I covered briefly the development of various types of reduction crushers of the gyratory family. Below you see a gyratory reduction crusher, which introduced the cylindrical top shell, flared head, and reversible concaves. Even with the older style of straight concaves, with which this machine was originally fitted, it represented a distinct step forward in secondary crusher design, and the later introduction of non-choking concaves increased its efficiency and permitted the use of finer settings than were originally allowable. This type of machine, although it has been superseded in the fine reduction field by more efficient types, still rates as a very excellent crusher for secondary crushing work.It has good capacity at moderate settings, is ruggedly constructed, and has, for comparable sizes, relatively large receiving openings, as compared to machines designed primarily for fine reduction work.
To show why this machine was a distinct step forward in secondary crusher design, it is interesting to compare the action of its crushing chamber to the standard crusher chambers already described. To make clear the fact that the machine had certain advanced features, even before non-choking concaves were developed, letsfirst show a diagram of its crushing chamber with the older type of beveled, straight-face concaves. It should be mentioned that these beveled concaves were not the very earliest type used in this crusher; they were preceded by plain, straight concaves, which utilized the full rated receiving opening of the crusher, but had the same disadvantage we noted in connection with this type, as used in the standard gyratory concentration of wear at the discharge point. The beveled type spread the wear out somewhat, although at the cost of some reduction in the effective receiving opening.
The distinctive feature of the design shown hereis the decided slope of the line-of-mean-diameters away from the center-line of the crusher, as this line runs down through the crushing chamber. As the volumes of the successive rings of material are functions of their diameters, as well as their areas, it is apparent that these progressively increasing diameters tend to offset the decreasing areas; in other words, the flared head spreads the material as it moves downward, thereby tending to minimize the ratio-of-volume-reduction. The actual compression-ratio in this chamber is about 1.5:1, which is lower than in either of the diagramspreviously discussed and very much lower than the case of the standard crusher with straight concaves.
This became the cone crusher and this departure from the older conventional design was a decided improvement for secondary crushing is apparent when we compare two machines of approximately equal head diameters, a logical comparison because the diameter of the bottom of the crushing head directly affects the area of discharge opening and, hence, the capacity of the crusher. This 10 reduction crusher, with its 40 head, compares closely, in this respect, with the 20 standard crusher, which has a 38 head. Using straight-face concaves, the permissible minimum open side settings are 1.5 for the former, and 3.5 for the latter. With non-choking concaves these settings are, respectively, 1 1/8 and 2 1/4.
Non-Choking Concaves To show the characteristics of this type of crusher when fitted with non-choking concaves we have prepared a diagram of the same size machine so equipped. You now have the cumulative benefits of the flared head and curved-profile liners. There is a marked reduction in the number of strokes required to shift plane O down to the discharge level; the choke-point has been raised, and the ratio of volume reduction is lower (about 1.2:1). There is a decrease in the effective receiving opening, as compared with the straight-face chamber, when using full-curve, non-choking concaves, which is the type shown in our diagram. This effective opening is established by the maximum angle of nip; therefore it varies somewhat for different materials, and in different sizes of crusher. For this crusher 26 deg. was chosen as the governing angle; about 28 deg. is the conservative maximum for the largest machines of this type.
High-Speed Crushers So far, all of the crushers we have been discussing have been of the low-speedclass; that is, with eccentric speeds ranging between the approximate limits of 100-200 RPM. It is customary, as before mentioned, to rate such crushers at their open-side discharge settings, because there is a definite relationship between these values. Most modern crushers, designed for what may properly be classed asfine-reduction crushing, are of the high-speed type. The eccentric speeds and shape of the crushing chamber in the machines of this type are such that the maximum one-way dimension of the product particles is established by the close-side discharge setting; consequently it has become customary to rate these crushers at this setting.
The Newhouse crusher was one of the early developments in the highspeed class of fine-reduction crusher incorporates several unusual features, at least one of which is unique in crusher design. The eccentric is direct-driven by a vertical motor mounted above the spider, the drive shaft running down through the hollow-bored mainshaft. Speeds range from 480 to 580 RPM, depending upon the size of the crusher, and upon the frequency of the electric current. Eccentric throws, as compared with those of the crushers we have been dealing with, are relatively low. This combination of small throw and high speed results in a very uniform product with a minimum amount of fines for any setting and ratio of reduction. A unique feature is suspension by means of cables, eliminating the usual foundation, although the crusher can be set on a foundation where required.
