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28 minimize the potential for errors in the coring and sawing the coring operation, and a milling machine to cut the cored operations that result in specimen rejection due to noncom- test specimen to the appropriate length. Based on a compre- pliance with the SPT specimen dimensional tolerances. hensive evaluation of the two proposals, the equipment proposed by Shedworks was selected for purchase in NCHRP Project 9-29. Although the Shedworks approach was consid- 4.2.1 Equipment Selection Process ered to be more risky, it had the potential to automate and General requirements for an automated coring and sawing simplify the specimen fabrication operations and thereby device were set forth in the First Article Equipment Specifi- accelerate the implementation of the SPT. The system pro- cation for the Simple Performance Test Specimen Fabrication posed by Pine represented only a marginal improvement over System developed by the research team based on experience available equipment, and did not address the primary objec- with the fabrication of many SPT specimens for other re- tive of the Simple Performance Test Specimen Fabrication search projects. The major requirements of this specification System, which was to automate and simplify the specimen are given in Table 12. fabrication operations. Proposals were solicited from several manufacturers that expressed interest in building the equipment during a work- 4.2.2 Equipment Development shop held in Phase I of the project. Only two manufacturers responded to the RFP issued on January 2, 2002 for the sys- A purchase order for the equipment was issued to Shed- tem: Shedworks, Inc. and Pine Instrument Company. Shed- works, Inc. on March 9, 2002. A five month schedule was works proposed an innovative approach where the gyratory provided for final design, fabrication, and delivery of the specimen is gripped by a chuck similar to that used in a lathe. equipment. After completing the design, Shedworks, Inc. Automated diamond-tipped cutoff blades saw the gyratory elected to subcontract the fabrication of the automated specimen to length, and an automated diamond-core barrel chuck components to another company. The automated then cores the test specimen from the gyratory specimen. chuck was designed to tighten against the specimen when Pine's system included a portable laboratory core drill, a spe- rotated. This aspect of the design was not only important for cially designed clamp to hold the gyratory specimen during automating the specimen fabrication process, but it also Table 12. First Article Specimen Requirements. Requirement Specification Assembled Size No larger than 60 in. by 96 in. by 72 in. high. Maximum Component Size No wider than 30 in. Electrical Power Single phase 115 or 230 VAC Cutting Fluid Air or Water Air Supply 125 psi max pressure, 10.6 cfm max volume Specimen Preparation Time Less than 15 min. Item Specification Note Average Diameter 100 mm to 104 mm 1 Specimen Dimensions Standard Deviation of Diameter 0.5 mm 1 Height 147.5 mm to 152.5 mm 2 End Flatness 0.5 mm 3 End Perpendicularity 1.0 mm 4 Notes: 1. Using calipers, measure the diameter at the center and third points of the test specimen along axes that are 90 apart. Record each of the six measurements to the nearest 0.1 mm. Calculate the average and the standard deviation of the six measurements. 2. Measure the height of the test specimen in accordance with Section 6.1.2 of ASTM D 3549. 3. Using a straightedge and feeler gauges, measure the flatness of each end. Place a straightedge across the diameter at three locations approximately 120 apart and measure the maximum departure of the specimen end from the straightedge using tapered end feeler gauges. For each end record the maximum departure along the three locations as the end flatness. 4. Using a combination square and feeler gauges, measure the perpendicularity of each end. At two locations approximately 90 apart, place the blade of the combination square in contact with the specimen along the axis of the cylinder, and the head in contact with the highest point on the end of the cylinder. Measure the distance between the head of the square and the lowest point on the end of the cylinder using tapered end feeler gauges. For each end, record the maximum measurement from the two locations as the end perpendicularity.

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29 allowed the chuck to adjust for creep that occurs in as- change to water as the cooling fluid required that the chuck phalt concrete under sustained loads. With this design, the bearing seals be redesigned to be watertight and that corro- gyratory specimen will not loosen during the sawing and sion resistant materials or finishes be used on all parts that coring operations as a result of the self-tightening action. would be exposed to water. Unfortunately, the chuck components were complex, and In July, 2004, Shedworks delivered the first version of the the subcontractor was not able to satisfactorily fabricate the Shedworks FlexPrepTM system. This unit, shown in Figure 25, components. In an attempt to keep the project on schedule incorporated the improvements listed above, but still used and within budget, Shedworks fabricated a manual chuck the manual screw chuck. During testing by the research team, that held the gyratory specimen in place using screws that it was determined that this chuck was not acceptable. Gyra- were manually tightened. This allowed Shedworks to as- tory specimens loosened in the chuck approximately 50 per- semble the device and shop test it in early November 2002. cent of the time, and when this occurred, a test specimen This version of the device was powered by a small single could not be obtained. Additionally, the core barrel tended to phase electric motor, used air to cool the cutting blades and break through the specimen leaving a ragged edge at the top. the core barrel, and pneumatic actuators to automate the The chuck failure rate was greatest for samples made with sawing and coring. The shop testing revealed several serious softer binders and harder aggregates. When the specimen did problems with this design as summarized in Table 13. Shed- not loosen in the chuck, a specimen meeting the tolerances in works requested and was granted additional time to resolve Table 12 was obtained except at the top edge where the break- the problems. through was occurring. Because the FlexPrepTM system Over the next 15 months, Shedworks designed and fabri- showed promise, Shedworks was granted additional time and cated modifications to address each of the problems identi- funding to develop an improved chuck and a back-up plate fied during the November 2002 shop test. The following to eliminate the breakthrough. major modifications were made: The breakthrough problem was resolved by adding a back- up plate. The back-up plate is held tight against the top of the 1. Cooling fluid: The cooling fluid was change from air to specimen by a pneumatic actuator. Shedworks considered water. many alternatives for the chuck, ultimately deciding that the 2. Motor size: The motor was increased to a 3 hp 208/230 V original concept was the only acceptable alternative. Several three phase motor. The phase conversion is done internal design changes were made to simplify the chuck mechanism, to the machine so that only a single phase supply is needed. and in July, 2005 Shedworks produced a prototype version of 3. Actuator fluid: The actuator fluid was changed from air to the chuck that functioned as designed. The major issue that a hybrid air/hydraulic system to provide better control remained was to develop seals to keep water and grit from over the cutting and coring forces and speeds. entering the bearings and operating mechanism of the chuck. This required a number of iterations. Finally a slinger-type In some cases these modification resulted in changes to seal was developed and the self-tightening chuck and seals other components in the device. For example, the decision to were installed on the FlexPrepTM System. This final version of Table 13. Operational problems identified during November, 2002 shop testing. Problem Possible Cause Possible Solution Saw Blade Flexure. The saw blades Actuator force or speed too high. Add blade bearing strips to support flexed after approximately in deep the saw blade against flexure cut. Cutting was stopped to avoid blade damage. Core barrel able to stall motor when Motor size too small 1. Increase motor size. Will cutting at appropriate coring force. require 208/230 V single phase power. 2. Switch to a hydraulic motor. Heat build-up when cutting at Inefficient cutting due to reduced 1. Increase motor size to allow reduced coring force melted binder coring force. higher coring force. and caused specimen to slip in the Air cooling may not be adequate. 2. Use coarser diamond blades and chuck. core barrels to provide greater heat dissipation. 3. Use water for cooling. Actuator control. Current pneumatic Compressibility of air. Switch to hydraulic actuators. actuators functioned smoothly under no load conditions. There is concern that control under load when completing cuts may not be acceptable.