How are the speed ratios distributed for a power transmission problem?

In summary, the conversation discusses the solution to a question involving calculating lifting load, power, motor selection, cable speed, and gearbox speed ratio. It also explains the decision for the last ratio of 1/4, which is determined based on the number of shafts available for the gearbox.
  • #1
hollidca
13
0
This is the solution to a question. I have followed it through with my own calculations and I'm getting good numbers. However I don't understand how the numbers for 8. are decided. Why is the last one 1/4? I need to work this out because it is putting my lifting speed 0.06m/s below the limit for my project.

1. Calculate lifting load: W=mg=21600 N
2. Calculate power: Plan VL = 0.1 m/s P=W VL = 2160 Watt
3. Motor selection: Dayton AC motor catalogue  Selected Motor: 4LX07 Dayton 2240 Watt
@1725 rpm (=180 rad/s)
4. Check for lifting speed: VL = Pmotor/W= 2240/ 21600= 0.104 m/s (OK in the range)
5. Calculate cable speed: For the cable-pulley configuration shown: Vcable =2VL=0.2m/s
6. Select: ddrum=25cm
7. Calculate gearbox speed ratio: ωdrum= Vcable /rdrum=0.2/0.125=1.6 rad/s  λ= ωdrum / ωmotor
=1/112
8. Distribute the speed ratio: (1/3) x(1/3)x(1/3)x(1/4)=1/108 (speed reduction over 5 shafts)
9. Check for lifting speed for λ= 1/108 : ωdrum= 1/108 xωmotor =1.67 rad/s  Vcable =rdrumωdrum
=0.125x1.67=0.208m/sVL= Vcable/2=0.104 m/s (OK in the range)
10. Select number of teeth for pinions and calculate number of teeth for gears: [Note: In
your project select N=14 for pinions]
11. Calculate gear pitch diameters: [ Note: In your project use helical gears with module
M=2mm, pressure angle φt=20 and helix angle ψ=30 degrees, for simplicity].

Any help would be greatly appreciated.
 
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  • #2
The last ratio of 1/4 is decided based on the number of shafts that you have available for your gearbox. Since you have 5 shafts, then each shaft has to be assigned a ratio of 1/4, 1/3, 1/3, 1/3 and 1/3 respectively. This way, the total speed reduction is 1/108, which gives the desired lifting speed of 0.104 m/s.
 

1. What is a power transmission problem?

A power transmission problem refers to any issue that affects the efficiency or effectiveness of transferring power from a source to a load. This could include factors such as mechanical failures, electrical faults, or losses in energy during transmission.

2. What are the common causes of power transmission problems?

Some common causes of power transmission problems include improper maintenance, overloading, environmental factors such as weather or temperature, and design flaws in the system.

3. How can power transmission problems be prevented?

Regular maintenance and inspections can help prevent power transmission problems by identifying potential issues before they become major failures. Properly designing and sizing the system for the intended load can also prevent problems from occurring.

4. What are the consequences of power transmission problems?

The consequences of power transmission problems can range from minor inconveniences to major disruptions. In a household, a power outage may result in loss of electricity to appliances and devices. In industrial settings, power transmission problems can lead to production delays, equipment damage, and even safety hazards.

5. How are power transmission problems diagnosed and resolved?

Power transmission problems can be diagnosed through various methods such as visual inspections, thermal imaging, and electrical testing. Once the issue is identified, it can be resolved through repairs, replacements, or adjustments to the system. In some cases, consulting with a professional engineer may be necessary for a thorough diagnosis and resolution.

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