Originally Posted by David Ashworth
I"m looking for help in selecting and installing linear actuators. wiring these to a remote control system seems simple enough. Selecting the right lengths is important because the shorter stroke allows me to install these more to the side but forces the location closer to the hinge. Requiring a lot more force. A longer stroke that would seem safer and require less overall force would need to be positioned in the stairwell and would not look so good.
Question is how do I calculate the force needed for the shorter stroke mounted closer to the hinge?
I recently installed a linear actuator to lift a bridge scene across the room entrance to my model railroad. Very different than your installation, but I did get to learn a little bit about LAs.
The one thing I did to determine my lift requirement was to purchase an inexpensive digital scale like this one. Probably way too light for what you're doing:
My load was much different than yours, much lighter, but I needed the same information you're needing. It strikes me the load requirement you have back toward the hinges is going to be rather immense. If you think about those huge railroad bridges that lift much the same way as your stairs, they have huge counterbalance on the back so the lift requirement is greatly reduced. I'm thinking you're going to need to figure out a way to move the LA out closer to the raised end, which will, of course, increase the complexity of the actuator to provide the amount of travel you need. I'm running about 60" of travel on mine. I'd want an actuator rated for about twice what the bridge appeared to need.
Here's the company I ended up purchasing from:
Once you decide how far out you can place an actuator, you might even be able to use a bathroom type scale with a pole of some sort resting on it and holding the bridge up about half way. I would think that might begin to give you an idea of the force required to lift the bridge. It would be pretty generalized. You'll likely need to think about using two actuators, one on each side to share the load.
I'm certainly no expert on this, just someone who had a need to figure out the same solutions on a different type structure.