Fuel tanks.

[Paul W]

Hi chaps,
I'm looking into having some fuel tanks made and not sure about thickness of ally to use. I have seen tanks that can only be 1mm at the most on a GTD and I'm sure I read somewhere that one of the manufacturers supplies them in 3mm ally. I'm going to have explosafe foam in them and a send/return fuel lines for when I upgrade to injection. (Am I right in thinking the send and return should be as far apart as possible for fuel circulation ?) I will also put on breathers at each end of the tanks - for parking on hills. Also there will be a baffle around the fuel level sender. I was also thinking about putting a baffle just before the filler neck so that the fuel has a bit of a chance to soak into the foam or is this unecessary. Having never used the foam before is it easy to compress like normal foam for seats ?
Any input appreciated.

 

[Chris Duncan]

Paul,

""I'm looking into having some fuel tanks made and not sure about thickness of ally to use. I have seen tanks that can only be 1mm at the most on a GTD and I'm sure I read somewhere that one of the manufacturers supplies them in 3mm ally.""

"Metal Fabricators Handbook" says 3003-H14 in .063"(1.5mm). "Engineer to Win" says 3003-H14 or 5052-H32. I ended up with .063" 5052-T3, came out nice. 5052 is stronger than 3003.

""(Am I right in thinking the send and return should be as far apart as possible for fuel circulation ?)""

At least 12", the thinking is that any air bubbles generated by sharp corners in the return system won't get sucked into the intake side.

""Also there will be a baffle around the fuel level sender.""

I wish I'd seen this sender that was mentioned in another thread. http://www.centroidproducts.com/ The cross section shape of a GT40 tank doesn't work that well with regular pivot arm senders. With this sender all you'd need in your foam would be a straight hole, no baffle.

""I was also thinking about putting a baffle just before the filler neck so that the fuel has a bit of a chance to soak into the foam or is this unnecessary.""

Guessing it's not necessary, this foam is very porous. The only place you might want a baffle is around the fuel pickup.

"" Having never used the foam before is it easy to compress like normal foam for seats ?""

Yes, easily compressible.

 

[StuartB]

Paul,
When you`ve got final dimentions, the full spec` and a price could you let me know, I may well be up for a pair myself, possible group buy with appropriate discount anyone? /ubbthreads/images/graemlins/grin.gif

 

[Paul W]

Thanks Kalun - good info I'm probably going to go for the senders you gave me the link for - do you know anybody that has used them.
I'm told by two different people with comletely different cars that they don't trust the guages on their dashes and prefer to reset the milometer trip when they fill up. Could this be because of the length of the tanks ???

Will do Steve - are you going tomorrow night ?

 

[Chris Duncan]

""I'm probably going to go for the senders you gave me the link for - do you know anybody that has used them?""

No, and I couldn't find a thread that says anyone here has used them, it may have been clubcobra.

""I'm told by two different people with completely different cars that they don't trust the gauges on their dashes and prefer to reset the milometer trip when they fill up. Could this be because of the length of the tanks ??? ""

It's probably because of the fitment issue I mentioned.

The standard pivot float sender swings in an arc. The standard GT40 kit tank has a cross section shape that has a flat top, one flat side and is curved on the other side and bottom. A quarter circle if you will. When you position the sender arc where it won't hit the sides then it doesn't reach the absolute bottom of the tank. Consequently it's inaccurate right at the bottom or empty end of the reading.

The only thing you can do is calibrate your gauge by running one tank until the gauge reads empty and then reset the tripometer and run it until it dies. Assuming of course your other tank has fuel. This way you know how far you have to go when the gauge reads empty.

Depending how the sender is set up it may never read empty but stop somewhere before that because the sender float has bottomed out on the curved tank side and not at the end of it's travel.

I set mine up to bottom at the end of it's travel but it's still about 1" from the actual bottom of the tank, so I need to do the calibration procedure when I get it on the road. This is how your sender should be calibrated and is how all the major manufactures do it. You want some additional fuel after the gauge hits empty. Honda actually tells you in the owners manual how much fuel is left after the gauge hits empty.

The straight tube sender should aleviate some of the fitment problem however it may still not be perfect depending on the exact cross section of the tank and access hole location. The bottom of the tank is all the way to one side and the access hole for the sender usually isn't directly on top of that. Consequently I'm going to have to say I don't recommend the straight tube sender in all applications depending on these issues.

One other thing, after building tanks from scratch, I would say the most difficult part of the design is the access panels. Specifically in getting them to seal. Quite by accident I ended up with a sandwich arrangement and used some very expensive solvent proof sealer to seal the bolt holes. I have since discovered another way to do it if anyone is interested I'll expand on that.

 

[Dave Wharran]

Paul,
ERA uses this type fuel sender feeding SW gauges. They work fine. I did have one fail where the readings got flakey and unrepeatable on it, but the one on the other tank and the replacement for the intermittent one have worked flawlessly.
Here's a few more links:
one
two

 

[Jim Rosenthal]

We are expecting to build aluminum tanks for my car as the cost of fuel cells/bladders is higher than I like. They will be powder coated outside and sealed inside with gas tank sealer. A word of advice...I recommend strongly AGAINST foaming an aluminum tank into the sponson area. It guarantees corrosion and leaking when water inevitably sits against the outside of the tank and eats it. Similarly, any place the tank rests on a steel structure it should be insulated with rubber or plastic so that a galvanic cell is not set up- otherwise you are very likely to have a hole in the tank rather quickly. Air space around the outside of the tank is essential so that trapped moisture can evaporate, better yet that it is vented to atmosphere. This may sound like overkill or not a big deal but it is; marine constructors learned the hard way that aluminum tanks need to be kept dry and galvanically isolated in order to maintain their integrity and not leak fuel.

