Announcement

Collapse
No announcement yet.

1/4" Air Tubing

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • sarge41
    replied
    Originally posted by Doozer View Post
    Automotive lifts are air over oil.
    It sounds like you were out of oil.
    It is a silly reason to condemn the use of air
    as a means to move things, when you had
    one bad experience with a system that was
    not functioning properly for one or more
    reasons. Shoot from the hip logic is not
    productive.

    -Doozer
    JoeLee: Doozer had it exactly right. Your auto lift was low on oil. It's a wonder you didn't throw the car off the lift. They have worked great for the last 75 years or so, maybe more.
    Sarge41

    Leave a comment:


  • Willy
    replied
    As mentioned the system needs to be properly engineered in order to function properly. This mean a smoothly operating mechanical apparatus that is assisted by the air cylinder. Any binding or the impairment in it's smooth movement will lead to disappointment.

    I have used the type of air over oil, single post automotive hoist for years, and yes when it was low on oil we knew about it before the car was a foot off of the ground. At this point the car was removed and the hoist was topped off with hydraulic oil immediately, no one wants to wear a car.

    This is a classic example though of where air is not a good choice as a working medium. A single post car hoist absolutely needs a hydraulics to operate safely. Why? Because it's lifting a load that is not properly balanced. Cars and light trucks are notoriously off-balance, 65% front/35% rear is not uncommon for a pickup. The lifting ram is constantly in a bind situation and absolutely requires the smoothness of hydraulics.

    No argument about the smoothness of hydraulics from me. I'm only stating that given a properly designed air lift application that operates smoothly, air can do the job the OP requested with minimal cost and complication. Only the OP can answer or validate how smooth his table is, but lifting it from one side is a fools errand and I'm sure he knows this already.

    Leave a comment:


  • Yondering
    replied
    Originally posted by JoeLee View Post
    The demo video is really deceiving because there is no load on the ram and it moves very freely in and out.
    You start to put a load on it the air is going to compress until there is enough pressure to move what ever it's pushing. I don't know if putting pressure on the retracting side of the ram is going to make any difference as it just acts as more of a load.The air is going to compress on either side of the dual action ram.
    Those are OK for moving light actuator arms where the ram stops when the arm hit's the end of it's travel, and slamming open and closed doesn't matter. I can't visualize it for moving heavy stuff accurately.

    JL...............
    You are correct, and because of what you describe, I've encountered issues with air power on systems with a lot of stiction. Flow controls don't help much in that case; pressure still builds up until the system moves, and if it's a lot of stiction, that can often be enough to force large (or even full) travel of the ram once it breaks free. Using a flow control system is better than an open system, but you still have the air spring inside the cylinder.

    Air works great for free moving systems. I don't see it working so well for a drill press table. Remember, air gives you force control but not very good displacement control.

    Leave a comment:


  • Doozer
    replied
    Originally posted by JoeLee View Post
    I had a shop a long time ago that had a floor hoist in it. It haden't been used for years.
    I found an H head that fit the cylinder and bolted it up. Hooked up my air supply to the valve system that was still in place so it would work.
    It did work but was really low on oil and there was a lot of air in the system.
    The first time I went to raise a car on it I'm standing there holding the lever listening to the air fill they cylinder and nothing was happening.
    All of a sudden the car jumped up about 3 feet and then stopped. I held the lever as the air continued to flow. All of a sudden the car jumped up another 2 1/2' and the cylinder slammed as it topped out, the car bounced a little. Scared the crap out of me, all I could think of is the cylinder coming out of the floor and the car crashing over me. When I went to let it down I'm listening to all the air being released and all of a sudden the car dropped about 3'. Air is not good to move things.

    JL..............
    Automotive lifts are air over oil.
    It sounds like you were out of oil.
    It is a silly reason to condemn the use of air
    as a means to move things, when you had
    one bad experience with a system that was
    not functioning properly for one or more
    reasons. Shoot from the hip logic is not
    productive.

    -Doozer

    Leave a comment:


  • Willy
    replied
    Originally posted by JoeLee View Post
    The demo video is really deceiving because there is no load on the ram and it moves very freely in and out.
    You start to put a load on it the air is going to compress until there is enough pressure to move what ever it's pushing. I don't know if putting pressure on the retracting side of the ram is going to make any difference as it just acts as more of a load.The air is going to compress on either side of the dual action ram.
    Those are OK for moving light actuator arms where the ram stops when the arm hit's the end of it's travel, and slamming open and closed doesn't matter. I can't visualize it for moving heavy stuff accurately.

    JL...............
    Never had issues with them in the past. Restricting the outflow will act as a snubber. Air systems are application specific, a drill press table should be in their realm of operation. Doing so hydraulically, while it can be done is usually not a viable option.

    Air cylinders will never be as controllable however as a hydraulic system because as you say air is compressable, fluids typically are not.
    However they do see a lot of industrial uses, you do have to choose your battles and engineer the system appropriately though.

    Leave a comment:


  • Willy
    replied
    Not sure what local pricing would be in your area but they can be had cheaply on Ebay.
    Although only 6mm these are a buck a piece USD. Even at local sourcing and prices a couple shouldn't break the bank.

    https://www.ebay.ca/itm/6mmAir-Flow-...53.m1438.l2649

    Leave a comment:


  • JoeLee
    replied
    Originally posted by Willy View Post
    What Joe mentions about air cylinder stiction is very true on cylinders that do not control the rate of piston extension and retraction. When in use for example, the cylinder extends, hangs up, and then pops out, sometimes violently.
    Without control this can sometimes result in a system that is almost unusable.

