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808 Adjustable Idler Pulley for Tevo Little Monster

808 Adjustable Idler Pulley for Tevo Little Monster

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by bLITzJoN June 14, 2021

It's about time to do some maintenance on the Little Monsters and have been toying with revisiting the idea of improving the idler pulleys. The last attempt was the needle bearing pulley. Of all the components on the printer, the bearings on the idler pulleys are rather weak and require regular replacing. I have a box full of robust, inexpensive 808 bearings remaining from the fidget spinner craze, so why not whip up a design using them. Now for REAL, No more crunchiness!

What is needed:
(3) 808-pulley-bot-v6.stl
(3) 808-pulley-mount-v6.stl (16 or 20 for length of screws available)
(3) 808-pulley-top-v6.stl
(3) M5x30mm Thumb screws (Note: if you purchase 10, you can use 3 on the heated bed along with compression springs for that leveling tweakyness)
(3) M5 nuts
(12) M4x20mm hex bolts
(6) M4 nuts
(6) M4 T-slot fasteners (reuse the stock ones)
(6) 808 bearings
(3) 15-19 mm segments from a 5/16" rod of your choosing (example)

Optional Parts:
(3) 3mm x 12mm magnets
(1) pulley-jig.stl - by sliding the rod into the hole, you can pinch while using a hacksaw in the guide to cut ~16mm segments. Also is helpful with installation in the track by inserting the tabs in between the t-slot mount and pulley.

Print Settings

Printer brand:


Printer: Delta (Little Monster)

Rafts: No

Supports: No

Resolution: 250

Infill: 50%

Filament brand: Polymaker

Filament color: Teal

Filament material: PETG


Any rigid material will work including PLA.

Step 1 - Pulley Bottom

Insert the M5 & M4 nuts in the bottom half of the pulley. Optionally, you can secure them with a dab of glue on the sidewall.

Step 2 - Bearings


Place the 808 bearings into place and tighten the M4x20 (picture shows M4x30) bolts until the bearings are snug. A gap is fine between the top and bottom halves; they do not need to touch.


Step 3 - Mount


Put the M4x20 bolts through the bottom mount with heads in the recessed holes and connect the t-slot fasteners. Connect the mount to the pulley via the M5 thumb screw leaving as much gap possible. The optional pulley-jig assists in maintaining a gap and tension during installation.


Step 4 - Belts


Now is a good time to install the belts. Feed the belt between the bearings with the rod removed. I use the optional magnet to hold the rod in place when installed.


Step 5 - Mounting & Tension


Press the pulley into the channel with the t-slot fasteners in the back tracks of the tower. The belt should be placed onto the drive gear. Rest on the top of the mount to provide light tension on the belts. If you use the optional pulley-jig, you may rest on the top of the pulley instead. Firmly tighten the t-slot fasteners. Repeat for all towers and adjust the tension to your liking with the thumb screws.

Note: I have the trucks pressed to the highest point of the towers. I strum the belts with a finger to produce a clean twang in tune with each other. The belts do not need to be extremely tight, just enough to make a clean sound without noisy vibrations of the trucks or its adjacent self.

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