This crusher is usually furnished with full-curve, non-choking concaves, which are reversible in the top shell. These concaves are of the same general contour as those shown in the above diagram of the reduction crusher chamber and in general the crushing chamber is similar, except that the chamber in the Newhouse crusher is somewhat deeper and, consequently, the head does not have as pronounced a flare. The important difference in the crushing action of these two machines lies in the difference in eccentric speed. That of the Newhouse crusher is so high that no material can drop through the almost parallel zone just above the discharge point without being caught between head and concaves and broken to a maximum oneway size closely approximating the close-side setting.
This crusher can be set somewhat closer than comparable sizes of the reduction crusher previously described. Although it cannot be classed as a fine-crusher it does belong to the fine-reduction class. Furthermore, by virtue of its large receiving openings, it rates as a machine for secondary reduction work. When so used it is usually fitted with concaves of the non-reversible, non-choking type, which are designed to make use of the full rated receiving opening of the crusher, although they sacrifice the feature of reversibility which permits wearing both ends of the concaves.
Cone crushers were originally designed and developed by Symons around 1920 and therefore are often described as Symons cone crushers. As the mechanisms of crushing in these crushers are similar to gyratory crushers their designs are similar, but in this case the spindle is supported at the bottom of the gyrating cone instead of being suspended as in larger gyratory crushers. Figure5.3 is a schematic diagram of a cone crusher.
The breaking head gyrates inside an inverted truncated cone. These crushers are designed so that the head-to-depth ratio is larger than the standard gyratory crusher and the cone angles are much flatter and the slope of the mantle and the concaves are parallel to each other. The flatter cone angles help to retain the particles longer between the crushing surfaces and therefore produce much finer particles. To prevent damage to the crushing surfaces, the concave or shell of the crushers is held in place by strong springs or hydraulics which yield to permit uncrushable tramp material to pass through.
The secondary crushers are designated as Standard cone crushers having stepped liners and tertiary Short Head cone crushers, which have smoother crushing faces and steeper cone angles of the breaking head. The approximate distance of the annular space at the discharge end designates the size of the cone crushers. A brief summary of the design characteristics is given in Table5.4 for crusher operation in open-circuit and closed-circuit situations.
The Standard cone crushers are for normal use. The Short Head cone crushers are designed for tertiary or quaternary crushing where finer product is required. These crushers are invariably operated in closed circuit. The final product sizes are fine, medium or coarse depending on the closed set spacing, the configuration of the crushing chamber and classifier performance, which is always installed in parallel.
For finer product sizes, i.e., less than 6mm, special cone crushers known as Gyradisc crushers are available. The operation is similar to the standard cone crushers, except that the size reduction is caused more by attrition than by impact . The reduction ratio is around 8:1 and as the product size is relatively small the feed size is limited to less than 50mm with a nip angle between 25 and 30. The Gyradisc crushers have head diameters from around 900 to 2100mm. These crushers are always operated under choke feed conditions. The feed size is less than 50mm and therefore the product size is usually less than 69mm.
Maintenance of the wear components in both gyratory and cone crushers is one of the major operating costs. Wear monitoring is possible using a Faro Arm (Figure 6.10), which is a portable coordinate measurement machine. Ultrasonic profiling is also used. A more advanced system using a laser scanner tool to profile the mantle and concave produces a 3D image of the crushing chamber (Erikson, 2014). Some of the benefits of the liner profiling systems include: improved prediction of mantle and concave liner replacement; identifying asymmetric and high wear areas; measurement of open and closed side settings; and quantifying wear life with competing liner alloys.
Various types of rock fracture occur at different loading rates. For example, rock destruction by a boring machine, a jaw or cone crusher, and a grinding roll machine are within the extent of low loading rates, often called quasistatic loading condition. On the contrary, rock fracture in percussive drilling and blasting happens under high loading rates, usually named dynamic loading condition. This chapter presents loading rate effects on rock strengths, rock fracture toughness, rock fragmentation, energy partitioning, and energy efficiency. Finally, some of engineering applications of loading rate effects are discussed.
