wedge fuel cells

[fastford]

you do not gain rear percentage with a wedge cell, put your car on a scale, put 50 lbs weight on the rear bumper, check wheel weights, then move that weight to the front of fuel cell and check your weight, you will find you lost rear weight percentage due to leverage, the advantage I can see is keeping the weight as close to the rear as possible, which helps eliminate the slinging effect that lateral Gs has going into the corner. for 30 lap or so races I like a smaller cell and a piece of weight I can move. JMO

[stock car driver]

you do not gain rear percentage with a wedge cell, put your car on a scale, put 50 lbs weight on the rear bumper, check wheel weights, then move that weight to the front of fuel cell and check your weight, you will find you lost rear weight percentage due to leverage, the advantage I can see is keeping the weight as close to the rear as possible, which helps eliminate the slinging effect that lateral Gs has going into the corner. for 30 lap or so races I like a smaller cell and a piece of weight I can move. JMO

The further forward your cell is the "LESS" rear % you lose due to fuel burn off during a race... that is gaining rear percentage at the end of the race.

It cant be explained any simpler than it already has in this thread.

[fastford]

The further forward your cell is the "LESS" rear % you lose due to fuel burn off during a race... that is gaining rear percentage at the end of the race.

It cant be explained any simpler than it already has in this thread.

im sorry, but that makes no since to me, your pivoting weight over an axes, ie the rearend, the farther you move the weight toward the rear, the more weight the rear contact point will gain. its basic leverage. if car is on scale, say with 10 gal of fuel in wedge , ill bet if you turn the cell around and put the wedge toward the rear, your rear percentage will increase,

[stock car driver]

im sorry, but that makes no since to me, your pivoting weight over an axes, ie the rearend, the farther you move the weight toward the rear, the more weight the rear contact point will gain. its basic leverage. if car is on scale, say with 10 gal of fuel in wedge , ill bet if you turn the cell around and put the wedge toward the rear, your rear percentage will increase,

I hope your joking around.

[fastford]

put your car on the scale ,if you have one, put a piece of lead in front of the cell, write your rear wheel weights down, now move that weight to the rear of the cell and check you readings again, then we will see who's joking, I do like to joke around, just not this time, sorry

[stock car driver]

put your car on the scale ,if you have one, put a piece of lead in front of the cell, write your rear wheel weights down, now move that weight to the rear of the cell and check you readings again, then we will see who's joking, I do like to joke around, just not this time, sorry

If I have one. lol.

Man you really should start reading this thread from the beginning again or at least read my reply to you originally.

Key words being FUEL BURN OFF, END OF RACE

[MasterSbilt_Racer]

No matter which cell you have, you will scale your car the same. The cell gets lighter as the fuel burns. The standard cell is like taking weight off the rear bumper. The wedge is like taking weight off further forward. There is the advantage. Rear weight disappears less quickly.

[TS3g]

Fastford, you're correct in the fact that the moving weight farther to the rear will create more rear %. However, we're not looking at the static % numbers; we're looking at the delta % numbers from full fuel load to empty, as Jeff noted. You’re also not taking into account that it is possible to still have the rear % start out the same, even though the fuel cell location/shape may be different.

So for example, let’s assume we have two cars, everything identical between the two (total weight, starting %, fuel cell shape, etc), only one has the fuel cell centered directly over the rear tires (not exactly realistic, well according to rules, however GRT tried it a few years back), and the other is the standard position behind the rear end. If both cars start with 60% rear and a full load of fuel, then run laps until the fuel cell is empty, the car with the fuel cell behind the rear tires will have lost more rear % than the car with the fuel cell centered.

As Matt explained, a wedge shape fuel cell has the CoG farther forward than a rectangle cell, thus it acts like it is closer to the rear tires and more resembles the car in our example with the fuel cell centered over the rear end.
You did bring up something else that too is an advantage of the wedge cell (or one mounted closer the rear end), that being reducing the “slinging” affect, aka, reducing the polar moment of inertia. By moving the CoG of the fuel cell close to the CoG of the entire car, the car will be able to change directions easier, and be less apt to have the weight from the fuel cell continue to push the rear of the car as the car is changing direction (the “slinging” you described).

