When you take the springs out, you are attempting to find out how far down the elevator can go, before the piston bottoms out in the cylinder. Of course, you would never want it to impact, because it could rupture the cylinder.
Lets say this comes out to 11" below bottom floor level. Piston is touching bottom of cylinder. This is the dovetail measurement.
Then you check the distance from the buffer strike plate to the buffer, when the car is at floor level. Say, it's 6". ("bottom runby")
What is the stroke of the buffer? 4"? ok, now-
Add 6" + 4", which equals 10". That's obviously less than the 11" of dovetail-
So now you know that when the elevator fully compresses the buffer, the piston will never be able to impact the bottom of the cylinder. In this case, there would be 1" of clearance between the piston and cylinder, on a fully compresssed buffer.
Dovetail must be a larger figure, than stroke + runby. Some inspectors say 1/4" more is a minimum. IDK what the code says about it.
Last edited by Vic; 11/19/11 05:11 AM.