I am doing a project where I will be making a winch that needs to release and unspool freely. I am using a banebot gearbox (64:1 most likely) and a bigger motor I found (~400 watts) and I want to winch a 300lb load around a 1" shaft. I was looking at a bunch of ‘Shift-to-neutral’ mechanisms from 2014 but I decided that they are rather big and might not fit in my project. I was also looking at electromechanical clutches that have 120in-lbs of torque holding capability, but I assume that it won’t be enough with the largest gear ratio (4:1) (the strap I am winching is around 3/16" thick, and I am winding about 1ft so by the time I winch all of it, it could be more than the torque rating)
I think a few more details are needed for a good answer.
You mention a size restriction - what is the restriction?
What resources do you have? Just 12V power? Pneumatics?
Does it have to wind on a 1 inch shaft?
A sketch would work wonders here. A description of the task would too (especially so that you take safety into consideration since it seems you are working with a large load)
Another caution about using Banebots gearbox is that they have a torque limit after which all the gears inside shear off their teeth. I haven’t looked in a few years, but it used to be 85 ft-lb.
To release you can drive the motor to release the load from the winch spool and use a second <something> to pull the stop out and unreel (you can use a smaller <something> if there isn’t a lot of weight on the winch spool)
Not sure if this is what you’re looking for, or if it’s within your budget ($45), but it’s a quick way to non-backdrivable mechanisms with a release (lifting the pawl out of place). Also, the gears are stainless steel but I couldn’t tell you the stress rating without putting it into CAD.
It doesn’t have to be 1", that is just my initial thought. I was either considering the banebot or the versaplanetary gearbox. 85 ft-lbs is over 1000 in-lbs am I wrong? That should be enough for around 300 lbs. I was also thinking of spooling it up, locking it in with something, then despooling it, then releasing the lock, but I am worried about having it snag or something. I was thinking about a winch, but they are too wide. It needs to fit within a 10x6x4 inch box.
I have about 32v to work with, but I was thinking an sensored Brushless RC motor with 8.4v (2s Lipo) that can pull around ~400w at a high enough ratio would be perfect. I like that route because the banebot is a 550 size and this motor I have in mind is a 540 size, same output shaft diameter. It wouldn’t be too hard to fit the motor to the gearbox. This isn’t for any FIRST robotics project so I can use pretty much any resource.
I like this design a lot actually, it fits my size requirements perfectly (from what I can tell.) Is there a way this thing free spools? If so, that would be almost perfect for me.
5188 has a ball shifter engage/disengage the motor + ratchet from a winch in 2014. We had a VP with a 18T gear and a ratcheting wrench on the output shaft. The 18T gear drove a 50T ball gear; when the ball gear was disengaged the winch was free to spin. When engaged, it could drive, but only in one direction.
I would think it works the same as a standard ball shifter, only when you pull the piston out and the balls drop back in it goes into “neutral”, so it unwinds.
