OMG Lowered and Lightened 2001 Edge Extended Cab

[bobbywalter]

dude....adding weight to the back of the truck via cooling system and batteries is the only way i have seen timed and g meter improved handling accomplished in this platform.

 

[stmitch]

dude....adding weight to the back of the truck via cooling system and batteries is the only way i have seen timed and g meter improved handling accomplished in this platform.

Exactly.

Losing weight anywhere is great for mpgs, but to improve handling, you need to make sure the weight lost is in the right places. Having the center of mass so far forward is just asking way too much from the front tires, while simultaneously not utilizing the rears enough.

 

[Bronco638]

I believe he's said that he cut the bottom leaf as well as the overload leaf (which are, basically, the two lower leaves in the pack). I figure that if you're going to remove the u-bolts, to remove the 2.5" spacer block, you might as well remove the leaves at the same time (instead of cutting them).

I didn't want the front lower than the rear which is not good aerodynamically. It increases drag under the rig. That half inch made a difference and removing the two bottom leaves felt too soft and dropped it too much.

You lost me here. I get the front-to-rear rake issue but what's the difference between cutting the leaves off and removing them? Or, did you not cut them completely (left a portion)?

 

[Blown]

You lost me here. I get the front-to-rear rake issue but what's the difference between cutting the leaves off and removing them? Or, did you not cut them completely (left a portion)?

I just cut both ends off leaving a 1/2 block.

 

[Blown]

This may help one understand why moving weight from behind the axle improves handling. It also applies to moving the radiator from the very front to the bed. It's not just the weight transfer that helps handling, it's getting the weight off the polar ends that improves handling.


Effect of Polar Moment of Inertia

The moment of inertia has to do with a body's resistance to angular acceleration. Polar refers to the ends. Consequently, the polar moment of inertia of a vehicle is related to the mass that is located near the front and rear. The effect of polar mass can be experienced by rotating a dumbbell back-and-forth around a central axis. The weight concentrated at the ends makes the barbell resist changes in direction. A ball of equal weight will reverse directions with little effort because the mass is concentrated at the center. Most passenger cars are designed with a relatively high polar moment of inertia. The engine is located over the front or rear axle and the fuel and luggage are located at the opposite end. The center of the vehicle is hollow to provide room for the occupants.
A low polar moment of inertia results in a vehicle with more responsive handling, but it also produces a more choppy ride. A vehicle with high polar mass is less nimble, but it offers a smoother ride. Sports cars tend to have a low polar moment of inertia for nimble handling, and they also tend to ride more roughly than passenger cars. Normally, a good balance between ride and handling can be achieved. The designer does not have to decide between one or the other extreme.

 

[stmitch]

Effect of Polar Moment of Inertia

The moment of inertia has to do with a body's resistance to angular acceleration. Polar refers to the ends. Consequently, the polar moment of inertia of a vehicle is related to the mass that is located near the front and rear. The effect of polar mass can be experienced by rotating a dumbbell back-and-forth around a central axis. The weight concentrated at the ends makes the barbell resist changes in direction. A ball of equal weight will reverse directions with little effort because the mass is concentrated at the center. Most passenger cars are designed with a relatively high polar moment of inertia. The engine is located over the front or rear axle and the fuel and luggage are located at the opposite end. The center of the vehicle is hollow to provide room for the occupants.
A low polar moment of inertia results in a vehicle with more responsive handling, but it also produces a more choppy ride. A vehicle with high polar mass is less nimble, but it offers a smoother ride. Sports cars tend to have a low polar moment of inertia for nimble handling, and they also tend to ride more roughly than passenger cars. Normally, a good balance between ride and handling can be achieved. The designer does not have to decide between one or the other extreme.

I get that. Learned a lot of that in school over the years. Trying to decrease the polar moment of inertia is essentially trying to centralize the center of mass to as close to the vehicles midpoint as possible. But, by only removing weight from behind the rear axle, you've actually moved that center of mass forward, INCREASING the polar moment of inertia.

Think of your truck as a set of old fashioned scales where two objects hang, and the heavier side drops. Having zero moment of inertia (good for handling) would be like having perfectly balanced scales. In our trucks, the rear is already the much lighter side, and you took weight off of that end. The result, is even worse weight distribution, and a center of mass that has moved even further from the center of the vehicle than it was when stock.