    I have used a lot of equipment that already had a standard air system so it was a no-brainer to utilize that system rather than add a hydraulic system when it was not needed due to the lower power requirements necessary for the intended application.
    We soon got educated on air cylinder control valves that offer smooth and constant motion.

    Have a look at the short video below to see what some of the options are.

    https://www.youtube.com/watch?time_c...&v=cYBIq74IikE
    The demo video is really deceiving because there is no load on the ram and it moves very freely in and out.
    You start to put a load on it the air is going to compress until there is enough pressure to move what ever it's pushing. I don't know if putting pressure on the retracting side of the ram is going to make any difference as it just acts as more of a load.The air is going to compress on either side of the dual action ram.
    Those are OK for moving light actuator arms where the ram stops when the arm hit's the end of it's travel, and slamming open and closed doesn't matter. I can't visualize it for moving heavy stuff accurately.

    JL...............

    Leave a comment:


  • BudB
    replied
    Thanks all! Looks like push fittings are the way to go. Flow controls in line and only enough pressure (30psi) to allow easy positioning.

    Leave a comment:


  • Willy
    replied
    What Joe mentions about air cylinder stiction is very true on cylinders that do not control the rate of piston extension and retraction. When in use for example, the cylinder extends, hangs up, and then pops out, sometimes violently.
    Without control this can sometimes result in a system that is almost unusable.

    I have used a lot of equipment that already had a standard air system so it was a no-brainer to utilize that system rather than add a hydraulic system when it was not needed due to the lower power requirements necessary for the intended application.
    We soon got educated on air cylinder control valves that offer smooth and constant motion.

    Have a look at the short video below to see what some of the options are.

    https://www.youtube.com/watch?time_c...&v=cYBIq74IikE

    Leave a comment:


  • JoeLee
    replied
    I had a shop a long time ago that had a floor hoist in it. It haden't been used for years.
    I found an H head that fit the cylinder and bolted it up. Hooked up my air supply to the valve system that was still in place so it would work.
    It did work but was really low on oil and there was a lot of air in the system.
    The first time I went to raise a car on it I'm standing there holding the lever listening to the air fill they cylinder and nothing was happening.
    All of a sudden the car jumped up about 3 feet and then stopped. I held the lever as the air continued to flow. All of a sudden the car jumped up another 2 1/2' and the cylinder slammed as it topped out, the car bounced a little. Scared the crap out of me, all I could think of is the cylinder coming out of the floor and the car crashing over me. When I went to let it down I'm listening to all the air being released and all of a sudden the car dropped about 3'. Air is not good to move things.

    JL..............

    Leave a comment:


  • JoeLee
    replied
    [QUOTE=wdtom44;1220096]
    Originally posted by JoeLee View Post
    Isn't using air going to be spongy as far as movement?

    Flow controls may help this. Look in McMaster for them. Install so the flow is controled when air is being exhausted, free flow when entering. With one on each side of the cylinder you can "tune" a cylinder down to a slow and controlled movement.
    Yes, you can control the flow but if there is any sticking or binding the pressure will build until there is enough force to move the part and then it will jump. If you can pump air through the system then why can't you pump fluid through it?

    JL..............

    Leave a comment:


  • Yondering
    replied
    Originally posted by JoeLee View Post
    Isn't using air going to be spongy as far as movement?

    JL................
    Yes, and potentially dangerous too unless some sort of damping mechanism is included; air is very springy. I work with a lot of air cylinder mechanisms, and the force applied tends to be a lot like a spring; it's fairly easy to control the force but much more difficult to control the rate of motion, and free travel usually results in high velocity and a hard bang against the end stop. Air systems are not at all like hydraulic systems where motion can be easily controlled through flow restrictions.

    With that said, air brake line as suggested earlier is the way to go. You can use either push connect or traditional threaded brass connections. The push connect fittings like ccwken showed work well, but they don't have to be metric. Only reason his are is because that's what the cheap chinese sellers are offering; good quality connectors from reputable suppliers are available in both inch and metric sizes.

    Leave a comment:


  • wdtom44
    replied
    [QUOTE=JoeLee;1220031]Isn't using air going to be spongy as far as movement?

    Flow controls may help this. Look in McMaster for them. Install so the flow is controled when air is being exhausted, free flow when entering. With one on each side of the cylinder you can "tune" a cylinder down to a slow and controlled movement.

    Leave a comment:


  • Willy
    replied
    Originally posted by paul463 View Post
    Try air brake tubing from an auto/truck parts store.
    Originally posted by Doozer View Post
    All the kool kids are using push-to-connect
    tubing fittings. Some good ones are Legris
    and SMC. Parker makes them too, but they
    are all brass and kind of bulky.
    I like to get them from McMaster Carr or
    AutomationDirect. No inner tube thingy
    is required.

    -Doozer
    Yes lots of options.
    Both of the two above are good choices that I have used a lot in the past with very good results. The determining factor is probably going to be ease of local availability.

    Leave a comment:


  • JoeLee
    replied
    Isn't using air going to be spongy as far as movement?

    JL................

    Leave a comment:

Working...
X