HI all I wonder if someone could help me out here. I run a structure borne noise & vibraton control company and have been passed an enquiry that is little off our usual field. We use a lot of springs in our business. The idea being that if something is vibrating and we support it on something with a significanlty lower natural frequency than the vibration frequency then we get isolation. The problem we have been given is this: A train wagon is feeding a glass furnace. The train runs round a track & up to the furnace door. If everything is in sync the door opens as the wagin arrives, it deploys it's load and moves off again. The probl;em is that the door occasionally fails to open and the wagon is hitting the doorcasing a lot of damage. The idea is to use one of our springs as a buffer. The info we have been given is that the wagin hits the door with a force of 140 N m. The problem I have is that I'm not sure whet the units are saying. As i understand them the definition would be 140 N of force acting through a distance of 1 metre along the direction of the force. What I am trying to do is calculate what the force the wagon hits the door with is in Kg. I can then select a spring with an appropriate spring rate and problem solved. Can anyone translate this to a recognisable unit for me?