Quote:
Originally Posted by Lil' Lavery
What type of sensors are you using to determine the status of the pinion gear? An encoder on the gearbox?
I assume the "default" state of the launcher is in a cocked position. How many teeth are engaged with the rack in the cocked position? Are you concerned or have you done any analysis on the potential of breaking teeth when only one (or two) are engaged right before you release?
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While it would be nice to have an angle sensor on the pinion shaft (it would be a
Cherry AN8 360 degree model), I do not believe it absolutely necessary. What is necessary is to have two endpoint sensors on the rack. We expect to mount one at the launcher extended point - probably an inductive prox switch from automationdirect.com to pick up the rack or some other steel target. The other sensor will pick up another suitable target with the launcher retracted and about 1/2" - 1" of linear travel left before the trip point.
We performed an Inventor FEA analysis on a single tooth of the rack gear - the results indicated the system could handle a 200 lb load with a 2:1 safety factor. The springs on the robot currently top out at a combined 160 lb. launcher load. As I stated above, we expect our cocked position to be in a spot 1/2" - 1" short of the pinion trip point, with multiple gear teeth in mesh.