[sudo-access] [omni-building] [sudo-discuss] help build a motorized front-door opener for omni commons

Jake jake at spaz.org
Thu Jan 19 19:04:53 PST 2017

On Thu, 19 Jan 2017, David Keenan wrote:
> - door arm (2x2 stick) and mechanism cannot extend lower than 2" below top
> of door. That's possible right?

yes my design includes not protruding more than 2" below the top of the door.

> - opening force of the motor cannot be too strong. I assume the rpm can be
> adjusted?

RPM is the speed, what you mean is the force, and yes it can be adjusted in
software!  we can dial it to exactly 5 pounds or whatever you want.
Also, we can entirely remove the automatic closing device that we have there
now, and use the motor for that purpose as well, although we might decide to
just keep both there.

> - per code if the door is blocked or hits someone/something, it needs to
> yield. What happens when the motor is stopped by something else, when the
> motor is engaged? Would that damage the motor?

the motor will not be damaged, if someone blocks the door it will just press
right through their soft flesh and bones without stopping.  This is what you
want right?

i guess if you prefer, we can tell it that if the force is more than the set
number of pounds, it just yields and waits, or perhaps times out and gives up
after a certain number of seconds.  It's not a problem.

> - Not related to the mechanics, but even if the motor is not heavy, the
> shelf upon which the motor sits will have to look and be very sturdy, like
> strong enough for someone to hang off of. Given the large transom, it will
> probably have to be a wide shelf, or perhaps stainless rods connecting to
> ceiling joists or something.

you're right about this, the motor is a bit heavy, maybe 25 pounds?  it's in a
milk crate next to the robot right now, and it will be used with the black
wheel (no tire) that is in the same milk crate.

I think that vertical supports into the ceiling joists would be appropriate,
but that's not my department.  Anyway there are a few bolts I found that fit
the threads cast into the motor, and they're duct-taped to its brake handle.

> Again for the mechanism, I would refer to guidelines here:
> http://www.constructionspecifier.com/understanding-new-accessibility-requirements-for-doors/

that's a lot of stuff to read.  I think we'll be fine.  I even have a battery
we can use for the backup power.

> Perhaps we can set up a time for me/others to come look at the equipment and
> figure out how to safely and securely mount it.

i'm busy this weekend but i'm at omni every tuesday at 7pm for Hardware Hacking
Tuesdays and I can come in on mondays or thursdays, hit me up.


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