Need a concept idea on using and electric motor to apply tension while supplied with power.

[Budmanlxxix]

I already pretty good on building things and I've been doing it as a side hobby for years. People that know me always say I invent stuff and I always have to correct them and say "No, I just build stuff that I can't afford to buy". You see I'm a bit of a pack rat, but not the crazy one that jumps in the dumpster ever morning digging though trash. But.... on occasion , and yes most of these occasions are my routine trips to the trash dumpster. So this and by other mean I will spot some item that even though I don't have a use for it at the moment I can see it's potential, if you will. And so over many years my collection has now grown considerably and I'm now known in the neighborhood as the miter fix it guy. If you need a in need and specific type of wire or cable or power supple power, Go to Chris. I'm called the "Master of turning junk into useful things". Self Proclaimed.

Which brings me to my dilemma. With all my useful crap I have to work with, I can't think of a simple design concept to basically supply a small amount of tension between two objects. In which both objects are containing a worm gear system. Both the axile side containing the worm wheel and the motor side containing the worm gear are mounted in such a way to allow the two gears to pivot apart a slight amount to disengage the gears to allow the axis piece to turn freely. In conjunction with a low tension spring and a wide variety of available electric DC motors. The largest being the one included with the photos. I'm trying to come up with a design that when power is supplied the secondary motor it pulls the two gears to together and the spring pulls them back apert when power is removed, whereas the axils with the mounted wheels spin freely again. As I'm sure most of you who may have possible solution for me, will also know that I can't just lock the motor up or it will fry it, but I need to maintain a certain level of tension between the two gears, not only overcome the spring used the pull the gears back apart when power is removed but also enough tension to prevent slippage while the primary motor is also being used. The forces being use here are rather minor and most of that tension can come from gravity itself. So I need some sort...., I guess it could be called a clutch of some sorts. Now I'm pretty good at usually finding a way to make it work with the stuff I've collected over the years, but unless there is a simpler way I that I just haven't though of. I don't think my skills are good enough to make a functional clutch assembled from random junk. So for the first time in a long time I need help. Maybe someone can see this from another angle or perspective or perhaps is just smarter than me, and can see a solution here that I can not see. Any help or suggestions would greatly be appreciated. Thank you for your time.

...and for those of you that are curious to what it is that I'm building. It is an automatic door opener. So when not in use the wheels turn freely to prevent drag and possible damage to the gears. But when supplied with power, if a solution is found that is, will engage the gears therefor depending to the polarity will either open or close the door from a switch. Also in the last included photo Is a car door lock actuator I used to make a switch controlled door lock. Just share for kick.

[Downunder35m]

Welcome and nice problem you present here!

I think, in a way, your problem is not the gears but the approach to the problem.
Worm drives are meant to lock the gear and to provide a good torque.
And they RELY on a proper alignment, without that the wear and tear on the gears can turn excessive quickly.
Maybe doing it "the other way around" would make it easier for you?

Let me try to explain:
Provide a FIXED system for the worm drive, meaning leaving the worm drive properly attached to the drive gear.
To allow for the freedom you seek:
Add a "clutch fork" and a second disc kept separated by a spring.
Like adding some slots to the drive gear and pins on the transport disk.
As long as the motor is not engaged the solenoid for the clutch will be off as well, resulting in free rotation of the system.
You engage the motor, the solenoid pulls the pins into the gear and all is locked.

The pics are a bit confusing though as it seems you are not trying to open or close the door but instead "lock" the door".
Then the pic before that shows how you want to drive the door with wheels....
I would opt for a lever on the door and to move the door with that.
Add two end stops so the motor can only engage in the right direction and to make it stop when the full swing is reached.
And a rounded lever you could even do this with basic contact points and a salvaged carbon brush - assuming you use low voltage on the motors and not mains voltage.
Maybe you are just thinking in a single direction for a reason, maybe you do it because of the damn forest
You know: Sometimes you just can#t see the forest because all those pesky trees are blocking your view

[liquidhandwash]

Automotive Air Cons and some ride-on lawnmowers use an electric clutch, which will freewheel and apply power they will engage. Applying a lower voltage/ current will allow it to slip. You could use a PWM motor speed controller to control the amount of torque required to make the clutch slip.

[Orngrimm]

Not sure if i understood your problem correctly, but here it goes:
- Your worm-Axle shall disengage from the cogwheel on Power-Off
- Your worm-Axle shall engage the cogwheel on Power-On

If i understood this correctly, i would approach the thing like this:
- a Spring makes sure to disengage the worm-axle from the cogwheel if nothing else is pulling...
- a Servo-Motor or even better a solonoid (Can be salvaged easy) pulls/pushes the worm-axle towards the cogwheel. Justz see to it that the solonoid/servo is stronger than the spring

The nice things here: Spring to disengage is automatic. If you wire the solonoid/servo to the main power of the motor, this engaging of the "clutch" is also automatic.

... But maybe i misunderstood your problem. Feel free to correct me