Kyosho Inferno TR 15
Big-buggy tech in a smaller package
Everybody wants an 1/8-scale, nitro-powered buggy. Even the most casual hobbyist knows that the big buggies mean business. Unfortunately, the whine of a free– breathing .21 engine and the space required to open one up can limit the real estate available for full-on 1/8-scale off-road action. Cost is a factor, too, no -%-scale buggy is what you would call cheap. Kyosho hopes to make the %-scale thrill factor accessible to more people by shrinking big-buggy tech down to Vio scale with the Inferno TR 15. The baby Inferno gets its name from the five-time IFMAR World Champion Inferno series, so Kyosho definitely has cred here. Let’s see if the little buggy makes big fun.
VEHICLE TYPE 4WD, .15-powered off-road buggy
BEST BUYER RC enthusiasts looking for 1/8- scale-style action on a low budget, all fun-oriented nitro fans KIT RATINGS (poor, satisfactory, good, very good, excellent) Instructions Very good
Parts fit/finish Very good Durability Very good
Overall performance Very good SPECIFICATIONS MODEL Inferno TR 15 MANUFACTURER Kyosho DISTRIBUTED BY Great Planes SCALE /o
STREET PRICE $269.99 DIMENSIONS
Wheelbase 10.8 in. (275mm) Width 9.5 in (241mm) WEIGHT Total, as tested 62.4 oz. (1,768g) CHASSIS Type Plate
Material 2mm stamped aluminum DRIVE TRAIN Type Shaft-driven 4WD Transmission ratio 3.36:1 Clutch-bell/spur-gear ratio 15/39 Drive shafts Dogbones Differentials Bevel gear
Bearing type Metal bushing SUSPENSION Type F/R Upper and lower wishbone/lower wishbone and camber link
Shocks Plastic-body, fluid-damped WHEELS
Type One-piece plastic 2.2-in. TIRES
Type Kyosho H-pin ENGINE AND ACCESSORIES Engine Kyosho GS15R Carburetor Rotary, single-needle Clutch 2-shoe centrifugal
Exhaust system Cast manifold and pipe
Fuel tank capacity 75cc LIKES Most of the fun of an le-scale buggy with less noise, cost and hassle. Reliable, easy-to-start engine. Enclosed radio box protects receiver. DISLIKES Weak servo-saver numbs steering response.
Doesn’t handle rough terrain well. No ball bearings or low-end carburetor adjustment. building & setup tips The Inferno TR 15 is an easy build that is speeded up by Kyosho’s partial assembly. Right out of the box, the drive train is assembled and installed on the chassis, and the parts spin smoothly on metal bushings. If you prefer to Install bearings, you’ll have to pull the drive train apart before continuing with the assembly Thankfully, the instruction manual includes all the steps required to build the kit from the ground up. Here are some tips I found helpful as I built my baby Inferno: Yes, I’m going to mention thread– lock. I know we tell you to use the stuff every time, but that just goes to show how Important it Is. In the case of the TR 15, you absolutely must apply medium-strength thread– lock to the grub screws that hold the outdrives, engine, clutch, bellcrank and pivot-ball screws. If you don’t, prepare to sift through the dirt to find the hardware that falls off your car during its first couple of runs. Increase the brake-pad spacing. The brake pads seemed properly set for the rotor from the factory, but when dirt got into the works, the brake began to drag. I backed out the screws on which the pads float, and that allowed dirt to fall away from the rotor after braking. A half turn of each screw was all It took. Don’t scratch the shafts! The thick aluminum rods that form the front upper arms are the kit’s prettiest pieces, and you’ll be bummed If you hack them up by holding them with a pair of pliers as you thread the rod ends onto them. Since the rods aren’t turnbuckles, you can easily thread the plastic parts onto them without touching the aluminum shaft with tools at all. Just thread the appropriate parts onto each rod by hand for the first couple of turns, then pass a wrench shaft through the molded parts to hold one end while you turn the other. Jack up the servos. The Included servo mounts hold the bottoms of the servos flat against the chassis, and that transmits chassis vibration directly to the servos. If the servos you choose to Install touch the chassis, place a washer between the servo mounts and the chassis to gain a little extra clearance. Add foam tire inserts. Kyosho doesn’t include foam inserts with the TR 15, but any foam inserts from a set of 2.2-Inch buggy tires will work. You’ll have to trim the fronts to fit the narrower front rims. If you’re really cheap, you can make your own strip-type Inserts from scraps of upholstery foam snagged from an upholstery shop.
