1J30.90 - Suspension Bridge
A suspension bridge assembly allows you to show tension in cable supporting the bridge and how dimensional relationships behave.
Set up two bench rods 77cm, inside distance, from each other. On the left side, place the white pulley in the bottom clamp. Drape the bike chain across the white pulley and attach the other end to the hook on the bench rod on the other side of the table. Hang a 300g mass from the chain to keep it from spooling off of the pulley. Make sure the orange marker is vertical. Insert the catcher assembly that mounts above the white pulley assembly and catches the orange marker if mass is added or removed.
Place the stainless steel hooks in order on the table with a 50g hooked mass for each of the hooks (13 total). Provide an additional 50g mass to attach to the 300g mass when the stainless steel hooks are added to the assembly. Provide an additional 750g (500g +250g) mass to attach to the chain when the bridge is fully loaded for force balancing.
Be sure to explain to the instructor to be careful when loading/unloading the masses as the catcher is not strong enough to hold a large unbalanced force.
With the bike chain draped over the pulley, note the 300g mass hanging to apply a balanced tension in the chain with the mass of the chain. Carefully add 50g to the balancing mass and hang each stainless steel hook from the strings that are colored green (every 3 links). When you are ready to load the masses, change the tension mass to 750g once the 350g do not hold the chain stationary. Then continue to add the 50g masses until all 13 are hanging.
Be careful to not let the chain be too unbalanced as the catcher mechanism cannot handle large unbalanced forces.
With the support for the suspension bridge set to a constant value, you can vary the mass of the bridge, tension in the chain, and height of the catenary depending on how much of the chain is used to make the bridge.