MATHEWS LX. Mathews LX. Ihave looked forward with anticipation to putting the new

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1 MATHEWS LX The Mathews LX with its new HP single cam is an outstanding bow that combines exceptional performance and shooting qualities. Ihave looked forward with anticipation to putting the new Mathews LX compound through its paces having viewed all of the features that have been incorporated in this latest and greatest addition to the Mathews stable. After digesting the results of my testing, I can say without hesitation that I am impressed. This is a bow that successfully combines superior performance with exceptional shooting qualities. I will opt for sweet-shooting qualities over performance whenever confronted with the choice, but the LX doesn t demand a choice, it provides both. It s a bow made for the cake-eater who won t let go of the cake. Let s examine it in detail. The LX is built on a fully machined aluminum alloy handle with an overall length of inches. The handle is reflexed, with the pressure point of the grip set approximately inches behind a line through the limb pivot axes. The sight window has a usable length of 7 inches. It is cut 7 16 inch past the center of the handle and there is an additional clearance cut of 1 4 inch at the arrow pass. The centerline of the lower limb coincides with the centerline of the handle, while the centerline of the upper limb is offset about 1 4 inch toward the bow hand side. This is accomplished by incorporating the offset into the upper limb pocket rather than using the same limb pocket for both upper and lower limbs. The offset in effect moves the track of the idler wheel into the same plane as the track for the shooting string on the lower cam unit. The obvious advantage of this design is that the shooting string tracks straight in both grooves eliminating the angular condition usually found on most single cam compounds. The plane of the shooting string is parallel to the vertical centerline of the bow rather than at a slight angle to it. In addition, clearance at the arrow pass is increased by about half the amount of offset of the shooting string track of the cam, or about 3 32 inch on this bow. Combining all of these cutouts and offsets results in a total clearance of approximately inch from the theoretical plane of the string to the surface of the upper riser at the arrow pass. This is more than ample for fletching and broadheads. The LX incorporates the Mathews harmonic damping system in the extremities of the handle. This system consists of a cylindrical mass unit mounted in a spoked elastomeric doughnut set in a inch diameter hole through the handle area behind the limb pocket. Two sets of mass units are furnished with each bow; one set is brass for maximum damping action, and the second is aluminum for damping with minimum weight gain. An optional third set of carbide mass units is available. The carbide units are twice as heavy as the brass units and offer additional damping action. A new limb mounting system was introduced on the Mathews LX and Conquest 3 compounds for This system, called V-Lock, employs a precisely machined, V-shaped, aluminum alloy limb pocket that accepts a high-durometer elastomeric liner that surrounds the tapered butt of the limb. When the November 2003 by Norb Mullaney Mathews LX Continued on page 63 Bowhunting World 61

2 The Tests: Mathews LX The test bow was rated at 60 pounds peak draw force. I was provided with several interchangeable cams to offer considerable versatility to establish an interesting test format. After some deliberation I settled on three test setups that would allow comparing the effect of changing letoff from 65 to 80 percent (nominal) and also the effect of reducing draw length by 2 inches from 30 to 28 inches. This was made possible by using three dif- ferent cams; the 30-inch cam (SLHP-AAR) that has one draw stop position for nominal 65 percent letoff, the SLHP-AR cam that has two draw stop positions, 30 inches at 80 percent nominal letoff and 29.5 inches at 65-percent nominal letoff, plus the SLHP-C.5R cam that also has two draw stop positions, 28 inches at 65-percent nominal letoff and 28.5 inches at 80-percent nominal letoff. The task of changing cams on the LX is a simple matter with a bow press. It is necessary to unhook the string and cable from the cam, but each anchor peg is stamped with a C or S so that even if you don t do this very often replacing the rigging is easy. I installed a New Archery Products PlungerRest and set the lateral adjustment so that the longitudinal centerline of the arrow was aligned with the plane of the string at brace height. Static tests are conducted using a force-draw machine equipped with a Mark 10 digital force gauge capable of reading to the nearest 0.1 pound. Force readings are taken at 1-inch increments from brace height to just beyond the test draw length in order to define the valley and back wall of the force-draw curve. The force data thus obtained are plotted versus draw length to yield the force-draw curves shown in Figure 1. The area under the force draw curve is integrated by elemental summation and then converted to foot-pounds to obtain the energy that is stored when the bow is drawn from brace height to full draw. Other pertinent measurements