Sign in to follow this  
tigert

gar springs

Recommended Posts

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

Share this post


Link to post
Share on other sites
Help AVSIM continue to serve you!
Please donate today!

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 :(

Share this post


Link to post
Share on other sites

>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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

>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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

>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

Share this post


Link to post
Share on other sites

It is possible to make a design which uses just one spring.For example you can use the same system used in a piston engine: the main axle of the yoke is connected to a lever turned 90

Share this post


Link to post
Share on other sites

Tuomas,The task is of course easier with a Cessna 152 where you have a mechanical trim wheel which can easely be linked behind the main panel to the rod of the yoke using your idea of a "dolly". I got the idea. Good one.But for my turbo prop which uses electric trim on the yoke based on a column it is a bit more tricky, thus the idea of the motor. I agree with you about the issue on using oil Damper without centering. It is only the half part of a good idea. In my mind as it seems to be in yours, the oil dampers are anly here to simulate the aerodynamic force on the controls. ( Or the simulated one via heavy hydro servos on airliners)You idea with the washing machine dampener is good also. I do use dampeners coming from fitness devices as you can see in one of my threads about rudder pedals made from fitness stepper.Cheers,Roger

Share this post


Link to post
Share on other sites

>Tuomas,>>The task is of course easier with a Cessna 152 where you have>a mechanical trim wheel which can easely be linked behind the>main panel to the rod of the yoke using your idea of a>"dolly". I got the idea. Good one.>But for my turbo prop which uses electric trim on the yoke>based on a column it is a bit more tricky, thus the idea of>the motor. I agree with you about the issue on using oil>Damper without centering. It is only the half part of a good>idea. In my mind as it seems to be in yours, the oil dampers>are anly here to simulate the aerodynamic force on the>controls. ( Or the simulated one via heavy hydro servos on>airliners)>You idea with the washing machine dampener is good also. I do>use dampeners coming from fitness devices as you can see in>one of my threads about rudder pedals made from fitness>stepper.Yep. You could use a "power screwdriver" to turn the threaded rod. Just hook it to AC power instead of battery and re-wire the operation rocker switch to your yoke?It is not that easy on the Cessna either - we need a "worm gear" to turn the rotation 90 degrees and we need to transform it somehow to the rod. But hey, we have built it this far already, so I guess we'll figure it out :)//Tuomas

Share this post


Link to post
Share on other sites

>It is possible to make a design which uses just one spring.>For example you can use the same system used in a piston>engine: the main axle of the yoke is connected to a lever>turned 90

Share this post


Link to post
Share on other sites
http://forums.avsim.net/user_files/90466.gifIn this image you can see an example:the yoke can be any form and assume any position (with respect to the spring raw force, that is necessary to keep it in the chosen center position; this means that in the above example the yoke itself is slightly bent to the left, the force the spring excerts needs to be high enough to sustain the forward pressure of the inclined yoke), the secret is in shifting the momentum from one direction to another, this is done using angled levers like i show in the example.The curved lever (curved just to make it visible) translates the spring axial force into a rotational force, that both dampens movement and centers the lever.Using various systems (gears, pulleys, whatever) this method can be adapted to every control, even roll and yaw.Hope i have cleared it :)

Share this post


Link to post
Share on other sites

Salve Claudio,It seems very interesting but sorry I have not understood how it can work. Is your view a side view or a front view. Could you "per favore" make a more detailled sketch.I spent nights and nights looking for a one gas spring solution and did never find it. CiaoRoger

Share this post


Link to post
Share on other sites

>Salve Claudio,>>It seems very interesting but sorry I have not understood how>it can work. >Is your view a side view or a front view. >Could you "per favore" make a more detailled sketch.>I spent nights and nights looking for a one gas spring>solution and did never find it. >>Ciao>>RogerIt is a side view - my only concern though is that the yoke does not rotate that much, so it might be that the movement of the short lever might not be enough?Still, thanks for the pic, it is an interesting idea.Roger: The thick black part is the yoke column. Moving it back and forth will move the green dot up and down - but as it is pivoted from the bottom, it also moves the green dot along the "arc" when the yoke turns, thus moving it also a bit to the right, towards the gas spring.It might work, but I am concerned if the short movement is enough. It might though, I need to think a bit.. Thanks!//Tuomas

Share this post


Link to post
Share on other sites

Hi Rog,Does the "Stepper" centralise itself? Can it be adjusted?Great idea if it can. Any idea where I can get one - I am in U.K.?TONY.

Share this post


Link to post
Share on other sites

Tony,The "stepper" does not center itself. But I do use it so since 10 years and I never missed that feature, simply because in a real plane the rudder pedals are not centering either.I cant say where you may find it in the UK, but there must be a sport shop carrying it, for sure.cheers,Roger

Share this post


Link to post
Share on other sites

>It seems very interesting but sorry I have not understood how>it can work. >Is your view a side view or a front view. >Could you "per favore" make a more detailled sketch.>I spent nights and nights looking for a one gas spring>solution and did never find it. It is a side view, the yoke is the gray part (more a cloche then a yoke, but hey it's hand drawn ;)), the spring is in blue, with the rod in black. In green the joint between the spring rod and the yoke support lever.The theory is this: a spring excerpts an axial force in one direction only, the goal is to transform the direction and axle of movement of the control, in another kind of movement along the direction of travel of the spring.Furthermore you can study how the middle position of the control, can be the maximum extension of the spring, thus makeing the spring not only a damper but also a centering means.In my example this is accomplished this way:the yoke is pivoted at the base, the gray arc is fixed in position at an angle to the yoke, accomplishing two results: shifting the center of pressure along the spring axle, makeing it possible for the spring to push towards a center position; and transforming the movement along the spring axle.The second result you could have accomplished just by bolting the spring to the yoke, but this way you would need a counterforce to obtain the centering function.Shifting the center of pressure, you obtain both results.>It is a side view - my only concern though is that the yoke>does not rotate that much, so it might be that the movement of>the short lever might not be enough?Be enough for what?You can adjust the force by moving the spring body nearer or farther from the yoke, thus applying more or less pressure.I think it can be accomplished: if two small springs can pull up the read windshield of a car, one should be sure enough for just a yoke ;)

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this