 

[Jim Glickenhaus]

Jim
GET FUEL CELLS! IT IS NOT SAFE TO DRIVE ONE OF THESE CAR'S WITHOUT CELLS.
Best

 

[Trevor Booth]

MkIV-J6- Fair comment but not all can afford them. Paul W is intending to use explosafe. This product is the ultimate in preventing explosion of fuel tanks.

Jim R I would be cautious about powder coat on outside of tank. In the event that you get a small hole in the coating you will get crevice corrosion of the alum at a rapid rate.

Paul W - Thickness of Alum tank depends on how tank is supported. 2mm is ok if the tank is supported at approx 300 ctrs, say in a mono tub and sitting on ribs. 3mm would be ok for support at say 500mm ctrs, say in a tube frame.
Soft cork provides a good anti chafing medium, rubber if used should preferably be lubricated. In either case tank should be secured to prevent movement.
For best results discuss with someone who makes tanks. They could then look at your specific application.
If you use the pivotting float type fuel sender set the float to be correct when tank is at lowest level (fuel pickup level) The arc that the float travels thru should be as close to the fore and aft centreline. The sender can be offset so that float does not contact curved side of tank.
Ciao

 

[David Morton]

"explosafe. This product is the ultimate in preventing explosion of fuel tanks"
I'm not really sure that this is altogether a correct statement and furthermore, I'm not all that sure that it has ever destructively tested - if it has, has any anybody got any data to support "explosafe" ?
I have it in my car (most GTD's do) but I would prefer foam filled fuel cells.

 

[BenL]

Once someone told me about foam beads you could dump into your fuel tank that would reduce the chance of an explosion. But a quick web search couldn't find anything. Does anyone know if such a product exists?

 

[Trevor Booth]

David, I witnessed a test of explosafe in Oz circa 80-81. Various vessels were used from 10 to 200 litres. Expanded metal company in the UK make the product. I set up a factory for expanded metal coy in OZ but they did not produce explosafe in OZ. It is manufactured from an aluminium foil sheet in the same way as expanded metal walkway mesh and radio speaker fronts etc, etc. They had available videos of testing. You will be amazed when you see the video. If you canot locate them let me know. I have their address plus all the tech info somewhere in the library in which I live!!
Ben, I have heard the same rumour but never sighted. To be effective the beads would probably need to be packed tight and occupy a fair degree of volume.
Ciao

 

[David Morton]

Just started a search on Google. Lots to read on Explosafe.
One site relating to aeroplanes quite interesting
http://members.eaa.org/home/homebuilders/building/fuel/Avoiding%20Fuel%20Related%20Problems.html
Interesting reading. Thank you Trevor.

 

[Dave Gilling]

According to this http://armor-pdi.com/contents/access_page3.htm ,foam has a limited life, 3 to 5 years /ubbthreads/images/graemlins/shocked.gif so what happens to it after it is time expired? Does it degrade and lay in the bottom of the tank? Block fuel lines?

 

[BenL]

[ QUOTE ]
so what happens to it after it is time expired? Does it degrade and lay in the bottom of the tank? Block fuel lines?

[/ QUOTE ]

I had 25 year old foam degrade and clog my fuel filter. It was very annoying.

 

[Dave Gilling]

I take it thats a bit of an understatememt? /ubbthreads/images/graemlins/smile.gif

 

[Jim Rosenthal]

We ARE going to stuff the tanks with Explosafe. I drew a removeable plate on the top that serves to put in the foam and remove it later on when it is old. I did look in to fuel cells; the problem is that they are basically rubber or plastic bladders filled with Explosafe. They still need a metal shell around them. I may put a rubber liner inside the metal tank shell, I am not sure. The Safir MkV cars have all come with aluminum tanks as I describe, and they are fine. A few HAVE been wrecked- but they did not catch fire or explode.

 

[DMatt]

Jim G,

I have given some thought to fuel cells but wondered about the price and the availability. Having all of that fuel at my hip does is not all that comforting. /ubbthreads/images/graemlins/frown.gif Who would be a good supplier and what would you think a ball park price would be?

 

[Howard Jones]

www.fuelsafe.com These guys will build you a custom cell. The Lotus cell looks close. I have no idea how much money.

The real problem is that I don't believe anyone makes a standard instock cell that will fit out cars. Things like location of fittings and fill neck are a big deal.

Fuel cells are not really a lot of money if you can find one off the shelf that will work. There are a lot of stockcar and club car cells that can be had for $400-$500.

If a group of owners of different types of cars got together and came up with a standard cell that would work for everyone we might be able to get fuel cells into our cars at a reasonable cost.

A look at rules such as scca and others as to placement and other things would be a good idea before getting a custom cell made also. It would be a shame to go thru all the time and expense and not be able to pass tech.

 

[Howard Jones]

This has got me thinking. What if we all posted drawings of our fuel tanks in the GT40 library under "Fuel tank drawings" At some point we will all take ours out of the car for one thing on the other and when we do we could make mesurements and do a drawing along with what type of car it came from.

In the end we would have a complete set for ERA,GTD,CAV,RF, etc. and then a common fuel tank could be designed, a drawing made and posted back on the forum.

With everyone out looking for a custon fuel cell made from that drawing I bet our collective work would yield some cool results.

I will need to take one of mine out in the next few months to run some wires and vent line behind it. If this hasn't got going before that I'll get it going then.

Please if you do it before I do please put it in GT40 library listed as "Fuel Cell Drawings"