The initial prototype design proposed attaching motor-driven gears to an all-thread rod to finely tune the position of an internal plate in the device. However, this design posed several issues, including potentially producing false thrust readings by changing the center of gravity and having unwanted effects on resonance by spinning the internal plate. Mounting components like the magnetron to the side of the device's cylinder could also be challenging and inaccurate.

1. Preliminary Prototype Design
The idea behind the initial design is to be able to fine tune the inner plate position using motor-driven
gears attached to an all-thread. Not only would this provide position sensitivity, but it could allow the
position of the plate to be changed without human intervention, potentially while RF energy is being
delivered.

2. Unfortunately there were several issues with this design:
1. Changing the position of the internal plate will change the center of gravity of the pendulum,
therefore we may see a false thrust reading.
2. Spinning the internal plate may have unwanted effects on resonance
3. Mounting the magnetron to the side of the cylinder is potentially challenging an inaccurate

3. 4.

4. clc
clear
close all
5. Preliminary Pendulum Mass Estimates
6. %mass of rod
r = .75/2; %in
h = 10; %in
V_rod = pi*r^2*h;
rho_delrin = 1.41; %g/cm^3
rho_delrin = rho_delrin*0.036127292; %lb/in^3
m_rod = V_rod*rho_delrin;
ri = 4.25/2;
ro = 4.53/2;
rho_alum = .098; %lb/in^3
L = 12;
V_cyl = pi*(ro^2-ri^2)*L;
m_cyl = V_cyl*rho_alum;
m_tot = .22 + 2.27 + .08 + .33 + .18 + .016 + .136 + .037;
m_tot_kg=m_tot/2.2;
7. Assuming a pendulum mass, what force resolution can we expect?
8. L = 5;
m=5;
g = 9.81;
F = logspace(-4,-2,100);
for i =1:length(F)
d(i) = L*F(i)/(m*g);
end
cm = d*100; %cm
mm = d*1000;
F = F*1000;
figure(1)
semilogx(F,mm)
xlabel('Force (mN)')
ylabel('Laser Displacement (mm)')

5. 9.
10. Published with MATLAB® R2013a

6. 11.

7. 12.