Re: OT: Repeatably lobbing "projectiles"

Don Y <blockedofcourse@foo.invalid> wrote:

On 11/21/2024 10:18 AM, bp@www.zefox.net wrote:

Martin Brown <'''newspam'''@nonad.co.uk> wrote:

>
One other thought you might be able to buy a tennis practice serve
machine off the shelf with high reproducibility.

 
The tennis ball thrower seems promising if the projectile weight is
close to right.
 
Another thought would be a crossbow-like mechanism with a motorized
winding mechanism. Range could be adjusted by moving the limbs to
vary the preload on the string. Bulk can be reduced by using a
reverse-draw layout.

 
The machine would have to move the limbs.  Once fabricated (and
"loaded" with a supply of projectiles), a human doesn't interact
with it.
 

[electronics content]
Many years ago I worked on a project to build a fast (microseconds)
opening gas valve. Introducing a flying weight (essentially a hammper)
between the first actuator and the rest of the control train improved
reproducibility by sharpening up the trigger impulse.  If you end up
using a pneumatic "gun" that would help regularize valve performance.
 
We used a pulsed coil accelerating an aluminum ring which then hit
the valve poppet to drive it off of its seat.
\[electronics content
 
A similar approach could be applied to a crossbow or catapult sear.

 
<frown>  This sounds complex.
>

It was.
 

What sort of performance did you see from "unassisted" valves?

Hammerless valves would start to leak millisconds before reaching
full flow.

I.e., what made it so important to have such a fast action?
 

The idea was to place a shaped "puff" of gas between two electrodes,
then apply high voltage to initiate an arc in the gas and compress it.
The experiment was called a  Z pinch. Since gas expands at the speed of
sound the puffing operation had to be finished in a few tens of microseconds.
Otherwise that gas would go places unwanted and cause trouble.

My point was that if your launcher's trajectory is disturbed by the release
mechanism, whacking the release out of the way will reduce the disturbance..

Thanks for reading,
 
bob prohaska