[philso]

beiju

Our team had a similar device mounted off to one side of a wide robot. It was not very effective. The drive train has 4 CIM motors each driving a Mechanum wheel. The robot would pivot toward the other side when the bridge pusher contacted the bridge. We concluded that only the two motors on the side with the bridge pusher were contributing thrust towards pushing the bridge down. We are in the process of replacing it with a sturdier device that is mounted in the center and powered by a geared-down van door motor. Our weight estimates show that we should be able to install a second pusher arm on the shaft of our mechanism.

One of the reasons for gearing down the van door motor is to get greater torque. This may allow us to help balancing by holding the bridge up and lowering it slowly, damping the sometimes violent oscillations. The other reason is to slow down the motion of the mechanism so that the limit switches have time to work. The first one that our team built was directly powered by a window motor. It would come down with a loud "whack". It eventually destroyed the limit switch. The motor only had to rotate about 90 degrees to deploy the mechanism and at 84 rpm, that takes only a fraction of a second. It is quite possible that the damage to the old arm was self-inflicted when it smashed into the end stops.