# sCISSOR LIFT sCISSOR LIFTsCISSOR LIFT sCISSOR LIFT sCISSOR LIFT, Essays (univeristy) for Mechanics

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NPD REVIEW

Chirag Shetty 16BME0536 Rajat Sharda 16BME0890

GROUP-18 NPD REVIEW

VOICE OF CUSTOMER Scissor Lift to reach a Height of 10m Carry a Load of 2000N or 205 kg

Main Components of the LIFT Primary Components 1. Hydraulic Cylinder – 46 mm diameter , Pmax=160 bar attached to the stationary

side of the scissor lift 2. Links- 2.309m long 3. Table-top 4. Supporting tube – 2.2m long 6. Base plates - - (2.26*0.81*0.05 ) m^3 7. Top plates - (2.26*0.81*0.05 ) m^3 Secondary Components Dual Front wheel rive Disc brakes Manual Platform lowering and raising valve Tires Tilt level sensor with Alarm Horn Charger, Inverter Power Supply 24V DC AC power supply to platform

MATERIAL SELECTION  LINKS-The main interest is made by the legs of the lift, this part

is subjected to a normal force which might cause buckling and shear force which cause bending, which possibly cause bending deformation or even braking of the part. Then such properties as strength, hardness, and stiffness are needed. An appropriate material for these purposes is Structural steel, more precisely the S355 steel.

TOP PLATES-The top plates take the load caused by a weight of lifting goods. The main needed property here is strength and the selected material is Mild steel.

BASE PLATFORM-Base Platform: this component is subjected to the weight of the top plat form and the scissors arms. It is also responsible for the stability of the whole assembly, therefore strength. Hardness and stiffness are needed mechanical properties. Mild steel is used.

HYDRAULIC SYSTEM- It is subjected to direct compressive force which imposes a bending stress which may cause buckling of the component. It is also subjected to internal compressive pressure which generates circumferential and longitudinal stresses all around the wall thickness. Recommended Material is Mild Steel.

 Hydraulic System Specifications 14.2 L ,24V DC(four 6V 225 Ah Batteries, 20Amps)

DESIGN SPECIFICATIONS Mass to be put on the Lift= 205 kg Taking a Factor of Safety(FOS) of 1.5 we get the effective Load to be= 205*1.5=

307.5 kg or 3016.575 N Mass of Top frame= 713.934 kg (2.26*0.81*0.05*7800 Density of Mild steel) Mass of Each Link= 82.9352 kg (2.309 m long each, Density of Structural steel) No. of Links= 20 Total Mass of Links= 82.9352*20=1658.705 kg Mass of Hydraulic Cylinder= 8 kg Total Mass= 713.934 + 1658.705 + 8 + 307.5=2688.1394kg Effective Load=1497.81 kg Force acting on cylinder= 14.693kN Pressure = Force/Area Force = Pmax *( ∏*D^2)/4(to calculate the diameter of the cylinder) D = 46.34mm ≈46mm Area= (46*46*3.1416/2)*10^-6=(46 mm diameter of Cylinder)=3.32*10^-3 m^2 Pressure= 14693/3.32*10^-3= 24.09 bar(required pressure from pump ) The Max rating of the Hydraulic System installed is 160 Bar(pre Designed)

To calculate the actuator length and length of scissor link

l=length of actuator F=14.693kN, L=14971 kg, h=10m h=nDsin60˚ From the above equations we get l=1.427m and D=2.309m

Maximum allowable Stress on the top platform = Yield Strength /Factor of Safety = 250*10^6 / 1.5 =166.67 MPa Stress acting on the Platform= 1092.89 Pa The Stress on the Platform is less than the maximum allowable stress

Tensile Forces acting on each Link= 1.3kN Maximum Tensile Stress= 1.3*1000/(0.1*0.05)=260kPa (Width and Thickness of Link)

Maximum allowable Tensile Stress on structural Steel= Re/n n=FOS=3 (safety standard ANSI) Re=355(For Structural Steel) Max. Allowable Tensile Stress= 355/3=118.3 N/mm^2=118.3 MPa

With the given specifications the Lift will reach a height of 10m when the angle between the links and horizontal becomes 60˚.

IDENTIFICATION OF DESIGN ISSUES Hydraulic Cylinder Malfunction-

Remove the cylinders , disassemble connect the necessary repairs

Loose Connections - Tighten the coupling nuts ,

Easing ,Tightening Sleeve cylinders – Tighten the Cylinders

Weakening of Bolts - Tighten the coupling nuts

Malfunction of Hydraulic Pump – Replace the Pump

Concept Generation A scissor lift is used to move cargo vertically. Despite this, it

is possible to move it horizontally, because the lift can be driven like an ordinary car. it will be driven by the force applied of one or more hydraulic cylinders or using an electric motor.

Additionally, the upper platform can be coupled with a cabin. This type of lift is known as scissor lift due to the fact that it is composed by two pairs of beams connected through their gravitational centers.

 These pairs are held parallel due to the beams with stipulated dimensions. By incorporating a close cabin, users could have work equipment inside it, avoiding damage to the equipment

The lift should be projected based on norms and codes in force.

The lift projected will have 10 scissor “pairs”. The lift is symmetric, so it will have 20 scissor thus in order to make it reach up to a height of 10 m.

It will be coupled with an extendable platform

It is driven by the force applied of one hydraulic cylinder, part of the hydraulic system. This system is responsible for the ascent and descent movement of the lift.

The platform should support 2000N. This value doesn't includes the weight of the platform and the cargo/users.

How?

FAST Why?

Produce a Lift

Hydraulic Actuator

Pump

Produce Pressure

Move around

Provide Electricit

yWithstan d

Compres sive

Stress

Dual front wheel drive

Support Platform

Acqui re

Powe r