In Chapter4, we have already seen the mechanism of crushing in a jaw crusher. Considering it further we can see that when a single particle, marked 1 in Figure11.5a, is nipped between the jaws of a jaw crusher the particle breaks producing fragments, marked 2 and 3 in Figure11.5b. Particles marked 2 are larger than the open set on the crusher and are retained for crushing on the next cycle. Particles of size 3, smaller than the open set of the crusher, can travel down faster and occupy or pass through the lower portion of the crusher while the jaw swings away. In the next cycle the probability of the larger particles (size 2) breaking is greater than the smaller sized particle 3. In the following cycle, therefore, particle size 2 is likely to disappear preferentially and the progeny joins the rest of thesmaller size particles indicated as 3 in Figure11.5c. In the figures, the position of the crushed particles that do not exist after comminution is shaded white (merely to indicate the positions they had occupied before comminution). Particles that have been crushed and travelled down are shown in grey. The figure clearly illustrates the mechanism of crushing and the classification that takes place within the breaking zone during the process, as also illustrated in Figure11.4. This type of breakage process occurs within a jaw crusher, gyratory crusher, roll crusher and rod mills. Equation (11.19) then is a description of the crusher model.
In practice however, instead of a single particle, the feed consists of a combination of particles present in several size fractions. The probability of breakage of some relatively larger sized particles in preference to smaller particles has already been mentioned. For completeness, the curve for the probability of breakage of different particle sizes is again shown in Figure11.6. It can be seen that for particle sizes ranging between 0 K1, the probability of breakage is zero as the particles are too small. Sizes between K1 and K2 are assumed to break according a parabolic curve. Particle sizes greater than K2 would always be broken. According to Whiten , this classification function Ci, representing the probability of a particle of size di entering the breakage stage of the crusher, may be expressed as
The classification function can be readily expressed as a lower triangular matrix [1,16] where the elements represent the proportion of particles in each size interval that would break. To construct a mathematical model to relate product and feed sizes where the crusher feed contains a proportion of particles which are smaller than the closed set and hence will pass through the crusher with little or no breakage, Whiten  advocated a crusher model as shown in Figure11.7.
The considerations in Figure11.7 are similar to the general model for size reduction illustrated in Figure11.4 except in this case the feed is initially directed to a classifier, which eliminates particle sizes less than K1. The coarse classifier product then enters the crushing zone. Thus, only the crushable larger size material enters the crusher zone. The crusher product iscombined with the main feed and the process repeated. The undersize from the classifier is the product.
While considering the above aspects of a model of crushers, it is important to remember that the size reduction process in commercial operations is continuous over long periods of time. In actual practice, therefore, the same operation is repeated over long periods, so the general expression for product size must take this factor into account. Hence, a parameter v is introduced to represent the number of cycles of operation. As all cycles are assumed identical the general model given in Equation (11.31) should, therefore, be modified as
Multiple vectors B C written in matrix form:BC=0.580000.200.60000.120.180.6100.040.090.20.571.000000.700000.4500000=0581+00+00+000.580+00.7+00+000580+00+00.45+000.580+00+00+000.21+0.60+00+000.20+0.60.7+00+000.20+0.60+00.45+000.20+0.60+00+000.121+0.180+0.610+000.120+0.180.7+0.610+000.120+0.180+0.610.45+000.120+0.180+0.610+000.041+0.090+0.20+0.5700.040+0.090.7+0.20+0.5700.040+0.090+0.20.45+0.5700.040+0.090+0.20+0.570=0.580000.20.42000.120.1260.274500.040.0630.090
Now determine (I B C) and (I C)(IBC)=10.5800000000.210.42000000.1200.12610.27450000.0400.06300.0910=0.420000.20.58000.120.1260.725500.040.0630.091and(IC)=000000.300000.5500001
Now find the values of x1, x2, x3 and x4 as(0.42x1)+(0x2)+(0x3)+(0x4)=10,thereforex1=23.8(0.2x1)+(0.58x2)+(0x3)+(0x4)=33,thereforex2=65.1(0.12x1)+(0.126x2)+(0.7255x3)+(0x4)=32,thereforex3=59.4(0.04x1)+(0.063x2)+(0.09x3)+(1x4)=20,thereforex4=30.4
In this process, mined quartz is crushed into pieces using crushing/smashing equipment. Generally, the quartz smashing plant comprises a jaw smasher, a cone crusher, an impact smasher, a vibrating feeder, a vibrating screen, and a belt conveyor. The vibrating feeder feeds materials to the jaw crusher for essential crushing. At that point, the yielding material from the jaw crusher is moved to a cone crusher for optional crushing, and afterward to effect for the third time crushing. As part of next process, the squashed quartz is moved to a vibrating screen for sieving to various sizes.
