Re: Why ballscrews for linear drive?

I'm sorry, I didn't read that closely enough.

You are absolutely right!

This can all be contained in the top section over the door. So that
chunk only has to be slightly wider than the opening.

Excellent!

I'm glad I went through all this, though, as I learned a lot about
ballscrews and steppers.

Thanks,
Steve Greenfield

"Carlos Guillermo" <carlos@v...> wrote:

> Steve -
>
> Why, oh why, do they need to be ballscrews?? If you're looking
> for simple and cheap, try this:
>
> 1.) Go out and buy a set of closet doors and hanger rails from
> Home Depot (paint /decorate/replace doors as desired). Choose a
> long enough rail (or two rails) so you can put both doors on the
> same track and open fully. Don't forget to use guide brackets for
> the bottoms.
> 2.) Mount a 1-2" dia. pulley between bearings over the top-middle
> of one side of the tracks
> 3.) Mount a direct drive, or slightly geared (backdriveable, if
> nec.), motor with 1-2" dia. timing belt pulley over the top-middle
> of the other side of the tracks.
> 4.) Hang a timing belt between the two (~1/2 wide), with enough
> tension to keep the teeth in contact and avoid sagging too much.
> 5.) On the inner top corner of one door, mount a bracket to clamp
> to the bottom side of the belt
> 6.) On the other door, same place, mount a bracket to clamp to the
> UPPER side of the belt.
> 7.) Mount one limit switch for closed and one for opened positions
> (only one door needs to be sensed, since they're coupled).
> 8.) Wire limit switches and motor to an open and a close circuit .
> 9.) For smoother motion, place friction devices (foam pads, etc)
> against some part of each door, and keep the doors light.
>
> The result of this is that, with one motor and one belt, the doors
> will travel in opposite directions, and it should only cost a few
> bucks. This should work fine, if all you need it for is a stage
> prop?
>
> Carlos Guillermo
> VERVE Engineering & Design