Spinner Energy

**typhoon_driver** · 15th January 2004, 21:21

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.

or in our case, shove half the weight in the disc and spin it up slowly (compared to other discs) and rely on driving skill.

this is a crazy random idea i had......

wot if a machine were somehow created that could take a blow from the most powerful disc but measure how much energy (or give a rough estimate) was delivered. Sorry its crazy and there are a hundred reasons against it but i thought id share it!

**stinger** · 15th January 2004, 21:51

WOW - thanks for all the interest - especially the websites, and even more to the souls at the start who published their statistics. It only seems like a moment ago that I launched this - now 2 archives already

:sad:

The formula derive from that bloke Newton and his Laws of Motion. They are Fixed Laws resulting in Kinetic Energy which is measured in Joules (Kilo Joules fit better in our situation). The skill is in how to make a simple assessment of all possible discs and work out the max permissible rpm for anything that might turn up at an event.

Also, each arena will need to have an Energy Rating, which will need careful monitoring by the FRA.

I believe it is possible to create a range of charts which represent all potential styles of disc (these represent different Mass Distributions) and with a few diagrams, its feasable to select the most appropriate chart by visual assesment of the subject.

Ive done the prelims which show Mass x Dia^2 on the vertical axis (log basis - sorry) and Speed on the Horriz. These each have 5 curves drawn that show 5, 10, 15, 20 & 25 KJ.

Visually assess to choose the best chart, Weigh, Measure and Multiply to find your M.D^2 value, plot this Horrizontally and compare your max permissible speed with the agreed allowable for that event.

The BIG problem is deciding where the limit should be set for different arenas. Clearly experience is going to play a major role and organisers (FRA) will need to be extremely cautious (coz if we get it wrong and hurt somebody - weve made ourselves liable for prosecution!)

All I can say is that My recomendation on Sat is that we start with an energy limit of 5KJ (which may be cut lower) - and roboteers should exploit this by building systems with alternative drive systems that have different potential speeds.

We will need proof of your potential speed and are likely to request the disc is removed (for assessment) and the shaft run up and checked with a tacho.

More after the weekend,
Cheers,
Kev.

15th January 2004, 22:49

To digress slightly - has anyone got any ideas for measuring the speed of a disc? I know we all like to talk big numbers (I do myself), but how do we get a little more science, anda little less bragging rights?

**jamesb** · 15th January 2004, 23:58

eddy, do you actually know whay a Kj is?
a Kj is watts per second.

If a disc has 4 Kj potential energy, and a 4000 watt spinning it, if it takes 1/4 second to stop it, you have applied 4x4 kj kinetic, and 4/4 motor power, ie 16Kw and 1kw = 17kw of impact energy.

ignoring the motor gives 16kw, thats 7% from the motor.

look at Eds.
3Kj in the disc, 4500watts off the motor.

1/4 second impact, and.....
12kw kinetic and 1100watts motor.
thats 10% of the total energy.

see, its not about the weight or MOI of the internals of the motor.
Hope this clarifies things.

**fwsorg** · 16th January 2004, 08:04

I agree entirely with that, but from my experience the length of an impact is a lot shorter than that, perhaps a 10th of a second at most. Of course I appreciate there are situations where, say, a large tooth spinning disc burries itself satisfyingly into a sheet of poly, and so will have a longer deceleration, but in most cases impacts last a very very short time- sufficient that the amount of energy produced by the motor that is directly transfered into the opponent is negligable in comparison to the energy the flywheel is transferring. It would be interesting to get a figure on what most people would regard as a typical impact time, but I would be fairly certain that it would fall short of 1/4s. Of course a shorter impact time is desirable, as its largely the rate at which the energy is transfered into an opponent that counts. Over the course of a days sailing, your average yaught sail must have had kilowatts and kilowatts of energy transfered into it from the wind, but nout happens in the way of damage. Focus all that energy at once (imagine some uber gust of wind) and you suddenly find youre missing your sail, mast, wrigging etc.

Im sure tooth design must play a huge factor in this- do people generally prefer the sharpish armour piercing teeth, or a bludgeoning type of tooth- Im sure that should perhaps be taken into account when deciding what is safe to run and in which arena- I would have thought that a thickish steel arena sidewall would be happier taking a bludgeoning, as opposed to a piercing, toothed spinner- thoughts gentlemen?

**robotwars** · 16th January 2004, 10:22

Well the RR arena, has 6mm steel plate as the kick board all the way round, and has proven strong enough for impacts, and spikes, and i would feel comfortable that it would take a general impage from a spinner.

However....

It is the worst case scenario that worries me about allowing spinners to run under controlled restraints.

ie flipper vs disc.... where horizontal becomes vertical etc... or its flipped over a wall.

thoughts?

Strip was very much untested and only had one real fight at inspire against Aaargh, the two discs met, vertical vs horizontal, and Aaargh enged up being thrown to the other side of the arena.

The 2 teeth are not piercing teeth as such because the tilted horizontal disc is designed to hit / throw opponents rather than pierce.

Jonno

**big_nipper** · 16th January 2004, 16:32

I Still think the motor plays a large part. Its not just about the stored energy. Take a stupid example where you have a 500mm disc with a tip speed of 100mph and only weights 1 gram. If you have a big enough motor (with no MOI) to maintain this speed and produces a torque of 500Nm then if Ive done my sums correcty you will have a point impact force of 100kG @ 100mph.

Dont all shout about it its probably wrong and completely ignores the stored energy in the disc as it does not weigh anything.

**jim** · 16th January 2004, 17:40

Jonno, would it be possible to put a thin (see-through) net or mesh in front of the polycarbonate to foul up any spinners which get above the kick board? I seem to remember chainsaw operators can get clothing with a fiberous layer designed to clog chainsaws, which is where I got the idea. Perhaps a widely-spaced net of really strong but flexible material like shark fishing line, for example?

Steve, would a strobe light be an effective way to check spinner speed? Its the only non-invasive way I can think of to check it. You could also attach a magnet to the spinner and use a coil or hall sensor to check it, but that might unbalance the flywheel.

**ewan** · 16th January 2004, 18:03

The spinner I have right now, relies quite alot on the actual torque and inner mass of the motor, at 3000rpm, it has lots of torque in itself, and will keep hitting, hit after hit. Yet the actual mass of the weapon is only about 2kg.
I think the featherweight spinners should be looked at more carefully, as they are evolving more and more. Strip could well have the power of many heavyweight spinners...