If you're trying to reduce the polar moment of inertia, then you need to take weight away from the heavier side, or add it to the lighter side. Relocating weight from the front to the rear would have double the effects because the heavy side gets lighter and the lighter side gets equally heavier. By removing all of that weight in the rear, you've forgotten one entire half of the truck, and it's the half that needs the weight loss the most.

Ultimately, if you're happy with your truck that's what is most important. If it suits your driving style, and feels better to you now, then more power to you. But I'd really like to see some evidence that the weight loss behind the axle has improved your handling, because the physics don't really support your claim.

 

[Blown]

Trying to decrease the polar moment of inertia is essentially trying to centralize the center of mass to as close to the vehicles midpoint as possible.

the physics don't really support your claim.

Now you are calling BS on me?


Wow, you can't see that removing and moving weight from the polar end, behind the rear axle, towards center helps with handling. The physics are there! It's right there in your own explanation in your first paragraph.

I also did nothing to increase the polar moment of inertia, no weight was added in front of the front wheels, the other polar or end.

I think you are confusing weight bias front to rear with the Polar effect.

 

[bobbywalter]

Now you are calling BS on me?


Wow, you can't see that removing and moving weight from the polar end, behind the rear axle, towards center helps with handling. The physics are there! It's right there in your own explanation in your first paragraph.

I also did nothing to increase the polar moment of inertia, no weight was added in front of the front wheels, the other polar or end.

I think you are confusing weight bias front to rear with the Polar effect.

not bullshit calling.



its the interpretation of the physics and assumptions.

you assume removing weight behind the axle will help. but your starting negative in the back. it is already out of balance and too light. quite by design. the truck will handle better with a specific load in the bed. if you only removed weight from the front of the front axle, then i would understand claimed handling enhancement potential.

doing what you did only upsets the applecart.


a slalom course with three different aggressive drivers and a g meter is a good way to test.

 

[stmitch]

I'm not calling you a liar, I simply think you're misunderstanding the definition of moment of inertia because the word polar is being incorrectly placed in front. I should've caught it sooner, but my last statics/dynamics class was several years ago, so I'm a bit rusty. What we're really talking about here is a moment of inertia (no "polar"), and the idea, is not to remove weight from the poles. The idea is to have equal weight at each pole, so that the item you're talking about is balanced. That's when the moment of inertia is low, because one pole isn't trying to swap ends with the other.

Since my last analogy with the scales wasn't effective, let me try again using the barbell analogy from the text you posted. The reason a barbell has a low moment of inertia, is because the weights on each end are equal. Removing weight from one end of the barbell would move the center of mass (aka centroid) closer to the heavier side, and increase the moment.
In terms of your truck, one side was already heavier to begin with, so it wasn't well balanced. The center of mass gets closer to the heavier side as the difference between the weights increases. So, you made the rear even lighter than it already was, which moved the center of mass even more forward than it already was. This INCREASES the moment of inertia, and as you already posted, increase moment of inertia leads to worse handling.

Now, this can be corrected by adding weight back to the rear, (which you've already done, and you've admitted that it helped) or by reducing the weight on the heavier end of the truck, the front.

I'm really not trying to offend you. Again, if you're happier with your truck now than when you started, good for you. Carry on.

 

[85_Ranger4x4]

Wow, you can't see that removing and moving weight from the polar end, behind the rear axle, towards center helps with handling. The physics are there! It's right there in your own explanation in your first paragraph.

Unless you bungie corded your spare tire, winch assembly, tailgate and bumper scraps to the front bulkhead of your bed you did not move any weight forward in your truck.

You moved the center of gravity forward by removing stuff from the rear... and the CG was too far forward to start with.

 

[Blown]

I am not offended, but I am also not wrong on the physics here. Let me try again.

By the thoughts expressed here, we should all be loading heavy cargo close to the tailgate in order to improve cornering. That is just wrong. Please consider a load of 180lbs at the tailgate vs over the axle. One can certainly feel a difference around the corners. On icy snowy roads it is noticeable where you load your sand. It really is that simple. Loading behind the axle greatly increases the polar moment vs loading over the axle. In the real world you can feel the effect. The change I made was of little consequence in moving the center of mass forward vs the gains in handling of lowering the polar moment.


