What's new
What's new
By:
Advanced search…

Pneumatic cylinders for door actuation?

Steve in SoCal

Steve in SoCal

Titanium
Joined
Oct 17, 2006
Location
Woodland Hills, Ca. and some times Hutchinson, Ks.
I am building a ramp door on the back of my trailer 10' tall, 8' wide. In contemplating door actuators I ran across some 2.5 and 3" air cylinders. My truck has an air compressor and supplies air to to the trailer so that is a plus. I seem to recall air cylinders being too fast acting in many cases? The door weighs around 375~400 pounds. Pneumatic cylinders are a good fit from a systems standpoint, would they be suitable for this application?

Steve
 
I made a gate actuator using a air cylinder and control the speed of opening and closing with an adjustable orifice on the discharge side. This is a two way cylinder so it has air pressure all the time on one end or the other. I used an electric solenoid air valve to control the operation being able to open or close the gate from various locations.
 
I have made a number of air-powered devices, some needed to move very slowly and some not so slow. As others have said, a fixed orifice works well if you are working with a fixed load. The problem with a ramp door is that at some point it will be 'over center' weight-wise, and the last third to half travel could be fast and unpredictable. You can use a simple, surplus hydraulic cylinder as a snubber that will keep the movement relatively constant. You can also use a double-acting air cylinder and play with the orifice ratios on both ends to get something that might work. No doubt there are other, better methods as well.
 
The cylinders I am looking at are double acting and, flow control would be a part of the system. I also have mechanical latches on the door. I could use hydraulics but, the weight is not that high and the onboard air just kinda gave me an idea. The two biggest concerns are flow restrictors and balance. The first for a line failure the second because air cylinders like hydraulics tend to have a weak and strong side.

I also want to have a fail safe system if a cylinder fails the other should be strong enough to support the door. It is one thing to have the fail to lift, it is quite another if the door fell from unlatched to the ground. I would use a remote control to operate the system and have a way to physically override it need be. The other nice thing about air is there is no mess with leaks.

I ran through using hydraulics, and an electric winch, pneumatic seems like it may be a good fit?

Steve
 
I've built a lot of machines in my life, some mechanical, some hydraulic and some pneumatic, and while pneumatic is more simple than mechanical and more clean than hydraulic, it is waaaaaay less controllable, just because of the compressability of the medium. I would look at anything other than air for this application.

12 volt linear actuators could be a good fit!

Stuart
 
I built a TV cabinet years ago using two actuators, one on each end of the cabinet. They both stayed timed together perfectly. I have no idea what your setup looks like but maybe you could pull it off with a single actuator if you counterbalanced the tail gate or ramp. A overhead garage door is heavy, but utilizing that big wound up spring it's easily moved with a small electric opener.

Stuart
 
The plan is to use cylinders on both sides about 12" up the door, the door weighs almost 400 pounds now, I scaled it tonight, it still needs sheeting and decking maybe another 100~125 pounds. It is hinged 3" below the door to allow the door to be even with the trailer floor when open. The range of motion is about 110 degrees. The 6000N actuators say they are 500mm stroke,


Steve
 
atomarc said:
I've built a lot of machines in my life, some mechanical, some hydraulic and some pneumatic, and while pneumatic is more simple than mechanical and more clean than hydraulic, it is waaaaaay less controllable, just because of the compressability of the medium. I would look at anything other than air for this application.

12 volt linear actuators could be a good fit!

Stuart
Click to expand...

Times 2 on that, ………...in your shoes I'd heed Atomarcs words.
 
I have used cheap 12v linear actuators on a couple of jobs, they work great, and they wont back drive, ie will hold there position. But check the specs closely, they are very slow moving in the higher torque units, something like 5mm a sec.
 
Pure gravity load...no problem with pnuematics.
Just look at any old car lift (yes, I have worked on the air/oil ones).

The problem I see, is as the door comes up, the load comes off.
When straight up, there is no load at all, so the speed will increase with
the same pressure applied.
 
The company I worked for had hundreds of swinging and sliding air operated doors. Most were commercially built by a company called Air-Lec.

Automatic Door Openers | Pneumatic, Swing, Sliding & Hangar – Air Lec

Most of their door opener/closers used an air cylinder with springs to both assist in the initial opening and help control the motion once the door started moving. Our applications were for large cooler and freezer doors. You might want to consider a similar combination system.
 
There are so many things available for air systems. There are cylinder mounted magnetic valves that use the position or the piston to switch restriction valves on off. Needle valves one way or bidirectional to meter the flow.

Look through Parker catalogs, never ending.
 
For a load that size, in an application where there are likely to be people standing around it, I would definitely stay away from air operated pistons. As said before, air pistons are springy and like to move in sudden jerks, and react differently to different loads. No matter how you look at it, you are sticking a giant spring in the system, and that's a place where energy can be stored and released in an uncontrolled manor. If you are set on using air, I would spec a linear actuator with an air driven motor. A pair of them may be tricky to sync up without a mechanical connection, but it certainly has been done before.
 
This is all conjecture as we haven't seen a picture of the exact layout, but here is my concern. If the door is 10 ft high and weighs over 500 lbs and you're thinking about putting your mechanism only 12" up from the hinge point I think you have some very serious engineering to do. The load at the point would be terrific and almost impossible to control with pneumatics.

While not quite as graceful as other methods, a small Harbor Freight 12 volt winch with some pulleys and attachment points at the top of each side of the door would open and close it with tons of power and control-ability.

Take a look at the link..it doesn't get any cleaner than that..IMHO! YouTube

It's a garage door in drag..pretty slick!

Stuart
 
You must log in or register to reply here.

Similar threads

M
Thoughts/review of 24' No Ramp hydraulic lowering trailer after ~1 year of ownership
2
Replies
28
Views
11K
Garwood
G
Z
Seal replacement for air operated drawbar actuator
Replies
6
Views
1K
atomarc
A
G
Mechanical supergenius looking for opportunity in central IA
Replies
9
Views
7K
topdawg
T
P
A Production Line Takes Shape
Replies
0
Views
5K
PracticalMan
P
P
Multitasking's "Big" Advantage
Replies
1
Views
5K
allloutmx
allloutmx








 

ABOUT PRACTICAL MACHINIST

With more than 10.6 million unique visitors over the last year, Practical Machinist is the most visited site for metalworking professionals. Practical Machinist is the easiest way to learn new techniques, get answers quickly and discuss common challenges with your peers. Register for the world’s largest manufacturing technology forum for free today to stay in the know.

Learn more about us.

STAY CONNECTED

Facebook Instagram YouTube LinkedIn Pinterest Twitter Tiktok

Register Become a forum member. Register today.

Sign Up Sign up for our e-newsletter.

© 2024 Copyright Practicalmachinist.com. All Rights reserved.

Back
Top