@WillAdams, where do you get your 40 lbs figure? Just empirically good?
If you look at some spec sheets, you get some “Working Tension” figures:
- 25 lbs / 111 N per inch of belt width
- “111 N for 25.4 mm belt” (equivalent to above)
- “6.25 lb / 2.8kg” (for 6.35mm width belts) -> implies 25lbs or 11.2kg (109.8 N, you mass/force confusing metric savages), and what appears to be linear scaling from the same spec as the above two
So for our 9mm belts, I think the working spec tension should be (9mm/25.4mm) * 25lbs = 8.86 lbs or 39.4N.
Does that sound right? That’s a bit more than the weight of a gallon of water. I could believe it, but my experience, like yours, says I probably use more.