Motorizing a cargo cart - Dealing with MY1016Z2 reverse drag?

[Carrolo25]

Hi everyone,

I’m currently working on an engineering internship project called "PapayaKart". The goal is to build a motorized assist system for a heavy-duty manual office/warehouse cart (carrying up to 120 kg / 265 lbs) to reduce operator fatigue.

The core requirement is that the cart must still function perfectly as a manual push-cart if the battery dies, meaning zero drag when pushing forward.

The Planned Build & Materials: We are aiming for a simple, robust, and low-cost MVP (Minimum Viable Product):

• Motor: 24V 250W MY1016Z2 Brushed Geared Motor (has an internal gear reduction of about 9.78:1 and comes with a built-in freewheel/ratchet sprocket).
• Battery: 24V 15Ah Lithium-ion pack.
• Transmission: Chain drive connecting the motor’s 9T freewheel to a custom 44T sprocket mounted on one of the cart's 10-inch rear wheels. (Total reduction is roughly 47:1).
• Control: Standard 24V brushed controller with a simple thumb throttle on the cart's handle.

The Problem / Seeking Advice: Because of the freewheel on the motor shaft, pushing the cart forward manually is effortless. However, we realized that pulling the cart backward (e.g., to maneuver out of a tight corner or elevator) will lock the freewheel and force the chain to backdrive the motor.

With a total mechanical advantage working against the user (~47:1 ratio), we will have to fight both the friction of the internal gearbox and the cogging torque of the brushed motor.

My Questions for the experts:

1. Are there better mechanical solutions? Should we ditch the freewheel, fix the sprocket, and just use a controller with an electrical reverse (sacrificing the manual free-rolling ability)? Or are there clever, simple mechanical ways to solve this problem to allow for reverse maneuvers?
   
   
2. How heavy is the backdrive drag on the MY1016Z2 in real life? Has anyone here backdriven this specific geared motor? I am planning to test the exact force required using a dyno, but I wanted to know if pulling it backward for short distances (1 to 2 meters) will be completely exhausting for a normal user, or if it's manageable.

Any insights, experiences, or alternative ideas would be hugely appreciated!

Thanks in advance!