How to Shim a Gel Blaster Gearbox
Shimming a gel blaster V2 gearbox means controlling how far each gear can slide along its shaft — that leftover movement is axial play — so the teeth mesh without binding. It is not a 0.1 mm recipe you copy onto every shell. Bushing height, hub width, shell thickness and bushes versus bearings all change the stack. This page teaches what you are feeling for and when to use a technician. It is not a clearance that “fits every V2,” and not a reason to open a box that already runs quietly on stock nylon.
What axial play is, and why it matters
Each gear sits on a metal post between the two gearbox halves. When the shell is closed, it should not rattle end-to-end like a washer on a loose bolt, and it should not be clamped so hard that it cannot turn. That leftover slide is axial play. Too much and the gear walks under load: mesh walks, teeth chatter, and nylon — later metal — wears along one edge. Too little and the faces drag on the bushing or bearing. Drag is heat, extra current, and a box that cooks in Malaysian weather after a short string. Axial play is not mesh depth (how deeply teeth engage) and not motor-pinion height. People who “add 0.1 mm on both sides of every gear” skip those distinctions and often bind one gear while leaving another sloppy.
If you cannot yet name bevel, spur and sector, or where the anti-reversal latch sits, read the gearbox diagram and internal parts pages first. Shimming is alignment work on parts you already understand.
Why a generic 0.1 mm recipe is wrong
A 0.1 mm shim is a piece of metal, not a specification. Bushing height, hub width, a proud shell half after a crack repair, and bearings versus bushes all change the stack. Mix a 0.1 mm washer from kit A with “just use two on the bevel” from brand B and you invent a bind that was in neither tutorial. The correct question is not “how many 0.1s.” It is: on this post in this closed shell, is there a hint of end-float, and does the gear still spin without grinding the next one? Answer that per gear. Also check that the sector still releases the piston and the anti-reversal still catches the bevel. A stack that quiets the spur but lifts the bevel off the latch is not a success. Measure what you used so you can put it back — not so you can claim a millimetre that fits every V2.
Tools and a concept sequence — not a spin-test
| Tool | What it is for |
|---|---|
| Correct screwdriver bits | Shell screws without chewing heads |
| Assorted shims | Several thicknesses so you can build this stack — not a bag of only 0.1 mm |
| Tweezers | Shims vanish into grease; note which face they sat on |
| Marker or a phone photo | Record which shim went above or below each gear |
| Light grease | A film on teeth and posts. Packed grease throws shims and holds grit |
| Manual and a tray | Spring-loaded latches jump. Pack disconnected |
- Disconnect power as the product instructs. Remove the magazine. Do not look down the barrel.
- Open the gearbox only if you have a reason — new gears, a known grind, a spring change that came with a new set. Curiosity is a bad reason.
- Work one gear at a time. Start with the bevel: its stack sets the bevel-to-pinion mesh, so set that first, then shim the spur and sector to it — motor height in the grip stays a separate screw adjustment. Seat it with a trial stack, feel for a small amount of axial play on the closed shell, then check that it still turns.
- Only then check the mesh with its neighbour. Quiet, even contact along the tooth is the goal. If you cannot feel drag versus rattle, stop.
- Motor height is a separate adjustment. Shimming the bevel will not fix a pinion that sits too high or too low in the grip.
- Reassemble fully before any powered test. Do not hold a battery to the motor on a half-open box. That is how fingers get pinched and anti-reversals get launched across the room.
After a real parts change — especially metal gears or a different spring — you re-shim. The gearbox upgrade guide is the pairing; this page is the alignment. A heavier spring without metal gears and a reinforced piston still strips nylon no matter how pretty the shim stack is.
When to stop and use a technician
Hand the box over if this is your first split and the shell already has a problem, if posts are bent, if you cannot find a stack that is neither rattly nor tight after two careful attempts, or if the anti-reversal and tappet will not sit when the halves close. A MOSFET and a new connector do not belong in a first shim session. Pinion height, a bent motor shaft, a warped half, or a dragging piston will not yield to more washers — adding shims until the gears lock is not “taking up the slack.” Confirm legal status of the exact item and activity with PDRM or qualified Malaysian legal advice before you modify a launcher. Read the legal-status warning. Shimming does not make a replica lawful.
Frequently Asked Questions
What is axial play on a gel blaster gearbox?
It is the small end-to-end movement a gear still has on its post when the shell is closed. A little is needed so the gear can spin; a lot lets the mesh walk and chew teeth; none usually means the gear is clamped and will heat up.
Can I just put 0.1 mm shims on every gear?
No. That number is a common washer size, not a fit for every V2 shell. Bushings, bearings, hub width and shell thickness all change what you need. Feel play per gear; do not copy a millimetre.
Do I shim a stock nylon gearbox that already sounds fine?
Usually no. Shim when you change gears, when something is clearly rattling or binding, or after a spring-and-gear upgrade. Opening a working box to “optimise” it is how lost shims and launched anti-reversals happen.
Should I spin the motor with a battery to test shims?
Not on an open or half-screwed gearbox. Finish the assembly the manual describes, then test as a complete, closed unit. Improvised spin-tests throw parts and tell you nothing reliable about mesh under a real spring.