Project On Tri-Wheel Stair Case Climbing Hand and

ABSTRACT . . This project aims at developing a mechanism for easy transportation of heavy loads over stairs. The need for such a system arises from day-to-day requirements in our society. Devices such as hand trolleys are used to relieve the stress of lifting while on flat ground. However, these devices usually fail when it comes to carrying the load over short fleet of stairs. In the light of this, the project attempts to design a stair climbing hand cart which can carry heavy objects up the stairs with less effort compared to carrying them manually. In present project, the trolley is equipped with Tri-Star wheels which enable us to carry load up and down the stairs and also eases the movement of trolley in irregular surfaces like holes and bumps<br>

TRI WHEEL DESIGN A Tri-Star wheel functions as an ordinary wheel on flat ground, but has the ability to climb automatically when an impediment to rolling is encountered. This wheel design consists of three tires, each mounted to a separate shaft. These shafts are located at the vertices of an equilateral triangle. The three shafts are geared to a fourth, central shaft (to which a motor may be attached). When geared in this quasi-planetary fashion, these triangular sets of wheels can negotiate many types of terrain, including sand and mud; they can also allow a vehicle to climb over small obstructions such as rocks, holes, and stairs. The wheel assembly may be gear-driven, with two wheels in rolling contact with the ground. The third wheel idles at the top until the lower front wheel hits an obstruction. The obstruction prevents the lower front wheel from moving forward but does not affect the motion of the driving axle. This causes the top wheel to roll forward into position as the new front wheel. This wheel usually lands on top of the obstruction and allows the rest of the assembly to vault over the obstruction.<br>

Deriving the Tri-Star wheel parameters depends on the position of Tri-Star wheel on stair
It depends on two parameters, the distance between the edge of wheel on lower stair
face of the next stair(L1), and the distance between the edge of
wheel on topper stair and the face of next stair (L2),
By comparing these parameters, three states may occur., as follow:
1. L1<L2
2. L1>L2
3. L1=L2 DESIGN AND C0NCEPT OF TRI-WHEEL<br>

In the design of Tri-Star wheel, five parameters are important which are the height of the stairs (a), width of stairs (b), radius of regular wheel (r), radius of Tri-Star wheel, the distance between the center of Tri-Star wheel and the center of its wheel (R) and the thickness of holders that fix the wheel on its place on Tri-Star wheel (t2), as shown in Figure<br>

Calculation for Tri star plates min max radius of wheels<br>

The basic external dimensions were considered based on literature survey only . But the designed model has the dimensions which are calculated based on the step size (height and width) where the fabricated model is going to be tested. The design of the vehicle is so modest allowing others to use stairs at once.
The external diameter of the solid shaft is taken as 25 mm.
The length of the shaft is 825 mm.
Two pairs of Quasi-static frames and a total of six rubber wheels are used .
The diameter of wheel is taken as 120 mm for suitable dimensions of the stairs which is about 140-150 mm in height and 300-350 mm in depth.
The inter-lobe angle of Tri-Star clamp is assumed as 120˚.
The distance between the centers of two wheel was taken as 190 mm.
The distance between two wheel frames is taken as 635 mm. Basic Dimensions OF THE CARIRER<br>

BODY OF THE CARRIER (TROLLEY) The body is designed for a height of about 650mm and is later fabricated with Mild Steel. The handle is attached to the extreme rails of the trolley body on either sides at an angle of 200 (with vertical). The base of the trolley is welded and it is made up of Mild Steel material. The design of trolley body side view and front view are shown in Fig3 and Fig4 respectively.<br>

Tri-Star Wheel Frame The following figure shows the design of
Tri-Star wheel frame as per the dimensions, which holds the three wheels together. The modification of the wheel frame is the main task in the project . To climb stairs with a single wheel is tedious. As per the wheel alignment to the frame Tri-wheel setup rotates when it hits the edge of the stairs in the climbing process. The design of frame is shown in Figure<br>

WHEELS OF THE CARRIER Stair-wheels are designed for traversing stairs with 140mm in height and 300mm in width. As per the stair dimensions, each wheel should be having the external and internal diameters as 60mm and 40mm respectively. The same is designed
as shown in Figure<br>

Force Acting On The Trolley The forces acting on trolley in x and y directions are shown in figure.When the trolley climbed up the stairs, it is needed to incline at about alpha degree.<br>

Force Acting On The Trolley<br>

Other Force Acting Upon Trolley<br>

MATERIAL SELECTION & FABRICATION The fabrication of the trolley begins with the
fabrication of quasi Tri-Star frame setup. Various
links are joined together using welded and bolted
joints A. Tri Star Wheel Frames It is used to hold the wheels together. The
wheels are joined to each of the arms of the frame
and while climbing the stairs Tri-Star setup rotates as
it hits the edge of the stairs. The sequence of
operations involved in the fabrication of Tri-Star
frame setup are oxy-fuel gas cutting, grinding,
drilling, and boring. Though straight wheel frame is
easy to manufacture quasi static wheel frame
is selected with a 50mm radius curve in
between two arms in order to provide strength and
stability to the wheels and the angle between two
wheel axes is 1200 for smooth functioning. The
maximum thickness is maintained as 5mm. Stainless
steel is selected with high chromium and low carbon
content in order to minimize corrosion & carbide
precipitation due to welding.<br>

B. Wheel The coefficient of friction between floor surface
and wheels should be taken into account while
selecting the material for wheel. The possible
materials available are rubber, steel, polyurethane etc. out of which rubber has more coefficient of friction with respect to concrete floors. Therefore rubber is chosen as the wheel material. Deep groove ball bearings are selected according to the wheel requirements and are fitted with Wheels and quasi frame assembly frame and shaft assembly C. Trolley body Mild steel is selected for the trolley body as mild
steel offers material properties that
are suitable for many applications than iron. The density of mild steel is approximately 7850 kg/cm3 the Young's
modulus is 210GPa. Mild steel has comparatively
low tensile strength, but it is cheap and malleable.
Therefore mild steel metal pipe of circular cross
section with one inch diameter is used to make the
handle & body.<br>

CONCLUSION The main aim of the project is stair climbing mechanism for load carrier with fewer efforts. Doing better work with lessor effort has been the main objective of human beings in any field. The main project as a platform we try to present mechanized stair climbing load carrier with reducing effort. Stair climbing mechanism in stair case load carrier which helps to carry the loads with help to carry the load with stair case. We completed the project to our best. The project work carried out exhibit expected result, and carry load across the stair very easily. Thus help in climbing across stairs the transportation of goods can be done very easily. This type of project work can be of very much useful for industrial use, dispatched with new household. This type of trolley will helpful to climb stairs with a particular height and width. According to the dimensions of stairs we can change dimensions of chair parts as well.<br>