locking a joint--suggestions?

[Joe G.]

Our robot design calls for an arm that, at the start of the match, is folded into kind of an upside-down V. Since this folding is only to keep the height down, at the start of atonomous one part of the arm is pushed up so that it is inline with the other part and stays there the rest of the match. Do you guys have any suggestions for a simple, lightweight, inexpensive locking system? Our team's two considerations are magnets or some kind of rachet gear, but if any of you have built something similar or have other suggestions, please tell.

[Ben Piecuch]

The Technoticks (Team 236) used a very simple locking shaft in 2005 on their Triple Play robot. Their arm would drop down upon the start of auto, and a pvc collar would slide down the shaft and cover the joint. Cost < $1, Weight < 1lb, Effectiveness = Brilliant! Here's a picture of it.

BEN

[Ianworld]

My team had a similar idea in 2005. We had a carriage on a beam system for our tetra manipulator. It ran along an aluminum 2" x 4" square extrusion and at the start of the match we would increase its length by folding up a second 2 by 4. Inside the top 2x4 was a slightly smaller chunk of metal that would drop down and lock the two together, short of going upside down gravity held it in place nicely.