I'm working on a project that uses a strong stepper motor to power a wheel that needs to be able to "coast" freely at times. The motor is too stiff when not engaged, and along with my gearing ratio, makes it impossible to get the free-spinning coast** that I want from the wheel when the motor is not powered. I only need the wheel to turn in a single direction, so I've been playing around with a design (see image) where the motor slides just a bit to engage via a small set of gear tracks to pull itself into the other gear. I was thinking that I would simply just reverse direction when I wanted to pull the motor away to enable free-spinning. Unfortunately, it doesn't work so well. The gear does engage, but the little bit of play it has when it slides causes it to make contact with the very last tooth of the tracks at the same time. This causes it to make a grinding noise, and certainly isn't efficient.
Does anyone know how I could get this to do what I want? I've been searching online, but haven't found anything and I am not sure of how to technically describe what I'm trying to do in a few search terms. So, I'd be grateful for any links to similar designs as well.
** Sorry, I forgot to add an important detail that will explain why I need to find a way to disengage the motor... The motor will turn the wheel forward, but when disengaged, the wheel needs to be able to turn freely in either direction.
So, it's two days later, and this is what I'm going to try next:
It consists of:
A drive gear (in red) that turns counterclockwise, with a one-way clutch bearing mounted to it. The clutch bearing turns freely clockwise.
There is an arm with an intermediate gear that will make contact with the large gear when engaged.
There is a spring attached to the arm. The spring pulls the arm down, to engage the gear. The important thing is that the spring is NOT strong enough to overcome the resistance of the idle stepper motor. So the arm will not move unless assisted by the stepper motor.
So here's how I hope this will work, assuming we start with it not engaged:
The stepper motor turns on, counterclockwise. The movement, in addition to the spring, engages the intermediate gear. The clutch bearing prevents the arm from dis-engaging the intermediate gear, yet allows the stepper motor to turn the gears freely.
To disengage, we simply reverse direction of the stepper motor just a few degrees. The clutch bearing will lock, pulling the arm away.
I have yet to prototype this, as my 3D printer is down for a few days. But I would be interested in feedback and whether anyone thinks this will work.