When SWorkz’ engineersset out to update their 1/10-scale 4WD buggy platform, they brought two-time IFMAR world champion Atsushi Hara onto the design team. The result is the S104, a design that adopts a lot of its cues from the S350 Evo2 Pro 1/8-scale buggy, including fully adjustable pivot-ball suspension and a shaft-drive system with three oil-filled gear differentials. Built on a solid-aluminum plate chassis with a carbon-fiber upper deck, which can be configured for a shorty or saddle battery pack, the S104 Evo also sports a floating servo mount that connects to a dual bellcrank steering system for ultimate control. Finished off with aluminum 14mm hex hubs that look like mini 1/8-scale ones, the S104 Evo begs you drive it fast around a track. Let’s get the S104 built and see what it can do.

1/8-SCALE INSPIRED DRIVETRAIN

The S104’s three-diff drive-train features a clamp-and-cam motor mount for easy gear mesh setting, and long steel universal center shafts are used to connect the center diff to the front and rear differential housings. Normally on cars like this, you’ll find a bevel gear with a shaft to which a drive cup is attached, but on the S104, the bevel gear and drive cup are one piece, which eliminates weight and reduces the risk of part failure. The pin that keeps the universal together is held in place by the bearings in the differential housing. Steel straight-cut bevel gears spin the front and rear gear differentials, which are sealed for tuning via changes to oil viscosity. Steel universal driveshafts run from the front and rear differentials to the hubs. The final connection to the wheels is made with 14mm hex hubs rather than the usual 12mm size. This makes for a strong setup, but because it’s a nonstandard design, wheel choice is limited.

The rotating-cam motor-mount system allows you to easily achieve proper gear mesh.

The center driveshafts’ bevel pinions are integrated into the universal joints to improve durability and reliability.

PIVOT BALL AND H-ARM SUSPENSION The most obvious suspension design cue the S104 Evo takes from its 1/8-scale big brother is the front pivot-ball suspension. This allows you to quickly and easily adjust front width and camber with a hex wrench. Caster can be adjusted by moving spacers around on the upper arm mount, and inserts are used to adjust roll center. The rear suspension uses the standard lower H-arm with adjustable upper-link setup. All of the lower hingepin mounts are made out of aluminum, and molded plastic inserts allow you to make fine adjustments to toe-in, arm kick-up, and anti-squat. A full set of 12mm bore shocks handle the damping duties, and threaded bodies allow for precise ride-height adjustment. The lower spring retainers feature molded-in guards that keep dirt from spraying on the shock shafts, and in the end, this will extend the life of the shock shafts and O-rings. The top of the shocks are mounted to thick lightweight carbon-fiber shock towers that help lower the center of gravity of the buggy and provide several mounting options. Thick carbon-fiber shock towers are used on both ends of the S104, which offer various mounting holes for the shocks and camber links in the rear and for various inserts for the upper control arms in the front.

The front pivot-ball suspension on the S104 offers a lot of adjustment. Width, camber, caster, and roll-center positions can be adjusted easily and quickly. Right - The 12mm bore shocks use dust shields that are incorporated into the lower spring retainer to keep the shock shafts clean even in the nastiest conditions.

ALUMINUM AND CARBON-FIBER CHASSIS The S104 Evo uses a stamped-aluminum chassis plate that has slight kick-up in the front. Raised sides increase stiffness, while various slots reduce the overall weight of the plate. Normally we see molded plastic side guards mounted to the chassis to keep debris out while on track, but the S104 comes with Lexan guards that help reduce weight and overall cost. They come clear, so you can give them a coat of paint or leave them be, and they are molded to fit the shape of the body perfectly. A two-piece carbon-fiber upper deck joins the front and rear ends of the car together at the aluminum center bulkhead to increase chassis stiffness. The design of the chassis allows the use of shorty and saddle-type battery packs, but the electronics need to be reconfigured to accommodate each setup. Carbon-fiber plates on the chassis plate keep the batteries from moving around, while carbon-fiber straps and thumbscrews keep them tight to the chassis. Molded plastic plates are included to mount the speed control and receiver, and rubber O-rings add a little cushion to the mount. Multiple holes in the chassis allow for easy repositioning of the electronic components.

The chassis can be built to accept shorty or saddle-type battery packs, and carbon-fiber plates on the chassis keep them from sliding around.

Without a size reference, it’s easy to mistake the S104 for an 1/8-scale buggy.

