Spinning Bar vs Spinning Disk

What are the Advantages, Disadvantages, Differences? etc.....

Thanks,

spinning disc
- more weight to the outside = greater kinetic energy
- Greater kinetic energy = longer spin up time

bar
- Can make the material very thick and there is little time for an opponent to hit the bar when rotating so it can be made stronger for the same amount of material
- Less material further out (assuming a uniform bar) = Less kinetic energy

The sums involving kinetic energy assume the same rpm of each design. At the end of the day you want a big mass, far from the center of rotation spinning as fast as possible.

You also have to consider vert vs horiz. Horizontal weapons generally can be made heavier as the gyroscopic forces involved act to keep the robot horizontal. Vertical weapons have the issues dealing with gyroscopic forces. If you want a good visual example then watch the middleweight final from extreme 2 when typhoon hit 259.

Vert weapons have the bonus that they react against the arena floor so more of the energy available goes into the opponent instead of being used to knock your machine away.

There's no real one answer beats all. Some are good and some are bad, usually when you do some basic sums it becomes apparent why. You can use the following calculator to get a rough idea of the kinetic energy involved.

http://www.teamcosmos.com/ke/ke.shtml

For reference, hornet 2 had a max of around 2kJ, I believe 360 is around the 5kJ mark and typhoon 2 could store around 40kJ at full speed. Last year boner had around 0.7kJ. More energy isn't always better.

That about sums it all up really.

Excellent thanks.

i like the idea of bar spinners but looking at videos etc, it seems they need to be very fast to cause as much damage. disk's are very effective but i really like the idea of drum spinners. i would love to build one yet i dont know all the ins and out of the safety etc

Get a close up look at various design ideas at the champs and ask many many questions. Everyone has their own thoughts about what makes a good spinner, you have to decide for yourself

I will!

I have a design for a spinner, thinking about maybe making a KiloBot next but I don't have the knowledge to engineer one, yet.

We'll see how Bitza gets on in Birmingham and take it from there.

im personally thinking of building a full body spinner out of a old car wheel i have laying about, it would need modifying and cutting down but i think it would work :)

full bodied spinners are a pain in the ar$e. I wouldn't bother for your first.

I have heard they can be and comming from you, I am 120% sure you know what your talking about, Mabey if I went with a disk that would be a little bit easier to build. And you can't go wrong with the classic speed 900 for featherweight spinners :)

Lol I never designed them, only drove them. However I do know first hand many of the teething issues with FBS and they are a pain. Also a pain from a drivers point of view. But yeah that sounds like a good plan, start small and get bigger.

Spinning Disks are a Pain :) as gary said main problem seems to be making them strong enough. I prefer horizontal disks since they tend to be more stable especally when flipped, but eveyone has their own preferance. We have tried our FBS with both a disc and bar, so far I think every fight with the bar threw itself out of the arena but the disks keep twisting :(.

Faster is not always better, we will find this out next week with 2 spinners entered, One bar (light and very fast) and one FBS bar (slow but more weight). Too fast and you will break your own robot first, not always a good idea :(.

Saftey is a problem. basically dont test at home.

i have heard some people say vertical are better for a first spinner since they can be hocked up to a motor alot easier yet if you have some extra time and cash then horizontal spinners are better

either one can be hooked up to a motor in either way. Neither one is easier nor harder.

Vertical ones are harder to deal with once you've built them largely due to the gyro effect being a lot more noticable, as it acts against you when you try and turn - and this can affect your overall design if you build to counteract that (by making the robot wider) - but in terms of ease of assembly they're pretty much equal as Gary said.