I. Intro
Date: March – April 2023
This is the lab of the lecture ME35400 Machine Design. In this lab project, my teammate and I learned the parameters of the gears, designed the dimensions of everything based on the 8” x 8” x 8” size limitation (including the clearance due to the printer), printed the parts, assembled them together, and tested the windmill.
A. Ultimate Goal: Generate the slowest rotation possible
From the slides:
- In wind turbine design, it is optimal to have an extremely high gear ratio so that the most power can be generated from slow rotations of the blades
- Since we will not be using a wind source, we will do this process in reverse
- The goal of this project is to design and develop a powered fan (using small motor) which is stepped down to the slowest speed possible (using a gearbox)
- In the final week of the project, each group (of 3) will test their turbine during class. The slowest fan (in rpm) wins, and the group will receive extra credit.
Even though the slowest fan wins, it must be observable. Since one can just use many gears to create millions of gear ratios, I suggest competing for the strongest wind or the fastest wind.
B. Rules
From the slides:
- All components of the design must fit within an 8” x 8” x 8” cube
- All gears will be 3/8” thick at maximum
- Cardboard/construction paper/cardstock is not an acceptable design material
- Designs must be self-supported, meaning nobody can be touching the turbine in any way during testing besides to attach leads/power
- Teams are expected to make their own gears, shafts, gearbox, and turbine blades
- Each group should supply their own battery pack
- Motors and bearings will be provided by TAs
II. Project Report
III. Gear Calculations
This code runs in MATLAB.
clear
clc
close all
%% info
% by Dingming Lu 03/2023
% All in mm
% Reference: https://www.youtube.com/watch?v=IBcGLpQnfYk
% gr: gear ratio,R/r
% n: number of teeth
% pc: pitch circle, radius
% d: pitch diameter
% cp: circular pitch, arc length
% m: module
% ac: addemdum circle, radius, outer most radius
% de: dedendum
% rc: root circle, radius
% wd: whole depth of the tooth profile
% cc: clearance circle, radius
% bc: base circle radius
% pa: pressure angle, deg
% In to Out: rc, cc, bc, ac
%% general info
gr=5; %gear ratio, R/r
total_width=178; %mm, tota width of 3R+r
n_small=12; %number of teeth, small gear
%% small gear
pa=15; % pressure angle, deg
pc=total_width/(3*gr+1); %pitch radius
cp=2*pi*pc/n_small; % circular pitch, circonference / number of teeth
m=cp/pi; % module, addendum
ac=pc+m; %addemdum circle, outter most radius;
cc=pc-m; % clearance circle
de=1.25*m; % dedendum
rc=pc-de; %root circle, at bottom land
wd=m+de; %whole depth
bc=pc*cosd(pa); %base circle, radius
rank_small=sort([pc,ac,cc,rc,bc]);
%root circle, clearance circle, base circle, pitch circle, addemdum circle
% rc, cc, bc, pc, ac
%% large gear
n_large=gr*n_small; %number of teeth
PA=15; % pressure angle, deg
PC=total_width/(3+1/gr); %pitch radius
CP=2*pi*PC/n_large; % circular pitch, circonference / number of teeth
M=CP/pi; % module, addendum
AC=PC+M; %addemdum circle, outter most radius;
CC=PC-M; % clearance circle
DE=1.25*M; % dedendum
RC=PC-DE; %root circle, at bottom land
WD=M+DE; %whole depth
BC=PC*cosd(PA); %base circle, radius