BEHIND THE WHEEL

My initial testing took me to SDRC Raceway in Miramar, California. Before I hit the track, I broke in the Pro-Line Electrons tires by spinning them on a drill and scrubbing them with sandpaper. Once the tires were mounted back on the buggy, I set its ride height at 24mm front and rear. On the track, I quickly discovered the 24mm ride height that works well on a 2WD buggy was too high for the S104. This made the buggy feel on edge in high-speed turns. I reset the ride height to 20mm, and with the car lowered, I hit the track again and the S104 felt a lot better. The SDRC layout was full of features that would really push the S104 and put it through its paces, including various size and style jumps; the S104 handled them all like a seasoned pro. The buggy jumped straight and level upon takeoff, and bringing the nose up or down was easily achieved with some input from the throttle or brakes. The 12mm big-bore shocks did a great job giving the S104 plush landings after getting some serious airtime. Coming out of turns, the S104 clawed at the clay surface to give it explosive but controllable acceleration coming out of turns. Going into turns, the box stock setup showed an excessive amount of steering that caused the rear end of the car to step out of the racing line. The free-spinning shaft drivetrain allowed the S104 to carry fast corner speed mid-corner off power that contributed to keeping lap times competitively fast. I wanted to tune down S104’s aggressive turn-in, so I went ahead and moved the front shocks out one hole on the tower and I swapped out the 5,000-weight diff oil in the front differential and put in 10,000 weight. Back on the track, initial turn-in was definitely less than before but still enough to get the S104 around the sharpest turns on the track with very little understeer. With a handful of runs under the S104’s belt, I was ready for my first race. After putting in a few packs’ worth of run time on the car, I noticed the ride height had lowered due to the shock springs breaking in. With a couple of turns of the shock collars, I raised the ride height to where it was before. With my test session in the books, I had more than enough confidence to run the S104 Evo in race conditions.

The S104 Evo felt right at home running on SDRC Raceway’s challenging layout and was able to effortlessly turn fast laps.

FINAL WORD

The S104 Evo has design roots that stem from 1/8-scale vehicles, and if you already race 1/8 scale, you’ll find transitioning to this buggy will be easy. From the first battery pack I ran on the S104, the handling has been consistent lap after lap, making this buggy easy to drive around the track fast. SWorkz definitely hit the mark when it aimed to design a high-performance 1/10-scale 4WD buggy with exceptional track manners right out of the box. If you’re sifting through the ultra-competitive field of 4WD buggies deciding which to buy, the SWorkz S104 Evo deserves a long look.

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VEHICLE SPECS Item no.: SWX-910021 Scale: 1/10 Price: $440 Weight, as tested: 4 lb. 3 oz. (1832g) CHASSIS Material: Hard-anodized aluminum Type: Plate with Lexan side guards SUSPENSION Type (F/R): Pivot ball/H-arm with upper camber link Inboard camber-link positions (F/R): 2/6 Outboard upper arm positions (F/R): 1/3 Shock positions, towers (F/R): 3/4 Shock positions, arms (F/R): 2/2 SHOCKS Bodies: Threaded aluminum, 12 mm bore Shafts: Coated steel, 3mm Volume compensation: Emulsion DRIVETRAIN Type: 4WD shaft Spur gear/pinion: 87T/19-tooth Differentials: Sealed bevel gear Driveshafts: Steel CV-style Bearings: Metal-shielded sealed ball WHEELS & TIRES Wheels: One-piece plastic dish, 14mm hex Tires: Not included + Lots of steering + Rigid chassis + Bulletproof drivetrain - A bit heavy compared to other cars in the class - 14mm hexes reduce wheel choice

TEST GEAR (NOT INCLUDED) Radio: Hitec Lynx 4S Receiver: Hitec Axion 2 HHR Speed control: Tekin RSX Motor: Tekin Gen3 6.5-turn brushless Servo: ProTek 160T Low Profile Battery: ProTek 4250mAh 2S 100C 7.4volt Shorty Tires: Pro-Line Electrons, clay compound Charger: Hitec X1 Pro DC/DC Multi-Charger/ Hitec ePowerBox 17-amp Power Supply SOURCES Paint job: C-Built Designs cbuiltdesigns.com Hitec hitecrcd.com ProTek amainhobbies.com Pro-Line prolineracing.com SWorkz amain.com Tekin teamtekin.com

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TEST GEAR Tekin Gen3 6.5-turn Motor The SWorkz S104 Evo was build to handle lots of speed, and I used a Tekin RSX speed control and Gen3 6.5-turn sensored brushless motor to get it there. The motor was shipped with 20 degrees of timing set on the end bell, and it easily helped the heavy S104 achieve warp speed on the track. The gearing I installed gave a perfect mix of low-end torque off the line with exceptional fast speeds on the straights. The motor can is vented more than most, which reduces its weight and provides a lot of airflow to keep it cool.