Fuel Tank Design Ideas

[FuelMan]

Hello Guys,

I am planning to design fuel tank for the 2011 competition and was brainstorming some ideas. Have you guys notices any great tanks out there in the competition?

I've seen everybody use Aluminum as their base material for the tanks, the reasons for which is obvious!! Although, I am looking to reduce weight of our already heavy 420 LBS car, I cannot sacrifice safety. We used a 3 tank design in our 2010 car to avoid sloshing. This worked pretty good but the design was very heavy (~8 Kgs) with the fuel of 4.5 L. I was wondering if anybody had some good suggestions for the design? Please post any pictures that you think might help. I will post the pictures of my tank in my next posting. Hope to receive some help from you guys!

[FuelMan]

Hello Guys,

I am planning to design fuel tank for the 2011 competition and was brainstorming some ideas. Have you guys notices any great tanks out there in the competition?

I've seen everybody use Aluminum as their base material for the tanks, the reasons for which is obvious!! Although, I am looking to reduce weight of our already heavy 420 LBS car, I cannot sacrifice safety. We used a 3 tank design in our 2010 car to avoid sloshing. This worked pretty good but the design was very heavy (~8 Kgs) with the fuel of 4.5 L. I was wondering if anybody had some good suggestions for the design? Please post any pictures that you think might help. I will post the pictures of my tank in my next posting. Hope to receive some help from you guys!

[BuckeyeEngines]

In previouse posts you will find discussion about fuel cell foam to prevent sloshing. You can also use baffles/ fuel trap. Also .030 aluminum for your base material.

[FuelMan]

Hello Branden,

The guy on board previously used the information on the forum and created a three tank design, which includes 2 tanks on each side and 1 surge tank at the bottom to avoid sloshing. This worked well in our competition but the problem was the center of gravity because it was too high. Can you give me some ideas and/or information to read up on the CG and how to reduce it.

Regards,

Rahim
Fuel Lead
University of Waterloo

[BuckeyeEngines]

Obviousely the lower your CG the better. This translates into keeping weight down low, as well as overall weight being minimal. I have not bothered with making a huge effort at reducing the CG of the fuel tank. Instead when worrying about CG I have looked at engine placement. Is it as low as possible? For us there are alot of other items that we are spending time on so just making a fuel tank that functions is usally the goal. We shoot for being able to run that tank down to .4 gallon with a 1.5G laterall load and not starve the pump. Beyond that you have to work with the space you have and make it as low as possible.

I hope that helps.

[bob.paasch]

Our 2010 fuel tank was rapid prototyped. RP gives you immense design freedom as to external shape and internal features. Our tank was a little over 3 liters.

[AxelRipper]

RP tank? really? thats different. Our tank for the last 2 years has been a split tank made of titanium. where we have the tanks keeps the weight down low in the chassis, though as it was our first car with a single cylinder we oversized the tanks substantially. IIRC, the tanks in our 09-10 car equate to 2.2 gallons, and we used .8 and .62 gallons in the 2 endurances that it ran.

For our next car, I was considering making a carbon fibre tank. A few of our team members tried this for the 09 car originally, but due to human error it leaked horribly.

For the RP tank, did you have to line it with anything? How does it hold up to gas/e10/e85? I am unfamiliar currently with RP materials, but am going to be looking into them for some parts in the future.

[bob.paasch]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by AxelRipper:
For the RP tank, did you have to line it with anything? How does it hold up to gas/e10/e85? I am unfamiliar currently with RP materials, but am going to be looking into them for some parts in the future. </div></BLOCKQUOTE>

The tank was sealed with epoxy. Haven't tried E85, but it holds up to gas/E10.

[flavorPacket]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by AxelRipper:
Our tank for the last 2 years has been a split tank made of titanium. </div></BLOCKQUOTE>

density of Al &lt; density of Ti

Why Ti?

