Articles

The JRX-S Story

Posted:  Thursday, April 07, 2005
Written By:  Todd Hodge, Team Losi
Copyright:© 2005 Horizon Hobby, Inc.
Todd Hodge's JRX-S.

Gil Losi Jr. and the Team Losi development team are noted for thinking outside the box, and indeed that's just what they've done with the revolutionary design of the JRX-S. The JRX-S is the first Touring Car with all the weight centered in a car with short arm suspension. The motor, battery and servo are all located along the centerline of the chassis, which gives the car a more positive feel and reaction to direction changes. Simply put, it handles quicker without losing the feeling of complete control, making it easier to drive faster than any other touring car. This arrangement also gives the car a perfect 50/50 weight distribution to both the front and rear tires for unequalled "balance," the number one priority of racecar drivers in virtually every form of motor sports. 

Putting the Power to the Ground

Gil Losi, Jr. tweaks a JRX-S.

One of Gil Losi Jr.'s crowning achievements for the JRX-S is the design of the LCD (Losi Constant Drive, Pat. Pend.). When using a front spool (locked front axle), the drive shafts used on virtually all other models on the market create power robbing harmonics and drivetrain chatter that adversely affect performance and handling. With the new LCD design that chatter is eliminated, resulting in more steering response, smoother transfer of power and greater corner speed. The LCD is also rebuildable like most other drives.

One Car, Two Drive Options

The JRX-S includes both a spool and a one-way drive for the center shaft/drive. The center spool increases 4-wheel braking and creates a smoother transition into the turns, while the center one-way allows the car to have more steering into the turn. The center one-way only allows rear-wheel braking, which decreases total braking but allows more steering control during braking. Also attached to the center drive shaft is a 128-tooth, 64-pitch spur gear that is easily changed within seconds if needed.

Shock-ing New Design

In order to take full advantage of the incredible balance and feel of the JRX-S, Team Losi also stepped up to the plate and designed all new shocks and springs. The new shocks are volume compensated shocks featuring molded bladders. These molded bladders prevent air from entering the oil-filled chamber and compensate for volume displacement as the piston moves in the cylinder. Additionally, the pistons are secured to the titanium nitride shafts with a button head screw to prevent any unwanted movement. A complete range of shock springs, pistons, and the use of single or double O-rings give the racer a wide variety of shock tuning options.

Pinned to the Road

A computer rendering of the JRX-S prototype.

Another new standard set by Team Losi is the use of pinned chassis components. The chassis components feature pins that fit into similar-sized holes in the chassis, securely positioning them to prevent the assembly from tweaking or twisting, particularly in impacts. This vitally important feature is crucial with graphite plate chassis and is yet another reason the JRX-S gives the driver an exceptional feeling of control and stability.

Adjustable for Any Surface

Yet another revolutionary feature is the adjustable diff height. The front and rear diff can either be raised or lowered .150" via the diff acentric. This is advantageous when you race on dramatically different surfaces like asphalt and carpet. By running the diff in the high position, you add traction to the JRX-S, which is desirable for running outdoors on paved surfaces. By running the diff in the lower position you experience less dramatic weight transfer and free up the car in the turns, which is necessary for racing on carpet and extremely high traction surfaces. This "best of both worlds" option is not currently available on any other touring car on the market. The diff acentric also allows the racer to adjust the front and rear belts in ten different tension positions for the ultimate balance of efficiency and power-handling performance.

Additionally, the roll center of the JRX-S is adjustable. The pivot blocks and shock towers are easily adjusted, allowing the roll center to be adjusted to the extremes needed for both indoor and outdoor racing surfaces. Changing from a high roll center to a lower roll center is easily achieved by simply flipping the pivots 180 degrees. The JRX-S also comes with shims to adjust the roll centers even more by placing them between the pivots and the chassis.

Improved Efficiency for More Power

The final product.

Lastly, the ultra efficient drive train uses no power-robbing idlers or belt tensioners. The JRX-S also has the largest pulleys on the touring car market. The method of creating efficiency in a belt drive car is simple-the less you bend the belt around a given circumference, the more efficient the drive train will be. The larger 42-tooth pulleys on the JRX-S let the belt enter and exit at a lesser angle, reducing friction and increasing efficiency. The result is outstanding acceleration with remarkable run time and efficiency.

The JRX-S is a revolutionary design that has already proven itself in the toughest indoor and outdoor competition. The unique design, unmatched adjustability, and superb handling characteristics make it easy to drive fast …… really fast! There is no doubt that JRX-S drivers will be found at the top of the podium in all levels of competition in the future.

Track Tested, Race Proven

Matt Francis' JRX-S at the 2004 IFMAR.

The first JRX-S prototype hit the racetrack as a XXX-S with shortened arms to test the short arm technology in mid-2003. The short arm suspension was the only way to get around the drive train and centered mass. With this new design, the car showed faster lap times with greater corner speed on both carpet and asphalt tracks. This encouraged the Team Losi development team to move onto building the first prototype JRX-S. The short arm XXX-S actually showed incredibly fast lap times at the 2003 U.S. Indoor Champs warm-up, but the secret could not be let loose so soon. One year later, a pre-production car was shown to the R/C public at the 2004 IFMAR World Championships in Kissimmee, Florida, in its first major competition. There were two JRX-S cars in the A-Main, finishing 7th and 10th. A few months later a pre-production JRX-S Top Qualified at the 2004 U.S. Indoor Champs in the modified Touring Car class that also saw as many JRX-S drivers (5) as all other manufacturers combined in the A-Main. The 2005 racing season started with Brian Kinwald winning in the 19T class at the prestigious Novak Touring Car Championships in Brookfield, Wisconsin.


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