… i cant find the link, but bunnings sells a set if mini files made by trojan.
Its gunna sound funny, but they have been invaluable in building gearboxes
There is an oval one with a point, and a flat one
The flat one will help you with the ar latch. You can hold it in place through the motor hole, and the oval one helps you position the gears when closing the box up
The oval one also is perfecy for checking shimming.
In 95% of all boxes, you want 0.05-0.1mm of movement once you close up the box. If there is no movement it’s probably too tight
The only box ive shimmed out 100% of movement and the gears still spun freely was the laylax Prometheus box
I personally start at the spur gear, then the sector, leaving the bevel last.
With the box empty, shim the spur, so its just clear of the box. Start with no shim, and add 0.1 until when you spin it, it spins freely, and doesn’t touch the housing
Close up the box, with a screw at the back, near the trigger, and one near the motor. Tip it upside down, and push the spur gear up with something pointy, that file I mentioned, and check movement. Should be heaps. And shim till there is very little
Next, the sector gear. Add that and you want to shim it until its just clear of the spur. Will be scratchy like the spur until its clear. Close up the box and do the above check.
If you have it right, you should be able to spin the sector and both gear should spin freely, and for a while, without grease. Bearings will spin longer, bushings should still get plenty of rotations
If you dont, something is too tight
Edit - forgot this bit.
Hold it flat and spin. Should be quiet. The. Flip it over and spin it. If its scratchy, shim the sector away from the spur a little more until its quiet both up and flat on both sides
Make notes as to how many shims per side per gear
There are a couple of different ways to shim the bevel
I shim the bevel until its like above but centered in the box. So the same number of 0.1mm shims either side
Take the top of the box, the bevel, and the shims for that side. Attached the pistol grip to the side of the box, add the bevel and shims, and add the motor.
Here you adjust the pinion height until the pinion is as centered on the bevel as you can make it.
If the bevel shifts, its to high, and pull a shim out of that side until it doesn’t shift. Make sure you add those shim to the other side.
If its loose, go the other way, until its not.
Make more notes
To test shimming, put all the gears and shims into the otherwise empty box, and see if you can spin the gears.
They should spin freely, but due to the bevel not like before.
If its too tight, youll struggle to spin the gears
Now you grease. If you try and spin the gears once greased, it wont spin. You have to do it before you add lube. Sounds silly, but …
Then. Build the rest of the blaster.
Dont forget to check the height of the ar latch. If you have had to shim the height of the spur plenty to clear stuff, like i had to with an mk box, your ar will catch, and you will need to shim. This will make the ar latch really hard to keep in place while closing the box. Ive found the $5 ar and the shs ar latches have a short shaft and suck installing.
The lonex latch is nice.
If you get spur and sector right, it should be very quiet.
If its still scratchy, the grip is out of alignment and the pinion is not centered on the bevel properly