Tighten those wheels! The friction-fit drive hexes require a good, hard crank on the axle nuts if they’re to stay put– and even then, it’s wise to cinch them up every run. Be especially wary of the right rear wheel; I spun it off the car twice. KIT FEATURES a Chassis. Like so many other 1/io-scale nitro– powered cars, the TR 15 is built on a chassis constructed of stamped 2mm aluminum. In this case, the underside is countersunk for all fasteners except the engine-mounting screws and a pair of screws for the steering and throttle servos (each has one slotted hole to accommodate servos of different sizes, and the slotted holes take button-head screws). The chassis’ radiused sides are much broader than those of most similar designs, and that helps maintain overall stiffness (despite an absence of significant upper bracing), and broad plastic mudguards are attached to the chassis’ sides. The sides’ radius is responsible for most of the chassis’ stiffness, but there is some additional bracing up top: a steel rod links the rear bulkhead to the center spur-gear mount, and a pair of plastic straps bridge the steering bellcrank posts and front bulkheads. Still, it’s easy to flex the front half of the chassis (as tested by the two-handed accordion-squeeze method). Whether that flex will show up to any ill effect on the track is another story. e Drive train. Like the IA-scale Inferno that inspired it (not to mention every other 1-scale buggy I can think of), the TR 15 has full-time, shaft-driven 4WD. Unlike the big buggies, the TR 15 does not employ a center differential; instead, the 39T spur gear is keyed directly to a pair of outdrives to accept front and rear dogbone drive shafts that send their spin into sealed front and rear gearboxes. The gearboxes are identical and house matching gear differentials that are driven via a cast-in ring gear and cast bevel pinion gear. If the gearboxes look familiar, it’s because you’ve seen them on the Kyosho’s QRC reverse-transmission nitro cars and the current SuperTen chassis. The parts are put to good use here and have the welcome feature of access holes for the diff outdrives’ critical grub screws. Dogbones get power from the diffs to the wheels at both ends of the car, and everything works smoothly. I was disappointed to find that the TR 15 uses metal bushings on all the rotating parts. At the very least, I’d prefer ball bearings on the diff outdrives, pinions and spur gear especially since Kyosho assembles the TR 15’s drive train for you, so you have to disassemble it if you wish to install bearings.
Since there isn’t a center diff, the dual-disc brakes of a three-diff car are not required, and the TR 15 uses a single disc instead. The rotor is molded of high-fiber plastic, and the caliper is a pair of plain steel pads. It’s a basic setup that should work well enough. The final drive-system components are the friction-fit drive hexes, which seem to be made of a harder alloy than the hexes of the other Kyosho vehicles that use the system. I hope they stay put instead of being pulled off with the wheels, as friction-fit hexes sometimes do. s Suspension/steering. The TR 15 takes an unusual technological turn in the suspension department. Both ends are equipped with unbraced lower arms that are attached to the chassis by 6mm pivot balls-one for each “leg” of each suspension arm (just look at the pictures, if the anatomy analogy is making your head throb). Screw pins pass through the outboard ends of the rear arms to capture the rear hubs in the usual way, but the front suspension makes use of pivot balls for the steering hubs, so there’s no need for hub carriers, but you do need a triangulated upper arm, since there is no hinge pin to hold a hub carrier perpendicular to the suspension arm. Although molded arms would suffice, Kyosho’s solution is an assembly of robust aluminum rods and molded eyelets that make a pleasingly high-tech-looking front end. And if you’re in the mood for wrenching, the setup permits caster and camber adjustments. Similarly robust (but otherwise entirely conventional) aluminum camber links hold the rear hub carriers in check. For you Kyosho completists out there, the front and rear hubs also appear on Kyosho’s F-Ten chassis. Of course, all the aforementioned suspension stuff is useless without a set of shocks. The plastic-body “sport” shocks include factory-installed seals and polished aluminum caps with molded eyelets. Unusual but welcome features are the stepped preload adjusters, which allow one of six settings to be selected without tools or additional parts. The shock’s pistons are also unusual in that they are metal, permanently attached to the shock shafts and have flats cut in the piston disc instead of holes. The front and rear shocks are identical, wear matching springs, but seem short for off-road duty even when fully extended. But thanks to the shocks’ deeply laid-down position-so low that the shocks don’t even require shock towers and instead bolt directly to the front bulkheads-the TR 15 still has adequate suspension travel.
