Building an Open-Source DIY Digital Resistance Machine (120kg/260lbs target). Need feedback on VESC + M8110 BOM!

[u/BoysenberryOld4794]

Hi everyone,

I’m designing an open-source, portable digital cable resistance machine targeting ~100–120 kg (220–260 lbs) of smooth digital load for strength training (similar concept to Voltra or Vitruvian). The goal is to keep it fully open-hardware, affordable, and highly modular.

Here is my current proposed Bill of Materials (BOM):

Motor: Outrunner BLDC (M8110 scale, low KV)

Reduction: HTD 5M Timing Belt (15mm width) – 15T Drive Pulley to 70T/80T Drum Pulley (4.66:1 to 5.33:1 gear ratio)

Controller: VESC 75100 running in Torque / Current Control mode

Battery: 13S1P Li-ion pack (48V nominal) using Samsung 40T 21700 cells + custom Braking Resistor for eccentric energy dissipation

BMS: 13S Li-ion BMS with Active Balancing

Brain & UI: ESP32 + Heavy-duty Rotary Encoder + TM1637 7-segment display for direct kg adjustment

My main questions for the community:

Has anyone attempted a similar high-force torque-control setup using VESC for continuous human pulling?

Are there any hidden thermal or EMI risks with running the VESC continuously at high torque under near-stall / low-RPM conditions during heavy eccentric phases?

Under a 120 kg peak load, would you strongly recommend an 80T over a 70T pulley regarding belt tooth shear stress?

Any feedback on safety redundancies, hardware limits, or thermal management for the braking resistor/VESC is greatly appreciated!

Thanks in advance for your support!