are also taken with the bow at brace height and at full draw. Comparative data from the static tests is tabulated in the first nine lines of Table 1. All tests were run with the bow set at 60 pounds peak draw force. Energy Storing Efficiency (E.S.E.) is calculated on a base of the product of peak draw force and the length of the power stroke. The difference in brace height ( 1 8 inch) between the two setups tested at 30 inches draw length can probably be attributed to the fact that it was necessary to use two different cams to obtain the two values of letoff. The same situation existed for the two setups at 65 percent nominal letoff, however, the brace height remained unchanged. For all three test setups the bottom-of-the-valley occurred at 1 8 inch beyond the test draw length at holding weights ranging from 0.8 to 2.2 pounds less than those at the test draw length. The effect of this on realized letoff is minimal at nominal 65-percent letoff, but quite significant at nominal 80- percent letoff. The comparison is shown in the following tabulation: Figure 1 presents the force-draw curves for the three test conditions. Observe that all three cams provide essentially identical initial force build-up characteristics, peaking at or near 18 inches draw length. For the 28 inches draw length the dwell begins to slope almost immediately, easing into the letoff, while for 30 inches draw length and 80-percent nominal letoff the dwell at peak force is maintained for 5 inches before letoff begins. For nominal 65-percent letoff and 30 inches Continued on page Bowhunting World November 2003

3 Continued from page 61 limb butt is seated in the pocket, the fit is very snug. It is described by the manufacturer as a zero-tolerance fit. This design is possible because the limb butt seats solidly in the pocket which pivots on the end of the handle. The handle is quite long for a bow with a nominal axle-to-axle dimension of 36 inches. This is necessitated by the combination of short limbs and relatively large limb angles. Consistent with the long length, the stabilizer and accessory bushings are positioned over 2 inches below the lower edge of the grip section. The flanged brass bushings are mounted in a through-drilled hole slightly off-center in the lower riser. The plunger hole, tapped UNF, is located in-line with the pressure point of the grip, centered 1 inch above the surface of the shelf. The standard ATA (AMO) 2-hole sight-mounting pattern is located on the offside of the upper riser. The LX is equipped with the Roller Guard system for cable control that was introduced by Mathews in This system consists of a pair of sheaves mounted on ball bearings and set at an angular orientation at the end of a special bracket that is bolted to the upper riser. The riser is slotted to accept the end of the bracket so that the outer surface of the bracket is flush with the surface of the riser, thus eliminating any interference with a sight or another accessory mounted in this area. As I see it, having the end of the cable guard increased in size and terminated inside the bowstring offers significantly improved safety for a shooter who chooses the reverse release. From a functional standpoint, restraining the rearward movement of the cable and return stretch of the bowstring increases the draw force as compared to the normal arrangement where they move aft as the bow is drawn. In addition, the sliding action of the cable and string in the slider unit or on the guard rod is eliminated. Instead, it is replaced by a rolling action operating on anti-friction bearings. Cable and string wear is substantially reduced with this system. Permanently lubricated anti-friction bearings and the rolling action they provide avoid the chatter often present with a slider unit moving on a guard rod, and the problem of keeping the guard rod properly lubricated. The black walnut one-piece grip that is bonded to the grip section of the handle is offered in two shapes, classic and competition. The classic shape provides a higher contour under the heel of the hand. The competition grip is available in a number of exotic woods. The limbs for the LX are inches long with a width of inches throughout most of this length. The exception is the butt where the width tapers to create the V-Lock limb-mounting configuration. The construction is one-piece, machined from solid blanks of fiber-reinforced, epoxy matrix, composite. This is a simple and very tough unit. The same string-suppressing unit is used on both limb ends. This is accomplished by mounting them on opposite sides of the limb tips. The bracket is machined from lightweight metal alloy that is attached to the limb tip with two socket-head screws November 2003 Bowhunting World 63