The TR 15 is pointed in the right direction by a pair of bellcranks that are joined to the steering hubs with threaded rods. A nonadjustable servo-saver is built into the left bellcrank, and its plastic spring is very soft; if you still manage to break a servo with this servo-saver, you must be some kind of super-hack. A wire linkage joins the bellcranks to the steering servo and is attached to the servo with a Z-bend. It works, but watch for slop in the servo arm. Engine and accessories. As you may have guessed from the “TR 15” designation, the little Inferno is powered by a Kyosho .15 engine-a GS15R, to be exact. It has a pull-starter, single-needle rotary carburetor, machined heat-sink head, snorkel-type air filter, dual crank bearings, machined connecting rod and nickel-plated sleeve. The IST metal clutch bell spins on a plastic-caged roller bearing and hides a 2-shoe dutch mechanism. Like other Kyosho engines, the GS15R is bolted directly onto the chassis without engine mounts; the screws are tapped into the crankcase. A tuned– style pipe is also part of the package. It’s a cast affair that’s clamped together with a pair of screws and features a deep convergence cone. The manifold is also a multi-piece casting and is joined to the pipe with a molded coupler.
A primer-equipped, flip-top, 75cc fuel tank feeds the engine and is mounted directly on the chassis without O-rings or any other means of damping chassis vibration. Will it matter? We’ll see at the track. s Body, wheels and tires. The TR 15 wears a downsized body that looks a little cartoony compared with an 1/-scale Inferno, but it’s about as svelte as it can be and still cover the chassis fully. The Motion Graphics paint job makes the most of the body’s chunky shape and, if nothing else, the TR 15 looks unique. Kyosho supplies a molded dual-plane wing with large side dams, and firm knobby tires cover the attractive mesh-pattern wheels. I like the black-on-black look of the wheels and tires, but I wish Kyosho included foam inserts for them. The round-carcass tires are easily deformed without inserts.
PERFORMANCE After the usual break-in procedure, I opened up the TR 15 on pavement to see what it could do. The single-needle carb didn’t allow fine-tuning for crisp, low-end throttle response, but once the GS15R engine was revved up, it ran strongly, with good mid- to high-rpm throttle feel. Satisfied with the carb settings, I moved to the dirt where the TR 15 is meant to play. The short, laydown shocks aren’t well suited to truly rough ground, and the little Inferno was tossed around easily by backyard-type terrain (but to its credit, it never flipped). Smoother surfaces, such as fire roads, baseball diamonds, BMX tracks and (of course) RC tracks are where the TR 15 performs best and is the most fun-that’s where I certainly had the best time. The Inferno doesn’t feel as planted as a heavy, “full-size” 1/18-scale buggy, but otherwise it drives much the same. You can drift through corners wide open, or brake to square off your line and get back on the gas with all four tires hooked up. Jumping rollers was easy and fun thanks to the midair control offered by four powered wheels, and backside landings were as smooth as shock fluid spilled on Teflon. The TR 15 also proved to be a tough customer when I cased some jumps and landed the Inferno on its nose, tail, side and various combinations thereof. The only trouble I had with the car was a loose drive hex, which required a dab of thread-lock to stay put.
THE VERDICT As a vehicle without a race class, the best way to measure the success of the Inferno TR 15 is to simply ask, “How much fun is this thing?” The answer: a lot. Though not well suited to the anything-goes type of terrain most play vehicles are pounded on, the little Inferno is probably the most exciting I/lo-scale, off-road nitro vehicle for track-style surfaces. For that type of play, I’d pick the TR 15 over a nitro truck or any other 2WD vehicle. I would make a few changes, though; I think a bearing set is a must, and foam inserts bring out the tires’ best. But even completely stock, the TR 15 a successful fun-run entry that we hope will garner a following-and then we’ll see if it’s still a vehicle without a race class. SOURCE GUIDE DURATRAX
Great Planes Model Distributors FUTABA
Great Planes Model Distributors www.futaba-rc.com. KYOSHO
Great Planes Model Distributors GREAT PLANES MODEL DISTRIBUTORS
2904 Research Rd., P.O. Box 9021, Champaign, IL 61826-9021; (800) 682-8948 KO PROPO USA INC.
16012 South Western Ave., Ste.
308, Gardena, CA 90247; (310) 532-9355; email@example.com; www.kopropo.co.uk MOTION GRAPHICS
2645 Robert Arthur Rd., Westminster, MD 21158; (410) 848-0008;
www.motiongraphicsweb.com TRINITY PRODUCTS INC. 36 Meridian Rd., Edison, NJ
08820; (732) 635-1600; www.teamtrinity.com
Copyright Air Age Publishing Apr 2001
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