Help with a latch design

[Tausen]

I have a design problem. I need a latch that holds as shown in the picture. The only ideas I have been able to come up with envolve parts being outside the revolving wheel to trigger the latching/un-latching. Does anyone have an idea on how to create a latch that would work within the revolving wheel?

Thanks

T.

[Jonathan]

I can, but it isn't clear what type of latch you want? I imagine that the form of latch isn't very crucial, its "output" can be altered with various mechanisms to the required form. I further imagine that your outside parts would invole a stationary cam (and a spring loaded rod attached to the wheel). In that case, you can make a small version of the cam, attach it to a pendulum, and attach the pendulum to any reasonable point on the wheel. It is important that the pendulum not swing, so it'd be heavy. The pendulum serves as an artificial ground, and as the wheel turns, the angular pointion of the springed rod with respect to the cam changes.
I had a similar problem before, where for some reason I had to keep a pin from moving outward until just the right angle, even though it wanted to go far earlier in the cycle. The latch and unlatch places were almost the same as yours. I used a hollow, centrally pivoted drum with a wedge missing and a pendulum attached, and the drum's missing area was positioned so that the pin moved inside just before it tried to go outward, and then when it was time to allow it to go, it reached the other end of the missing area (by going the long way around) and escaped.
EDIT I bet that wasn't very clear, so here is a small animation. To clarify it, between 9 and 10:30 the outward force is not there, and so gravity pulls the pin inward. I can't remember the mechanism to explain why this is, but I remember the latch.

[Oxygon]

I have a design problem. I need a latch that holds as shown in the picture. The only ideas I have been able to come up with envolve parts being outside the revolving wheel to trigger the latching/un-latching. Does anyone have an idea on how to create a latch that would work within the revolving wheel?

...

A "gravity latch" (basically a lever latch) which catches/releases accordong to its angle relative to down/gravity...???

Is that what you mean...?

[Fletcher]

I have found small domestic "gate latches/catches" to be handy. i.e. the ones that are usually hung on wooden fences & that you reach thru to to flip the release mech. Any hardware store has them. They are gravity activated for opening & closing so angle them accordingly for position & timing considerations. Happy building !

[Patrick]

Hi Tausen;
See images, sorry for poor quality; new digital camera and haven't read instruction book yet.
This simple design 'engages' at bottom and 'releases' about three quarters up; opposite of your diagram/ but can be reversed depending upon where/how it is attached to the wheel. Just a simple peg attached by a pin that is free to rotate perpendicular to the wheel. Key point is that it is gravity 'activated' and can be used to trigger an independent input. I will try and get better images.
--Patrick

[Tausen]

Interesting Patrick, I will concider it and see if I can make it work. Thank you Jonathan, I had a similar picture of a latch as you shown but had a brain fart as to how to make it work.

Thanks,

T.