. Whatever is made of plastic is like PVC for me. What I meant was to use the kind of pipes used for pressurized hot and cold water. They withstand well over 100*C and a pressure over 10 bar. That's probably polypropylene or other stuff. Now I realized that PVC is the easily-cracking grey tubing used for water drains. So forget about the PVC name. I can easily buy automotive coolant hose (both rubber or silicone) but I need to cover some distance in a perfectly straight line so plastic pipes will be definitely more elegant than zip-tied rubber hose.

4. I will go with alu for the A/C then, but I always thought that copper is more pliable and has a greater stress resistance than alu.

5. Strange stuff with the brakes. Whenever I search for brake lines, brakes and brake kits, I only find copper tubes. I've asked mechanics and they only use special, certified, copper tubes because they bend easily and don't corrode. So nobody even thinks about any other material than copper.

[fasteddy47]

Thanks for the replies. Maybe I got some things wrong, so here is the update:

1. Water tank cannot be made of any kind of plastic because it has to be custom fitted between frame rails, driveshaft and other stuff. So it will really have lots of bends. Building the tanks from aluminium will only be the cost of materials and this is much cheaper than even buying a plastic water tank, not to mention making a custom-fit one. I am planning to have an ultraviolet lamp installed inside in order to prevent bacteria growth.

2. The fuel tank stuff is obvious. There are lots made of alu so no problem with that.

3. With the PVC maybe I got it wrong. Whatever is made of plastic is like PVC for me. What I meant was to use the kind of pipes used for pressurized hot and cold water. They withstand well over 100*C and a pressure over 10 bar. That's probably polypropylene or other stuff. Now I realized that PVC is the easily-cracking grey tubing used for water drains. So forget about the PVC name. I can easily buy automotive coolant hose (both rubber or silicone) but I need to cover some distance in a perfectly straight line so plastic pipes will be definitely more elegant than zip-tied rubber hose.

4. I will go with alu for the A/C then, but I always thought that copper is more pliable and has a greater stress resistance than alu.

5. Strange stuff with the brakes. Whenever I search for brake lines, brakes and brake kits, I only find copper tubes. I've asked mechanics and they only use special, certified, copper tubes because they bend easily and don't corrode. So nobody even thinks about any other material than copper.

Copper is legal in UK.....not North America.... Here's a link
http://law.justia.com/cfr/title49/49....36.2.7.9.html

[cnynrat]

I talked with Mario of Adventure Trailers once about using stainless for a water tank vs. the plastic (polyethylene?) that they use. The thing I don't like about the plastic is it imparts a taste to the water. He noted that one of the reasons they choose plastic over stainless is it adds a fair amount of thermal insulation around the tank which will keep the water cooler in hot weather, and perhaps more importantly help resist freezing in cold weather.

I know you said your tank shape will be complex. It is possible to make some fairly complex shapes out of polyethylene by "welding" sheets together (not sure if that's the right term, but the seams look like they are welded). I think the limitation is that curved shapes are tough to create, but anything that is rectilinear is quite feasible.