Flail as a Weapon

[typhoon_driver]

Flails are great at whipping out and then stopping without stopping the main body of the mechanism they are attached to when they hit something hard. This means they are wonderful for cutting grass on rocky and uneven ground as I have found out recently having purchased a flail mower. They are however not all that great when it comes to transferring energy to an opponent in the arena which is what you would want it to do. For a flail to be of use, I'd say that you would have to have around 30 to 40 percent of the machines weight in the flail head. Make it as heavy as possible.

One weapon, one purpose and keep that purpose as simple as possible. Multiple weapons on one machine or multiple uses for one weapon rarely if ever work well because you have to make too many sacrifices to try and include all the elements. Jack of all trades yet master of none.

[Matthew]

I like the idea of a flail, although I can see why they can be ineffective. The flail rope will have to be retractable to avoid entanglement, I think a design similar to an elastic key fob would work. Although I'm running out of weight spare.
Counter rotating wheels do make the robot spin fast enough to put quite a lot of force into a flail. (Force=Speed * Mass)

[Matthew]

Spikes would increase piercing ability, although they would not spin very fast, as friction would twist the flail while spinning and cause it to bounce.

[typhoon_driver]

You are focusing on the wrong equation. Firstly the equation you state deals with motion in a straight line not rotationally. Secondly you should focus on the rotational kinetic energy not the force as this will not be a force that your opponent sees unless you are continuing to accelerate into them (unlikely). A spinning weapon of any sort generally reaches a velocity and then stays there.

https://www.google.co.uk/search?q=ro...enJoixaq-jg_gH

Have a read and a play with the numbers.

[Matthew]

Thanks Typhoon_driver, I am now thoroughly confused in the realms of rotational kinetic energy. The problems with being 14.

[typhoon_driver]

Apologies. Let's take it back to basics. So the equation for kinetic energy in a straight line = 0.5 x mass x velocity squared. Now when it comes to rotational kinetic energy instead of mass we use a term called the moment of inertia. Without going into detail this is a term which relates how the mass is spread around the center of rotation. There are various standard figures for this and other more complex ways to calculate it. Instead of linear velocity we use a term call angular velocity. The units of this are in radians. The long and short of it is that there are 2 x pi radians in 360 degrees (without going into detail). So we instead get 0.5 x moment of inertia x angular velocity squared.

Another way to calculate it is using this handy online calculator http://www.teamcosmos.com/ke/ke.shtml

That's probably confused you some more but dinner is ready so I need to go.

edit - Just to add, I would go speak to your physics teacher about this. Being able to put it in a real world example will certainly make equations of motion more interesting!

[Matthew]

Thanks Typhoon helps a lot. I am struggling to think of a suitable weight. I was thinking about a metal yo yo or a golf ball with screws sticking out to pierce or able to transfer more force into the opponent.
Any ideas?

[typhoon_driver]

I'd look at using a solid lump of metal. Now this being for a beetleweight, something like the head of this hammer might be a suitable candidate with the hickory handle removed and a chain attached through the hole.

http://www.ebay.co.uk/itm/Geological...item2a4cbacf99

I suspect you could find something similar for cheaper. But a big lump of steel or similar is likely to be your best option for a flail head.

edit - I'm not sure what access to workshop equipment you have?