4 that thread into the base of the bracket after passing through a metal reinforcing plate and the tip of the limb. The extending end of the bracket accepts a molded elastomeric damper that contacts the bowstring when it is at brace height. A new single cam design termed HP for High Performance has been introduced on the LX. In reality, this is a family of cams since Mathews does not use a modular system for draw length and letoff change. Primarily this cam series offers improved performance as compared to most other Mathews compound and cam arrangements, combined with very smooth and pleasant drawing and shooting characteristics. In fact, the manufacturer states that the HP SoloCam, considering brace height and draw weight being equal, is the fastest cam they have ever tested. The HP cam carries an oversized perimeter weight and features three tracks. It is fairly large in diameter with a running mate idler wheel that is inches in diameter. The various cam sizes provide for both 65 and 80 percent nominal letoff by employing a draw stop to arrest the draw prior to reaching the bottomof-the-valley, thus establishing a holding weight high enough to qualify for the reduced percent of letoff. I have used the term nominal in conjunction with the percent of letoff advisedly, because on the bow and cams that I tested, the letoff was somewhat less than 65 percent and significantly less than 80 percent when calculated at the standard draw weight of 30 inches ATA. There is more detail on this when I discuss the test results. In most instances an individual cam provides for two draw lengths about 1 2 inch apart. This difference in draw length and the resulting change in holding weight are used to offer the nominal 80-percent letoff at the longer draw length, and the Continued from page 62 draw length, there is a slight slope to the dwell amounting to about one pound before significant letoff is achieved. Considering the care that I used to optimize cam timing, I have to attribute this to slight differences between the SLHP-AAR and the SLHP-AR cam contours. It is really nothing to cause concern Comparative data from tests of the Mathews LX compound set to three different conditions. 64 Bowhunting World November 2003 nominal 65-percent letoff at the shorter draw length. Neither of these draw lengths will necessarily coincide with the bottom-of-the-valley. The draw stop, which is the key to this adjustment, is mounted on the bow-hand side of the cam, and the position for each setting is clearly marked. The draw stop consists of a piece of aluminum alloy tubing surrounded by a tubular rubber bumper. The assembly, which has a length of 1 2 inch, is bolted in either of two positions by a socket-head screw. Not all cams in the series have two draw stop locations. The draw stop rotates with the cam as the bow is drawn and bottoms against the string suppressor bracket to arrest the draw. The rubber bumper is sufficiently resilient so that it yields a bit after contacting the suppressor bracket thereby easing the initial reaction with the wall. I found this effect to be consistent with about 1 4 to 3 8 inch of draw stroke before an abrupt increase in draw force is obtained. The rigging for the LX consists of a 22-strand Zebra bowstring and a split-yoke cable that has the ends of the yoke anchored on split sheaves located on the outboard ends of the upper axle. The shooting string has a inch center serving, and both the cable and return stretch of the string are served in the area where they contact the cable guard rollers during the draw. The LX is available in draw weights of 40 to 70 pounds, with a 10-pound downward adjustment potential. Draw lengths offered are 25 to 30 inches with half-inch lengths from 25.5 to 29.5 inches. The bow can be had in any of four colors root beer, blueberry, kiwi and black cherry plus Realtree Xtra camo. because both cams deliver similar levels of stored energy. In my mind the case for limiting letoff to 65 percent is head-in the-sand posturing. With the widespread use of draw stops, where the holding weight is determined entirely by the shooter, the argument for such restriction is meaningless. Static hysteresis is a measure of friction in the system. It is obtained by subtracting the energy represented by the letdown curve from that represented by the force-draw curve. From tests of many bows, I have found that it usually ranges from about 5 to 12 percent of the stored energy. Unquestionably aided by the use of antifriction bearings in the cam and idler wheel, the LX is outstanding in this area with static hysteresis ranging from 4.64 to 5.12 percent of stored energy. The dynamic tests also reflect this superiority with recorded levels of dynamic efficiency the highest of any bow I have tested to date. Dynamic tests are conducted using a shooting machine and a double chronograph arrangement. The standard chronograph, a Custom Chronograph Model 1000, was positioned 3 feet down range from the back of the bow at the arrow pass. The checking chronograph, a Custom Chronograph SpeedTach in this instance, was located immediately adjacent (down range) to the standard unit. Seven test arrows, ranging in weight from 360 to 650 grains in approximate 50 grain increments, were each shot and chronographed a minimum of five times to establish a credible value of average initial velocity for the individual arrows. The arrow weights and velocities are used to calculate experimental values of virtual mass. A curve of virtual mass is determined by linear regression from the experimental values. This permits the calculation of initial arrow velocity and dynamic efficiency for any desired arrow weight. Including all of the energy losses in the system when determining virtual mass Tabulations of dynamic or bow efficiency and initial arrow velocity for a wide range of arrow weight for the three test conditions.

