Catapult releasing mechanism

[Ether]

Originally Posted by Sparkyshires

If I can make a recommendation, take a look at jvn's bot. they use a ratchet wrench to spin it into position, then just let go and it won't spin back.

What "jvn's bot" are you referring to?

[rwkling1]

Originally Posted by Ether

What "jvn's bot" are you referring to?

http://www.youtube.com/watch?v=Gm96S8gdhR0

[jwfoss]

A high strength magnet, or even an electromagnet may be a suitable latch for your design.

[Tungrus]

Originally Posted by jwfoss

A high strength magnet, or even an electromagnet may be a suitable latch for your design.

Magnet? Assuming that its powerful enough to hold the catapult, how would you release it? Electromagnet may be an option, it it must be seriously powerful (to hold down about 50lb equivalent force need to throw the ball).

[Ether]

Originally Posted by Tungrus

Electromagnet may be an option, it it must be seriously powerful (to hold down about 50lb equivalent force need to throw the ball).

There are 12V COTS electromagnets with force rating higher than that.

And it doesn't have to be that powerful if you can figure out a way to use leverage. Think about the trip mechanism on a mouse trap for instance.

[Ether]

Originally Posted by rwkling1

http://www.youtube.com/watch?v=Gm96S8gdhR0

I am familiar with the JVN Ri3D bot.

But are you sure that's what the poster had in mind?

That cam and linkage would be quite a challenge for an inexperienced team with one week left in the build season.

[Madison]

Originally Posted by Ether

I am familiar with the JVN Ri3D bot.

But are you sure that's what the poster had in mind?

That cam and linkage would be quite a challenge for an inexperienced team with one week left in the build season.

It's been a challenge for our experienced team. The forces present in a mechanism that can score the ball from >20' are tremendous (and a little bit terrifying).

[wireties]

Originally Posted by Madison

It's been a challenge for our experienced team. The forces present in a mechanism that can score the ball from >20' are tremendous (and a little bit terrifying).

I can't agree more. I've warned the students a 1000 times during the prototyping process how dangerous this can be. And that a robot w/o bumpers can shatter their ankles!

We were lucky enough to get picked by Aren Hill's (now an engineer at IFI and on JVN's Ri3D team) team in 2008 at the Colorado Regional. So we were familiar with the "choo-choo" cam and decided to use it as we were walking out of the kickoff presentation. Still it is a challenging effort!

[rwkling1]

Originally Posted by Ether

I am familiar with the JVN Ri3D bot.

But are you sure that's what the poster had in mind?

That cam and linkage would be quite a challenge for an inexperienced team with one week left in the build season.

True, the poster may have meant a different robot. With your post, I assumed you weren't familiar with Team JVN.

[Ether]

Originally Posted by rwkling1

With your post, I assumed you weren't familiar with Team JVN.

It's precisely because I was familiar with the challenging cam/linkage design of the JVN Build Blitz bot that I asked Michael what bot he was referring to. It didn't seem to fit his description "then just let go".