Leaf Spring cum Coil Spring (LS cum CS) - NEW IDEA AND INNOVATION

Leaf Spring cum Coil Spring (LS cum CS)

NEW IDEA AND INNOVATION

By K.K.GANGADHARAN & K.G.BALAJI

Abstract 

Our new Design innovation name is Leaf Spring cum Coil Spring (LS cum CS). Simply saying, we have introduced coil springs in between the leaf spring, that’s all. It is mainly related to automobile engineering. Normally the leaf spring is used in the automobiles to achieve suspension.  

When we travel by bus, car etc., even we sit comfort, sometimes due to uneven roads or sudden break or load difference we experiences ups and down which creates uneasy to us. It is not only happening to human, but also happens to things which are stored in the truck, lorry, van etc. To overcome this problem we have to do some modification in the leaf spring.

Leaf spring shape and arrangement 

Leaf springs are nothing but referred as semi-elliptical springs is one of the oldest form of suspension used in the vehicles like car, bus, van, lorry and also especially in heavy vehicles like truck, container etc. A leaf spring looks similar to a bow without the string or rope. It consists of a stack or layer of curved narrow plates of equal width and varied length clamped together with shorter plates as well as it is fasten tightly with a bolt at the center to form a combined semi-elliptical shape. The center of the arc provides location for the axle and spring eye with bush are provided at either end for attaching to the body. It is provided to the vehicle to improve the suspension which overcomes shake, shock and ups and down. By doing some modification in it, we can get still better suspension. 

PRESENT LEAF SPRING DESIGN

Purpose of the leaf spring

In a modern vehicle, the suspension device design is the parabolic leaf spring in shape. It has a mono-leaf or multi-leaf arrangement. It has fewer leaves in comparison to the semi-elliptical multi-leaf springs whose thickness varies from centre to the end and it follows a parabolic path. This arrangement not only withstands weight but also gives greater flexibility which helps pickup ride quality. Using parabolic leaf spring is reduced load carrying capability.

DISADVANTAGES

    There are so many types of leaf-spring systems are available in the market and it is very difficult to identify which leaf spring system is suitable, safety, economic and reliable.

    The suspension compliance is not completely satisfied.

   The inter-leaf friction between the leaf springs reduces the ride comfort.

   The leaf springs may tend to lose shape and sag over time due to frequent change in weight of the load. So it is possible to form uneven sag. If the sag is uneven, it alters the cross weight of the vehicle which changes the handling and the axle mount angle.

  The vehicle weight is completely rest on the leaf spring.  So the acceleration and braking torque cause wind-up and vibration. It may require additional fuel consumption      

  When the vehicle faces uneven road, the body of the vehicle causes ups and down which affect driving and also un-comfort to travel.

If we want to overcome the above disadvantages, it needs some modification which should be simple, economic and has good performance in all aspects. 

  Coil Spring – Arrangement – Models

It is called Balance Board (See some models)

Thanks for above Google images..

Leaf Spring cum Coil Spring (LS cum CS) arrangement details:

Fitting Procedure:

1. Take top or big leaf spring which has three holes, one hole is at the center and another two holes are provided at the equal distance from the center such as the bottom or small leaf spring’s three holes should be matched.

2. Take three nos. connecting long length bolt, nut and washer with required size and inserts into the three holes of the top leaf spring one by one.

3. Then insert a rubber bush into the long bolt such that the rubber bush is just below to the leaf spring which helps to hold and keep the coil spring in a steady position to withstand shake, jerk and vibration. The same has to be done for another two long bolt.

4. Then insert another bush in another two long bolts. Then insert next leaf spring.

5. Ensure that in between every leaf spring a coil spring with two rubber bushes which is fix at the top and bottom and should be connected a long bolt.  

6. This has to be continued up to last leaf spring.

7. Finally tight the bolt before insert a coil spring as well as a washer. So that the leaf spring adjusts the vibration, shock, shake and ensure maximum suspension. 

Now we can use this Leaf Spring cum Coil Spring (LS cum CS) as usual.   

New CS cum LS Advantages:
1. Generally the leaf springs are arranged one below one in rigid manner.  Due to this rigidness, the friction among the leaf springs becomes high. But it has reduced by introducing coil springs in between the leaf spring.
2. The vehicle’s weight as well as its gravity force is transferred through all coil springs which are provided in the every leaf spring. So the weight impact to the wheel is minimized. So the wearing of tyre is reduced that is the life of the tyre is increased.
3. Coil springs absorb vibration and leaf spring sustains vehicle weight. The no. of coil springs to be provided in a leaf spring is depended upon the length of the leaf springs and the weight of the vehicle.
4. The coil spring is having a quality, it compresses when pressure or weight is applied and return its original shape when the pressure or weight is emptied. Due to this flexible character, the uneven roads’ ups and down is managed without any impact to the driver as well as traveler.
5. Vibration is caused by the uneven roads less to the driver as well as passenger too which is uneasy for journey. It has overcome by the coil springs.
6. It helps smooth and comfort journey.
7. Front and rare wheels vibration effect become less due to its ups and down movements.
8. Maintenance is very much minimized and damage of leaf spring is very less.
9.   Suspension performance is high.
10. Coil spring's stored energy helps to lift the weight against the gravity.
11. In the normal leaf spring, the stress distributed to the leaf springs only. But in the CSCLS the stress is distributed leaf spring and coil spring alternatively. So the stress and vibration are minimized.
12. No. of leaf springs can be reduced.
13. Nowadays in the Automobile Engg, the engineers reduce the weight of the vehicle. When the weight is reduced automatically the vehicle suffers much due to irregular road surfaces which is caused vibration to the vehicle. This vibration affects driver and travelers. So it leads to uncomfortable in the journey. Due to this situation, the leaf spring needs some modification to overcome this problem; we have introduced coil springs in between the leaf springs. It helps to adjust the vibration, even the vehicle is heavy weight or less weight.
14. Leaf spring absorb vertical vibration, impacts due to road irregularities, load variation (empty or full load), less friction of leaf springs. So the vehicle runs smoothly because the coil springs absorbs and adjust sudden shacks and shocks.
15. Both the leaf springs and coil springs are elastic element, due to this property it deflects when it is loaded and it returns the original shape when the load is emptied.
16. Less impact when breaking and accelerating.
17. A ride in a leaf spring suspension is quite bumpy and the leaf springs do not absorb the shocks easily, a lot of the shocks are transferred to the passenger. The stress and strain are taken care by the coil springs.
18. The coil springs keep balance due to dragging force because the coil spring can move in any direction that is up, down, front and back.
19. The load in the vehicle as well as the vehicle's weight resists by the coil springs in some extent. So the vehicle can run more speed.
20. Coil springs create some gap between two leaf springs. This gap acts as a air pockets and helps indirectly in many ways like less friction, absorb vibrations etc,.
21. It helps to drive the vehicle steadily especially for tanker load vehicles.
22. Due to less friction, fuel consumption is reduced some extent.

Ansys output

     Thank you