# Rack and Pinion motor selection

Summary:: I want to design a mechanism consisting in 4 rack driven pinions , like an elevator and i need help in choosing the right motor.

Hello!I want to design a mechanism consisting in 4 rack driven pinions , connected to each other via shafts, used for a positioning system , a moving up and down platform. It has to carry a load of 1.5 kg and has a speed of 0.036m/s.(the length of the rack is 110 mm(module 0.4) and the platform has to go from the bottom of the rack to the top in 3 seconds).The motor has to hold the whole load when the mechanism stops , it has to have a break.I need help in calculating the parameters of the required motor .Thank you for your time !
The gears atatched to the racks are spur gears , module 0.4 with 20 teeth and the gears connecting the shafts are miter gears with module 0.5 , 20 teeth.

Mentor note: Moved from Mechanical Engineering forum, so no template.

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jrmichler
Mentor
Is this homework? If so, we can move it.

You start with the total moving mass, then calculate the torque needed to move that mass vertically from the gear pitch diameter. Then you calculate the RPM for the desired speed.

Dr.D
It is for my senior thesis , my tutor doesnt help me so much so i found this forum :D, thank you !

Baluncore
Welcome to PF.
The “Metric Module” system is used to design standard compatible gear systems.
https://en.wikipedia.org/wiki/Gear#Standard_pitches_and_the_module_system

Start by calculating the radius of the pitch circle on your 20 tooth module 0.4 gear.
Then calculate the tooth pitch of a module 0.4 rack.
Check your result against a measurement of the (irrational pitch?) rack.

Each turn of the pinion will move the stage by 20 * rack pitch = ? mm.
You must raise the load 110 mm in 3 seconds. Start by ignoring the acceleration.
The total mass of the platform and maximum load will be what in kg ?
The change in potential energy PE = m·g·h; of the moving mass will be what in joules ?
Power is the rate of flow of energy; watts = joules / second.
How much power will be needed in watts ?

How much energy will be needed to accelerate the total load to maximum speed ?
Kinetic energy; KE = ½ m·v²
Is that significant compared with the change in PE ?