What is the formula for calculating moment of inertia in RTG crane design?

In summary: The acceleration was also request by the operation team, based on the load experience during the operation. I never asked for the speed or the acceleration.The speed and acceleration of the crane can be determined by using the following equation:= V/2π x rpmThe speed and acceleration of the crane can be determined by using the following equation:In summary, the crane manufacturer uses a partial equation to calculate the horsepower needed for hoisting. The equation is used to calculate the moment of inertia for hoisting. The equation is also used to calculate the acceleration force.
  • #1
Ridzuan
19
1
Hi guys...
appreciate if somebody can help me on the design calculation of the RTG crane...
I am stuck to understand the following formulas, used by MITSUBISHI to calculate as follow:

1. Moment of inertia for hoisting
= [Lifting weight (kg) x Lifting velocity^2 (m/min)^2] / [π^2 x motor rpm^2]
= [(52,920 kg) x (23 m/min)^2] / [(3.142)^2 x (1,000)^2]
= 2.84 kgm^2

Please help guys...tq
 
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  • #2
Ridzuan said:
Hi guys...
appreciate if somebody can help me on the design calculation of the RTG crane...
I am stuck to understand the following formulas, used by MITSUBISHI to calculate as follow:

1. Moment of inertia for hoisting
= [Lifting weight (kg) x Lifting velocity^2 (m/min)^2] / [π^2 x motor rpm^2]
= [(52,920 kg) x (23 m/min)^2] / [(3.142)^2 x (1,000)^2]
= 2.84 kgm^2

Please help guys...tq
Welcome to the PF.

Could you post the source for these equations? Is there a picture of the crane, or a figure that goes with your question? Is this for schoolwork?
 
  • #3
berkeman said:
Welcome to the PF.

Could you post the source for these equations? Is there a picture of the crane, or a figure that goes with your question? Is this for schoolwork?

I got this formula from the crane manufacturer document. It is a partial calculation used to calculate the required motor horsepower for hoisting.
You can go here to look fornthe crane i meant
http://www.gosan.net/imagenes_aplicaciones/puerto/grua_rtg_grande.jpg
 
  • #4
This picture is no help at all in understanding what MMOI is required.
 
  • #5
And the equation that was originally posted is more of a force equation, no? Not a MOI calculation. And MOI isn't involved much int power lifting for a crane...
 
  • #6
The pi
Dr.D said:
This picture is no help at all in understanding what MMOI is required.
The picture is just to answer mr berkeman request "the picture of the crane".
Yes, i myself also cannot understand the calculation and seeking help here...
 
  • #7
berkeman said:
And the equation that was originally posted is more of a force equation, no? Not a MOI calculation. And MOI isn't involved much int power lifting for a crane...
Sir...
The calculation is made by the japanese. Maybe there was translation issue. Maybe it is not MOI. Maybe you are true (force)... i am not sure... seek your help to clarify the formula used...
 
  • #8
This is my understanding...
The final unit is kgm^2. So it is MOI.
This value is later used to calculate the acceleration force. This is justified as MOI is the resisting force in acceleration...
 
  • #9
For those wanting the basis and context of this calculation see pg. 8 of the below document
http://dl.mitsubishielectric.com/dl/fa/document/manual/inv/sh060004eng/sh060004engb.pdf

And for the referenced Tech Note no. 30 calculation see pg 133 of the below document
http://dl.mitsubishielectric.com/dl/fa/document/manual/inv/sh060003eng/sh060003engg.pdf

I found all of this through a determined websearch, your welcome

In the end, I don't see how the Note 31 pg 8 Moment of Inertia equation is somehow a substitute for one of the Note 30 pg 131 Moment of Inertia formulas

Maybe someone else can figure this out.
 
  • #10
You are very hepful sir. I thank you so much
 
  • #11
JBA said:
For those wanting the basis and context of this calculation see pg. 8 of the below document
http://dl.mitsubishielectric.com/dl/fa/document/manual/inv/sh060004eng/sh060004engb.pdf

And for the referenced Tech Note no. 30 calculation see pg 133 of the below document
http://dl.mitsubishielectric.com/dl/fa/document/manual/inv/sh060003eng/sh060003engg.pdf

I found all of this through a determined websearch, your welcome

In the end, I don't see how the Note 31 pg 8 Moment of Inertia equation is somehow a substitute for one of the Note 30 pg 131 Moment of Inertia formulas

Maybe someone else can figure this out.

Dear JBA
I found the formula as link given is similar with the design calculation, but only the crane designer put a figure in front:

Load MOI = 4 x W x (V/2π x rpm)^2

What does the "4" stands for?

tq
 
  • #12
The formula in your first post reads as follows:
Ridzuan said:
= [Lifting weight (kg) x Lifting velocity^2 (m/min)^2] / [π^2 x motor rpm^2]

If you look at the above formula you see that 2π is used where only π is used in the first post formula (converting that first formula to the same format as the above one gives: Load MOI = W x (V/π x rpm)^2). The result of the second formula is that the (2π)^2 in the denominator cancels out the 4 in the numerator, so the two equations are actually identical. As to why the crane designer used 2π instead of simply π and then canceled the 2 out with the 4 in front, I don't have a clue.
 
  • #13
How do you determine speed and acceleration of crane?
 
  • #14
cranelift said:
How do you determine speed and acceleration of crane?
For my case, the speed was request by the operation team, based on the operation performance record
 

1. What is an RTG crane?

An RTG (Rubber-Tired Gantry) crane is a type of mobile gantry crane commonly used in ports and terminals to load and unload shipping containers from trucks and vessels. It is equipped with rubber tires for mobility and a gantry system for lifting and moving containers.

2. How is the design calculation for an RTG crane determined?

The design calculation for an RTG crane takes into account factors such as the weight and size of the containers to be lifted, the height and distance the crane needs to reach, as well as environmental factors like wind speed and seismic activity. Engineering principles and industry standards are used to calculate the appropriate crane size, capacity, and structural design for safe and efficient operation.

3. What are the key components of an RTG crane?

The key components of an RTG crane include the steel structure (gantry, boom, and spreader), the rubber tires and drive system, the hydraulic system for lifting and moving, and the electrical system for controls and power supply. These components work together to lift and move containers in a highly controlled and precise manner.

4. How does the design calculation ensure the safety of an RTG crane?

The design calculation for an RTG crane undergoes rigorous testing and analysis to ensure the crane can withstand the expected load and environmental conditions. It also takes into account safety features such as overload protection, emergency stop systems, and stability controls. Regular maintenance and inspections also play a crucial role in ensuring the safety of an RTG crane.

5. Can the design calculation be customized for specific needs?

Yes, the design calculation for an RTG crane can be customized to meet specific needs and requirements of a particular port or terminal. Factors such as the type and size of containers, the layout of the terminal, and unique environmental conditions can all be taken into consideration when designing an RTG crane. This ensures that the crane is tailored to the specific needs of the operation for maximum efficiency and safety.

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