Nitro Engines

**geoff** · 7th April 2004, 14:43

Sorry guys,
Flame throwers are banned!!

FRA rules 12.7 to 12.7.3.3. applies

(And I dont need to check that one with Sam!!)

James, nitro powered spinners 20-25,000RPM 1:1 on a relitivly large dia. strong very lightweight disc...More than possable.. Totally devastating, they behave more like a circular saw than a KE weapon. But depending on engine can have a reletivly slow spin up time, and need some form of clutch to prevent motor stalling on impact, already done the maths and basic designs for one a while back!

**fwsorg** · 7th April 2004, 17:06

The deceleration of a large fia disc from 20krpm to 0 during an impact is mind boggling. Something wull break, preferably the opponent :-)

Its spin up times that are the important thing with feathers now. Feather anenas arnt pearticularly big, and it takes a very short time for your opponenet to be on you. Im tempted to try and design something to kick start the disc up to about 1krpm in a second or so. Any thoughts on such a design? I machined some suitable clutches today at work for a client, and they got me thinking about some kind of air or spring powered device to give the disc an initial power burst right on the activate, and then disengage and let the motor do the rest. Am I being silly? Thoughts?

Eddy :-)

**geoff** · 7th April 2004, 18:15

Eddy, lets put it this way..A nitro spinner is a wonderfull dream! As I said I did the maths on one back when Scorpion Jr. was on the drawing board and I concluded that one of two things would happen, one, it would take too long to get up to a useable speed (2kg disc, 250mm dia, 15cc motor via a centrifugal clutch would take around 9 seconds to reach full speed) or two, If you did get it there the KE would be in the order of 43Kj!!! and something WILL come apart!(More than likely a catastrophic failing of your machine. 43Kj is somewhere around twice the energy that our lynch powered heavyweight spinner produces!)
At that point, I went right off the idea!!
You might do better in using one to run a cutting / saw blade rather than a KE weapon.
Far less mass, quicker spin up time and no problems with impact shock.
Just some thoughts, I think anyone trying one of these needs to be EXTREMELY CAREFUL!!!

**ewan** · 7th April 2004, 18:53

Is it the speed thats the dangerous part???

**geoff** · 7th April 2004, 19:10

Its a combination of the very high speed and the extreme KE in any rotating mass! Unless you seriously know what you are doing I would leave well alone!

**fwsorg** · 7th April 2004, 20:24

EDIT: see below

**fwsorg** · 7th April 2004, 20:25

Ewan, The stored energy of a flywheel is determined by the equation:1/2Iw2Where:[*]1/2I is half the moment of inertia of the flywheel,[/list]and[*]w2 represents the angualar velocity (radians/sec, which is just another unit of speed of rotation (i.e. rpm) ) squared.[/list]So you can see that the speed has a far greater bearing on the energy of the disc- doubling the speed will yeild 4 times the stored energy, triple the speed yields 9 times the stored energy et cetera. So in otherwords, yes it is the speed that is the dangerous part!