Crushers are widely used as a primary stage to produce the particulate product finer than about 50100mm. They are classified as jaw, gyratory, and cone crushers based on compression, cutter mill based on shear, and hammer crusher based on impact.
A jaw crusher consists essentially of two crushing plates, inclined to each other forming a horizontal opening by their lower borders. Material is crushed between a fixed and a movable plate by reciprocating pressure until the crushed product becomes small enough to pass through the gap between the crushing plates. Jaw crushers find a wide application for brittle materials. For example, they are used for comminution of porous copper cake. A Fritsch jaw crusher with maximal feed size 95mm, final fineness (depends on gap setting) 0.315mm, and maximal continuous throughput 250Kg/h is shown in Fig. 2.8.
A gyratory crusher includes a solid cone set on a revolving shaft and placed within a hollow body, which has conical or vertical sloping sides. Material is crushed when the crushing surfaces approach each other and the crushed products fall through the discharging opening.
Hammer crushers are used either as a one-step primary crusher or as a secondary crusher for products from a primary crusher. They are widely used for crushing hard metal scrap for different hard metal recycling processes. Pivoted hammers are pendulous, mounted on the horizontal axes symmetrically located along the perimeter of a rotor. Crushing takes place by the impact of material pieces with the high speed moving hammers and by contact with breaker plates. A cylindrical grating or screen is placed beneath the rotor. Materials are reduced to a size small enough to pass through the openings of the grating or screen. The size of the product can be regulated by changing the spacing of the grate bars or the opening of the screen.
The feature of the hammer crushers is the appearance of elevated pressure of air in the discharging unit of the crusher and underpressure in the zone around the shaft close to the inside surface of the body side walls. Thus, the hammer crushers also act as high-pressure, forced-draught fans. This may lead to environmental pollution and product losses in fine powder fractions. A design for a hammer crusher (Fig. 2.9) essentially allows a decrease of the elevated pressure of air in the crusher discharging unit . The A-zone beneath the screen is communicated through the hollow ribs and openings in the body side walls with the B-zone around the shaft close to the inside surface of body side walls. As a result, the circulation of suspended matter in the gas between A and B zones is established and the high pressure of air in the discharging unit of crusher is reduced.
Crushers are widely used as a primary stage to produce the particulate product finer than about 50100 mm in size. They are classified as jaw, gyratory and cone crushers based on compression, cutter mill based on shear and hammer crusher based on impact.
A jaw crusher consists essentially of two crushing plates, inclined to each other forming a horizontal opening by their lower borders. Material is crushed between a fixed and a movable plate by reciprocating pressure until the crushed product becomes small enough to pass through the gap between the crushing plates. Jaw crushers find a wide application for brittle materials. For example, they are used for comminution of porous copper cake.
A gyratory crusher includes a solid cone set on a revolving shaft and placed within a hollow body, which has conical or vertical sloping sides. Material is crushed when the crushing surfaces approach each other and the crushed products fall through the discharging opening.
Hammer crushers are used either as a one-step primary crusher or as a secondary crusher for products from a primary crusher. They are widely used for crushing of hard metal scrap for different hard metal recycling processes.
Pivoted hammers are pendulous, mounted on the horizontal axes symmetrically located along the perimeter of a rotor and crushing takes place by the impact of material pieces with the high speed moving hammers and by contact with breaker plates. A cylindrical grating or screen is placed beneath the rotor. Materials are reduced to a size small enough pass through the openings of the grating or screen. The size of product can be regulated by changing the spacing of the grate bars or the opening of the screen.
The feature of the hammer crushers is the appearance of elevated pressure of air in the discharging unit of the crusher and underpressure in the zone around of the shaft close to the inside surface of the body side walls. Thus, the hammer crushers also act as high-pressure forced-draught fans. This may lead to environmental pollution and product losses in fine powder fractions.
