Ive only recently started a crusher but the design for it has been up in my head and I have had most of the parts for it since October 2005.

My advice would be to first of all get your power source (linear actuator, electric motor/gearbox or other) and design around it. When I bought my linear actuator I came up with plans to have it mounted in the robots base (like Razer) as I figured itd be about 20cm long so wouldnt take up much room, and have it on a 3:1 or 4:1 leverage ratio.

That went out the window as soon as I got the linac, realised it was 40cm long and a 3:1 ratio would only give it about 115kg of crush. So I played around with the parts and now have the linac mounted vertically in a way that its 1:1 and giving the almost full 400kg of crush.

The CAD of it is on my profile and theres some pics of the prototype here: http://s31.photobucket.com/albums/c367/ayrshirerobotics/Snakebite%20-%20Build/http://s31.photobucket.com/albums/c3...e%20-%20Build/

As Mario said, the best way to do it is creative thinking, as thatll achieve the most unique look to your robot. Having the parts on hand to move around to find the best fit/determine the shape of your robot makes life easier and if, like me, you can stare at a pile of parts for 30 minutes or more just imagining all the ways it could go together, or how awesome itll look once its finished, youll be able to produce a pretty cool and effective machine.

Basic parts list:

Base - needs to be strong, particularly where the actuator mounts (unless you attach it to the chassis). Im using 4mm 6082 aluminium with a strip of 4mm hardox running the width of the robot where the actuator attaches.

Weapon drive - most likely a linear actuator, ebay will be your best bet for a cheap one, anything less than 400kg force probably wont be enough to do any damage.

plus he usual, batteries, motors, speed controllers, armour, and something to control your weapon. Im just using a servo microswitch system at the moment but the battleswitches on Gimson Robotics would probably be fine (I think youd need two)

Only safety stuff I can think of is links on both the drive AND weapon and a securing pin/device to lock the arm in place to prevent movement while in the pits - the usual FRA rules really.

Ill have my crusher at Robochallenge Thinktank in December; if youll be there youre more than welcome to poke and prod it (it wont bite you, just other robots! )