Ratcheting screwdriver

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Revision as of 20:55, 23 September 2007

Ratcheting Screwdriver Parts List

Part #	Part name	QTY	Function	Wt.(kg.)	Material*	Process*	Photo
001	Screwdriver Shaft	1	Holds the screwdriver bits in its tip, while the base is connected to the handle.	NA	Aluminum
002	Screwdriver Handle	1	Allows the user to grasp the screwdriver for use.	NA	Rubber/Plastic
003	Ring Gear/Ratchet Housing	1	Rotates opposite the engaged pawls, and allows for the ratcheting of the screwdriver.	NA	Aluminum
004	Pawl	2	Engages the ring gear to stop rotation in one direction, allowing rotation in the opposite direction, thereby allowing ratcheting. both pawls can also be engaged to sllow no ratcheting such that the screwdriver can be used as a regular/static screwdriver.	NA	Steel
005	Pawl Spring	2	The spring pushed the back end of the pawl, forcing it to engage the ring gear.	NA	Aluminum
006	Ball Bearing	1	Allows free left and right motion of the button.	NA	Aluminum			[]
007	Body Screw	1	Attaches the screwdriver shaft to the screwdriver handle.	NA	Steel			[]
008	Button	1	Can be switched left, right, or middle, allowing left or right ratcheting or stopping motion.	NA	Aluminum
009	Button spring	1	Pushes the ball bearing against the rear of the button.	NA	Aluminum			[]

Portable Screwdriver/Drill Parts List

Part #	Part name	QTY	Function	Wt.(kg.)	Material*	Process*	Photo
001	Screwdriver/Drill Housing	1	Houses the internal parts of the drill	NA	Plastic
002	Drill Cover	1	Covers the nose of the drill	NA	Plastic
003	Drill Motor	1	Rotates the sun gear, draws current through the wires at the base of the motor to determine the direction and speed of rotation	NA	Plastic/Metals
004	Rechargeable Battery Pack	1	The power source for the drill, draws power from the battery chargin power input and stores the voltage.	NA	Metal, Plastic, and Chemicals
005	O Ring	1	Clamps the drill housing to the drill shaft	NA	Metal
006	Gear Housing	1	Acts as a cylindrical ring gear that houses the planetary gear system.	NA	Copper
007	Reset Button	1	A button on the external part of the body that will reset the drill when depressed.	NA	Plastic
008	Battery Charging Power Input	1	Draws voltage from the power cord and send it to the rechargeable battery pack where it is stored.	NA	Plastic/Metal
009	Housing Screws	2x3	Holds the plastic housing together	NA	Steel
010	Trigger	1	Switches the direction of the drills rotating output.	NA	Plastic			[]
011	Washer	1	Keeps the drill motor and gear housing tight together.	NA	Copper			[]
012	Planetary Gears	1	Gears within the gear housing that rotate around the sun gear, they increase the torque by reducing the speed.	NA	Copper			[]
013	Sun Gear	1	Transfers the rotational output of the motor to the planetary gears.	NA	Copper			[]
014	Intermediate Gears	1	Keeps smooth rotation between planetary gears and the gear housing.	NA	Copper			[]
015	Drill Shaft	1	Attached to the output of the gear housing and extends through the drill cover. Holds the drill bit in its external end of the shaft.	NA	Steel			[]
016	Lights	1	Red, yellow, and green lights that tell when the drill is charged, charging, and needs charging.	NA	Plastic/Metal			[]
017	Wiring	1	Basic red and black wires running current between electrical parts of the drill	NA	Plastic/Copper			[]
018	Switch Box	1	Switches the direction of voltage to the motor depending on the direction of triggers depression.	NA	Plastic/Copper			[]

Mechanical Analysis

Analysis of the Gear Ratio for the Electric Screwdriver:

The electric motor within the electric screwdriver produces a very high rotational speed, but very little torque. However, the customer needs a device capable of producing a relatively high amount of torque, but not necessarily at such a high speed. Thus, the electric motor is geared down before it is attached to the bit. After the dissection of the drill, we found that a planetary gear system was used to accomplish this. In this gear train, the annulus was held stationary within a housing. The sun gear was used for the input, and the output was therefore the planet carrier. This planet carrier in turn was connected to the sun gear for the next level. In total there were three levels of gears, each of which reduced the torque by a factor of 1/(1+A/S), where A is the number of teeth on the annulus, and S is the number of teeth on the sun gear. With three levels, the total gear ratio is 1/(1+A/S)^3.