Bridge question

[Jim Wilks]

Originally Posted by Brainless96

It took 60 lbs on each side to keep the batteries at 28 inches on the better side (the one that will go to 16 in before tipping). With 60 lbs on each side it makes transporting it a real problem so it is not very practical to use this as a final solution.

Just make the 60lbs on each side removable and transport as before.

[DonRotolo]

Adding weight will not make the bridge behave differently.

You need to add a variable force, such as a spring or bungee cord, between the bottom of the bridge and the baseplate, and calibrate that until you get the right motion. Do this on both sides, of course!

[indubitably]

Originally Posted by DonRotolo

Adding weight will not make the bridge behave differently.

You need to add a variable force, such as a spring or bungee cord, between the bottom of the bridge and the baseplate, and calibrate that until you get the right motion. Do this on both sides, of course!

We tried adding springs, and while it passes the battery tests, it still does not behave as the real ramp would as it falls down slowly. I think we will try adding weight next.

[Joe Johnson]

Originally Posted by DonRotolo

Adding weight will not make the bridge behave differently.

You need to add a variable force, such as a spring or bungee cord, between the bottom of the bridge and the baseplate, and calibrate that until you get the right motion. Do this on both sides, of course!

I think you are certainly wrong on this count.

Higher weight will make it harder to lift the CG of the bridge (which you certainly will do if you move edge of the bridge down).

It is pretty easy math. The pivot to the CG of the bridge (assuming symmetry) 3" (=barrier width/2 ... actually from the this video it looks like the hinge point may be a bit wider than the barrier, but close enough). The pivot to then edge 41" (44"-3").

If it takes 15lbs at the edge, then the bridge weight must be ~200lbs (15*41/3).

Joe J.