| Year | 2007 |
| Date | 03-Aug |
| Volume | 199 |
| Issue | 4,305 |
| Page | 144 |
| Category | General |
| Part | 104 |
| Title | Letters to a Grandson |
| Author | M.J.H. Ellis |
| Notes | Continues his treatise on gear trains. "What use is a potato to an engineer?" Table of ratios using two gears in the range 20T to 65T, see 199 4309 392 |