Has anybody ever though to create a CD launcher? A very flat barrel with one side having rubber to put a spin on the cd's...
It would be insane.
I have been thinking about making one of these for years. The only problem is collecting the spent amunition.
Posted: Fri Sep 28, 2012 8:01 pm
by Fnord
You'd be better off with a slingshot-based disc launcher in most cases.
There's not much surface area on the edge of a cd for the air pressure to act on, and you'd also have a large amount of gas blow-by.
Although I agree there is not alot of surface area for the air to contact the cd. I do not agree on the blow by. This project would be made from solid aluminum bar. The barrel, being flat, would be machined on a mill. The air that blows by would be directly related to the amount of clearance I give the cd. If I only give 1/64" clearance, the cd should launch fine.
I guess the next step is to grab a bunch of cd's and measure to see the build tolerance in thickness.
Posted: Sat Sep 29, 2012 6:45 am
by Insomniac
You'd need an exceptionally high pressure to get decent performance. You've got a lot of surface area which will be contributing to friciton, and very little which will contribute to the launch. Some sort of sabot would be wise.
Posted: Sat Sep 29, 2012 7:10 am
by gyrotech
something like this,
Posted: Sat Sep 29, 2012 7:12 am
by gyrotech
I've considered a foam sabot. I'd like to make this semi automatic. So I'd like to stay away from the sabots if possible.
Posted: Sat Sep 29, 2012 7:17 am
by gyrotech
Cd's measuring at 0.042" to 0.045".
Tolerance being 0.010" for slop on the thickness.
You may notice a second cut in the middle, another 0.020" and roughly 1.6" wide. If you pick up a cd you can see a raise bump on the bottom.
Posted: Sat Sep 29, 2012 10:51 am
by Technician1002
A couple of issues come to mind. The first is the so called horsepower/weight ratio. Due to the small cross section area for air pressure, the total power that can be applied is quite low in relation to the overall mass. This is like shooting a plastic slugs several inches long. Add brakes on one side to provide spin and the result is even worse. Air blowby will tend to wave the flag as the flow becomes chaos instead of laminar. A CD has limited rigidity wiich will result in considerable energy loss making a reed horn out of the CD which may result in destruction of the CD in higher pressure applications.
As mentioned above, a sabot can drastically change the acceleration curve.
Other designs that work well include a slot with spinning tire pairs that progressively increase the speed. The tire design with high kinetic energy is able to launch a stack of 100 CD's in machine gun fashion for a very impressive launch.
Another serious issue is the relation of the cross section of the bore to the surface area of the bore. There is lots of surface area for windage drag. All of the flow is within 1/8th inch of a fixed surface. This provides high drag on all the air flow.
