Re: Looking for some insight: Mechanical hammer linkage
 

DISCLAIMER: I am not a Mech E (IANAM?)

It might be fun to see if you can rig your drive motors to power the hammer. Perhaps with a funky transmission you can save the weight of additional powerful motors.

Start with a stored energy approach - the springs sound good, but I am sure there are many more options.

Then add some sort of winch/ratchet. The point is to store the energy and then be able to disconnect the motor.

At this point we have a system that feels a lot like many of the other posts. To make it fun, lets add a cool transmission. The goal is to power the winch sometimes and the wheels other times. You could simply go with a tranny that selects one of two output shafts.

I believe a straight up differential would do the trick, with one output going to the motors and one going to the winch. When the hammer is unsprung, the differential will split the motors torque between the two. As the spring stores energy, the back torque will increase. Eventually it will be "infinite" load such that all the power is transmitted to the wheels. The ratchet will then hold the energy until you release it.

The obvious down side to this system is that you are immobile immediately after firing.

Good luck!

Re: Looking for some insight: Mechanical hammer linkage
 

The easiest way to do this would be to use a "quick return crank" mechanism with the fast stroke set down with the hammer and assisted with springs or surgical tubing to help pull it down. The up stroke could be set so that it has enough power on the up stroke to re-stretch the springs. there would only be one extra part in this mechanism over a direct drive and could get very fast down strokes.

http://www.wisc-online.com/objects/i...objID=ENG20704
that website explains the mechanism. For your hammer application just remove the slider part and use the beam with the slot as your hammer shaft.

Re: Looking for some insight: Mechanical hammer linkage
 

You might want to try and search for time-tested mechanisms like a fly press, or a blacksmith's power hammer.

Re: Looking for some insight: Mechanical hammer linkage
 

So, amazingly, 57 had something like this on the robot this year. For punching pesky tubes out of the way. Or out of reach of other bots. Admittedly, it only worked for 2-3 rounds at the end of LSR and then the plate was broken off from a ram delivered by another robot, but the idea proved sound eventually.

It was a stored energy system much like people are considering here, high stiffness springs attached to a PVC shaft that was pulled back. The trick we discovered is that pulling back something under high tension is (relatively) easy. But the more stress a release mechanism is under, the more difficult it is to release. Usually.

Our final solution was to retract the shaft via spectra cord wound onto a pulley. The pulley was driven by a worm gear with the worm on a BB tranny/motor combo. Now here's the trick. The BB tranny + worm assembly was pivoted and sprung so it would naturally pull away from the worm gear. Unless it was pushed into the worm gear by a cam on a servo.

So, starting with the shaft extended it went: turn servo cam to engage worm, start motor to retract punch, stop motor via micro switch when retracted, wait for the right moment.... turn servo cam to release worm gear and pulley, AND reverse motor briefly to break static friction.

The two important details we discovered were that last bit there and that turning the worm in one direction made it tend to pull into the worm gear, while turning the other direction pushed away. It's pretty important to use the former for retraction and the latter for release, else you might put too much pressure on your servo cam. The other trick is simply deciding on how to balance retraction speed and rate of fire with the speed and power of the punch/hammer.

I can take some pics of the silly thing if all of that was about as clear as mud. But I think you could make a pretty hard hitting hammer with this even at beetleweight. Making a swinging, Deadblow style hammer would just substitute torsion springs and direct driving of the hammer shaft.

Now you do have to consider good-ole Mr. Newton here. Hitting something very hard is also going to transfer a good amount of force to your own robot. For a swinging hammer, this is going to translate into your robot jumping everytime you fire. For the punch, hitting another robot will push you backwards, though the force there in on the springs and spring supports which should already be able to handle it. If you miss, though, something on your robot is going to need to arrest that punch pretty rapidly, and that could be as rough on your robot as your punch is on another. So I wouldn't recommend missing.

Re: Looking for some insight: Mechanical hammer linkage
 

I was considering building a hammer bot myself when I was watching the carnage at Robogames the other day.

My basic idea is to store a bunch of energy in a flywheel, and use a small servo shifter to transfer the power into the hammer when I want to strike. The hammer could then be returned to the stowed position with some kind of spring.

Re: Looking for some insight: Mechanical hammer linkage
 

HMMMM, a lightweight device that is designed to drive a pointy thing into something you say?

The people at Paslode already cracked this nut:

http://www.paslode.com/

There is some not insginificant tinkering to be done, but the guts of the finish nailers don't weigh all that much.