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Spinning disk question
Posted: Sat Jun 07, 2008 4:00 am
by Carlman
If i had a spinning disk that measured 8cm in diameter and i wanted the outside to be moving at 300km/hr how many RPM would the disk have to be spinning at?
Posted: Sat Jun 07, 2008 4:27 am
by jackssmirkingrevenge
So, the disc has a circumference of (pi x diameter) around 0.00025 kilometres, so at 1 rpm the outside is travelling at 0.015 km/h
You want 300 km/h however, which means that your disc is going to have to be spinning at (300 / 0.015) the grand rate of 20,000 revolutions per minute.
Do I sense a centrifugal launcher in the works...?
Posted: Sat Jun 07, 2008 4:36 am
by SpudFarm
mabe he is making something like the steam cannon mythbysters made?
(i saw only 3minutes of that episode)
Posted: Sat Jun 07, 2008 4:38 am
by Carlman
jackssmirkingrevenge wrote:Do I sense a centrifugal launcher in the works...?
maybe...
your too good JSR! 
Posted: Sat Jun 07, 2008 4:39 am
by SpudFarm
you will need one hell of a thing to spin it.
Posted: Sat Jun 07, 2008 4:42 am
by Carlman
spudfarm wrote:you will need one hell of a thing to spin it.
rc airplane motor and gears
Posted: Sat Jun 07, 2008 4:43 am
by SpudFarm
frakin NICE!!
Posted: Sat Jun 07, 2008 4:51 am
by jackssmirkingrevenge
Carlman wrote:rc airplane motor and gears
That will have to be quite a substantial motor, considering the load it will be under, I suggest you read up on the
theory before attempting anything, or simply use the biggest motor you can find and go from there
Posted: Sat Jun 07, 2008 4:52 am
by Carlman
just found this on ebay
link
worth getting?
Posted: Sat Jun 07, 2008 4:53 am
by SpudFarm
oh i thought you was using a nitro engine
Posted: Sat Jun 07, 2008 4:55 am
by Carlman
jackssmirkingrevenge wrote:Carlman wrote:rc airplane motor and gears
That will have to be quite a substantial motor, considering the load it will be under, I suggest you read up on the
theory before attempting anything, or simply use the biggest motor you can find and go from there
yea well that is the thing im debating on a hard slog at a centriugal lancher like the PEST or a tennis ball laucher style used for bbs.
Posted: Sat Jun 07, 2008 4:58 am
by jackssmirkingrevenge
Looks good for the price.
Load Speed (rpm) : 39000
That should suit you fine, probably without a gearbox... now get your hands on some epoxy and carbon fibre matting and make yourself a lightweight yet strong disk
Posted: Sat Jun 07, 2008 5:10 am
by Carlman
this could be fun
Posted: Sat Jun 07, 2008 6:33 am
by POLAND_SPUD
put some pics when it's ready...
Posted: Sat Jun 07, 2008 8:27 am
by TurboSuper
Hook it up to a Dremel, those things run at a clip of around 30,000 RPM at max speed.
I've even seen some knock-offs that claim to go up to 40,000 RPM.