Design and Fabrication of Stair Climbing Trolley – Mechanical Project 

Abstract
In the modern world though there are many developments in the field of engineering. Still there are difficulties to carry heavy loads over stairs. Development of lift simplifies the effort of carrying heavy loads over stairs, it is not possible to use lift in all places like schools, college’s constructional areas. This project aims at developing a mechanism for easy transportation of heavy loads over stairs. The need for such arises from day to day requirements in our society. Devices such as hand trolleys are used to relieve the stresses of lifting while on flat ground. However these devices usually fail when it comes to carrying the load over short fleet of stairs .Our project attempts to design a stair climbing trolley which can carry heavy objects up the stairs with less effort compared to carrying them manually .The main objective of the project is to find an efficient and user friendly method of carrying various objects through stairs using minimum effort from the user and to also provide a smooth movement while climbing the stair. Under this project we have manufactured a stair climber with tri lobed wheel frames at both sides of the climber and three wheels on each sides are used in the tri lobed frame. The wheel assembly is rotated by a gear- motor mechanism where a DC gear motor is used to provide the necessary power for rotation and a pinion- gear mesh is used for reducing the rotating speed of the wheel. The motor is connected to a lead acid battery of similar ratings and they are in turn connected to DPDT switch.

INTRODUCTION
In day today life we may have to carry so many goods and objects of various quantities through stairs especially in offices, schools, colleges, hotels, industries, apartments etc. where the lifts may not be available, may be crowded with people or may be under repair .It is highly tiresome to carry various objects through stairs manually for higher floors for so many times. The various applications may be carrying bundles of answer sheets in a school or a college, carrying furniture in different buildings, different apparatus in colleges, in hospitals etc., carrying electronic items in houses and offices .So there should be a way to carry the objects through the stairs in a more comfortable and tireless manner without forcing the user to apply more force. Here comes the application of a stair climber.

In order to get a proper grip to our project we have extensively referred various articles and websites over the internet. We also referred to the project done by others under the similar projects.

Design and Fabrication of Stair Climbing Trolley
Design and Fabrication of Stair Climbing Trolley

DESIGN AND ANALYSIS
The CAD model of the product was designed to determine the external dimensions of the stair climber. The stair climber consists of a two pair of Tri-Star clamp. This Tri-Star clamp is used to hold the wheels with the help of nuts and bolts and make Tri-Star wheel setup and this Tri-Star wheel setup is connected at ends of the hollow shaft to make Tri-Star wheel assembly. The Tri-Star wheel assembly is powered by a motor setup.

Determination of Basic Dimensions
The basic external dimensions were decided based upon the study of stair climbers. The external and internal diameter of the hollow shaft is considered as 25mm and 18mm respectively. The length of the shaft is 700mm. Two pairs of Tri-Star clamp and six rubber wheels are used. The diameter of wheel is decided as 150mm for appropriate dimensions of the stair which is about depth of the tread is 300-350mm and height of the riser is 140-150mm. The inter-lobe angle of Tri-Star clamp is taken as 120˚.Suitable motor and gears were decided based on requirement.

Tri-Star Wheel Setup:
The Tri-Star clamp is used for connecting the wheels together. While climbing the stairs it is tedious to climb with a single wheel. Here, the wheels are connected to each of the arms of the clamp and while climbing the stairs Tri-Star setup rotates when it hits the edge of the stairs. The Tri-Star is fabricated using gas cutting process. The wheels are placed between the two clamps and are held with the help of the nuts and bolts.

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