So I bought a small room AC for my 8’ x 12’ office. With one printer going to can be unbearable to work in it while a print is going.
It came with a window vent thingy. That isn’t optimal in my tight space so I have to have a “through the wall” vent adapter for it.
The through the wall bit is done. I need designed a door for it. Now I am onto designing the hinge for the door.
Design needs: It needs to close to keep spiders and what not out (as well as can be expected) with impinging the flow of air. It would be best if it shades the top from rain. It also needs to close with a reasonably small bit of deflection and yet with little friction. And lastly it needs to be made so I can experiment and add weight to help make sure it closes without impeding air flow. For ease of printing It will be an assembly. The pic below shows the orientation. The ribs on the door are to prevent warping and restrict air flow a little less.
The 90 elbow, while nicely done and printed was discarded after I read the instructions (my bad, read them first) where is said “No 90 degree bends”. The blue sketch is where my hinge is being noodled
So I have a door that weighs 151 grams. I have MG90S micro servos on the way. I want to program a Seeed to open the door with an airflow switch to activate it and close it when the airflow switch opens (normally open switch).
I am not sure if the MG90S servo is up to this job. It has metal gears and torque of 1.8 kg·cm
The larger MG996R at 10 kg·cm I suspect would be up to the task but I do not have the mechanical engineering skill to determine if it does. Experimentation will be in order I guess. I have to add a fulcrum arm to the door bracket… If anyone has any ideas feel free to let me know.
Added a 5 second delay before the door closes. Pressure will build and air flow will stop if the door doesn’t open fast enough. The delay should mitigate that. The switch relies on continual air flow.
I ended up using the Miuzei MS62. It is over kill at 25kg but has water “splash” resistance so it will be suitable for outside my building in rainy Oregon… I hope.
Honestly the easier route would have been doing a vent damper style actuation, you would have saved yourself a lot of work. Spring loaded closed, electrically activated open and held open during operation.
I thought about a louvered solution too. But like clothes dryer vents here they are besieged by young Orb Weaver webs if they are not used for a while.
I’d have suggested first trying out the 90 degree bend anyway. The reason I say that is because in my place of work the server room has a wall mounted aircon unit that runs 24/7. The exhaust tube runs through a wall into a huge bus repair workshop and there was some issue with exhaust fumes from buses there getting back through the airon exhaust and into the server room. The aircon guys fitted an extension pipe to the aircon exhaust and it’s 90 degrees upwards. Been like that for at least four years without any issues.
Happy to report this project is done! Works as planned. Putting the 5 second delay before closing was crucial. The initial air flow pushes the switch closed but because the door is not open yet the flow pauses enough to cause the switch to open until the door gets moving. The switches “bounces” on then off more or less until the door is open. The added delay would be considered “Hysteresis”?
Next time I might try a vertical sliding trap door. I beat the heat so my AC is ready to go. I’m more used to designing for thermostat controlled systems than mechanical systems.
If anyone has any ideas feel free to let me know.
