In the middle of the belt run (half way between the two pulleys), it should deflect about 1/2" with 10 lbs of pressure.
How to measure the 10 lbs? You could use one of these:
http://www.jpcycles.com/product/600-439
Or, if you're too cheap for that, use a fish scale from a sporting goods store that sells fishing equipment. To test it's accuracy weigh a new 10 lb bag of sugar, and mark the scale where it registers.
Answers & Comments
A quick and dirty check:
In the middle of the belt run (half way between the two pulleys), it should deflect about 1/2" with 10 lbs of pressure.
How to measure the 10 lbs?
You could use one of these:
http://www.jpcycles.com/product/600-439
Or, if you're too cheap for that, use a fish scale from a sporting goods store that sells fishing equipment.
To test it's accuracy weigh a new 10 lb bag of sugar, and mark the scale where it registers.