A design for a hammer crusher (Figure 2.6) allows essentially a decrease of the elevated pressure of air in the crusher discharging unit . The A-zone beneath the screen is communicated through the hollow ribs and openings in the body side walls with the B-zone around the shaft close to the inside surface of body side walls. As a result, circulation of suspended matter in the gas between A- and B-zones is established and high pressure of air in the discharging unit of crusher is reduced.
For a particular operation where the ore size is known, it is necessary to estimate the diameter of rolls required for a specific degree of size reduction. To estimate the roll diameter, it is convenient to assume that the particle to be crushed is spherical and roll surfaces are smooth. Figure6.2 shows a spherical particle about to enter the crushing zone of a roll crusher and is about to be nipped. For rolls that have equal radius and length, tangents drawn at the point of contact of the particle and the two rolls meet to form the nip angle (2). From simple geometry it can be seen that for a particle of size d, nipped between two rolls of radius R:
Equation (6.2) indicates that to estimate the radius R of the roll, the nip angle is required. The nip angle on its part will depend on the coefficient of friction, , between the roll surface and the particle surface. To estimate the coefficient of friction, consider a compressive force, F, exerted by the rolls on the particle just prior to crushing, operating normal to the roll surface, at the point of contact, and the frictional force between the roll and particle acting along a tangent to the roll surface at the point of contact. The frictional force is a function of the compressive force F and is given by the expression, F. If we consider the vertical components of these forces, and neglect the force due to gravity, then it can be seen that at the point of contact (Figure6.2) for the particle to be just nipped by the rolls, the equilibrium conditions apply where
As the friction coefficient is roughly between 0.20 and 0.30, the nip angle has a value of about 1117. However, when the rolls are in motion the friction characteristics between the ore particle will depend on the speed of the rolls. According to Wills , the speed is related to the kinetic coefficient of friction of the revolving rolls, K, by the relation
Equation (6.4) shows that the K values decrease slightly with increasing speed. For speed changes between 150 and 200rpm and ranging from 0.2 to 0.3, the value of K changes between 0.037 and 0.056. Equation (6.2) can be used to select the size of roll crushers for specific requirements. For nip angles between 11 and 17, Figure6.3 indicates the roll sizes calculated for different maximum feed sizes for a set of 12.5mm.
The maximum particle size of a limestone sample received from a cone crusher was 2.5cm. It was required to further crush it down to 0.5cm in a roll crusher with smooth rolls. The friction coefficient between steel and particles was 0.25, if the rolls were set at 6.3mm and both revolved to crush, estimate the diameter of the rolls.
It is generally observed that rolls can accept particles sizes larger than the calculated diameters and larger nip angles when the rate of entry of feed in crushing zone is comparable with the speed of rotation of the rolls.
Jaw crushers are mainly used as primary crushers to produce material that can be transported by belt conveyors to the next crushing stages. The crushing process takes place between a fixed jaw and a moving jaw. The moving jaw dies are mounted on a pitman that has a reciprocating motion. The jaw dies must be replaced regularly due to wear. Figure 8.1 shows two basic types of jaw crushers: single toggle and double toggle. In the single toggle jaw crusher, an eccentric shaft is installed on the top of the crusher. Shaft rotation causes, along with the toggle plate, a compressive action of the moving jaw. A double toggle crusher has, basically, two shafts and two toggle plates. The first shaft is a pivoting shaft on the top of the crusher, while the other is an eccentric shaft that drives both toggle plates. The moving jaw has a pure reciprocating motion toward the fixed jaw. The crushing force is doubled compared to single toggle crushers and it can crush very hard ores. The jaw crusher is reliable and robust and therefore quite popular in primary crushing plants. The capacity of jaw crushers is limited, so they are typically used for small or medium projects up to approximately 1600t/h. Vibrating screens are often placed ahead of the jaw crushers to remove undersize material, or scalp the feed, and thereby increase the capacity of the primary crushing operation.
