Automatic Garage Door Analysis

byTyler Blanks Greg Arrington Bambo Awokoya

Automatic Garage Door AnalysisTable of Contents

• Problem Statement• Analysis of Torsion Spring• Dynamics of Garage Door• Chain Operations and Simulations• Economic Analysis• Recommendations and Conclusions

Automatic Garage Door AnalysisProblem Statement

• In the past several decades electric garage door openers have become a standard addition to the American home. This popularity has lead our team to look for ways to improve on the current design.

• We will investigate possible ways to improve performance without exceeding the strength of the drive chain or increasing the noise output of the system. We will also perform an economic analysis on the system to find any areas for improvement.

• The test specimen for this investigation is a double insulated Chamberlin garage door.

• This door has an opening height of 7.5ft and is made of five 18in panels.

• The door is powered by a 1/3hp LiftMaster electric opener which is assisted by a single torsional spring.

• The torsional spring is 2.5in in diameter, has a wire diameter of 0.25in and has 3.83 coils per inch along its 44in length.

Automatic Garage Door Analysis Physical Parameters and Assumptions

Physical Parameters• Total Weight- 185 lbs• Total Height – 7.5 ft• Total width – 9 ft• Single panel Height- 18 in• Single panel width – 9ft• Single panel weight- 37 lbs

Assumptions• No friction between wheels and track• Chain remains tight and does not slip• Chain and gear is lubricated and clean• Door opens at a constant velocity

Automatic Garage Door AnalysisAnalysis of Torsion Spring

•Spring is slid over a solid shaft being supported on one end and fixed to the shaft on the other end.

•Barrel rollers are joined to each end of the shaft and aligned to be directly above the door track.

•Steel wire cables are attached to each roller and run down the door track connecting to the last or bottom door panel.

Automatic Garage Door AnalysisAnalysis of Torsion Spring

• Manufacturor suggest that the spring needs to be pre-tensioned on shaft before adding weight of doors.

• This is done by rotating the spring a full nine rotations then fixed to the shaft. The tension in the spring is pulling up from the floor.

• By pre-tensioning the torsion spring, the free length of the linear model spring becomes 70.69 inches above the position of the torsion spring or the door.

• The free length is determined by multiplying the circumference of the spring by 9.

• The pre-tensioned torsion spring has an advantage over a linear spring with the same spring constant (K) for it can be positioned lower or closer to the top of the door.

Automatic Garage Door AnalysisDynamics

0

0

y M S W

x

F F F F

F

At Equilibrium L=36in0MF

0 1 2 3 4 5

0

( ) (sin sin sin sin sin )

37(sin 0 sin 0 sin 46.23 sin 90 sin 90)

(102 ( 70.69))

1.0076 /

y S W

S W

panel

F F F

F F

k L L W

lbk

in

k lb in

At L=0in At L=102in

0

37(sin 0 sin 0 sin 0 sin 0 sin 0) 0

0

( )

1.0076 / *(0 ( 70.69))

71.22

W

y S M

S M

M

M

M

F lbs lbs

F F F

F F

k L L F

lb in in F

F lb

Automatic Garage Door AnalysisDynamics Cont’d

H, in Fw, lbs Fs, lbs Fm, lbs

0 185.000 173.9905 11.00948

18 174.719 155.8545 18.86401

36 137.719 137.7185 0

54 100.719 119.5825 -18.864

72 63.719 101.4465 -37.728

90 26.719 83.31055 -56.592

102 0.000 71.21989 -71.2199

0 1 2 3 4 5

0

( ( ) (sin sin sin sin sin )

y M S W

M S W

M panel

F F F F

F F F

F k L L W

The negative forces represent forces required to overcome the spring and force the door back down from any height above L=36in.

Automatic Garage Door AnalysisSimulation- Chain Operation

4 6 8 10 12 14 160

5

10

15

20

25

Power vs Number of Teeth on Gear

Nominal Power 1/3 HP Allowable Power 1/3 HP

Number of Teeth on Gear

HP

Automatic Garage Door AnalysisSimulation- Chain Operation

4 6 8 10 12 143

5

7

9

11

Chain Velocity 1/3 HP

Actual Chain Velocity Max. Exit Velocity

Number of Teeth on Gear

Velo

city

(in/s

ec)

Automatic Garage Door AnalysisSimulation- Chain Operation

• Increase Pitch diameter• Results of reduction in angle

of articulation– Reduces chain noise – Increases chain life

1 1.5 2 2.5 3 3.5 4 4.5 510

15

20

25

30

35

40

Angle of Articulation vs Pitch Diam-eter

Angle of Articulation

Pitch Diameter (in)

Degr

ees

Automatic Garage Door AnalysisEconomic Analysis

Cost Optimization• Analyze Operating Cost of Motor Under Normal Load• Compare Operating and Initial Costs of Alternative Motors with Improved

Performance

Considerations• General Residential Energy Rates for Raleigh area (Progress Energy Utilities)• Considered Operations Costs over 20 year lifetime of door• Constant Power Usage from motor (neglected start up surge)• Initial Prices are Based From Industrial Supplier.

Automatic Garage Door AnalysisEconomic Analysis

9 10 11 12 13 14 15 16 17 18 192.85

3.35

3.85

4.35

4.85

5.35

5.85

6.35

80

85

90

95

100

105

110

115

120

125

130

Performance versus Cost

Operating Cost

Initial Cost

Lift Time (s)

Cost

($)

1 hp

3/4 hp

1/2 hp1/3 hp

1/4hp

1 hp

Automatic Garage Door AnalysisRecommendations and Conclusions

• Replace the 8 tooth drive gear with a 10 tooth gear– Decrease lift time of door– Reduce noise of Chain/Gear contact– Reduce wear on Chain

• Confirmation of correctly powered motor– Initial Cost justified by lift time– Operating Costs at a minimum

Automatic Garage Door Analysis

Questions?