[AxelRipper]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by flavorPacket:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by AxelRipper:
Our tank for the last 2 years has been a split tank made of titanium. </div></BLOCKQUOTE>

density of Al &lt; density of Ti

Why Ti? </div></BLOCKQUOTE>


That is a very good question, and maybe one of our more senior team members will chime in here, but I believe that we did it mostly because we could. We got a sizable sheet of Ti sponsored to us for that purpose and went with it.

[Wesley]

Our tank design didn't change much in the years I was on the team. Mostly looks like a 10"x10" cube with one edge lopped off to clear the seat. The smaller the footprint, the better it deals with sloshing, but the higher the CG. To combat this, we've used both baffles and a secondary pump. The secondary pump system worked the best, we just had a small chamber inside the tank that a low pressure pump fills, and the high pressure drew from. When it was done right it would completely empty the tank without stalling under lateral G's.

I don't know that much about this years tank, but I think it's pretty spiffy.

[ZAMR]

Yo yo. I'm just going to jab in here about the CG height of the fuel tank. These tires we run are extremely load insensitive, so lowering the CG by changing the fuel tank isn't going to do much.

So slosh prevention (elastic weight transfer) would be more important to control from both a vehicle dynamics perspective and a fuel starvation perspective (I guess why foam is so popular).

This year sooner racing team gas tank utilizes the same 2 pump system Wes described above, but with internal pumps, mostly for packaging efficiency. Its about 1.2 gallons up the filler neck, even though we burn through significantly less than that.

[flavorPacket]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by AxelRipper:
we did it mostly because we could. </div></BLOCKQUOTE>

You made your car heavier because you could?

good god.

[Mbirt]

AxelRipper wasn't there. While I agree Al would've been lighter, the Ti tanks were an afterthought to replace the failed CF tank. I'd say the material's thinner than .030" and we got it cheap. The tanks aren't exactly simple shapes and the flats were water-jetted. I don't believe our mounting scheme done in Al would've held up to 450x-grade vibration, either.

My theory for carrying 2x the safe amount of fuel inside tanks of Ti is that we dearly missed the weight of the f4i when switching to the 450x and had to take measures to get some of that weight back. We didn't want to go straight from Rosie O'Donnell to Olsen twins.

[Demon Of Speed]

Al does have a problem with E85 from what I have heard, which is what we were planing on running, and part of the reason the tanks are much larger than needed.

[HenningO]

An old trick is to have a "cup" around the pickup. The cup has some small openings at the bottom (and obviously a large one up top. Then have the return fuel line (if you are running one) have its outlet into the cup.

Works like a charm!

[Thrainer]

Be careful with composites and E85. I would say cured prepreg is safe, but most adhesives are not resistant long-term. We didn't have any problems with aluminium in E85.

You can find an article about E85 modifications here (remove the blank spaces): ht tp :// www. amzracing.ch/amz/files/amz1384.pdf

[Stef.V.]

Coming back to the rapid prototyping of the fuel tank... Is it possible to share something about the wall thickness of your tank?
Weight density compared to aluminum seems to be important, unless you need off course a 3 times bigger wall thickness...

Thanks beforehand!
Stef Vanparijs (Belgian student @ Tallinn team)

[CB23]

Well, I'm a non-FSAE lurker, but I use a system that might be of interest to y'all. I autocross an open wheeled car. Which is ballasted to be just above minimum with an empty gas tank.

I use a go-cart gas tank. Not a fuel cell. No foam. It has a small flat spot on top where the gas cap is, then angles down to a wedge. Rather like a rubber door stop in shape. A narrow door stop. . . (narrow being important to the design) The fuel exit is at the knife edge of the wedge. So sitting "correctly" on the ground, there is JUST clearance for the fuel line to clear the floor. It is spec'ed at one gallon, holds a bit less in my configuration. Enough for five normal autocross runs, or four long ones.

There is a small "cup" around the fuel outlet, inside the tank, as described here earlier.

And I have tilted it up on edge quite a bit, so the fuel exit plug is down. It kind of sits on the floor in a "V" shape, sharp edge down.

