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Machine Drivetrain Efficiencies
2

Machine Drivetrain Efficiencies

Machine Drivetrain Efficiencies

(OP)
Machine Drivetrain Efficiencies

What is best way to determine the sum of machine drivetrain efficiencies?

Example:
20 hp motor driving a gearbox (98% efficient), which drives a timing belt (89% efficient) which drives a roller chain(89% efficient).  What is total efficiency of the drive system?

See attached file.

RE: Machine Drivetrain Efficiencies

Somewhere I have some formulae (formulas?) on calculationg efficiencies -- if I have an opportunity and nobody else answers, I'll look them up.

However, until then, at least a rough estimation could be obtained through the "square root - sum of the squares" method: √(ηg2 + ηt2 + ηc2)

where the subscripts refer to the gearbox, the timing belt, and the rolling chain, respectively.

Patricia Lougheed

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RE: Machine Drivetrain Efficiencies

Isn't it just 0.98*0.89*0.89 ???

And I can't see how "square root - sum of the squares" would work with the figures quoted, as you appear to end up with a number greater than 1 ???

RE: Machine Drivetrain Efficiencies

Multiplication as Peter says is the key.  
98% of 100% is 98%
89% of 98% is 87.2%
89% of 87.2% is 77.6%
etc, etc.

You don't magically make up for lower efficiency with a higher efficiency, it still lowers the overall, just not as much.

James Spisich
Design Engineer, CSWP

RE: Machine Drivetrain Efficiencies

PeterCharles & JSpisich

You're right -- that's what I get for giving an off-the-cuff answer.  The SRSS doesn't work for percentages.

 

Patricia Lougheed

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