TEAM 33: DESIGN REVIEW

Shadae Boakye-Yiadom, Jonathan Bruns, Jarred McDuffey, Jolene Ng, Julia Roth

OVERVIEW

ZONE 4

FUNCTIONAL REQUIREMENTS & SPECIFICATIONS

Able to lift up three cubes at a time (207.36 grams)

(3* 69.12 g where 69.12 grams is the weight of one cube)

Able to travel back and forth from the border between zones 3 and 4 to the goal in 1 minute

(2.7 inches/sec)

Able to reach the goal height to score points

(12 inches)

Able to push the largest block F =2μsN = 2.5 lbs

DESIGN CONCEPTS COMPARISON

DESIGN CONCEPTS COMPARISON (continued)

FINAL DESIGN

FINAL DESIGN SUBSYSTEMS

CAD

Final Design:

CAD Subsystem 1: Scissor Lifting Mechanism

CAD Subsystem 2: Dustpan Mechanism

CAD Subsystem 2: Dustpan Mechanism

ANALYSISSubsystem 1: Moving the blocks out of the way

Assume that the gear ratio is the highest gear ratio

FD = FF/2 = 5.56 N

TD= ƒs*r*FD = (1.5)(5.56)(.0381) = .5889 Nm

Planetary Gearbox:

At 4.5 V: At 6 V:

TS=.0013NmTS=.0173 Nm

N0=10200 rpm NO= 13600 rmp

TR= .2*ɣ*TS = .2*.15*.0173 = 5.19*10-4Nm

MR= TD/TS =.3178/ 5.19*10-4 = 1134.7

Shovel moving up and down

Subsystem 2: Scissor mechanism moving up and down

Subsytem 3: weight idea analysis?

Torque:

Speed:

motor and gear ratios:

**Any other important analysis

TD≤ ɣ*M*TS .15*400*.0173 = 1.038 and .5889 ≤ 1.038

TSg= 1.038

M = 400

N0g=1/M*13600 = 34

T = -.0305*n+1.038

n = 14.72 rpm

%n = 14.72/34 *100 = 43.3 %

Not within the maximum operating efficiency while pushing but will provide us enough torque to be able to push the blocks out of the way.

Analysis (cont)

Total weight of Scissor lift and rack = 4.52 N

The radius of the pulley is .5 inches.

Torque needed to pull the scissor lift up with safety factor of 1.5 = .0861 Nm

We found that a planetary gear motor with an 100:1 gear ratio can lift the weight with 34% of the total torque (approximately 4% away from the range of maximum efficiency).

T_D = 1.5*4.52* .0127 = .0861 Nm

T_sg = .15*100*.0173 = .2595 Nm

T_sg > T_D

Using the equations for an operation line:

T= - (.2595/136)n+.2595

Plugging in T_D for the torque we get that n = 90, which is 66% of the no- load speed.

Subsystem: Scissor lift

Analysis (Cont.)

Required weight to lift = 1.13 N

24 tooth gear connected to pinion.

1 inch pulley connected to the shaft, belt and other pulley( .5 inches) connecting this shaft to the motor.

T_r = 1.5*1.13*.0127 = .02153 Nm

T_m = T_r*(d_m/d_r) = .0127*(.02153/.0254) = .010765 Nm

Using the metal gear box we would use 6% of the total torque which is not within the range of maximum efficiency.

T_metal = 1.13(.15) = .1695

T_m/ T_metal = .0635

Using the planetary gear motor with a 20:1 gear ratio we use 20.7% of the total torque which is within the maximum efficiency of the motor.

T_max = .2*.15*.0173 = 5.19 * 10^(-4) Nm

M_max = T_m/T_max = .010765/5.19*10^(-4) = 20.7

T_D = .15*20*.0173 = .0519 > .010765 = T_m

T_m/T_D = 20.7% which is within maximum efficiency of the motor, therefore we will be try to use the planetary gear motor in order to raise the shovel up to its required height.

Gears and motor to lift the shovel

SUMMARYEXPECTED CHALLENGES:

Stability throughout the RMP especially with so much weight on the front

Staying within the size limitations

ensuring the blocks do not fall of the table when we push them

Getting both moving parts to work together

RISKS:

turning the dustpan to drop the cube without the use of a motor

Pushing the blocks into an area that we will later need to travel

Getting our RMP to go in between both blocks surrounding the goal without damaging our RMP

Assumptions and Procedure

Assumptions:

We have assumed that everything is going to be cut exactly to the correct size.

We assumed that the density of the Aluminum in the lab is also 2.7 grams/cm^3

We will be able to fit the cost of extra planetary gear motors into the budget.

There will be 1 inch and half inch pulleys available for the belt we will use to transfer torque to our gears on the rack.

The weight of the pinions is negligible compared to the weight that the rack is putting on the scissor lift.

Procedure:

Used the density and dimensions of all the parts to approximate all the weights of our parts that we will be lifting.

Found the torque necessary to lift the weights of the parts and checked every single motor to see which ones we could possibly use to generate the necessary torque.

Once we had the motors narrowed down we used further analysis to find which motor and gear ratio would be the most efficient.

Made sure that the motors we have chosen will fit into our design without any spacing issues.

ANALYSIS CONTINUEDDouble gearbox:

At 6 V:

TS=.0031 Nm

NO= 11500 rpm

TR= .2*ɣ*TS = .2*.15*.0031 = 9.3*10-

5Nm

MR=.3178/ 9.3*10-5 = 3417

M = 344

TD≤ ɣ*M*TS .15*344*.0031 = .15996 and .3178 ≮ .15996

Therefore it will not provide enough torque to push blocks

Analysis Showing the double gearbox and metal gearbox do not provide enough torque to push blocks:

Metal gearbox:

At 6 V:

TS=1.13 Nm

NO= 100 rpm

TD≤ ɣ*M*TS .15*1*1.13 = .1695 and .3178 ≮ .1695

Therefore it will not provide enough torque to push blocks

ANALYSIS (continued)

Weight Analysis

Mass of the shovel:V*D = (4.2)*(5.5)*(1/16)*(44.23) = 63.86 grams

Mass of cubes: 3*17 grams = 51 grams

axle is placed at (⅓)*(2.25) = .75 from the left side

L1 = 2.25”

L2 = 0.75”

Taking moments about the axle is

mshovel and cubes *((l1/2)- l2 ) = mW*l2

mW ≥ 31.93 grams

l2

l1