i regularly use various bikes, a single speed, a mountain bike, and a couple of ebikes. i’ve been thinking of starting a new project converting a normal single-wheel trailer into a motorized self-propelled trailer. I need some input.
primary consideration is that i want it to be self contained, mostly meaning it carries its own battery and electronics, and preferably i do not want any cabling from the trailer to the bike.
i want the trailer’s motor to engage when the bike is in motion, and provide torque to offset trailer weight, etc.
the idea i have in mind is using an accelerometer tied to the throttle input of the motor controller to detect when the trailer is in motion and engage the motor. this way i could just start pedalling and then the trailer’s motor kicks in, and disengages when the bike’s speed drops below a threshold (or when i hit the brakes). i’d also have a switch of some sort to prevent the motor from engaging when the tow bar is not connected.
is this stupid? is there a better way? am i missing something important?
A trailer might try to push the bike, which could be a bit unstable around a corner. Especially if you are meaning to slow down but circular acceleration thinks you are speeding up.
You might want to consider adding something like how mechanical trailer brakes work as an additional switch in the motor system.
To accomodate vehicles without a braking connectiong via wiring, some automotive trailers have towing framei as a sliding two piece mechanism with a sensor. When you are actively towing the system elongates slightly and there is no braking. When you start to slow down the trailers inertia pushes itself into closing a pressure switch or hydraulic system, that switch/system applies braking force to a hydraulic or electric brake system. So it self regulates braking. You could have it so when you pull ahead the switch let’s motor know its OK to engage. When the switch gets compressed closed the motor knows your bike is moving slower than trailer speed so it should ignore acceleration sensor info if it is getting any.
I believe some motorised trailers use a sensor in the tow bar to detect if the tow bar is under tension or compression. Under tension, increase the throttle, under compression, decrease the throttle. They also might have brakes which could be applied under strong compression.
I’ve never used one myself though.
