Hello, new member here so first post, I apologize for any unintentional faux pas. Anyway... I have a problem which I have been asked to sort out in my work place. We have a rig which is used to move a pneumatic ram up and down. Currently it is on an electrical winch system and I have been tasked in finding a way to make this safe for people working under it by having a secure safety system in place just in case the winch fails. The easiest way that I can think of doing this is by having a pin pass through the two outer edges of the RSJ it is attached to and go under a protruding piece of steel work of the movable section, as shows in the image below: What I need to do is stop it dead in its tracks, if the pin bends and jams under the movable part of the rig that is fine, it can be sorted later. What it cannot do is break the pin upon impact. The numbers I have gathered from varying sources are below, all i want to know is what is the thickness of the pin that i need? O.k. I am assuming a weight of 500kg, this is a lot and much more than what it actually weighs but if i overestimate then I have a little wiggle room. The pin will have the following characteristics: A density of 7.85g/cm3 A length of 250mm The impact point on the pin will be 20mm in from the end which is unsupported by the RSJ The bend point will be where the pin goes into the first upright of the RSJ at 50mm from the end. The steel has a yield of 250MPa An ultimate strength of 400MPa I think the modulus of elasticity is 30.3Mpsi It has to withstand a weight of 500kg falling 110mm. The fall will have the following characteristics: Time to fall: 0.149779026187 seconds Velocity: 1.46883048716m/s kinetic energy: 539 joules.. or 539kN worked out using the following formula: mass x gravity x height = 500 x 9.8 x 0.11 = 539 If anyone could help I would appreciate it. If any of the numbers do not seem right in your eyes please tell me and I shall investigate further. I think I have everything i need to do the maths but I can't figure out how to do the maths. Every example I have seen has the impact in between the supports and not outside them, so just to clarify I have attached another diagram below which should make it clear what I am after: On a separate note, would the shape of the pin in question make a difference? I.e. a hex shaped pin, or a more square one rather than a cylinder? Also I read somewhere that boring a hole through the center of the pin could strengthen it for this type of impact due to the larger surface area, is this true? Sorry for all the questions. Hope to hear from you soon, if you need any more info please ask.