Any Mech engineers out there, or the like - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 
Thread Tools
post #1 of 9 Old 03-19-2017, 08:17 AM - Thread Starter
AVS Forum Special Member
 
kgveteran's Avatar
 
Join Date: Apr 2004
Location: Rochester NY
Posts: 6,796
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 487 Post(s)
Liked: 178
Any Mech engineers out there, or the like

I have a door I built to separate my videoroom from the rest of the house. Part of the door has a magnetic door seal like a fridg, the other part needs a expandable air seal that can inflate with as little as 5-10lbs of pressure.


the whole thing and air tubing will be covered up by the OC703 board and mounted to the doors face...



I designed a device, which I have no idea what to call, but it will do what I want. The gravity of the rod in the PVC tube along with the seals and some silicone lubricant, should give me the amount of pressure, but I have no knowledge how to ever approx. design the rod as to weight, what size rod or how many pounds must the weight be. Could it be a direct correlation of 5lbs of steel equals 5lbs of pressure ???


Help



As of Feb 20th still looking for a Marantz SR7010
**HT Build http://www.avsforum.com/forum/19-ded...-door-0-a.html **


DIY HT builds, are 90%planning, 10%construction

Last edited by kgveteran; 03-19-2017 at 08:44 AM.
kgveteran is offline  
Sponsored Links
Advertisement
 
post #2 of 9 Old 03-19-2017, 04:16 PM
AVS Forum Special Member
 
smoothtlk's Avatar
 
Join Date: Feb 2002
Location: Michigan
Posts: 1,712
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 82 Post(s)
Liked: 45
So, you are building an "air lock"?
I believe the pressure will be the weight of the piston (steel) minus the friction of the seals.
Calculate the Sq in of the piston end. Lbs / sq inch will be the result.
Area = Pi * R^2
so if the piston in one inch in diameter:
.79=Pi*.5^2

If the weight was 10lbs:
10lbs / .79 sq inch or 8lbs / sq inch

One inch round steel bar is 2.67 lbs / inch

So, you will need a bar 3 3/4 inch long x 1 inch

Or something like that
smoothtlk is offline  
post #3 of 9 Old 03-19-2017, 04:51 PM - Thread Starter
AVS Forum Special Member
 
kgveteran's Avatar
 
Join Date: Apr 2004
Location: Rochester NY
Posts: 6,796
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 487 Post(s)
Liked: 178
Quote:
Originally Posted by smoothtlk View Post
So, you are building an "air lock"?
I believe the pressure will be the weight of the piston (steel) minus the friction of the seals.
Calculate the Sq in of the piston end. Lbs / sq inch will be the result.
Area = Pi * R^2
so if the piston in one inch in diameter:
.79=Pi*.5^2

If the weight was 10lbs:
10lbs / .79 sq inch or 8lbs / sq inch

One inch round steel bar is 2.67 lbs / inch

So, you will need a bar 3 3/4 inch long x 1 inch




Or something like that

Wow, Ty. Whats an airlock used for, setups like this. I had imagined this thing being huge due to my lack in math skills


If I make it bigger, just a little overkill can I add a pressure gauge, just for a cool factor, and if that's easy, can I limit the pressure easily if 10psi is too much, like a shut off valve, or a limiting valve.....

As of Feb 20th still looking for a Marantz SR7010
**HT Build http://www.avsforum.com/forum/19-ded...-door-0-a.html **


DIY HT builds, are 90%planning, 10%construction
kgveteran is offline  
 
post #4 of 9 Old 03-19-2017, 06:25 PM
AVS Forum Special Member
 
smoothtlk's Avatar
 
Join Date: Feb 2002
Location: Michigan
Posts: 1,712
Mentioned: 5 Post(s)
Tagged: 0 Thread(s)
Quoted: 82 Post(s)
Liked: 45
Don't forget I didn't put any losses in for Oring friction...that's a matter of your precision, the type of O'ring and lubrication.
smoothtlk is offline  
post #5 of 9 Old 03-25-2017, 06:16 AM
Member
 
