imaginator
Mechanical
- Jan 27, 2003
- 2
I am looking at design alternatives for a gearbox section that will need to offer one reduction ratio forward and one reverse. I know I can use a single planetary set to get the ratios (and directions) I need with a sun gear input, locking the carrier and using the ring for output (reverse) and locking the ring and outputting on the carrier (for forward), but this will require 4 clutches including 2 on the output shaft! Not pretty from a control point of view.
Going to 2 simple planetaries is relatively easy, as I could simply shift from one sun to the other, but I would need to anchor the ring of one set and the carrier of the other to the case. This leads me to think I could use a single ravigneaux set and just anchor the ring to the case, always outputting the carrier. One sun would drive through a second planet, giving me a reverse. Simple and maybe cheaper.
Question: When calculating ratios in a ravigneaux gearset, presuming the planets have an equal number of teeth, are ratios calculated exactly as they are with simple planetaries, that is 1 + ring/sun = ratio? Any other references, hints and comments on the subtleties of ravigneaux geartrains would be appreciated.
Going to 2 simple planetaries is relatively easy, as I could simply shift from one sun to the other, but I would need to anchor the ring of one set and the carrier of the other to the case. This leads me to think I could use a single ravigneaux set and just anchor the ring to the case, always outputting the carrier. One sun would drive through a second planet, giving me a reverse. Simple and maybe cheaper.
Question: When calculating ratios in a ravigneaux gearset, presuming the planets have an equal number of teeth, are ratios calculated exactly as they are with simple planetaries, that is 1 + ring/sun = ratio? Any other references, hints and comments on the subtleties of ravigneaux geartrains would be appreciated.