Question

Problem 3
A power screw such as lead screws of lathes and screws for vises, presses and jacks are used to transmit
power, and change angular motion into linear motion. When used in a jack, the power screws lifts a load F
by using an external torque T given by,
T =
F dm
2 l + πf dm
πdm − fl
Here, dm is the mean diameter of the screw thread, f is the coefficient of friction, and l is the lead of the
screw. The lead can be calculated from
l = np
where n is the number of starts on a thread.
If the outside diameter, d, and pitch, p, is known, the mean diameter can be calculated from:
dr = d − p; dm =
d + dr
2
Write a matlab function called hw4_p3_lastname that accepts as inputs:
• outside diameter (mm)
• pitch (mm)
• number of starts
• coefficient of friction
• load (N)
and returns the torque as the output. Your code should also print a line to the command window
formatted as follows:
Torque = xx.xx N*m
Here the torque should be given to 2 decimal places and have the units print afterward.

Answer 1

function hw4_p3_lastname()

%Initialising Constants
pi = 22/7;

%Reading Values
prompt1 = 'Enter the Outside diameter in mm: ';
d = input(prompt1);
prompt2 = 'Enter the pitch in mm: ';
p = input(prompt2);
prompt3 = 'Enter the No. of Starts: ';
n= input(prompt3);
prompt4 = 'Enter the Coefiicient of Friction: ';
f = input(prompt4);
prompt5 = 'Enter the Load in Newton: ';
F = input(prompt5);

%Calculations
l = n*p;
dr = d-p;
dm = (d+dr)/2;
torque = (F*dm/2)*((l+(f*pi*dm))/ ((pi*dm)-(f*l)));

%Output
fprintf('Torque = %0.2f N*m\n', res);

end