Thursday, October 25, 2018

Week of 10/25/2018

10/25/2018 Akash Sandhu

For this week, we worked on 3D printing the design of the main component of the spring loaded guide arm. Pictures of the rapid prototype are provided below; the prototype is half-scale. From the damper calculations, I also contacted a possible vendor to obtain information about cycles/min. I also performed FEA on the last week's design, and changed dimensions so it can fit inside the 12 cm gap of the tracks. The parts has a low factor of safety, just above 1. I went back redesigned the wheel and spring holder. I relocated mounting points, add ribs, and increased material on the new design iteration. This increases safety factor to 2 for one component, and 10 for the other. Pictures are located below.

Thursday, October 18, 2018

Week 10/18/2018

Akash Sandhu 10/18/2018

Spring Loaded Guide Arm.

In preparing for the presentation I performed calculations for max load the spring needs to handle and spring rate. I also researched for the damper criteria need for damper selection. I research the the wavelength for roughness/straightness of light rail tracks. Then I went on to calculated the frequency need for the damper and the Max energy absorbed. The natural frequency of the guide arm assembly is much lower than the frequency of force given by the track. Looking at my calculated information for the damper Dr. Furman than concluded that the damper would not be practical or cost-efficient for the maker-faire model. Nevertheless, I will still continue designing for damper, but it will not be included in manufactured design. It was confirmed with the guide-way team that the track gap distance will remain the same at 12 cm. So currently, I am working to redesigning the whole design to be smaller using smaller wheels. While redesigning, I am taking into account my FEA results from previous design version. The plan is to 3d print the spring loaded component for rapid prototyping. Below I have attached some of the CAD designs and my MATLAB calculations.

ME 195a Spring loaded guide Arm calculations

Akash Sandhu

Force calculations

M = 500:100:7000; % kg, weight of whole bogie and loaded podcar
total_length = length(M)-1;
% v_min = 2;
% v_max = 20;
% dt_v = (v_max-v_min)/total_length;
%
% v = v_min:dt_v:v_max  % m/s, operating speed of bogie
v = 1 % m/s
r_min = 8;
r_max = 50;
dt_r = (r_max-r_min)/total_length;
r = r_min:dt_r:r_max;   % m,   smallest radius

for i = 1:length(M)
    for j = 1:length(r)
        f(i,j) = 2*((M(i)*v^2)/r(j));
    end
end
figure(1);
surf(M,r,f);
xlabel('Mass [kg]');
ylabel('Radius [m]');
zlabel('Force [N]');
title('Force vs Curvature and Mass');

v =

     1

Spring Calculations

clear all; clc;
M_tot = 2000 +300; %[kg]
M_eq = M_tot/3;
x = .13; % [m]
v = 1; % [m/s] about 2 mph
r = 8; %[m] radius of curve
F = 2*((M_eq*v^2)/r); % [N]
fprintf('The force acting on each spring is %1.3f N\n ',F)
k = F/x; %[N/m]
fprintf('The Spring rate is %1.3f N/m \n',k)

The force acting on each spring is 191.667 N
 The Spring rate is 1474.359 N/m

Damper (Shock Absorber) Calculations

F = 2*((M_eq*v^2)/r); % [N]
M_tot = 2000 + 300; %[kg] pod + bogie
M_eq = M_tot/3; % [kg]
v_y = 13; % [m/s] speed going straight
L = 0.016;% [m] stroke of damper
theta_deg = 13; % [degree] angle of curvature
theta = theta_deg*(pi/180); % [rad]
v_x = tan(theta)*v_y; %[m/s] speed at impact
FS = 2; % factor of safety
E_1 = 0.5*M_eq*v_x^2;
E_2 = F*L;
E_tot = E_1+E_2;
E_max = FS*E_tot; %[Nm] max energy absorbed
fprintf('The max energy the damper needs to absorb is %1.3f Nm\n',E_max);

wavelength = 0.05; %[m] irregularities observed at
freq = v_y/wavelength; % [Hz]
fprintf('The forcing frequency from the track irregularities will be %1.3f Hz\n', freq);
freq = freq*60; % [ cycles/min]
fprintf('The damper will need to be able to do %1.3f cycles/min\n',freq);

The max energy the damper needs to absorb is 6912.052 Nm
The forcing frequency from the track irregularities will be 260.000 Hz
The damper will need to be able to do 15600.000 cycles/min

Thursday, October 11, 2018

Week of 10/10/2018

Week of 10/10 Akash Sandhu

For this previous, I worked on some problems on the design I created. These problem came across when I trying running FEA. This week I fixed some mating issue I was having with the slot which would not allow me FEA. Furthermore, Dr. Furman had recommended, during office hours, to incorporated dampers into the guide arm, to reduce vibrations of the spring. This week I began looking at damper. However, I have come across two problem; I do not know exactly how the mounting hardware works for dampers, and I am trying to find the a way to do calculations to pick the correct damper. Also, I did some consideration of the forces that would be acting on the guide-arm wheels and spring, and Dr. Furman and I concluded only centripetal force needs to considered. I then went and created a MATLAB 3-D plot which is attached below. I was also able to complete the FEA on the part with 2000 N force to see area of concern. Lastly, the design is a little to big for the current with so I decided to go with smaller wheels to accommodate for the clearance problem; Nevertheless, now the design will change in dimension due to smaller wheels.

Thursday, October 4, 2018

Week of 10/4/2018

Week 10/4/ 2018 Akash Sandhu
During the team meeting, I learned how some basics of performing FEA using Guide Arm. Also, I considered with the team the forces that need to be considered for further analysis. Also, I worked on the first individual writing assignment. I was also introduced to a Tuned Mass Damper (TMD), which could help eliminate the vibration of the arm of the guide arm system. Also, Joshua and I attended ANSYS seminar and were introduced new ways of optimizing designs. During the FEA, I came across some problems on the second design of the guide arm, so I might have to redesign the whole concept. A more detailed study is need to solve the problems in the design. There was also discussions for rapid prototyping; the goal will be to use 3D- printer.

Akash-Sandhu