Join Date: Mar 2017
Posts: 44
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
Liked: 9
Keep in mind that pounds is a total force and psi is force/area. Do you need it to provide a total of 10lbs total force or does it need to resist 10psi over the area of the panel? This works for the former but will require a bigger system for the latter unless your movable panel is only 1 square inch.
Kigmatzomat is offline  
post #6 of 9 Old 04-06-2017, 07:53 PM
AVS Forum Special Member
 
Bigus's Avatar
 
Join Date: Feb 2003
Location: The South
Posts: 4,960
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 412 Post(s)
Liked: 386
How long does this system need to main pressure? I have concerns about low level leaks around o ring seals inside typical readily available pipes and tubes. Especially if you want a reasonable amount of friction so the weight actually moves in the tube. I can imagine the friction getting out of hand trying to maintain a seal, the rod having to be increased in length to compensate, then the friction becoming a bit inconsistent such that you get a situation where the rod doesn't move... until it does, then pressure spikes up rapidly.

But I'm just concerned. It might turn out OK.
Bigus is offline  
post #7 of 9 Old 04-06-2017, 08:36 PM
AVS Forum Special Member
 
Bigus's Avatar
 
Join Date: Feb 2003
Location: The South
Posts: 4,960
Mentioned: 9 Post(s)
Tagged: 0 Thread(s)
Quoted: 412 Post(s)
Liked: 386
Just a suggestion... consider a sealed bladder with a weight resting on top if you have room for that physical arrangement. Rock on a balloon. Easier to maintain seal. If it needs to be tall and thin, could be a slender balloon. Just a thought.
Bigus is offline  
post #8 of 9 Old 04-07-2017, 10:45 AM - Thread Starter
AVS Forum Special Member
 
kgveteran's Avatar
 
Join Date: Apr 2004
Location: Rochester NY
Posts: 6,796
Mentioned: 4 Post(s)
Tagged: 0 Thread(s)
Quoted: 487 Post(s)
Liked: 178
The seals are about $400 for both. Thats not going to work, i can spend that somewhere else.

I have seen door seals at the bottom of a door that seal when the door is closed, im going to research the design and see if i can apply it to my situation, the magnetic seals should be done next weekend, so i will have a much clearer picture of what my options are.......

I cant seem to get the lighting right to take pics

As of Feb 20th still looking for a Marantz SR7010
**HT Build http://www.avsforum.com/forum/19-ded...-door-0-a.html **


DIY HT builds, are 90%planning, 10%construction
kgveteran is offline  
post #9 of 9 Old 04-07-2017, 11:25 AM
Advanced Member
 
djc11369's Avatar
 
Join Date: Jan 2009
Location: Upstate NY
Posts: 992
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 286 Post(s)
Liked: 161
Quote:
Originally Posted by smoothtlk View Post

If the weight was 10lbs:
10lbs / .79 sq inch or 8lbs / sq inch

One inch round steel bar is 2.67 lbs / inch

So, you will need a bar 3 3/4 inch long x 1 inch

Or something like that
Close

10lbs / .79 sq inch or 8lbs / sq inch should be 12.7 lbs/in2

A one inch round steel bar is 2.67 lbs/ft or close to it depending on what you use for density. As a double check (density) x (volume) = weight so steel density that I used back in my engineering classes many many years ago is .284 lbs/in^3. So (.284 lbs/in3) x ((.79in2)x12in) = 2.69 lbs or divided by 12 to make units easier to follow is 0.224 lbs/in

So with this corrected info for a the 1" bar to exert 10 psi ignoring frictional losses you would need, F= 10*0.79 which is 7.9 lbs. 7.9 lbs divided 0.224 lbs/in is 35.9in.

This was fun, makes me really miss my Mechanical days.
djc11369 is offline  
Sponsored Links
Advertisement
 
Reply Tweaks and Do-It-Yourself

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off