Universal Arm System | Phone/Tablet/Laptop Holder

Universal Hypocycloid Arm System | Phone/Tablet/Laptop Holder

UPDATE 15.03.2026

Added two new parts to give you more customization for reducer:

• hypocycloid-7teethf-fast (replace hypocycloid-nineteethf)
• hypocycloid-96idlegear-fast (replace hypocycloid-idlegear)

These upgrades allow you to choose between lower speed with more torque and higher speed with less torque. 

The rest of the reducer parts remain the same – simply use these new ones if you want more speed at the expense of torque, or stay with the originals if you prefer more torque at the expense of lower rotation speed.

UPDATE 11.04.2026

Added new accessories for enhanced flexibility and mounting options:

• Ball Joint Connection– enables precise positioning of the holder in all directions, allowing fine adjustment of angle and orientation.
• Rotary Joint Connection – allows smooth and accurate rotation of the arms along their axis for better alignment.
• G-Clamp Base – provides a secure mounting option for attaching the model to a wide variety of surfaces.
• Side Panel Base – designed for easy attachment to vertical side panels of beds, cabinets, and other.
• Desk Small Base – a compact solution for mounting on horizontal surfaces.

UPDATE 16.04.2026

This update expands the functionality of the Universal Hypocycloid Arm System (UHAS) with a set of new modular adapters, transforming it into a truly universal mounting solution for creators, makers, and professionals.

• Xiaomi Camera Holder – secure mounting for Xiaomi smart cameras
• Tapo Camera Holder – compatible with TP-Link Tapo cameras
• Action Camera Holder – perfect for GoPro-style devices
• Camera Holder 1/4” – standard tripod thread support
• Camera Holder 3/8” – for professional gear and heavier setups
• Microphone Holder 5/8” – compatible with standard microphone mounts
•  SKÅDIS Base Adapter – seamless integration with IKEA SKÅDIS pegboard systems

UPDATE 27.04.2026

Added optional double-sided knob shaft (hypocycloid-shaft2sided) if you want knobs on both sides of the reducer.

Fully 3D-Printed Modular Arm System with Stepless Angle via Hypocycloid Reducers

• You don't have to loosen or tighten bolts to change the angle between arms - just spin the knob until you get the angle you want.

   

• The main goal of this project was to create maximum flexibility with the fewest possible unique parts. The result is an engineering-inspired design with an excellent strength-to-material ratio - maximum rigidity while using minimal filament. It can be printed with PLA or PETG.

   

• Hypocycloid reducers connect arms of any length and other attachments in almost unlimited combinations, with smooth, continuous, stepless angle adjustment. Unlike most modular arms that only offer fixed steps, this system gives you truly precise and fine-tuned positioning. 

   

HYPOCYCLOID REDUCER

The hypocycloid reducer is the key component that makes the system exceptionally flexible. Although it may look complex, it is extremely easy to assemble. The knob can be mounted on either side, depending on convenience.
The hypocycloid reducer consists of: hypocycloid-10teethm   hypocycloid-7teethf-fast and hypocycloid-96idlergear-fast for higher rotational speed or hypocycloid-9teethf-slow with  hypocycloid-98idlergear-slow for lower rotational speed but higher torque   hypocycloid-shaft   hypocycloid-knob   two hypocycloid-screws.

This is a video of my seven-year-old daughter assembling a hypocycloidal reducer in less than 30 seconds. The idea of using hypocycloid reducers as adjustable angle joints was actually hers.

BASES

Desk Base
This base clamps to the edge of your desk or table. The plate and counter are linked by a hypocycloid reducer - just turn the knob for smooth, secure tightening.
An extension can be added if mounting to a thicker desk is required.
The static plate can also be used independently for smaller configurations without attaching it to a desk.

Tripod Base
This base is suitable for floor, desk, or uneven surfaces and does not require mounting. You can also use hypocycloid reducers to adjust the tilt angle of the tripod legs.

ARMS

The arms are made from a 20 × 20 mm square profile, providing excellent rigidity and load capacity while maintaining modular compatibility. Arms are available in multiple lengths depending on your needs. In combination with the 20 mm extension piece, you can achieve any length that is a multiple of 10 mm. They can be connected using hypocycloid reducers, directly to one another or through various directional connectors. This allows full control over reach, direction, and positioning.

CONNECTIONS

Various connectors are included to change direction whenever necessary, enabling complex and highly adaptable configurations.

HOLDERS

Clamp Holder
The clamp consists of two jaws connected by a hypocycloid reducer and can hold objects up to 150 mm wide.
If a larger clamp is required, it can be extended using additional arms. The clamp can also be used independently as a standalone clamp without attaching it to the main structure.
The clamp grips easily and extremely securely almost any object - perfect for phones, cameras, flashlights, lamps, mirrors, and much more.

Device Holder
The device holder consists of two parts connected by a hypocycloid mechanism and an arm of suitable length, allowing stable and adjustable positioning.

Basic Sets

ACCESSORIES

Ball Joint Connection
Rotary Joint Connection
G-Clamp Base
Side Panel Base
Desk Small Base

ADAPTERS

Xiaomi Camera Holder Xiaomi Smart Camera - C200, C201, C300, C400, C500 Pro, C700, C701 Xiaomi Mi Home Security Camera 360° - 1080p, 2K, 2K Pro, Basic Xiaomi IMILAB - A1, C20, C20 Pro, C21, C30, 016 Basic, PTZ 360
Tapo Camera Holder Tapo Home Security Wi-Fi Camera C210, C211, C220, C222, C230, TC70, TC71, TC72
Action Camera Holder GoPro, DJI Osmo, and more
Camera Holder 1/4”,  3/8”
Microphone Holder 5/8”
SKÅDIS Base

Notes

• Important: the central gear (hypocycloid-96idlergear or hypocycloid-98idlergear) must be inserted with the correct orientation - the side with 9 teeth should face the housing with 10 teeth (hypocycloid-10tееthm), and the side with 6 (or 8) teeth should face the housing with 7 (or 9) teeth (hypocycloid-7tееthf or hypocycloid-9tееthf). Don’t count the teeth - if the mechanism feels stuck, just flip the central gear over and try again :)

   

• Depending on the selected components and configuration, the structure can support different loads. Overall, it is significantly stronger and more stable than most conventional holder designs.

   

• For smoother operation, apply a small amount of lubricant to the hypocycloid mechanism. Rubbing the shaft (hypocycloid-shaft)  with candle wax noticeably improves performance.

   

• If you need free movement in a joint, simply remove the central gear (hypocycloid-96idlergear or hypocycloid-98idlergear) from the hypocycloid mechanism.

   

• In some print profiles, certain plates need to be printed more than once. This can be misleading when estimating filament usage and print time!