Unlimited Rotational Kinetic Energy Storage?

[Guest]

Unlimited Rotational Kinetic Energy Storage?

Thanks Mark,

Is that 7600kJ the chemical energy in 500ml of fuel? If so, do you have a good sense of how efficient a small motor is? I recall something like 30-40%. 2.2MJ still makes an ICE pretty attractive.

The whole flywheel idea is to be able to buffer your ICE or electric motor energy output so that you can run the motor at 100% until the flywheel is at its max design speed (Im thinking more like hundreds of RPM). Then you can extract energy from the flywheel as needed by a weapon or whatever and have the motors continue to pump restoring energy into it. Then you arent limited by the peak power output of the motor for each weapon use.

So now I must think on the ICE powerplant instead of the electric motor. As a mechanical engineer, that suits me just fine

Mack

[maddox]

Unlimited Rotational Kinetic Energy Storage?

Thanks Mark.Your answer has done what I hoped for. Proving that CO2 power isnt everything, and that to build a good system, you need to take everything in account.

Oh, and it will take longer than 3 seconds to vent a 2 kg CO2 bottle.The let trough is rather small.
And expanding slowly? Not for a flipper or axe Im afraid, we want explosive reaction, to have as much force in the action as possible.The bottles that come out of a robot used in combat, those are frozen all over, and sometimes solidified CO2 is heard to rattle in the bottle.

[Guest]

Unlimited Rotational Kinetic Energy Storage?

Some small methanol RC motors do about 40000RPM and peak at over 2000W (but only weighing about 300 grams each).

Youll need some monster gearing to bring that down to a sensible speed, but for a spinning disc?

[mark_m]

Unlimited Rotational Kinetic Energy Storage?

Mack: I read somewhere the actual energy content of petrol was 50MJ/kg but most engines are only 15% efficient. This is immaterial though becasue its the weight and performance of the whole package that counts.
I think you idea for using an internal flywheel to store energy from an ICE is interesting. It could work really well on a crusher to allow you to quickly get a nip on your opponent, using all the energy youve stored while manouvering for position. Given the way hybrid car designers are going though, I think it would probably be easier and more efficent to use the engine to drive a motor/generator to charge your batteries, then when you want max power out use the engine and motor in parallel.
Mario:You know much better than me about the realities of CO2. I was thinking that to get the most power out you would charge multiple buffer tanks, allowing the phase change to allow over a relatively long time, then empty them quickly into a ram. Am I correct in thinking that CO2 freezes at -50C? If all the gas cooled to this level I think you would still get about 20kJ out. Does this sound reasonable to you? I heard that Gravity can get about 100 flips. 100 flips of 1m high is 98kJ! Does Gravity have 2 2kg tanks as by my calculations that would be just over 100kJ stored on board.
Chrisitan:Can you give me some more information on those engines (Supplier, price etc). The gearing in RC cars handles that power with a gear ratio of about 8:1 and doesnt weigh too much. The belt drive to the disc can handle the rest of the reduction.
The bit that appeals to me the most about using a setup similar to this is that many RC cars use an automatic transmission, meaning that you could have low gear ratio for a fast spin up time, but then the high gear would kick in and still give you high maximum energy storage. The only problem with this is I dont know how much heavier the system would be after you had reinforced it enough to survive in the arena. Have any uk featherweights used nitro engines succesfully?

Mark

[maddox]

Unlimited Rotational Kinetic Energy Storage?

Mark, Gravity uses 2 2kg bottles,and 2 buffertanks.Newer versions of this set up use more but smaller buffertanks, to get more surface to exchange heat.
Now, WJ never tested Gravity on the amount of flips he has, but 50 good ones reasonable reasonable.As demonstraded in the wars, After about 30 weaponactions enough force was applied to get Dead metal turtle.
CO2 solidifies on -79°C.And has something like 15 bar at -10°C-this is a guestimate.The ram of Gravity was 100 bore 180 stroke with a leverage of 4 to 1. On 15 bar that still gives you a 295 kg shove for a lifting hight of 720mm.This is more than some other FP using heavies have with warm bottles.(Hard for example).

Oh, and by the way, my grasp of the porperties of CO2 are all based on practical tests, not a lot of calculations.Only the safetyfactor on the used materials and mechanical parts are calculated toroughly.

[Guest]

Unlimited Rotational Kinetic Energy Storage?

Mark, the one I was thinking about is manufactured by OS Engines.

http://www.osengines.com/engines/osmg2071.htmlhttp://www.osengines.com/engines/osmg2071.html

The price should be about £200 (but as a foreigner, Im not 100% certain about this).

[mark_m]

Unlimited Rotational Kinetic Energy Storage?

thanks Christian. I too found it for about £200 on the net.
http://www.centrehobbies.co.uk/acatalog/engines_car_os.htmlhttp://www.centrehobbies.co.uk/acata...es_car_os.html
Is more expensive but shows a range of engines. Its interesting to compare them in price and performance to a Magmotor:
._______________|___Mag______|__OS .21 V-R__|
cost____________|___£269_____|___£210_______|
peak power______|___2234W____|___1875W_____|
weight__________|___1.7kg_____|___0.315kg____|
max revs________|___6000RPM__|___42000RPM__|
peak torque._____|___14Nm_____|___~0.5Nm____|

If the nitro were geared to the same max RPM as the electric it would still only produce a peak torque of 3.5Nm. I think this must be why such light drive-trains can handle such relatively high power in RC cars. It also shows why they have multistage gearboxes.
Mario:I based all my figures on calculations using basic formulas so wouldnt expect them to be too accurate. Ive found a phase diagram for CO2 that basically agrees with what youve said.
Do you have any experience of CO2 being use to power rotary actuaters? Given pnuematic systems high max power to weight ratio they should be good for accelerating a disc.
Mark

[Guest]

Unlimited Rotational Kinetic Energy Storage?

But for a small spinning disc (with one of those three stage gearboxes), theyll probably great!