Gears & Pulleys for Compressor Pump Project

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Discussion Overview

The discussion revolves around a theoretical project involving a compressor pump that operates at 500 RPM and requires 12 horsepower (hp), with the challenge of powering it using a 3480 RPM AC motor limited to less than 10 hp due to cost constraints. Participants explore various mechanical solutions, including pulley and gear systems, to achieve the necessary speed reduction and torque requirements.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant questions whether speed reduction through pulleys will increase torque sufficiently to meet the power needs of the compressor pump.
  • Another participant asserts that power cannot be increased at the driven end and that the output will likely be less than the input power due to conservation of energy principles.
  • It is noted that a 10 hp motor could theoretically drive the compressor at a lower RPM (416 RPM), but this would result in reduced output of compressed material.
  • Concerns are raised about the torque characteristics of electric motors, particularly at low speeds, which may affect performance even if the motor's horsepower rating is adequate.
  • A suggestion is made to consider using worm gears as an alternative to pulleys for achieving the desired speed reduction.
  • One participant humorously suggests using a different pulley size configuration to achieve the necessary speed reduction.
  • The original poster clarifies that this is a homework problem and not a practical project, seeking guidance on motor selection within specified constraints.

Areas of Agreement / Disagreement

Participants generally agree that a 10 hp motor cannot provide 12 hp to the compressor, but there is no consensus on the best mechanical approach to achieve the desired performance, with multiple competing views on the effectiveness of pulleys versus gears and the implications of torque and power requirements.

Contextual Notes

Participants express uncertainty regarding the specific torque requirements and the implications of using different mechanical configurations. The discussion also highlights the importance of analyzing the inertia of the system when selecting an electric motor.

Who May Find This Useful

This discussion may be useful for students or individuals interested in mechanical engineering, particularly those exploring concepts related to power transmission, motor selection, and the practical implications of theoretical mechanical designs.

jwest22
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hiya, i need some help for a project I am working on, basically i have a compressor pump that runs at 500rpm and @ 12 hp.

now the problem is (this is a theoretical problem) i have to power it using a 3480rpm ac motor which has to be less than 10 hp (cost reasons).

rough calculations show that a 20cm pulley on the compressor pump and a 3cm pulley on the motor will give me the correct speed reduction, but what do i do about power?. will the speed reduction increase torque giving me the power i need? if this is the case what is the minium sized motor i could use?

what if i used gears, id be looking at a ratio of 1:0.15?

hope that's clear, any websites or calculations that can help me with this would be amazing as I am really baffled.

thanks a lot.
 
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there is no way you can increase the power at the driven end. In fact you ll end up with a lil bit less at the driven end.

P = T*ω, Ideally P remains constant(conservation of energy), Torque varies inversely to any variation in ω.

velocity ratio of almost 7 for a belt drive is a bit tooo much.(I dunno, I m not a practicing engineer yet, ;) ). Have you looked into worm gears?
 
As ank_gl pointed out there is no way you can get 12 hp out of a 10 hp motor.

But you can still build something. Just remember that the 12 hp on the compressor spec is the power required to drive it at 500 rpm which is propably the ideal for that piece of equipment. If the compressor is a fixed displacement type, the rpm is approximately proportional to the power you deliver to it. So your 10 hp can drive it at 416 rpm. If you can live with the reduced qty of compressed material, gear the 3480rpm motor down to 416.
 
I hate to say it, but even if you had a 12 HP electric motor, there's no guarantee that it would work. It could be completely lacking in torque where you need it, usually at the low end of the speed range. When selecting an electric motor you need to look at the inertia of the system as well.
 
Is this a homework problem? Perhaps the goal here is to provide an rpm at the pump which results in the pump requiring only 10 hp...
 
FredGarvin makes an important point. Don't start building this until you analyze the torque requirements.
 
Try 9 inch pully on motor and 2 inch pulley on the pump AND HANG ON TO YOUR HAT LOL
 
hi thanks for the reply's, sorry i should of said this is a homework problem (i dint notice the homework sub forum when i posted the prob) so I am not actually going to build it, does that help. the pump spec is 500 rpm @ 12hp minimum, and i need to locate a motor that can power it which runs at 3000-4000rpm not costing more than $700.

any ideas? thanks
 

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