Electrical 'Clutch' for winch

[Chadfrom308]

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)

Does anyone have any other suggestions?

[aldaeron]

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.

One solution may be to adapt your motor/gearbox to drive something like this:
http://www.harborfreight.com/1200-lb...nch-65115.html.

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)

-matto-

[Bryce2471]

This probably isn't quite what you were looking for. But this is what my team did in 2014 when faced with a simular challenge:
http://www.chiefdelphi.com/media/photos/39470

[Chadfrom308]

Originally Posted by Bryce2471

This probably isn't quite what you were looking for. But this is what my team did in 2014 when faced with a simular challenge:
http://www.chiefdelphi.com/media/photos/39470

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.

[Sh1ine]

Originally Posted by Chadfrom308

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.

It think they are using a VEX Shirter Output Shaft. One position the winch engages the pawl the other position it free spins.

[Bryce2471]

Originally Posted by Chadfrom308

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.

Thank you. It has a pneumatic cylinder that disengages the spool from the rest of the mechanism so it can free spin.

Originally Posted by Sh1ine

It think they are using a VEX Shirter Output Shaft. One position the winch engages the pawl the other position it free spins.

Ours was machined custom, and it did take some fine tuning to get right. I do think however, that a similar setup could be createdusing the vex shaft.

[Chadfrom308]

Originally Posted by Bryce2471

Thank you. It has a pneumatic cylinder that disengages the spool from the rest of the mechanism so it can free spin.

Ours was machined custom, and it did take some fine tuning to get right. I do think however, that a similar setup could be createdusing the vex shaft.

Do you have any designs or pictures of that? I don't know how exactly I would go about using a pneumatic cylinder to disengage the spool.

[Knufire]

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.

[asid61]

Originally Posted by Chadfrom308

Do you have any designs or pictures of that? I don't know how exactly I would go about using a pneumatic cylinder to disengage the spool.

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.

[Bryce2471]

Originally Posted by Chadfrom308

Do you have any designs or pictures of that? I don't know how exactly I would go about using a pneumatic cylinder to disengage the spool.

Here's some more links that might help explain it:

http://www.chiefdelphi.com/media/photos/39469
http://www.chiefdelphi.com/media/photos/39455

The pneumatic cylinder connected to blue piece in the pictured cross section view.

[Chadfrom308]

Originally Posted by aldaeron

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.

One solution may be to adapt your motor/gearbox to drive something like this:
http://www.harborfreight.com/1200-lb...nch-65115.html.

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)

-matto-

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.

Thanks for the reply!

[jkelleyrtp]

If you're looking for a ratchet-release mechanism, check out McMaster-Carr gear pawls.

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.

[IKE]

If you are willing to spend a few bucks, I would recommend looking at one of these:

http://www.harborfreight.com/2500-lb...rol-61840.html