Spinner Energy

[revolutionroger]

Spinner Energy

Many thanks to you Joseph for reinforcing the difference in KE between Vortex and strip (though not quite as extreme as I got - But probably much more acurately) I feel vindicated.

Geoff - Fantastic find - Everything needed, and by your component method.

Ed - Hope you are not too dissapointed in the KE produced by Vortex - Vortex speaks for itself. (compliment).

Roger.

[jeremy_cuss]

Spinner Energy

Im impressed with the erudition of the above posts, but the purpose of this exercise must be to define a fairly simple limit for the KE of a spinner that is a bit cleverer than Mentorns 1500rpm rule. The limit needs to be crude enough to be checkable. That rules out any consideration of weight distribution. Here is how I would do it for heavyweights:-

Spinner weight(kg) * (Radius(m) * Speed(RPM)) squared 5,000,000

Then we get into the more interesting argument about whether 5 million is too much!

Jeremy

[robotwars]

Spinner Energy

while finishing my final degree project.... which was to design a new robot arena, i went through all of the sums.

Ill have to pop into uni and pick up the report, but as far as i can remember it is very difficult to work out the ke,

You have to know what the time taken for the disc at full speed to decelerate to nothing in Milliseconds is )


Then you put that into a formula with the other values and hey presto, you have a value.

They do the same for crash tests and if you look in the books, they use experimental method to determine the time.

I will look it out.

jonno

[s8nsmum]

Spinner Energy

That website says it perfectly, good find geoff. I think it may start to get misleading though if people start to talk (boast) about their spinners in terms of KJ of energy, to me it means very little as strip has far more KJ than vortex but if is far less destructive (from what ive seen). Does anyone know a good way to measure a discs effectiveness numerically?

[geoff]

Spinner Energy

Guys,
If you thought that section was cool...Just check out the rest of that site!!

http://homepages.which.net/~paul.hills/http://homepages.which.net/~paul.hills/

[ewan]

Spinner Energy

Try this it does all the work for you...
http://www.teamcosmos.com/ke/ke.shtmlhttp://www.teamcosmos.com/ke/ke.shtml

[storm]

Spinner Energy

Why would I be dissapointed ?

Vortex can go on delivering a 3Kj hit time... and time... and time... and time again

In terms of total Kj delivered into opponent during a fight I would fancy Vortexs figures over anyone else

Ed
http://www.stormrobot.comhttp://www.stormrobot.com

[fwsorg]

Spinner Energy

At least for the time being....

[big_nipper]

Spinner Energy

In terms of disc power is KE due to disc size/weight all there is? If you have a light disc with a very very powerful motor has anyone worked out the effect of the motor. The energy stored in the motor itself must add to the overall Enery in a hit. I might be wrong but the electrial power within the motor should have an effect.

[john_frizell]

Spinner Energy

Id guess that the only energy the motor can deliver is KE stored in the spinning rotor. Since that is close to the center of the disc its contribution will be very small.

[jamesb]

Spinner Energy

Eds motor, say it was a 2kw magmotor, is producing 2Kj of energy, and as his disk is twice that, to ignore the effects of the motor in this equation is silly.

[fwsorg]

Spinner Energy

James thats not entirely true in that were talking about potential energy in flywheels, not the fact that his 2kw motor is producing 2kj/s of energy of energy, which obviously affects how fast the disc spins up, but not the amount of stored energy. In terms of what Mark and John where talking about, the MOI of a mag rotor would have little bearing on the final outcome. So ignoring the effects of the motor in that equation is entirely justifiable :-p

Having said that, with talk of LEMs and such, I would have thought the MOI of a LEM rotor, especially in terms of featherweight weapons, is reasonably substantial, and so should be taken into consideration.

With reference to Marks question, taking it to the extreme of, for example, an antweight spinning blade attached to a GPA 750, then obviously the MOI of the rotor would have a big effect, but more importantly its about the maximum potential K.E your flywheel can store- a smaller, lighter disc, will not have such a large potential. This means that it does not take your very big powerful motor much time to fill it up (a yuck way to put it, but you get my point) with energy. So, choosing some fairly arbitary values, your disc may have a maximum potential of 1kJ, and your motor may be 4kW- or 4000 Joules/sec, so obviously the motor will fill (yuck again) the disc with energy rather quickly. So, as the light disc is rapidly dissipating its energy into its opponent that its just hit, the motor is pumping loads of energy back in, thus keeping the disc going and going- its the relationship/ratio between the power of the motor and the energetic potential of the disc. I suppose this could bring us to the same point that the flipper folks have got to- trying to find the sweet combination or golden ratio between larer bore (so more powerful) rams which consequently take longer to fill up, and less powerful rams which actuate more quickly. In our case, its a question of having a bigger/heavier/faster disc that takes longer to gain its max potential K.E, or more powerful motors/bigger batteries that get a disc with less potential up to speed more quickly, and keep it there.

[revolutionroger]

Spinner Energy

To add more controversy over how good a measure KE is of a disks potential damage / safety issue etc.

The disk on Revolution 3 is a 12kg 8inch disk @2,500rpm and is very capable (done it) of flipping a 100kg robot clean over - easily.

If you calcualte its KE, it is not much more than that of Strip (about 7,500 KJ) - But in terms of damage potential / safety concerns, it is far greater (or so I would like to think).

Perhaps a simple table would work ie Disk Weight crossed with Disc Diameter and find Max permitted speed - This would still allow people more scope to optimise designs within the restraints.

[jim]

Spinner Energy

Roger, what makes you think Revolutions disc is more dangerous than Strips? (Dont take that question the wrong way!) To my mind, flipping a 100kg robot should take a certain amount of energy; if Strips disc has that then it should be able to do it too. The only differences I can think of would be the length of the collision, which would be the most difficult variable of all to pin down.

[fwsorg]

Spinner Energy

The little bit on the theoretically distance you will throw your opponent when you hit them with you spinning disc, whilst highly theoretical, and ignoring a million other factors, is nonetheless quite interesting!

The maths says my feather should throw another feather 60m. Ill beleive that when I see it!