5 Force-draw curves depicting draw cycle characteristics for the LX for each of the test conditions. and 30 inches ATA draw length. ASTM standard F was created to detail and control the testing procedure necessary to determine the Rating Velocity. It establishes two different test arrow weights, 360 and 540 grains, because some bows that yield similar Rating Velocities with the 540-grain arrow demonstrate substantially different Rating Velocities when tested with the 360-grain arrow. In other words, some bows gain arrow velocity at a greater rate than other bows when arrow weight is reduced. The method for obtaining the Rating Velocity set forth in ASTM standard F uses the average of five shots of the specified arrows to establish the value. The method I have used for the Bow Reports involves 35 or more shots to establish a performance profile for the bow. The Rating Velocity is calculated from the velocity curve that is part of the profile. The results of the two methods seldom differ by as much as one foot per second. The Bow Report method actually includes the F procedure, hence it is possible to provide both values given in the following chart. These levels of Rating Velocity are particularly noteworthy considering the shooter-friendcauses the virtual mass value to vary with arrow weight. The greater the arrow weight, the higher is the value of virtual mass. Bow or dynamic efficiency is the initial kinetic energy of the arrow expressed as a percentage of the stored energy of the bow. In other words, it is the energy obtained (initial arrow kinetic energy or output) expressed as a percentage of the energy or work applied to draw the bow (stored energy or input). Kinetic energy is the energy the arrow possesses as of result of its mass and velocity. Table 2 presents values of bow or dynamic efficiency and initial arrow velocity for the LX for each of the original test conditions. Values are given in 25-grain increments of arrow weight for the wide range of arrow weight tested. It is important to note that even with arrows of quite low weight, the dynamic efficiency exceeded 80 percent. With the heavier arrows the dynamic efficiency topped 86 percent. This establishes a new level of excellence for this criterion among my test records. It is one reason why the LX performance presented in the second chart of Table 2 is exceptional. The curves of initial arrow velocity shown in Figure 2 were plotted from the data tabulated in Table 2. The Rating Velocity is a performance parameter developed by ATA (AMO) to permit standardized comparison of the performance of various bows. Simply stated, it is the initial velocity of an arrow of specific weight shot from a bow set at 60 pounds peak draw force November 2003 Bowhunting World 65

6 Curves of initial kinetic energy of the arrow plotted versus arrow weight. ly characteristics of the Mathews LX. Here is a compound that is a distinct pleasure to shoot, that delivers a level of performance heretofore found primarily on bows with very aggressive, even unpleasant, cams and low brace height. The kinetic energy carried by an arrow is related to the penetration potential of that arrow when it strikes a target medium. The actual penetration is a function of the target medium as well as the kinetic energy. Of course, the form characteristics of the specific arrow also affect the actual penetration. To properly evaluate the actual penetration effect as related to kinetic energy, the target medium must be consistent and the arrow must be identical. To recognize the effect of changing target medium, I use the term penetration potential rather than penetration because the target medium can be a highly variable factor and it can be eliminated by using the term penetration potential. The kinetic energy, which is a function of the mass of the arrow and its velocity, is the primary determinant that concerns us. The arrow is assumed constant in all cases. Figure 3 presents curves of initial kinetic energy plotted versus arrow weight. At all arrow weights tested, the difference in initial kinetic energy between nominal 65- and 80- percent letoff is no more than one foot-pound. A two-inch reduction in draw length costs about 8.5 foot-pounds of kinetic energy. General Commentary At 30 inches draw length the included string angle measured between and 78 degrees. Reducing the draw length to 28 inches increased the included string angle to 83 degrees. I experienced no problem with finger pinch using finger release. With the fixed position of the cable guard rollers the cable clearance is predetermined by design. I measured it at inch from the inside edge of a 5 16-inch diameter shaft, nocked and set in the plane of the string, to the nearest cable at the level of the arrow pass. If I were to purchase an LX and desire maximum letoff, I would select a cam corresponding to a draw length (in the maximum setting) about a half-inch shorter than my desired draw length so that I could obtain my draw length at the bottom-of-the-valley. Then I would use a smaller diameter draw stop in the maximum draw length position specifically sized and/or shimmed to stop the draw at that point. There are many options available to achieve this end. In my opinion the Mathews LX is one of the outstanding bows presently available to the archery community. It combines performance and shootability in a manner that we do not often see. 66 Bowhunting World November 2003