KeenOne Belt Drive Equatorial Mount

I have built equatorial mounts utilising harmonic reduction and cycloidal reduction mechanisms. This time, I designed an equatorial mount using pulley belts for reduction. A three-stage reduction of 1:5.33 was combined with a Nema11 motor featuring planetary gears at 1:5.18, achieving a total reduction ratio of 1:785.8. Microsteps were set to 16, achieving 6,985 steps per degree.

Admittedly, it cannot match metal in terms of rigidity, but modern autoguiders absorb all of that. Surprisingly stable autoguiding is possible.

Add missing bearing to list (1 Mar 2026)
x2 - Bearing 6805 27mm x 35mm x 7mm

Belt Length (21 Jan 2026)
I have corrected the belt length. I wrote 296 but it was 246 by mistake. I am truly sorry for the mistake.
I'll write it again. The correct length for the GT3 belt is 246 teeth mm.

DEC_BottomPlate (Added 18 Jan 2026)
I made a mistake and called it BottomPlate_x2, but RA and DEC are completely different parts. I added a new DEC_BottomPlate. The previous BottomPlate_x2 has been changed to RA_BottomPlate.

RA_ArcaDisk_v2 (Updated 24 Dec 2025)

BOM

Motor

• x2 - Nema11HS3401-PG

Bearing

• x2 - Bearing 6812 60mm x 78mm x 10mm

• x2 - Bearing 6805 27mm x 35mm x 7mm

• x2 - Bearing 6802 15mm x 24mm x 5mm

• x8 - Bearing 686 6mm x 13mm x 5mm

• x8 - Bearing 695 5mm x 13mm x 4mm

Belt

• x2 - 246-3M (GT3)-10mm

• x4 - 246-3M (GT3)-6mm

Screws & Nuts

• x1 - M3 6mm

• x14 - M3 10mm

• x2 - M3 20mm

• x8 - M4 30mm

• x2 - M5 30mm

• x4 - M5 60mm

• x6 - M5 70mm

• x4 - M3 Nut

• x4 - M3 Square Nut

• x8 - M4 Nut

• x2 - M5 Nut

• x6 - M5 Square Nut

• x2 - M6 Nut

• x2 - M8 Nut

• x1 - M12 Nut (For Counter Weight Shaft)

Acrylic Plate (Option -If you require a window in the body)

• 70mm x 30mm x 5mm (RA Body)

• 50mm x 30mm x 5mm (DEC Body)

The controller Board is installed in a tight space. I created a dedicated board that fits there. I'd appreciate it if you could purchase it from the link below, which also supports this project.

Controller Board

• ESP32 K1 Board (Original OnStepX Plug and Play Board)

• You can buy this board on this page.