Anybody ever use pneumatic cylinders?

[Krusty]

I'm toying around with the idea of using some lightweight 24" stroke air cylinders to raise and lower the roof of my teardrop. The whole roof if probably under 100lbs so my wife and I can lift it without too much issue, but it would be nice if there was some kind of mechanism to lift it for us.

The only problem I am having now is I have absolutely no idea what I'm looking for. I know I'll probably make use of a tiny 12VDC air compressor that could probably pressure up to 100-150psi. Ideally I'd like the cylinders to be around an inch in diameter and, of course, really cheap. It would need to offer a 24" extension in order to fully raise the roof. Anybody have any good starting points for researching this?

Anybody have any experience in perhaps building something like this? Theoretically I may be able to piece something together with some PVC but that would wind up being large enough that I'd need to put it on the exterior of the trailer and would need to put in more effort to figure out how to mount it. And, of course, it may not work at all.

[MtnDon]

IMO, you would have an easier job of it to use gas springs. Them come in a myriad number of lengths and capacities. There has been some info here on them though I don't have any links. I have also seen a calculator some place online. Again I have no links. Sorry. If you really wanted a powered lift I would look at linear actuators; many lengths and capacities are made. Run them off 12 VDC.

[Krusty]

Know of any gas springs which are 24" longer open than when closed?

[MtnDon]

I doubt you need that much extension. You can get lots of lid movement by using the correct geometry. My hatcback lifts are only something like 16" collapsed, but open the hatch about 120 degrees.

A quick search of the forum brought up the following 2 links. There may be others

one... has a link to an xls calculator. have not used it myself.

two

also have a look at this page

[Krusty]

Alas, no amount of geometry can help me out of my predicament. I built the trailer in a hi-lo style. 24 inches straight up in all 4 corners is what I am aiming to accomplish. Only way around that would be to use a fulcrum of some kind which would wind up getting in the way.

[MtnDon]

Well that changes things. Have you looked at linear actuators? We used one with a 30" stroke for a TV lift a couple years ago. You might be able to use one at each end with guide tracks in the corners.

[KCStudly]

The trouble with an air system is keeping everything synchronized. If one corner has less weight or friction than the others it will go up first racking the roof and potentially binding.

I would prefer a cable pulley system like the OEM's use, and if you want to have it be power operated you could look into a small 12v ATV or boat winch. Using small cable and pulleys, this kind of system can be very compact, and once adjusted will always pull all four corner equally.

[dales133]

The other downfall with air is you need a compressor, tank plus all the associated plumbing involved .alot of cost and work for something a simpler solution and do just as well

[Krusty]

Well that changes things. Have you looked at linear actuators? We used one with a 30" stroke for a TV lift a couple years ago. You might be able to use one at each end with guide tracks in the corners.

I did start looking at linear actuators. Looks like it'll be $90-$100 per actuator so far. I found some on alibaba for $30 each but I need to order 10 at a time. I'll continue my searching this weekend.

[Krusty]

The trouble with an air system is keeping everything synchronized. If one corner has less weight or friction than the others it will go up first racking the roof and potentially binding.

I would prefer a cable pulley system like the OEM's use, and if you want to have it be power operated you could look into a small 12v ATV or boat winch. Using small cable and pulleys, this kind of system can be very compact, and once adjusted will always pull all four corner equally.

There may be enough room to work in something with a few pulleys. I'm less concerned with automating it and more concerned with making it easy. If I can hook it all to a hand winch that'll be good enough for me. I'm just trying to think of a way that doesn't involve me on one side and my wife on another struggling to bring the thing up evenly and then put the pins in.

[Krusty]

The other downfall with air is you need a compressor, tank plus all the associated plumbing involved .alot of cost and work for something a simpler solution and do just as well

I was thinking about something like this:
http://www.harborfreight.com/12v-100-ps ... 61788.html
.
Not sure how long it would take to pressurize 4 cylinders though.

[dales133]

Yea I've got one of those and it's what I ment by compressor but I think you'd find you'd need a tank even if small to maintain proper regulated pressure.
It can be done like used with air lockers on diffs but like I said it's starting to get complicated.
Have a search on YouTube I saw a guy with an airlift system on a camper roof but he had to make all the airlines the same lenth and iron out alot of bugs so it lifted evenly as KC eluded to.
I'd go with actuators , I don't think it would cost any more when all said and done.or pulls and a hand winch or something

[bdosborn]

Here's a hydraulic system. Looks complicated.

https://bulletxv.wordpress.com/2009/01/28/the-lift-system/

Bruce

[KCStudly]

Over on my build thread I am using a pair of linear actuators for my hatch ('cuz I had a pair land in my lap). The thing is that they are strong enough to do some serious damage if they don't operate in synch. The motors can have different current draws, friction, and minor variations in loading. Worst case scenario is one side failing due to a bad wire, harness plug coming loose, or whatnot. So I have been looking into controllers/synchronizers. Fortunately my actuators have position feedback and a synchronized controller is available for a two actuator setup; not sure if there is a similar setup ready made for a 4-way.

With only ten inches of throw these actuators list for $140 each and the controller is $119, not including the harness for the second actuator. In my case I want to be able to operate the hatch from outside, so an auxiliary marine grade DPDT rocker switch will be used, keeping the non-weatherproof switch panel/program interface that comes with the controller tucked away inside of the cabin.

And I'm still looking into the details.

[Krusty]

Now I'm looping all the way back to the idea of just using a winch. I ordered a few parts to see if I could make a PVC pneumatic cylinder to experiment with, but after some of the thoughts here it seems unlikely that air power is going to be consistent enough and it seems that pneumatic actuators may run a risk of busting up my trailer if they ever get out of sync.

A good old fashioned cable and pulley system, however, would be quite simple.

Either way, I'm not going to have time to work on it before our camping trip at the end of this month. For this trip we're just going to lift the bugger by hand and pop in a couple of pins to keep everything upright and safe. I'll need to see about rigging a winch system after the trip (and after finishing up a backlog of chores around the house to keep the wife happy).