Information about Gas Springs and their Application
This is a door on a chicken coop.
This is the door on a small chicken coop. It is opened to gather eggs and clean out the coop. It is hinged at the top and the dimensions are 325 mm high, and approximately 1000mm wide. The width doesn't matter in this case as it uses 2 springs, and when looking at the application from the side it doesn't matter how wide the door is. This isn't one of the dimensions I enter into GASSIM. I am just giving it for educational purposes. The weight of the door is approximately 44N. This door should open around 130 degrees, and when it is closed I want the gas springs to work to pull it closed. This will insure a tight seal, and prevent the wooden door from warping over time. When it is lifted I want the handle load should not be excessive, and after opening it part ways I want the springs to take over and open the door, coming to a soft enough stop not to pull the mounting screws out of the wood over time. When the door is closed I also want the handle load to be around 22N or less. This application uses a pair of gas springs purchased off Ebay some time back. They are stainless steel springs from China used for cabinet applications. They are 150N springs with 90 mm of stroke. 245 mm extended length and came complete with mounting brackets. So there's the basic information, and the application looks something like this.
I start by entering the basic information into GASSIM. For mounting points I first start with my best guess for my moving point. Eventually we ended up with the following (-50, -50) for my moving point, and (-50, -235) for my fixed point. I wasn't thrilled with these points, but the geometry of the application restricted the applications. In this application the fixed Y point is the last point you would select. Moving it up and down will have very little effect on the geometry of the spring in the application. It is really decided by the length of the spring and the opening angle. I know the extended length of my spring was 245mm. So, I moved the fixed Y up and down until the extended length of the spring called for was 245 mm with the door open to 130 degrees. I was happy with the results of these points, so my door was complete. Here is what the results from GASSIM looked like.
At 0 degrees the handle load will be slightly less than 60N. As you open the door this handle load will drop until you reach around 37 degrees of opening angle. At that time the gas springs will take over and open the door to the full 130 degrees. The force at the end is not very high, and the way the spring is mounted there is an oil dampening effect at the end which will cushion the stop so the door doesn't "bang" open. The closing handle load is around 40N and once you reach that same 37 degree point the door will shut on it's own. If you open the door to anything less than 37 degrees and release it, it will shut again. This is not exactly the performance I was looking for, but it isn't bad. With the limitations of the mounting points this was pretty good. I am a little concerned about the quality of these springs. There is no name on them, and I wonder about the quality control. If these dont last of course another spring can be purchased with the same dimensions and the same mounting brackets may be able to be used. You always take a chance when you buy no name brand springs. Below I have included a picture of these springs in action as well as a little video showing the springs opening and closing the door.
