Flail as a Weapon

I am currently building my first bot and was wondering about making a variant of a thwack bot. If I attach a rope and a weight to each side of my robot, when the robot spins the weights will spin in a large orbit due to centripetal force and would also spin faster than a normal thwack. Also during collisions the robot I hit would be affected like a normal hit from a horizontal spinner yet my bot would be unaffected due to the rope being slack. Although I worry about being entangled by a spinner.
I hope my ideas make sense.
Please could you help diagnose any problems before I get pummeled in an arena.
Kind regards,
Matt.

You mean basically like Nuts? The concept works, just don't expect to do any damage, and spend most of the time tangled in your own flails :L

Flails are an out dated weapon, and were very ineffective when they were used. The moment they hit anything they wont dig in or do any damage because they can just swing to the side.
You are best doing a design like Stinger (UK) or Blade Runner (US) with heavy weight on the end to spin around rather than a flail.

Thx

Your machine needs to be tough enough to take its own forces but, this is the Blade Runner style thwackbot Alex mentioned. If driven well and with some speed behind it it's pretty nasty.

http://vignette2.wikia.nocookie.net/...20121229225958

As Eventhorizon says, its outdated but somewhat fun if you want to try. The only thing is its hard to move around the arena whilst spinning - and people tend to either avoid you or hit you so hard its ineffective.

Realistically for a first build i wouldnt worry about spinners. Come along to live events and enter the whiteboards there. You will receive little damage and can develop the skills needed to build a full on competition robot.

Once your at that level, in the world champs you need to consider spinners. However then you have the problems as stated before.

Go for a flail. Is it ineffective? Compared to conventional spinners, yes. But it's something a bit different and I'm sure it'd be fun to use. At my very first event, there was a robot called Pannibalism that had heavy flail weighs on ropes, but they were also elasticated so that when the robot wasn't spinning on the spot, the weights were retracted, reducing the risk of getting caught on your own weapon.

Actually, found a picture:

http://i31.photobucket.com/albums/c3...psgkxvnt6e.jpg

The weights were brass and chunky, you could feel the bass in the floor as they spun around. Flew out on chains when spinning and retracted via elastic when driving around normally. They made quite a mess of the red and yellow robot by the end of the fight, although it was only made of chipboard.

A flail and a short length of chain on the end of a rod (think mace, not flail) can be fairly effective. It can act as a temporary entanglement weapon against spinners - my bot Scissorhands got absolutely wrecked when it sucked the end of the flail between the blade and the body. A weapon like that can also work as an overhead thwack bot to damage the lightly protected top of your opponent. Lastly the rod can be used as a keep-away device to avoid spinning weapons.

The trick is to make the rod longer than the weight + the chain so that your bot never gets tangled in its own weapon.

Just expanding on that idea, I'd like to see how this design would work:

http://www.nswrfc.org/Nick/mace.jpg

This has five weapons in one: the weight itself, a spear point for stabbing and wedging and points on the back of the spear for grappling and pulling. Finally, the arm can be used as a keep-away stick against spinners. The single arm allows it to work vertically or horizontally.

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.

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)

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.

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.

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

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!

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?

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?