Technical Gas tank baffles ( how many )

Building an aluminum gas tank, .100 aluminum.
Tank is 35"x 13" x 8" has an angle on the front and the top is 35" x 10 3/4".

Wondering how many baffles I need in the tank, one in the middle or 2 that will split the tank into 3 compartments

Larry

 

2 should do perfectly the more the more the slosh will be controlled

 

I would put two in as well, certainly won't hurt.


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My tank that I made that is a similar size to yours has 2 baffles making 3 even compartments. Don't make the holes too big and make sure there is a small gap at the top. JW

 

Ok, thanks, 2 it is and I'll probably leave 1"at the top and cut 2" out of each bottom corner.

I think that should do the trick.
On a side note, is there any special trick that you guys know of to cut nice clean threads in aluminum ?
I'll be welding in a 1/4" thick pad inside where I want to thread for the gas cap and the fuel pickup. And for the sending unit.
Also installing a drain bung.

I don't think I will center the gas cap as is common as I think I prefer it towards the driver side for easier fueling.
sure the car is tiny ( my 26 RPU ) and reaching to the middle would be easy, but I'm getting older

 

external or internal on the threads and what size ?? and also what number on the aluminum alloy

 

The threads will go through the .100 and the 1/4" pad welded inside.
Not sure on the alloy.

 

on threads up to 1" a new sharp tap and good tapping fluid thats made for aluminum ( ez tap ) and take it slow and 1/2 turn in then back up 1/4 to clear the chips

 

Larry, have you checked out bung king?
They have all sorts of stuff and most available in aluminum, stainless and mild steel.
http://www.bungking.com/aluminum-blind-threaded-tank-bungs/

 

Thanks , I'll check them out.

 

Larry, I'm in the same boat as you are with your fuel tank. I had the thought of making my tank out of steel, but I have considered aluminum and stainless as well. I'll be interested to see your progress. I figured I'd make provisions for a send and return line, as well as a drain. That way I'm set up for any unforseen changes later down the road. I ordered steel NPT bungs, which look great. I also wanted to use one of my Moon caps, so I ordered a filler neck from them, not giving it a second thought as to what it would be made out of. The picture on their site looks to be steel. It showed up this week - aluminum haha. Which makes sense thinking about it now since they sell aluminum tanks....Duh... So now I'm wondering if I shoud try my hand at cutting external threads on my ancient lathe in a stub of steel pipe/tubing, or order a few aluminum bungs, or ??? There are just too many options these days!

 

I have never had an issue threading aluminium when using the method stimpy suggested just take it slow and clean the chips out often.

 

I'll end up posting a few pictures on my build thread when I get the tank and mounts built over the weekend.
I'm going to do a fuel pickup, no return as I will be running a mechanical fuel pump and there is no chance ever that I would need a return line as in fuel injection
The roll over vent I ordered came with a weld in aluminum NPT bung and I'll use another one in the bottom for a drain.
The threads will be for that fancy gas cap and the fuel pickup and the sending unit for the gauge.

 

Larry, can you post a pic of the roll over vent? Cheers, JW

 

Sure can, here you go.
Tank can draw air as needed, but won't leak fuel and also won't leak fuel if you wind up upside down

 

Much obliged. JW

 

Larry, sounds like we're building very similar tanks. The only thought I had with a provision for a return line was for "the next guy", as I too am running a mechanical fuel pump. I don't plan to sell my car (ever), but who knows what things will be like 50 years from now, you know?

Cutting threads for your sending unit and gas cap will be a piece of cake. What I would do is make some giant aluminum ~1/8" - 1/4" thickness "washers" if you will before you weld anything to the tank. You could cut them out with a hole saw even. Make the IDs and ODs the size of your ID and OD of cap and sending unit. Then, get them securely clamped and transfer punch the bolt pattern. After that, you can drill your pilot holes, followed by the drill size for your particular tap size. Then, apply some lube and slowly tap the threads, as mentioned about 1/2 turn at a time, backing the tap up about 1/4 turn for every 1/2 turn to keep the chips out of the cutting teeth. When you tap a hole by hand, make sure you visually inspect your progress from a couple different angles to ensure you're getting a nice straight up and down cut. Especially with NPT (taper) threads, it's easy to get them a bit crooked. Take your time, and it will turn out great!

 

Larry,
I'm thinking you have something else on your mind about the hole tapping. I'm sure you have tapped thousands of holes. What is different that you are questioning your normal procedure?

 

I'm sure it will be fine, I actually plan to weld in a re-enforcing pad of 1/4" aluminum inside the top of the tank in the areas I want to drill and tap.
By the way, someone asked the grade of the aluminum I have, it is 5052.

Yes, I have tapped a great many holes, just thought that someone had a trick to make it smoother and easier to get quality threads in aluminum.
Had a guy tell me one time that he lubed his taps with a soft bar of ivory soap when threading aluminum
I never tried it, always used rapid tap.
But the rapid tap formula seems to have changed from what it was a while back so ?
I'm sure it will work fine.
Larry

 

the 5052 will tap ok , but machining wise it can cause some problems as its softer than 6061 .

 

larry, i asked about cutting threads in aluminum awhile back, hope this helps

http://www.jalopyjournal.com/forum/threads/cutting-threads-in-aluminum.271847/

 

6061 would be better to tap, try WD-40 or Kerosene as a tapping fluid. Softer aluminum does not tap or machine very well, its gummy. Soft alum bends well. 2" cut corners might be too large on the baffles.

 

I'm not at all afraid of threading aluminum and I have looked at all the tips and points of view on the other thread also.
I've threaded aluminum before without problems, I have also used rivnut style inserts successfully.
I'm going to look into the rivnuts again as an alternative, they give good quality steel or stainless steel threads and in my experience hold very well when installed correctly, even in aluminum and plastics.
( I have special tools ( expensive ) to set them and get them installed securely).

 

you know they sell rivnuts for fuel cell applications , they are for aircraft so you might have to buy them thru a aircraft supplier like Aircraft Spruce

 

I made it as far as having the baffles in

 

Nice work! Looks good as usual.


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Cool !! JW

 

Now it's welded up

 

And no going back!! Looks very cool. JW