Mini 4WD Chochin vs Hikuo Guide
"Chochin" (提灯, Japanese for lantern) and "hikuo" are not two competing systems — hikuo is a lower-mounted development of the same idea. Both are mass-damper rigs built around an arm that runs from the rear stay or bumper, over or beside the body, carrying a freely moving weight. The arm strikes the chassis on landing, then the mass damper itself swings or slides, giving the car two staggered damping events instead of one. The difference is where that second event happens: a classic chochin holds its damper high, above or well clear of the body; a hikuo tucks the same mechanism down close to the body's side or top, trading some arm throw for a lower centre of gravity. Neither is a shortcut to more top speed — both exist to stop a 3D-course landing from launching the car back into the air.
What each term actually describes
A mass damper on its own is a small weight held by a screw that is free to move a short distance. Tamiya sells purpose-made mass damper sets, and builders also cut arms from an HG Mini 4WD Catcher sheet or shape FRP plate to extend the damper's reach away from the chassis. "Chochin" is the general term for hanging a mass damper from such an arm off the rear stay or bumper — the arm and weight swing independently of the chassis in flight, then compress on landing. "Body chochin" is a related variant that lets the whole body shell float and re-settle instead of moving a separate arm. "Hikuo" keeps the same rear-stay-to-arm-to-damper chain but re-routes the arm so the mass damper sits low, near the body's side or top surface, instead of held high above it — the same two-stage strike-then-swing action, repackaged into a lower envelope.
Chochin vs hikuo at a glance
| Trait | Chochin (classic lantern) | Hikuo (low-mount) |
|---|---|---|
| Mass damper position | High above or well clear of the body | Low, tucked against the body's side or top |
| Arm origin | Rear stay or bumper, extending up and out | Rear stay, extending low over or beside the body |
| Effect on centre of gravity | Raises it slightly, since the weight sits high | Keeps it lower than a tall chochin for the same damping action |
| Damping stages | Arm/catcher-sheet flex, then damper swing | Same two stages, compressed into a shorter, lower throw |
| Typical build material | Cut HG Catcher sheet or FRP plate + mass damper set | Similar materials, shaped and mounted for a low profile — some builds reuse Super X/XX-family FRP rear roller stays and FRP multi-reinforcing plates for the base |
| Where it's common | Long-established default on jump-heavy 3D courses | A refinement widely used alongside chochin on current 3D-focused builds |
Why the height matters: rules context
Both mechanisms have to fit inside what Tamiya's official race regulations allow: under 105mm wide, under 70mm tall and under 165mm long, with at least 1mm ground clearance and a minimum 90g all-up weight including motor and batteries. A tall chochin arm sits closer to that 70mm ceiling than a low hikuo does, so measure the car at rest and again with the arm compressed before assuming it clears. On mass damper placement specifically, the current regulations state that installation positions are no longer restricted, which is what lets both the high chochin and the low hikuo layout exist side by side in Open Class racing. Stock Class is stricter: per the official Stock Class rules, additional parts are limited to Tamiya Mini 4WD, R/C Mini 4WD and Dangun Racer parts, chassis cutting and new screw holes are not allowed, and mass damper holes cannot be widened beyond their original size. A scratch-cut catcher-sheet arm or reshaped FRP base is generally an Open Class technique — check R1 and R2 against your parts list, and remember organiser rules and on-day technical inspection have the final word over any article, including this one.
Building and mounting basics
Both rigs share the same mounting logic. The arm's fixed end anchors to the rear stay or bumper with a screw or a pair of screws — spring-loaded screws or a small hinge let it pivot rather than bind. The free end carries the mass damper, usually threaded onto a long screw so it can slide, or hung from a loop so it can swing. For a chochin, that free end runs high, often bridging most of the car's length so the weight sits well clear of the body in flight. For a hikuo, the same free end is shaped and mounted to keep the damper low and close to the body instead — many hikuo builds reuse rear FRP roller-stay and FRP multi-reinforcing-plate combinations already on the car rather than adding a tall separate tower. Whichever you build, start with the arm loose enough to move freely with no binding against the body or wheels, then add or reposition mass only after confirming it travels cleanly through a full compression cycle by hand.
Choosing between them
Pick chochin first if you're building your first mass-damper rig — the geometry is easier to see and adjust, and a tall arm gives more travel to tune before touching the mass itself. Move to hikuo once your chassis, stays and roller geometry are already settled and you specifically need a lower centre of gravity — heavy 3D sections with banked turns after a landing reward the lower mass position more than raw arm travel does. Either way, treat the damper mass as the last variable, not the first: get the arm's pivot and travel right, referring to a dedicated mass damper guide for weight selection, before adding more grams.
Frequently asked questions
Is hikuo faster than chochin?
Not inherently. Both use the same strike-then-swing principle; hikuo just repositions the mass lower for centre-of-gravity reasons. Lap time comes from motor, gearing and tyre choice — see the motor and gear ratio matching guide — with the damper rig deciding whether the car stays on track after a jump, not how fast it accelerates.
Can I run either one in Stock Class?
Only within Stock Class's own limits: parts restricted to Tamiya Mini 4WD/R/C Mini 4WD/Dangun Racer items, no chassis cutting, no new screw holes, and mass damper holes that can't be widened. Read R2's full FAQ and the official rules and technical inspection checklist before building a scratch arm for a Stock Class car.
My chochin arm keeps hitting the wheels or body — what's wrong?
Almost always geometry, not weight. Recheck the pivot point on the rear stay, shorten or reshape the arm so it clears the tyres through a full compression stroke, and confirm the car still sits under the regulation height limit compressed, not just at rest.