Automobile Handling:
"Mass near the ends of a car can be avoided, without re-designing it to be shorter, by the use of light materials for bumpers and fenders or by deleting them entirely. If most of the weight is in the middle of the car then the vehicle will be easier to spin, and therefore will react quicker to a turn."

Here is more from here: http://www.timskelton.com/lightning/race_prep/weight/weight.htm

'Weight in ahead of the front axle or behind the rear axle is undesirable, as it increases the polar moment of inertia (picture the bar that high-wire artists use to keep them stable). As shown in the graph to the right, the farther that weight gets from the centerline of the vehicle, the more the vehicle resists direction changes. Additionally, once the rear gives up and the truck goes into oversteer, the pendulum effect causes weight in the back (especially behind the rear axle) to want to keep going around. Just ask someone who drives an air-cooled VW or Porsche 911. Removal of the spare and hitch, for instance, helps lower the polar moment of inertia."

Now I still think someone is confusing center of mass/weight bias front to rear with polar moment. They are two distinct variables and both effect handling.

 

[stmitch]

It sounds to me, like you're trying to reduce the severity of oversteer, by reducing the 'pendulum effect' caused by weight behind the axle. Is this true?

 

[Blown]

It sounds to me, like you're trying to reduce the severity of oversteer, by reducing the 'pendulum effect' caused by weight behind the axle. Is this true?

What this is like is you are an armchair quarterback questioning what I am doing on the field. In the real world what I have done works. I read about tried and proven handling concepts, tried one that works and got a positive result! I tried to give it to you with physics and you confuse and combine two distinct handling variables in theory land, center of mass and polar moment of inertia.

I am frustrated with you and the others that jumped in on your thoughts!

It really is simple in the real world and why we don't typically load a heavy object at the rear of the bed, common sense, or trial and error tells us that will effect the handling/cornering. Weight behind the axle adds to the force that wants to pulls the rear around which is described in physics by the polar moment of inertia.

Yes I think you are gettng it now.................

The better handling/cornering effect of reducing weight aft of the axle is greater than the slight change I made in center of mass and thus I netted a positive handling gain.

 

[stmitch]

Ok, now that you've actually stated your goal clearly, let's examine the situation. I agree that reducing weight behind the rear axle will reduce the pendulum effect. You are correct there. What you've done should reduce the pendulum effect. Congrats!

The problem in my eyes, is that the pendulum effect you are trying to reduce only happens AFTER the rear has lost traction and you begin to oversteer. Whether it happens in snow, or not, your traction has to be lost in order for what you've done to work. What I'm suggesting, would allow you to keep traction longer, and avoid overrsteering in the first place. You solution is a reaction to a problem. My suggestion, would prevent the problem from occurring in the first place, by aiding traction/grip in the rear.

From your earlier post:
"As shown in the chart to the right, the farther that weight gets from the centerline of the vehicle, the more the vehicle resists direction changes."

You've moved the weight (center of mass) forward, ever so slightly, which has made the vehicle more resistant to directional changes. That's not helping your handling. That's what everyone here has been saying. They're not just 'jumping in on my thoughts', they understand the science behind it.

I'll repeat myself from earlier. It's your truck. IF you're happy with it, then just be happy. Who cares what math and science say? But, beware the placebo effect that modding can have. Many times, we think all of our hard work has made an improvement when it actually hasn't.

Finally, I'm not just standing on the sidelines here. You can see my truck. It's designed primarily for handling/grip. If you want to see what my 'crazy theory of weight distribution' does for handling lets go autocross sometime. My blown 3.0 against your blown 4.0. I'll even put some sandbags or something behind the rear axle.

 

[85_Ranger4x4]

Weight behind the rear axle does increase the "pendulum" effect before it breaks loose too, my brother's '68 VW is far easer to oversteer with than just about anything else I have driven considering it lacks the power to break the tires loose on its own. The engine (as massive as a magnesium 1600cc flat 4 is) is essentially hanging off the back end of the car.

However his stock Mustang has almost a perfect 50/50 weight balance (like most sporty cars) and will almost pull a full G on a skidpad.