Another aspect of a wedge cell not mentioned but should be, depending on the actual wedge shape (which is normally larger at the top than the bottom), a wedge cell will also have a higher CoG than a rectangular fuel cell of equal volume. Not only that, during fuel burn off, the CoG of a wedge cell will lower less than that of a rectangular cell. What does this mean? The CoG of the entire car will remain more consistent through fuel burn off with a wedge cell, and say the cell is mounted in the same position as a rectangular cell would be; the CoG of the entire car will be higher as well.

[fastford]

your last paragraph is the most important aspect of running a wedge in my opinion. all the tire contact point knows, as far as rear weight percentage is concerned, is the weight applied to the springs , if you could put the cell over the axle, wouldn't you have to add lead to get the same rear percentage as with the cell moved all the way back? if you apply the leverage effect of moving this weight, you would have to.

[MasterSbilt_Racer]

your last paragraph is the most important aspect of running a wedge in my opinion. all the tire contact point knows, as far as rear weight percentage is concerned, is the weight applied to the springs , if you could put the cell over the axle, wouldn't you have to add lead to get the same rear percentage as with the cell moved all the way back? if you apply the leverage effect of moving this weight, you would have to.

Yes. But unless you have a heavy car, this shouldn't be an issue at all. Actually, a heavier car that remains more consistent is likely better than the lighter one that changes balance more.

[fastford]

Yes. But unless you have a heavy car, this shouldn't be an issue at all. Actually, a heavier car that remains more consistent is likely better than the lighter one that changes balance more.

I agree with you, I was trying to explain to the original poster that the inertia factor of the wedge cell is far more important than worrying about rear weight percentage change. as ive said before, I prefer a smaller cell and the ability to move some lead around when running under 50 laps, but that's just me. as far as spending your money on one and considering what they cost, for most Saturday night racers like me, I don't feel there worth it.

[Matt49]

Blackmagic...Sorry...my original reply to your post was not so much directed at you as it was a response to Brian's assessment of my explanation as a "theory" (which is why I quoted the word). My theory is scientific fact. That being said, Brian wasn't necessarily questioning my logic but he was making another point that was also somewhat valid and probably misplaced his words. No biggie...

Anywho...I think we're all kind of agreeing on some points here about the rear percentage CHANGE and how a wedge cell makes a difference. And perhaps I did a poor job of explaining it initially. All that being said, a Mastersbilt wedge fuel cell doesn't cost much more than a standard square cell but I see the benefit of having a more consistent car over the period of a race. When we scaled with varying fuel levels we found that the wedge deal held it much closer to our desired numbers over a given burn-off. As mentioned, it doesn't take a back-of-the-pack car to the front but it does eliminate some variables which is a pretty big deal in my book.
If somebody disagrees that's fine. It's your money, spend it where you like.
The moment of inertia argument is VERY interesting as it applies to dirt cars (or doesn't). I'd tend to agree that getting the bulk of the cars sprung mass CENTERED is important but I wonder to what degree it really matters on dirt ovals as we don't change rotational direction that much. Where I have seen this discussed heavily is in the F1 community about cars in chicanes and tight turning scenarios. But with dirt cars, even on tight cornered tracks, we are almost always rotating in the same direction. We're rarely calling on the car to be overly "maneuverable".
I'm not saying there isn't benefit to eliminating the "pendulum" effect and all of the other things associated with large moments of inertia. I truly believe there is a benefit. I just wonder if we'll ever be able to quantify it to determine how much it helps us on dirt oval cars.
I've seen guys with lead mounted just in front of the rear bumper win races. Then again, I've seen cars with a flat tire win races. But I didn't see anybody the following weekend unload their car with flat tires.

[DRTRCR22]

Ok then.. what is the difference between a wedge cell, and the teardrop cell that has been around for many years...? same idea right.. move the fuel weight forward and all the other benefits you mentioned..? I just replaced my big square cell with a teardrop cell, and mounted it high up against the decking, and as far forward and to the left as possible on my MBSmack. This should accomplish the same goal for a whole lot less $, right? Are guys not using teardrop cells in late models anymore for a reason...???

[7uptruckracer]

Some don't use teardrop because its bottom feed and rules or because most are 32 gallons and they aren't allowed or don't need it, some don't because I believe the wedge does a better job at what the teardrop is trying to do.

[hpmaster]

One of the cars I work with is a 2007 Mastersbilt and we needed a new cell, 32 galllon rectangle was leaking. Masters sold us their 26 gallon wedge with brackets for $750.00. Not a $250.00 cell but hardly a deal breaker. Most the other brands were $1140.00 to $1700.00 JMHO