Just a lil update

Well we have finished building the dealybob that is going to lift and rotate the grabber. We have bent the copper rod running through the wheels so that the whole mess fits a bit better within the width limits. I have not checked the blog recently for updates by Chuck, but I expect that pictures either have been uploaded or shortly will be.

To quote Mr. Podmers and several other people, "It's never too late for a major redesign." Our redesign is not late, nor is it major, so we're in good shape. The grabber we had built before was originally meant as a prototype, but we decided to include it in the robot anyway and reinforce it as necessary. We now know that decision was flawed and we are correcting our design as necessary. The grabber prototype was fixing to be quite high off the ground indeed.It would be possible, though difficult to grab a golf ball. This is because the gears linking the grabber arms are placed under the grabber arms in our current design. The gears are not shown in the image below, but they would be approximately where the text "grabber arm" is on each side, meshing together behind the golf ball.

One way to remedy the problem of the high-off-the-ground grabber arms would have been to tilt them from this sort of doohickey:

To this sort of doohickey:

However that change would be cumbersome and flimsy. Neither design would likely be able to lift a golf ball anyway, as the gears slip on the copper rods pretty darn easily (this was before we started building keys). Oh, let me take a moment to explain what's going on with those. Gears often slip on copper rods. It's a fact of life and a fact of this engineering class. We have developed a solution to this problem. Ya sand down the copper rod and stick it through a small piece of wood. Then screw an eyelet into the wood so that it presses into the groove in the copper rod. This wood is now locked in place; it's going nowhere. Simply bang on the gear as usual, and to glue it to this piece of wood, as shown in the picture:

Additionally, in our old design the servo was placed high above the grabber like so:


The center of gravity for the old design was high, so the servo that was supposed to rotate the grabber would have a hard time doing what we needed it to, even with a counterweight. The grabber arms have to be close to the ground, so a counterweight that compensates for a high center of gravity would either need to be below the ground or really heavy and so close to the axle that it collides with the various gears hanging out about the dealybob.

Therefore we have decided to scrap our old grabber and build a new one. The new one will have a servo close to the ground, glued directly to the grabber arm, which is glued directly to the gear. There will be no copper rods involved, except for holding gears in place, and therefore no potential slippage in the first place. Keys are too bulky for this sort of work anyway. Additionally, the counterweight will be more practical because it will not have to balance out such a high center of gravity in addition to the weight of the grabber.