Please help. Homework. I'm Stuck

[disoblige]

ok

 

[J_J]

can you give me a hand in the easy part. how did you get the displacement and the rpm?

I used the calculators in the hydraulics section. I assumed that was a diesel, running at about 2500 rpm. Some trial and error will find out what you want to know.

 

[kennyd]

There are also some great calculators here:

Baum Hydraulics

 

[dynasim]

Don't forgot about efficiency. I think it has been said here that the pump efficiency is ~80%.

Chris

 

[J_J]

(26 x 3000) / 1714= 45

It appears that your formula is using an efficiency of 85 % according to the people that wrote the formula from the hydraulic site. So if that is true, then you lose some HP in the transfer of power. That means that you have 45 HP going to the pump using a 53 HP engine.

I believe this is correct, but if not, someone will correct it.

 

[J_J]

Don't forgot about efficiency. I think it has been said here that the pump efficiency is ~80%.

Chris

Chris, I believe the 80 % efficiency is the HP from hydraulic pump to hydraulic motor. The other figure is from gas engine HP to hydraulic pump HP.

I could be wrong, so double check .

 

[disoblige]

It appears that your formula is using an efficiency of 85 % according to the people that wrote the formula from the hydraulic site. So if that is true, then you lose some HP in the transfer of power. That means that you have 45 HP going to the pump using a 53 HP engine.

I believe this is correct, but if not, someone will correct it.

I did some research what is the difference.

your site uses hp = psi x gpm x .0007
This equation means the engine is 85% effiecient and calculates what is the horsepower need for engine to run the pump.

hp= psi x gpm / 1714 x overall.eff of pump
This equation means at 100% efficient engine and finds the pump HP. This is what we used in school.


Required HP Calculator (two answer) . correct me if i am wrong. In conclusion your site using the more accurate equation.

 

[J_J]

Your 1714 number is for 100% efficiency, but don't forget the efficiency from hydraulic to hydraulic motor.

Use the Theoretical Hydraulic Calculator,.

Permco Hydraulic Calculator

 

[disoblige]

My rough copy. I think i am missing something or i did it wrong? Also My pump Hp is off by .5. I do not know why.


Given: 55.3Hp engine and 35400lbs

Efficiency (I made up)
Pump: .94
Motor: .9
Gear:0.95

55.3 x .94 x .9 x.95 = 44.44 HP output

44.44hp x 33000
-------------------- = Speed (FT/MIN)
35 400lbs

=41.4314 feet per minute OR
=497.1769 in/min

Choosen Drum is 8 inch diameter
8in x 3.14 = 25.12in circumference

Finding RPM
497.1769 in/min
---------- = 19.79 rev/min
25.12

Chosen Gearbox 50:1 . Chosen motor 5 cu.in disp motor. (HUGE)

Finding Torque:
4in(radius of drum) x 35400lbs
--------------------------- = 2981.1526 in lbs
50 (0.95)

Finding pressure:
2981.1526 x 2 x 3.14
--------------------- = 4160.3640psi
5cu.in x .90 (eff)

Finding flow :
19.79rev/min x 5cu.in x 47.5
----------------------------- = 20.3468gpm
231

Finding out HP of pump (checking):
4160.3640psi x 20.3468gpm
---------------- = 52.5352
1714 x .94

 

[disoblige]

How about telling us what it is you are trying to pull, and is it a rolling load or a static load. or is this just a test question.

You do know, that with the proper gear ratio, you can just about move anything. IE, torque multiplier.

He want us to pull a egyptian pyramid using our last 3 student number x 1000lbs and gave us a sand co-effiecient friction of 0.6. He wants all the calculations.