gar springs

[tigert 0]

Howdy.I just realized a gas spring on a normal office chair, when adjusted to middle position, will both center the spring and also has a spring force on both directions which appears to be pretty equal on both directions..This might work for yoke and pedal centering, right? Has anyone tried this? It would avoid the "two springs cancel each other" -problem of building special mechanical linkages and would allow a very simple construction if it would work..Thoughts? Any idea how much those cost as spares?//Tuomas

[Guest Erups]

Never thought of this, but my test solution i never tried, is to use the gas springs often found on the rear of any car: you can get them pretty cheap in every scrapyard, and they go in pairs as each car has at least two.And a major pro for them is that they usually have mounting holes at both ends.I never tried it because where i leave scrapyards are not friendly and easy places, rather they tend to be sneaky and get as much money from you as they can.Nowhere near "Scrapheap Challenge" unfortunately :(

[tigert 0]

>Never thought of this, but my test solution i never tried, is>to use the gas springs often found on the rear of any car: you>can get them pretty cheap in every scrapyard, and they go in>pairs as each car has at least two.Yes, but those have the "cancelling each other" issue. So you need to pay extra effort to make a construction that only compresses one spring for each direction. Otherwise you just get a bit of suspension but no centering force. Or, has someone figured out a nice, clean way of using two springs or gas cylinders like this on a yoke? How did you avoid the problem?//Tuomas

[Guest SHORT360]

Hi Tuomas,I do have a good experience handling with gas-springs. I discovered them some years ago because in my city is located an european leader in that field and I know very well the people there for having asked them several times for advices. see: http://www.bertholdmarx.com/eng/html/fr1.htmAs matter of fact there is no gas spring able to respond in both direction. There only exists two sorts, like the steal springs: traction and compression.I do you currently two in my yoke and will next week change them with two hydraulic dampers I did find for 6 euros each. RegardsRoger

[tigert 0]

Well, my interesting discovery is that my chair has one that does respond to two directions. I think it is called "gas spring with elastick locking position" - it makes your chair "smooth" to sit on when you adjust it to the correct height.Now, the question is, has anyone used this kind of springs? If it works like I think it does ( *bounce bounce* :)) it does simplify the construction of an airliner-type yoke a lot.Here's an example from www.suspa.com (click "sprachauswahl" to make the site english, then Industrial -> lockline)http://www.suspa.com/upload/c39a2dXf79a055...neuestgross.jpgnotice there's pressurized gas on *both sides* of the piston and thus it looks like it would work as a push/pull suspension that always centers..?UPDATE: Added pic//Tuomas

[Guest SHORT360]

Probably one housing and two piston,because how could it work "physically". I cant explain it otherwise. I kown that there are oil dampers working in both direction, but I never heard about a gas spring working on traction and compression.But the people of Berthold Marx are very helpfull. The know everything about gas springs. Send them a mail or better give them a call, you will with no doubt get the answer you wish.CiaoRoger

[tigert 0]

Yea, see the pic I added - it is a gas-filled chamber with a valve *in* the piston - open valve, piston moves freely. Close valve = you "lock" it in position, and the compressed gas gives you a cushioning effect that might be just usable in our hobby.//Tuomas

[Guest SHORT360]

I am impressed, Tuomas, indeed. Great founding. I would be too very interested in that kind of gas spring. It's the chair you talking about by fortune made by Ikea ??Roger

[Guest SHORT360]

I just got a glimpse on their catalog and could not find the type of gas spring you are describing. The gas spring found in chairs are just blockable - You can block the position but there is no center point with a traction/compression gas spring. I am really be keen if you find some more infosRoger

[tigert 0]

>I am impressed, Tuomas, indeed. Great founding. I would be>too very interested in that kind of gas spring. >It's the chair you talking about by fortune made by Ikea ??>>Rogerno, its another brand. But I bet many of them use the same springs made by some large manufacturer.Now, got to find spares and see if they cost a lot.. :)Also note that there are two kinds of those lockable ones - basically the difference is the pneumatic stuff. If it is gas, it will compress, thus you get the cushion. If it is oil, it will not compress and you get a rigid lock. Now, the question remains, if the "cushioning" effect is enough for yoke centering? It definitely is strong enough when you compress lots, but will it center in the middle well enough? In any case, if this is going to work, it will make it very easy to build a "pole"-yoke - just hook up the gas spring on the bottom.//Tuomas

[Guest Stephan Haas]

Roger,Would you be so kind as to show us some pictures of your setup?As I understand it at the moment you use 2 gassprings without having the "cancelling each other out" effect. And why will you exchange them for the oily things?At the present I'm working with ordinary springs, but I'm not totally satisfied.Kind regards,Stephan Haaswww.lemont.nl/b767flightdeckhttp://www.pic767flyingclub.com/images/sas544.jpg

[Guest perchas]

Hi TuomasLook at these.SaludosRafaelhttp://forums.avsim.net/user_files/90400.jpg

[Guest perchas]

Other one.Rafaelhttp://forums.avsim.net/user_files/90402.jpghttp://forums.avsim.net/user_files/90404.jpg

[Guest SHORT360]

Stefan,I cant get my digital camera in the next days. Sorry. But the first pictures shown by Rafael tells approximately the same way I did use. My system is a bit more complex mechanism but the principal is the same. When pushing on one Gas spring you need to "manage" some "room" indenpently from the piston on the second gas spring. I can show you an old picture of a concept made for about 10 years ago on my first yoke.Later one of my column (pitch) was made with oil dampers. As a pilot I can say that oil dampers gives you the real feeling. Gas spring are recentering the controls and that's simply WRONG! An aircarft control comes in fact back to an initial position, but not the " center ". It comes back to the trimmed position. Ideally, the perfect system would need oil dampers and an heavy motor able to counteract the dampers, bringing always the controls back to the " trimmed' position. That's the state-of-the-art system used in real simulator and even used in "fly-by-wire" airliner in order to give to the pilot a kind of force feeback. Joysticks or plastic yokes with metallic springs are just not serious.It's good for gamer not for cockpit builder.RegardsRogerhttp://forums.avsim.net/user_files/90410.jpg

[tigert 0]

>An aircarft control comes in fact back to an initial position,>but not the " center ". It comes back to the trimmed position.>Ideally, the perfect system would need oil dampers and an>heavy motor able to counteract the dampers, bringing always>the controls back to the " trimmed' position. That's the>state-of-the-art system used in real simulator and even used>in "fly-by-wire" airliner in order to give to the pilot a kind>of force feeback. One can do a "dolly" that contains the whole centering spring setup. Then use threaded rod that, when rotated, slowly moves the whole "dolly" back and forth. Then make the trim rotate the rod so you can move the centering point around. That is the idea I have in my mind and I am just wondering if this gas spring on chair might work for it - since then I'd just need to move the attachment point of the gas cylinder, simplifying things a lot.Roger: We have a washing machine dampener on our Cessna simulator yoke at the club. It's like a car suspension but just smaller. It's hooked to the yoke column behind the panel and it just gives a very nice *slow, resistance* so you have to use force to move the controls.It is not too bad, but we will need a centering point as well - but it has to be moveable like I described above - that's our next task. Trimming the aircraft to level flight can be done with a non-centering yoke, but it is just quite hard - and it really hurts you when practicing IFR approaches in IMC. Accidentally push the yoke around, it does not center back and your airspeed goes waaay off from what you wanted it to be. It just adds a lot to the workload, that's why we want to build a centering mechanism. But I agree with you - it *must* move the centering point with trim.Rafael: That's true, that is the way to do it. And since I have limited tools in my use, I am trying to avoid that setup :-)//Tuomas