Locking Mechanism for Catapult?
 

Hi Guys!

My team (Team 1758) has been working on a locking mechanism for our catapult in the past couple of weeks, but we can't seem to come up with a smoothly working design. Our most recent idea was using the locking mechanism of a doorknob. The latch of the doorknob holds down the catapult and a piston pulls back the patch to unlock the catapult. However, due to friction, this mechanism does not work all of the time (maybe 50% of the time). Do you guys have an suggestions for a good working lock mechanism for a catapult system?

Thanks! :]

Re: Locking Mechanism for Catapult?
 

Gate latch. Ball shifter with gear removed. Pin through an eye bolt with a teflon insert. Pawl. Over-center lever. Door-lock electromagnet (are those legal this year)?

Re: Locking Mechanism for Catapult?
 

Our team is using a gate latch. It's very simple, strong, easy to use, and easy to release.

Re: Locking Mechanism for Catapult?
 

Doorknob.

Re: Locking Mechanism for Catapult?
 

Any particular model? The OP said they were using a dooknob and it wasn't working for them:

Re: Locking Mechanism for Catapult?
 

Pneumatically actuated hatchet that cuts the rope.
(worked back in the day just fine).

I suppose that has the disadvantage of only working once.

Our team is partial to rope clutches (from sailboat). It can take a lot of force to release, but if you are more clever than we are, it can probably be mitigated.

I like systems that are "balanced" and the force to release them does not fight against the holding force. For example, a rope wrapped around a post. It holds if the tension is perpendicular to the post, but if you rotate the post down, the rope slides off the top.

Re: Locking Mechanism for Catapult?
 

2008 Chevrolet Impala truck latch. Should be available at any Chevrolet dealership.

A little awkward to package/mount, but will hold a lot of load and can be easily released with a servo.

Re: Locking Mechanism for Catapult?
 

Could you possibly describe how your team's gate latch works?

Re: Locking Mechanism for Catapult?
 

How would those work?

Re: Locking Mechanism for Catapult?
 

Sure! So our team purchased a gate latch similar to this:
http://www.menards.com/main/tools-ha...218-c-9694.htm
And what we have, is we attach the "peg" or whatever you want to call the piece that goes into the actual latch is mounted to our shooter. We attached a pneumatic cylinder onto the actual latch, so that when the cylinder is extended, the latch is closed, and once we retract it, it pulls back the latch, releasing the shooter. We also have a limit switch making sure that we don't winch the shooter down to much.

Re: Locking Mechanism for Catapult?
 

Was that what you used for your famous Einstein winning hang?

Re: Locking Mechanism for Catapult?
 

Hey we tested with this exact same thing! It worked really well but we ended up going with a different shooter instead, however I would recommend it for you guys!

Re: Locking Mechanism for Catapult?
 

In 2010 we used a gate latch to hold and release out kicker. You can see it in this photo before the kicker was installed in the robot.



It was activate with a 1 inch throw cylinder, as seen here.

Re: Locking Mechanism for Catapult?
 

I've used a pneumatic coupler and a cylinder to pull the collar back. A ball lock device.

Re: Locking Mechanism for Catapult?
 

In 2008, we just used a piston to lock. You can see it up close in the beginning of this video. http://youtu.be/JKdTJSR-KuU

Re: Locking Mechanism for Catapult?
 

This works well for us.

http://www.mauriprosailing.com/us/1-...ts/HAR418.html

https://drive.google.com/file/d/0B3y...it?usp=sharing

Re: Locking Mechanism for Catapult?
 

We have prototyped a latch actuated with a short stoke cylinder. The prototype used a 1/2" diameter shaft supported on bearings to simulate a CAM roller. The latch was cut from 1/8" AL flat stock such that the latch would follow the radius of the shaft and go just over top dead center. The latch is also cut away from the shaft at an angle to allow the catapult to flex down when the ball enters.

We have not completed the competition version; however, have high confidence it will work reliably. If not, thanks to the posters for alternatives.

Re: Locking Mechanism for Catapult?
 

Could you post a picture or two? I can't quite get a mental image from your description.

Thank you.