Both cone and gyratory crushers, as shown in Figure 8.2, have an oscillating shaft. The material is crushed in a crushing cavity, between an external fixed element (bowl liner) and an internal moving element (mantle) mounted on the oscillating shaft assembly. An eccentric shaft rotated by a gear and pinion produces the oscillating movement of the main shaft. The eccentricity causes the cone head to oscillate between the open side setting (o.s.s.) and closed side setting (c.s.s.). In addition to c.s.s., eccentricity is one of the major factors that determine the capacity of gyratory and cone crushers. The fragmentation of the material results from the continuous compression that takes place between the mantle and bowl liners. An additional crushing effect occurs between the compressed particles, resulting in less wear of the liners. This is also called interparticle crushing. The gyratory crushers are equipped with a hydraulic setting adjustment system, which adjusts c.s.s. and thus affects product size distribution. Depending on cone type, the c.s.s. setting can be adjusted in two ways. The first way is by rotating the bowl against the threads so that the vertical position of the outer wear part (concave) is changed. One advantage of this adjustment type is that the liners wear more evenly. Another principle of setting adjustment is by lifting/lowering the main shaft. An advantage of this is that adjustment can be done continuously under load. To optimize operating costs and improve the product shape, as a rule of thumb, it is recommended that cones always be choke-fed, meaning that the cavity should be as full of rock material as possible. This can be easily achieved by using a stockpile or a silo to regulate the inevitable fluctuation of feed material flow. Level monitoring devices that detect the maximum and minimum levels of the material are used to start and stop the feed of material to the crusher as needed.
Primary gyratory crushers are used in the primary crushing stage. Compared to the cone type crusher, a gyratory crusher has a crushing chamber designed to accept feed material of a relatively large size in relation to the mantle diameter. The primary gyratory crusher offers high capacity thanks to its generously dimensioned circular discharge opening (which provides a much larger area than that of the jaw crusher) and the continuous operation principle (while the reciprocating motion of the jaw crusher produces a batch crushing action). The gyratory crusher has capacities starting from 1200 to above 5000t/h. To have a feed opening corresponding to that of a jaw crusher, the primary gyratory crusher must be much taller and heavier. Therefore, primary gyratories require quite a massive foundation.
The cone crusher is a modified gyratory crusher. The essential difference is that the shorter spindle of the cone crusher is not suspended, as in the gyratory, but is supported in a curved, universal bearing below the gyratory head or cone (Figure 8.2). Power is transmitted from the source to the countershaft to a V-belt or direct drive. The countershaft has a bevel pinion pressed and keyed to it and drives the gear on the eccentric assembly. The eccentric assembly has a tapered, offset bore and provides the means whereby the head and main shaft follow an eccentric path during each cycle of rotation. Cone crushers are used for intermediate and fine crushing after primary crushing. The key factor for the performance of a cone type secondary crusher is the profile of the crushing chamber or cavity. Therefore, there is normally a range of standard cavities available for each crusher, to allow selection of the appropriate cavity for the feed material in question.
The main task of renovation construction waste handling is the separation of lightweight impurities and construction waste. The rolling crusher with opposite rollers is capable of crushing the brittle debris and compressing the lightweight materials by the low-speed and high-pressure extrusion of the two opposite rollers. As the gap between the opposite rollers, rotation speed, and pressure are all adjustable, materials of different scales in renovation construction waste can be handled.
The concrete C&D waste recycling process of impact crusher+cone crusher+hoop-roller grinder is also capable of handling brick waste. In general, the secondary crushing using the cone crusher in this process with an enclosed crusher is a process of multicrushing, and the water content of waste will become an important affecting factor. The wet waste will be adhered on the wall of the grinding chamber, and the crushing efficiency and waste discharging will be affected. When the climate is humid, only coarse impact crushing is performed and in this case the crushed materials are used for roadbase materials. Otherwise, three consecutive crushings are performed and the recycled coarse aggregate, fine aggregate, and powder materials are collected, respectively.
The brick and concrete C&D waste recycling process of impact crusher+rolling crusher+hoop-roller grinder is also capable of handling the concrete waste. In this case, the water content of waste will not be an important affecting factor. This process is suitable in the regions with wet climates.
The renovation C&D waste recycling process of rolling crusher (coarse/primary crushing)+rolling crusher (intermediate/secondary crushing)+rolling crusher (fine/tertiary crushing) is also capable of handling the two kinds of waste discussed earlier. The particle size of debris is crushed less than 20mm and the lightweight materials are compressed, and they are separated using the drum sieve. The energy consumption is low in this process; however, the shape of products is not good (usually flat and with cracks). There is no problem in roadbase material and raw materials of prefabricated product production. But molders (the rotation of rotors in crusher is used to polish the edge and corner) should be used for premixed concrete and mortar production.Get in Touch with Mechanic