Perhaps the leading case applying the doctrine of promissory estoppel to subcontractors' bids is a 1958 case decided by the California Supreme Court.3 In that case, a general contractor preparing to bid on a school project received a bid by telephone from a subcontractor for the paving portion of the job.
Basically, four different types of DC motors are used in industrial applications: series wound, shunt wound, compound wound, and permanent magnet. Several factors must be considered when selecting a DC motor for a specific application.
The grey/green cylinder is the brush-type DC motor. The black section at the bottom contains the planetary reduction gear, and the black object on top of the motor is the optical rotary encoder for position feedback.