DIY Linear Actuator or...

[Rvjimd]

Guys,

I am ready to try and remote/automate the four doors on my lock chamber. I want to try and do something myself for the challenge and maybe to save a bit of money vs buying frigilli brand units or the like. I am NOT convinced that linear actuators are the only or best way to do this but seems like one choice. I have also thought about a curved rack and pinion setup.

I'm looking for ideas. Here is a pic of the open and closed position of one door. I have the zip tie in position for a test of the potential geometry.

http://i1291.photobucket.com/albums/b554/Slotcarjim/D54B00E6-10B8-4BEA-AA10-6F2C8B789898_zpsyh2xu6n3.jpg

http://i1291.photobucket.com/albums/b554/Slotcarjim/DB4C68B1-90DD-4D94-ABDB-E99844CD0455_zpsfvkanidt.jpg

Jim

[Bo Wallen]

Interesting Project. What if using something like this bugger ? Trapezoidal Lead-screws.http://www.hpcgears.com/n/products/linear_motion/leadscrews/leadscrews.php

[Doggy]

Servo and scissors? I think it would look good, not use much space. I am just not sure about how much torque you need for that, as that will define the final price.

[Rvjimd]

This is the first prototype of a door actuator. I used a 298:1 gear motor and 10-24 threaded rod. I drilled out the black delrin and threaded the first 1/2" to match the 10-24 all thread. Then I clearance drilled the remainder of the delrin to the threads only engage the first part of the delrin, otherwise there would be a lot of drag. The hard part is the deep clearance drilling of the delrin, you are limited by how deep you can drill. I did all this on the lathe. The motor mount is a section of aluminum channel with a set screw holding the motor.

I made a coupler/adapter to attach the threaded Rod to the motor. It is drilled to fit the 10-24 rod on one end and the smaller motor shaft on the other end. Then I installed two set screws to fasten each end.

https://youtu.be/ttvLRUiM-M4

Jim

[Finster]

Looks good so far. I have a suggestion which I don't know if it would be an improvement or not, but here goes: Since you mentioned it's difficult drilling the delrin deep. How about instead you use a tube (brass/Al perhaps) and fix a nut (glue/weld/braze/pin) on the end inside to match your threaded rod. No deep drilling required and if you need more throw just lengthen the tubing and threaded rod.

[Rvjimd]

Fin,

Thanks for the idea, I was actually thinking the same way! The leverage and torque is real good with the 10-24 thread and I was able to move the actuator closer to the pivot so that shortens the throw requirement and reduses the required overall length. I'm going to refine the prototype and see how I like it, then decide how to proceed. I think the delrin is going to work and I like the look, but brass tube would probably look nice also.

Thanks again for the idea! Do you have any thought on how to make it "freewheel" at each end of the travel, and then re engage to go the other way? If I could figure that out I could eliminate the need for limit switches.

The reason I am thinking about this is because I have an actuator on the flaps of my airplane that does it that way. The motor can continue to run at each end without causing problems.

Jim

[Finster]

Hmmm...

Making it freewheel at both ends is a much more difficult problem. Something I'd really need to think about. You could grind down the threads at each end so the screw would just spin but you'd need some sort of spring arrangement (or something) to re-engage the thread when you wanted to move in the other direction. Looking for a solution I did come across this which I know is different altogether but you might be able to adapt the concept.

https://www.youtube.com/watch?v=5xZKDlhF_os

It's an interesting problem. I'll keep thinking about it...

[Rvjimd]

Ya, that thing looks cool!

Jim

[Finster]

Jim,

Found two more variations of a diy actuator with a clutch.

Output positions subject to input motion direction 3 by thang010146
https://www.youtube.com/watch?v=Zhz2hkQtg6U

And this one is pretty much how I was thinking of doing it.
Kraftheber mit Spindelantrieb und Rutschkupplung
https://www.youtube.com/watch?v=kQmJMxQA5C8

[Bo Wallen]

How about spring loaded door and rope and pulley system ........? Little motor and a drum......cheapest solution i can think of today.