Liquid Ballast vs. Iron Weights

Alright, there are quite a few intelligent people here, so I need to pick your brains. I am involved in an argument with my father about which takes more power to move, iron weights or liquid ballast. We understand the whole CACL rust issue, the toxicity of Glycol and the cost of installation/maintenance differences. Our argument is based purely on which requires more HP. I won't state which side of the fence that I am on, but I do believe that my opinion is supported by the laws of physics.

These father/son arguments seem to be abundant. The only consolation that I get is that even though I am alway wrong according to dad, in several months he will prove my point to himself and preach it as the gospel according to his experience.

Any and all opinions are welcome and the more the better. Thanks for your time!

Why? The fluid inside the tires does not rotate, while the tire does rotate. The water exerts a small amount of friction against the tire, which causes the tire and fluid to heat up. This heat is lost energy, which translates to lost power. The amount of power consumed by this parasitic drag is infinitesimal relative to the total power produced by the motor, but it is real.

The cast iron weights, on the other hand, create almost no drag. (Assuming that they are fastened good and tight to the wheels.)

Duane had the right idea, but he has it backwards: it's the hard-boiled egg that will spin the longest, not the raw egg.

Benjb had some interesting math, but he answered the wrong question. He calculated the rotational inertia of the ballast, which affects the power required to accelerate the tractor to operating speed. That is of little consequence. First, the tractor spends most of its time at a constant operating speed. Second, when you stop you recover the energy that was used to accelerate the tractor, assuming you don't touch the brakes.

You can verify this with any physics textbook, or prove it yourself with a rotating mass such as bicycle wheel. Spin the wheel up to speed. Does it stop spinning when you quit applying power? No, although it will eventually slow down because of friction in the bearings. Now stop it by holding your hand against the tire. Did your hand get hot? That's because the energy stored in the spinning wheel was converted to heat.

Right on.

Sometimes cans of food and boiled eggs are better than all the science and physics you can find.

Best regards,
Clay

To illistrate, suppose you have a wheel with a 20 in minor radius and a 25 in major radius. You have the choice of putting a 1000# (treated as mass) wieght, with a 10in radius, or 1000# of fluid. The inertial for the weight would be .5*1000*10^2 or 50000 h's (arbitrary unit). The inertia for the fluid would be .5*1000*(20^2+25^2) or 512500 h's . The fluid in this example definitely has more inertia (about 10 times more) and would require more horse power. (to find the exact horse power difference you would need to get to standard units and plug into a few mor equations).

Another point to consider is that the fluid doesnt fill the entire tire. My Allis B manual said that originally they came filled with only 75% fluid. that means that the weight is not balance with respect to the axis of rotation. Which is easy to turn and keep turning, a balance flywheel or one with a large chunk taken out. In both regards it appears that the solid wheel weights require less HP in order to move the machine forward

P.S. The closer the mass is to the axis of rotation, the less rotational inertial it has.

Given that tractor tires operate at only a few rpm in real world conditions, there is near zero additional power required to operate the tractor with water in the tires, beyond the dead weight of the water which really only has an effect during acceleration and deceleration, again something tractors in the real world do very little of.

A friend of mine once told his father "Remember, some day you will be old and in a wheelchair and if you're lucky, I won't push your a$$ down the steps!".

This nonsense about Galileo's "law of fall" is often quoted but rarely understood. Physics teaches us that two bodies of different weight fall (towards the center of earth) at exactly the same rate IN A VACUUM (no atmosphere). That condition does not exist anywhere on earth.

Therefore, the rate of fall of any two objects is based largely upon aerodynamics, at least until terminal velocity is achieved. Due to the mass/surface area ratio of the human body, the heavier guy falls faster than the lighter guy, assuming both are in the same relative position (feet first, fetal, limbs extended, etc.)

Now here's one to chew one. A bullet is dropped by hand onto the ground from 5'. At exactly the same time, a bullet is fired from a rifle pointed directly at the horizon. The rifle is at 5' from the ground. Which bullet hits the ground first?

I'd guess that they'd hit at about the same time wouldn't they? Lateral speed would have nothing to do with the vertical drop would it?

Allan

BINGO! You just made my day!

Ron

If it were a static weight, it would take more force to move the fluid, since it is located further away from the axle. It would then take more braking power to bring it to a halt also for the same reason.

But, fluid in a tire is not staic. The fluid tends to remain stationary while the tube/tire tends moves "around" it.

Therefore, me thinks it doesn't make 6 eggs worth of difference between fluid and iron weights. :>)

Allan

Maybe you should take your "I hate liquid ballast" routine on the road, Quebec or wherever. No doubt they would pass a law forbidding anybody from operating a tractor without your approval.

Let's get something straight, every one of us who actually use our equipment find what works best for us. We all use different tractors, with different implements, on different soils with different moisture levels, for different tasks. The amount of ballast and tire pressure and type of tire, and size of tire are choices we make based on our different needs. Ballst is also very much a safety issue; anything you do to lower the center of gravity keeps you from testing your ROPS (or your head if you don't have one). Nothing is more effective at lowering the center of gravity than LIQUID BALLAST.

Do I ever hear you on that one! 15lbs is crazy, if ya ask me.

Allan

Ouch!!

I sure wasn't talking about anyone else's outfit except mine and mine alone. Geeeze!

Allan

I have this uncanny ability to make people mad; been fightin' this curse all my life. I'm the only guy I know that can make someone mad by just saying "good morning" to 'em.

Rumor has it that when I was born, my mother took one look at me and turned around and slapped my dad.

I was the original prototype of the "A Boy named Sue" identity profile. :>)

Now, about this ballast issue..... ..naw, I don't wanna go there. :>)

Allan