Fuel exits the tank, goes through a filter, through my fuel pump and into a small fuel "sump." A cylinder of aluminum about an inch and a half in diameter, with a cone on the bottom. In total about five inches tall. Fuel enters at the top and exits through the bottom, going to the carbs.

My carbs have no float bowls. I have sustained. . . let's say very high lateral g forces. . . at Little Talladega - flat, perfect, high-grip asphalt. And many other places. I have never seen fuel starvation.

And when I run out of gas, there is likely only a few tablespoons of gasoline in the car. . . There is an integral mechanical fuel pump on the first carb that sucks the lines and the sump dry (or so I hope). http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Rex Chan]

FuelMan: 8kg for 4.5L of fuel seems kind of high, but then again, we didn't weight ours before we put it in the car. We ran a 9L tank (for an E85 CBR600RR), and used 5.8L at FSAE-A 2010 comp. Our tank would have been about 2kg. With fuel less than 1kg/L, that would have to mean that your tanks were more than 3.5kg? Our tank is a triangle, with base much wider than top, to fit under the seat. We run a Delphi MRA fuel pump system, with the pump & regulator in a plastic module that sits in the tank, pushed against the base with springs, and attached at the top of the tank. We never had fuel supply issues, but that probably has a lot to do with our large capacity. Our tank does keep the CoG low though.

Using CF for the fuel tank seems like an odd use of resources, as the problems if it leaks are rather large: running out of fuel in enduro; fire. Also, the idea of 2 pumps seems to increase the complexity, mass, cost, space, and hence chance for failures to end your event. Wouldn't it be easier to make a larger tank, and take the weight penalty? If your engine tune changes a lot, then you have spare capacity to tap into.

Aluminium parts of the fuel & intake system should be anodized.

[Rex Chan]

Just an update on our 2011 fuel tank situation: today we got delivery of our new 2011 tank (made by our awesome sponsor Rob Black Engineering).

It was designed to hold 8L (leaving space for the Delphi MRA, and not counting the filler neck). Including the fuel pump/MRA ring, but not bolts, it weighs in at 1704g. It is made of 2mm 5052 AL.

We also had the 2010 tank on hand, to weigh and compare: it weighed 2211g (including ring and bolts). The extra weight comes from being made of 3mm AL, and designed to hold 9L of E85.

here's a YouTube video of it: New 2011 Fuel Tank 1 (http://www.youtube.com/watch?v=7-PGdXG4nE8), New Fuel tank 2 (http://www.youtube.com/watch?v=1tytCGCGFx4), and Fuel pump into fuel tank (http://www.youtube.com/watch?v=hAoRSB_GaA0).

As for starvation issues, the Delphi MRA/fuel module has built-in mechanisms to prevent surge: I think it fills the reservoir/bucket using excess fuel flow in the return line (jet pump), so that all fuel in the tank is able to be used (important I suppose for OEMs). We never seem to have surging problems on track: it just stutters then engine dies. See the Delph site for the official version: Delphi Series 7000 Fuel Module (http://delphi.com/manufacturers/auto/powertrain/fuelhandling/series7000/). Using this system also gets rid of heavy, bulky return lines.

[patsodt]

Rex, thanks for the info on your fuel system!

I'm interested in that Delphi fuel module, but I wasn't able to get many specs online... do you have any data sheets? Also, do you purchase it straight from Delphi?

Thanks

[Rex Chan]

I'm pretty sure its an OEM spare part, so look up common model cars and their replacement fuel modules. Lots of websites have lists of car spares.

Delphi is our sponsor, so we get it through them direct. I have test results for the specific pump model we're using, but the one you buy will be different.

[patsodt]

Ok, I'll take a look some more at OEM ones. The issue I'm having is I can't find spec sheets for any of them since they're model specific. I'd be interested in specs for the specific pump you're using, or else if you have any insight into which ones are best.

Also, does yours have an adjustable pressure regulator, or do you know if you can get them with one?

[AxelRipper]

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