I have been thinking about geometry and forces a little, so I decided to create a spreadsheet to figure it out. Assuming 116 inches between sprockets, sprockets 18 inches above work area, and a 20 lb sled, I get the following:
| Locations | tensionLeft | tensionRight |
|---|---|---|
| lbf | lbf | |
| Center | 17.1 | 17.1 |
| Top Center | 33.7 | 33.7 |
| Top Right | 10.3 | 20.9 |
| Middle Right | 4.7 | 18.8 |
| Bottom Right | 3.3 | 18.5 |
| Bottom Center | 13.3 | 13.3 |
| Bottom Left | 18.5 | 3.3 |
| Middle Left | 18.8 | 4.7 |
| Top Left | 20.9 | 10.3 |
Here’s the spreadsheet if anyone wants to see details.