How much am I pulling?

[Turfman]

Just trying to figure how much weight I'm pulling with a full 60" Land Pride box blade. With a 60" width, 17" high moldboard and a bucket depth of 22" I figure the bucket has a capacity of about 12-13 cubic feet. Nearly a half yard. At about 2700-3000 lbs per yard of soil, that makes a weight of around 1300 lbs in the box. Am I figuring this correctly?

 

[boustany]

yup, assuming the box is completely full, which is unlikely. I would think that friction and the effects of (more or less)shearing the soild at the blade would add a lot more to the load from the tractors' perspective.

 

[Soundguy]

I think you are overestimating the weight of a yard of material. Nominally, a cy of dirt should weight about 2000lbs, give or take for moisture. A yard of 3-4kpsi concrete is going to be closer to the 3k# figure, again, give or take.

A mechanical engineer will be better able to comment on the weight carried, and apparent load at the blade, friction coefecient, etc, etc.

Soundguy

<font color=blue>"Just trying to figure how much weight I'm pulling with a full 60" Land Pride box blade. With a 60" width, 17" high moldboard and a bucket depth of 22" I figure the bucket has a capacity of about 12-13 cubic feet. Nearly a half yard. At about 2700-3000 lbs per yard of soil, that makes a weight of around 1300 lbs in the box. Am I figuring this correctly? "

 

[hazmat]

<font color=blue>A mechanical engineer will be better able to comment on the weight carried, and apparent load at the blade, friction coefecient, etc, etc</font color=blue>

I'm a mechanical engineer. Here is the result of my detailed analysis.

You are pulling much more than you could without the tractor /w3tcompact/icons/grin.gif

 

[Soundguy]

See... I knew someone would step in. What was the old joke people always used to tell me?.. Ok.. What is the difference between a civil engineer, and a mechanical engineer? Civil eng's build targets.. mechanical eng's build the toys to use on the targets.

Guess I better go start building some targets....

Soundguy

<font color=blue> mechanical engineer will be better able to comment on the weight carried, and apparent load at the blade, friction coefecient, etc, etc

<font color=red>I'm a mechanical engineer. Here is the result of my detailed analysis.

You are pulling much more than you could without the tractor

 

[hazmat]

Here is the real answer to your question. I've calculated a theoretical drawbar pull for your tractor. I've made a few assumptions:

1. After all the losses in the driveline, You get 20 HP to the wheels. (optomistic)

2. You have enough traction to use all 20 HP (also optomistic)

3. I'm assuming a 100:1 gear reduction
You can go about 4mph in low gear, & your rear tire is about 4 feet in diameter
4mi/hour*hour/60min*5280ft/mi = 352ft/min
4ft*pi=12.6ft/rev
(352ft/min)/12.6ft/rev = 28rev/min wheel speed
engine 2800rev/min / 28 rev/min = 100:1

Torque calculation
20HP * 550 Ft-LB/sec = 11000 ft-lb/sec
11000 ft-lb/sec * min/2800 rev * 60 sec/min = 235 ft-lb per rev

235 ft-lb/rev * 100:1 gear reduction = 23500 ft-lb/rev

23,500 ft-lb/ 2 ft radius = 11,750 pounds drawbar pull!

Consider this a maximum, It is optomistic, I could be off by a factor of 3 +/-

I took an educated guess at your gear ratio, it may be off.

Like I said before, much more than you could pull without the tractor /w3tcompact/icons/grin.gif

 

[Soundguy]

The local mobile home dealer made a special 3pt. mobile home toter. What it is, is a dolley that supports the tounge weight of the mobile home on a swivel with two small wheels. From the dolley is a 5' bar that attatches to the back of the tractor via a 2" receiver. ( looks like the modified or made a beefy standard trailer dolley, then modified it to be tractor powered. )

Anyway, they move those mobile homes with a big case/ih.. older model. I saw them moving one the other day.. was only going like 2-3 mph.. but id didn't look like there were any problems. Amazing what you can pull with gear reduction, sufficient traction, leverage, and a rolling load.

Soundguy

<font color=red>"Consider this a maximum, It is optomistic, I could be off by a factor of 3 +/-

I took an educated guess at your gear ratio, it may be off.

Like I said before, much more than you could pull without the tractor "

 

[EdKing]

<font color=blue>Amazing what you can pull with gear reduction, sufficient traction, leverage, and a rolling load.</font color=blue>

I pulled a mobile home up a slight grade with a my 36hp Long/Landtrac, just put it in low and used the diff-lock till I got it rolling. Pulled it right up to the pad with no problems.