Figuring the weight of obects

[joshuabardwell]

The problem with guesstimating based on volume is that most humans are very bad at estimating volume, especially of irregular shapes. If you must estimate based on volume, I suggest measuring the object and approximating to a regular shape (e.g. a sphere, cube, cylinder, so forth) and then using geometric formulae to calculate the volume. This will likely get you in the ballpark, assuming your density assumptions hold.

If you need to measure density, take a sample of the object (e.g. by chipping of a chunk of the rock or something), measure its weight using a scale, then submerge it in water and determine the volume of water displaced to get its volume. Density = weight / volume.

 

[IslandTractor]

The problem with guesstimating based on volume is that most humans are very bad at estimating volume, especially of irregular shapes. If you must estimate based on volume, I suggest measuring the object and approximating to a regular shape (e.g. a sphere, cube, cylinder, so forth) and then using geometric formulae to calculate the volume. This will likely get you in the ballpark, assuming your density assumptions hold..

I usually just pace off the object with my size 12 boots and mentally convert the object into something square sided so I can estimate cubic feet. That keeps pi out of the equation and is generally good enough for tractor work. I'm mostly interested in whether something is A)less than 1000 lbs (no sweat), B) 1000-2000 (OK but ballast an issue if moving) or c) >2000lbs (need max ballast (BH, bush hog) and might be able to lift it if close to pivot points and definitely don't want to move it far)

 

[bcp]

Show off... :laughing: :thumbsup: Better to have a tractor beam on your tractor than a grapple with that one...

View attachment 273073


Weight of materials-list:

http://www.smithy.com/machining-reference/inch-and-metric/page/41

http://www.harmonysandgravel.com/charts.htm

Bruce

 

[MossflowerWoods]

View attachment 273073


Weight of materials-list:

Weights of Materials | smithy.com

Bruce

SWEET!

David

 

[madmax12]

Heres one: Boulder Sizing and Weight Estimation

AND

I got this link from DavesTractor:


Specific Gravity Weights Of Materials from READE

 

[ricklman]

I usually just pace off the object with my size 12 boots and mentally convert the object into something square sided so I can estimate cubic feet. That keeps pi out of the equation and is generally good enough for tractor work. I'm mostly interested in whether something is A)less than 1000 lbs (no sweat), B) 1000-2000 (OK but ballast an issue if moving) or c) >2000lbs (need max ballast (BH, bush hog) and might be able to lift it if close to pivot points and definitely don't want to move it far)

That's good to hear, because Pi has been wrong since its inception... See my signature!

 

[IslandTractor]

That's good to hear, because Pi has been wrong since its inception... See my signature!

I think the same people who believe in global warming are the ones who believe in pi. Big conspiracy. Rush will break the story on pi soon.

 

[bcp]

A bill was introduced in Indiana to regulate the value of PI.

The Straight Dope: Did a state legislature once pass a law saying pi equals 3?

Bruce

 

[vtsnowedin]

I use this method too. Best to keep a few figures in your memory so you can make field estimates as you are rarely near a computer or reference book when figuring out how to lift something. Average weights can be easily guesstimated by figuring the cubic volume in feet and then multiplying by density as weight per cubic foot. Granite: 170lbs/cubic ft (most stone is lighter). Concrete: 150lbs; Soft wood: 35lbs; Hard Wood: 60lbs; Gold 1200lbs; Neutron Star 6x10 to the 15th power lbs/cubic foot (make sure you have enough ballast!).

I don't know about the star but the rest of that is a good list. I'd add in loose sand at 90 lbs/cubic foot and good stony gravel at 130. The trick is measuring an odd shaped rock that tapers in all three directions and not in straight lines. You can just take the thickness at the middle times the width in the middle times the total length and usually be pretty close but if one part of it is a lot thicker then some end break it up in your mind into two or three pieces and then add the results together. After all of that when you go to pick it if the relief valve whines you know it weights more then your loader can pick.

 

[bigdeano]

If it's bigger than your tractor you probably can't lift it. If it's smaller give it a try and see what happens.