 to all of you. I am Mr. Sheshikaand Gosavi, Assistant Professor, Department of Civil Engineering, Vulturendha Institute of Technology, Sulapur. Today I am presenting an online educational resource on operating efficiencies of clamshell. The learning outcomes of this online educational resource on clamshell are at the end of this session, learners will be able to analyze the operating efficiencies of clamshell and they will also be able to calculate the production capacity of clamshell for given job efficiency. You can see this giant machine. It is a part of the machine which is also called as the clamshell bucket. It works in a very simple manner. You can see the parts. There is a hoist wire at the top. There are arms and there are cutting edges which are placed down at these locations. So, when I am interested in working with the clamshell, I have to operate these particular edges. The clamshell is a construction equipment of one piece container. It consists of two hoists joined by a hinge area. The structure comes together to close. In the working of the clamshell, the bucket is lowered directly into the material in the open position. The clamshell is closed. The bucket is lifted out and then the material is transported and placed at a desired location. In the sketch, you can see both the position. The first one is regarding the open position of the clamshell and this is the position wherein it gets closed. Within this particular two arms, whatever is the material that will get collected and then it will be transported and dumped at the required location. Clamshell is normally operated with a crane shovel equipped with a crane boom and the clamshell bucket is actually collecting the material. The buckets are of three types. Medium bucket, light bucket and heavy bucket. Medium bucket is for general purpose work, including the excavation of loose soil. Light buckets are for handling bulk material such as sand and gravel. Heavy buckets are for digging medium soils. Bucket penetration depends on bucket weight, the teeth of the bucket and the disadvantage of using the clamshell as compared to drag line or as compared to shovel is it lacks the positive digging action and it also lacks precise lateral control. For the loose fragmented material, clamshell is advantageous as compared to rest of the machines. Secondly, its boom is sufficiently long and therefore if you want to shift the material from one location to the other location you can always do it by using clamshell. The parameters of cycle time are always important in any construction equipment. The maximum allowable load that is bucket weight plus soil weight is one of the very important factor. It is obtained from the manufacturer's clamshell loading chart for continuous operation. The other important parameter in cycle time is fill factor for buckets. The percentage of the bucket that is filled is called as the fill factor. It is normally ranging between 75 percent to 90 percent. Mr. Bray and Emmons have prepared a chart which enables us to find out the fill factor for clamshell buckets. The other important factors contributing to the cycle time are bucket velocity, particularly in the vertical direction, so fall velocity. Swing angle which is 120 degree in majority of the cases. In a reverse direction if you will count it will become double of that. Swing velocity that is its default value is 21 degree per second. Time to open and close the bucket is also an important part of the cycle time. The depth is also an important factor which governs the cycle time. This is the chart I was speaking about. As you can see bucket fill factor is a function of the bucket size. As the bucket size goes on increasing from 0 meter cube to 10, 20, 30, 40, 50 cubic meter, the respective fill factor keeps on increasing which indirectly means that large size bucket is having better bucket fill factor. This is a typical chart which is developed for loose sand. For different materials this particular chart keeps on changing. This is just a sample that I have shown for our information. Cycle time of clamshell is dependent on use of lightest bucket capable of digging the material or heaviest. The lightest bucket will enable a larger bucket to be used and will usually increase production. Cycle time is reduced by organizing the job so that the dumping radius is the same as the digging radius. Keep the machine level to avoid swinging uphill or downhill. Non-level swinging is hard on the machine and usually increases the cycle time. This particular chart shows you movement of the drag line bucket in a horizontal as well as in a vertical position. This is bucket loading time against swing angle. So start of the digging cycle starts from there. It goes over here. The material is filled in. Loaded swing happens in this way. Dumping happens at this location and again it comes back with empty bucket to its starting position. This is another chart in a vertical positioning. So bucket is loading from here. Digging completes. Loaded swing happens. Dumping happens. Empty swing happens from there and it comes back to the starting point. Remember the variable factors affecting the operations of this clam shell are the difficulty of loading the bucket, the size load obtainable, the height of lift, the angle of swing which is a difference between the location where the sediment is dropped and the location where the sediment is excavated. The method of disposing of the load and of course the experience of the operator. The clam shell output per hour is elaborated with this example. A 1.5 cubic meter bucket is assumed to be used to transfer let us say sand 8 meter above the ground. So vertical height is 8 meter. The average speed of moist line is 45 minutes per minute, 45 meters per minute. Time per cycle approximately can be calculated with following assumptions. Loading takes 6 seconds. Lifting and swinging is given as 8 meter with 45 meter per minute. That means within a minute 45 meter is possible. So for 8 meter only 10 seconds are sufficient. Dumping load requires let us say 6 seconds. Swinging back to stockpile requires 4 seconds and then combined together we will get the total time 30 second with assumption that accelerating the accelerating loss is 4 seconds. So total time is 30 seconds. Maximum number of cycles per hour now can be calculated. Hour consist of 60 minutes. So 60 into 60 gives us the seconds and 30 second is the total time for one cycle. So 60 into 60 divided by 30 gives us 120 number of cycles per hour. Maximum volume per hour in this particular case will be 120 multiplied by 1.5 cubic meter bucket capacity. Combined together gives us 180 meter cube as the maximum volume possible to be manipulated per hour. If the unit operates 45 minutes per hour then the output is 180 multiplied by 45 divided by 60 giving us 135 cubic meter per hour as a lose volume. Production in lose cubic meter can be calculated by using a simple formula as has been shown 60 into 60 divided by cycle time multiplied by bucket capacity multiplied by bucket fill factor multiplied by 60 divided by job efficiency. Please pause the video for a while. And answer the following question. Estimate the production in lose cubic meters per hour. For a medium weight clamshell excavating lose earth, heaped a bucket capacity 0.75 cubic meter. The soil is common earth with a bucket fill factor of 0.95. Estimated cycle time is 40 seconds. Job efficiency is estimated as 50 minutes per hour. Now by substituting these values in the equation we get 53 lose cubic meter per hour as the production answer. For preparation of this online educational resource I have used the following references. It is a paper by Dushyant and Deshmukh and another presentation of estimating production and cost for clamshell mechanical ranges. It is a thesis by Robert Fletcher submitted by the Office of Graduate Studies of Texas. Your comments, questions, queries are most welcome. Thank you very much.