Originally Posted by Bob Miller
is there any reason that the method I described would result in a significantly different set of numbers than your method?
It all depends on how you define significant
. There are a couple of factors at play.
A $5 spring scale costs $5 for a reason: they are designed to be consistent
, but not precise
. Ever notice the spring scales in the produce section of the grocery store? They usually have a sticker on them from the County Inspector with a disclaimer that they are for Customer Convenience Only and not to be depended upon, and you use them at your own risk. You cannot sue the grocer for cheating you based on those scales. The scales built into the check-out counter are a different story. Those are designed and tested often
to be legally precise (+/- 0.1%)
enough for taxable business transactions, and the grocer has to invest $1000 per checkout stand for the scale alone, cash register is extra. You can
sue the grocer if those scales are wrong.
Waste transfer "truck scales" have a 100,000 pound capacity and read in 20 pound increments. So your trailer's axle weight reading can be off by 40 to 60 pounds, which is not commercially
significant. Your $5 spring scale with the 300 pound range probably reads in increments of 5 pounds or less, but can be 1% or 3 pounds off and still be considered "OK." The spring scale's 3 pound acceptable error could be within the truck scales 60 pound acceptable error and the combined errors may not be significant
if the truck scale is in error near the low side of its tolerance window and the spring scale is in error near the high side of its tolerance window, you could possibly decide that the tongue is slightly too heavy when in fact it is not.
If you get both hitched and unhitched weight readings from the same scale
your calculated tongue weight will be more reliably true.
I wish I had a dollar for every complaint I get from Gyms and Doctor's offices who have multiple scales of different types who say they're wrong because they don't exactly match each other! Scales are rarely exact, they are only "within tolerance."