Technician A says that all of the ratios in the Simpson gear set are simple planetary power flows using only one of the two planetary gear sets. Technician B says all are simple power flows except first gear, which is a compound flow that uses both the front and rear planetary gear sets. Who is correct?

Technician A says that all of the ratios in the Simpson gear set are simple planetary power flows using only one of the two planetary gear sets. Technician B says all are simple power flows except first gear, which is a compound flow that uses both the front and rear planetary gear sets. Who is correct?

• A. Technician A
• B. Technician B
• C. Both Technician A and Technician B
• D. Neither Technician A nor Technician B

Answer: (B)

In the Simpson gear set, two planetary gear trains are used together to create multiple gear ratios, and the power flow can be either through a single gear set or through both sets in sequence. Most ratios can be achieved by routing power through just one planet set with the other held, giving a simple power flow. First gear, however, is arranged as a compound path where power passes through the front planetary set and then into the rear planetary set in a sequence, effectively multiplying two reductions. That compound flow is what gives the first-gear ratio and isn’t possible with a single gear set alone. So Technician B is correct.

In the Simpson gear set, two planetary gear trains are used together to create multiple gear ratios, and the power flow can be either through a single gear set or through both sets in sequence. Most ratios can be achieved by routing power through just one planet set with the other held, giving a simple power flow. First gear, however, is arranged as a compound path where power passes through the front planetary set and then into the rear planetary set in a sequence, effectively multiplying two reductions. That compound flow is what gives the first-gear ratio and isn’t possible with a single gear set alone. So Technician B is correct.