If you have anyone moving up from shop operations into estimating, quoting, or engineering, I think that this tutorial will make them error proof on conversions. Bookmark this one.
Guest post from NotUrOrdinaryJoe on CR4 Engineering Forum:
Although we don’t do homework here, I thought it would be nice to offer a tip that was very useful. Frequently the point in which students become bogged down is nothing more than getting some answer into the terms that is required. This technique is rather obvious to some, but it couldn’t be any more straight forward.
When you have something like a rate of change of something in one set of parameters and you wish to convert it to another set of parameters the first step will be thinking of the rate as a fraction. So, if you take some rate such as:
X gallons/minute and you want to convert it to Y liters/second
On the left (above) is :
| X | gallons |
| minute |
Where the magnitude of the rate is X, the terms are gallons (in the numerator) and minute(s) in the denominator. Any step you need to use simply lists the conversion factor in the same way. So to convert you set it up like this:
| X | gallons | 3.785 | Liters | minute | |
| minute | gallon | 60 | seconds |
Note that the number 3.785 is the magnitude of Liters per Gallon, and 60 is the number of seconds per minute. The word “per” is the clue to draw your horizontal line to seperate the numerator from the denominator.
Next, since like terms cancel, you can draw a line through both sets of terms “gallons” and “minutes” leaving only:
| X | 3.785 | Liters | |||
| 60 | seconds |
The magnitude is X times 3.785 divided by 60
and the left over terms verify that you ended up where you wanted. That is to say that the left over terms (the ones that did not cancel) are Liters per second.
I still remember how easy this became when I first treated it like multiplying fractions together. And it checks your work by looking at the remaining terms. Good Luck and no, we don’t do homework problems.
Speaking of Precision Comment:
For more information on the Factor Label Method check out Wikipedia entry here.
We were pleased to see this post on CR4 Engineering Forum, Where we have participated for many years. There is only one caveat: the Factor Label Method only works on converting units that share a constant ratio, (linear relationship) rather than a constant difference. For example, it doesn’t work on degrees Fahrenheit to Celsius. See the Wiki link for why.
What indispensable but easy to use technique do you have that makes your technical work easy to do? We’d love to post and share it as a best practice for our craft.