MECHANICS OF MATERIALS

PROJECT REPORT

STRESS CALCULATION ON SMITH MACHINE

(GYM EQUIPMENT)

GROUP MEMBERS:

MUHAMMAD UMAR FAROOQ (2015-IM-07)

MUHAMMAD YASIR ILYAS (2015-IM-08)

SUBMITTED TO:

SIR.ADEEL SHEHZAD

INDUSTRIAL AND MANUFACTURING ENGINEERING

UNIVERSITY OF ENGINEERING AND TECHNOLGY, LAHORE

Abstract:

The Smith machine is a pervasive weight training apparatus, used extensively by a wide population of weight trainers, from novices to high-level athletes. Behind each vertical post (runner) is a series of slots on which the barbell can be hooked. This means that unlike an ordinary barbell, the Smith machine need not be re-racked after a set of repetitions: it can be secured at any point. This supposedly makes it safer for those who lift without a spotter, as one only needs to twist the wrist in order to lock the barbell in place in the event that the weight becomes too great. Most models also incorporate blocks, pegs, or other devices which can be adjusted to automatically stop the barbell at a predetermined minimum height. This does not fully eliminate the inherent danger in having a heavy weight on one's back To ensure that appropriate adjustments are made to the athlete’s training regiment, the practitioner should consider the full set of findings of the present paper.

Introduction:The Smith machine is a weight machine used for weight training. It consists of

a barbell that is fixed within steel rails allowing only vertical or near-vertical movement. Some Smith machines have the barbell counterbalanced. The machine can be used for a wide variety of exercises though it is most commonly used to perform "Smith machine squats".

Overview:

Uniquely engineered Smith Bar provides a light starting weight combined with a large weight capacity and exceptionally smooth, natural feel all while reducing high wear components

Equipment Features:

Instructional placard

Squat & Bench Press with QR codes to access instructional videos

Adjustments 8 Bar hooks @ 6 in / 152.4 mm increments

Standard Features● Adjustable safety stops easily accessed from the user position● Six weight plate storage horns● Foot pads and heavy duty leveler device accommodates uneven floor surfaces

Rubber Feet Yes

Equipment Specifications:

Starting Weight 68.4 lb. / 30 kg

Max Load Weight 524.4 lb. / 230 Kg Olympic Weight Plates

Weight Storage Pins

Four Storage horns at 6 in / 15.24 cm from top to bottom length each (four per side)

Grip Diameter 1 in / 25.4 mm

Standard Frame Colors

Grey

Equipment Dimensions & Weight:

Length (cm/inches) 52 in / 132.08 cm

Width (cm/inches) 1.5 in / 3.81 cm

Height (cm/inches) 72 in / 182.88 cm

Machine Weight (base equipment)

(kg/lbs.)342 lbs. / 150 kg

Delivery Dimensions & Weight:

Length (cm/inches) 52 in / 132.08 cm

Width (cm/inches) 1.5 in / 3.81 cm

Height (cm/inches) 72 in / 182.88 cm

Delivery Weight (kg/lbs)

524.4 lbs / 230 kg

ADVANTAGES AND DISADVANTAGES:Use of the Smith machine is frowned upon by many strength training devotees as it

forces the user to adopt an unnatural straight-up-and-down "bar path" which can put shear stress on the knees or back (if squatting) or shoulders (if pressing).

The constrained movement of the bar also reduces the role that stabilizing muscles play versus an exercise using free weights. This may allow heavier weights to be lifted, at the expense of engaging less muscle mass overall.

As with other exercise machines, the Smith machine is often preferred by casual or inexperienced strength trainees who do not know how to safely perform free weight exercises involving heavy weights.

Many gyms cater to casual trainees and thus may provide Smith machines instead of power racks, which are a piece of equipment critical for safely performing squats and other barbell-based free weight exercises. As a consequence, free-weight squatting may not even be an option at many gyms.

The Smith machine does have some advocates amongst experienced trainees, however. The "bar path" issue is minimized for exercises involving a short range of travel such as calf raises and shrugs. It is potentially good for performing exercise variations when progress has slowed using other exercise forms, although care must be taken to avoid joint stress issues. The removal of stabilizing muscles as a factor can also allow one to increase the intensity applied to primary muscles

Practical Applications:

CALCULATIONS:

Ultimate stress of cast iron = σ ultimate = 57×103 psi

Factor of Safety = FOS = 3Allowable Stress = σ allowable= 19×103 psi

Area at bottom = A = 2×1.5= 3 in2

Allowable load = Fallowable = σ allowable× A

= 1.14×105 lb

Mass of Rod = mrod = 30 Kg

At ‘A’Mass on both sides of rod = mW = 200 KgTotal Mass = mT = 230 Kg

= 524.2 lb.

Stress at upper hook ‘A’ = σ A =F

2× π4

(d2)

=524.4

2× π4

(12)

= 334.01 psiHence, it means the stress on one side of hook is 167 psi.

At ‘B’Mass on both sides of rod = mW = 170 KgTotal Mass = mT = 200 Kg

= 456 lb.

Stress at 2nd hook ‘B’ = σ B =456

2× π4

(d2)

=456

2× π4

(12)

= 290.44 psi

Hence, it means the stress on one side of hook is 145.2 psi.

At ‘C’Mass on both sides of rod = mW = 120 KgTotal Mass = mT = 150 Kg

= 342 lb.

Stress at 3rd hook ‘C’ = σ C =342

2× π4

(d2)

=342

2× π4

(12)

= 217.83 psi

Hence, it means the stress on one side of hook is 108.91 psi.

At ‘D’Mass on both sides of rod = mW = 70 KgTotal Mass = mT = 100 Kg

= 228 lb.

Stress at Last hook ‘D’ = σ D =F

2× π4

(d2)

=228

2× π4

(12)

= 145.2 psi

Hence, it means the stress on one side of hook is 72.61 psi.