Re: OT: Repeatably lobbing "projectiles"

On 21/11/2024 07:04, Don Y wrote:

We're trying to make a mechanism that will allow for the
REPEATABLE lobbing of small projectiles over short (0-20 ft)
distances.
 We've tried using a constant force with a variable launch angle
(higher for shorter).
 And, a variable force with a constant launch angle (push harder
to throw farther).

Trebuchet is probably the method of choice. There is a bloke round here with one big enough to lob a watermelon about 100m. It is an impressive beast and flat packs into his pickup traler.
https://en.wikipedia.org/wiki/Trebuchet
He takes it around rural summer fetes to raise money for charity (and buying more water melons). They land with a very satisfying splat!)
One to throw a tennis ball 20ft would be a bit dangerous close to but very reproducible if that is what you want.

 The former seems to be easier to get repeatability.  But, still
not great as it constrains HOW you develop the force to be applied.
 A ferrous projectile would probably be easier to control
(think: rail gun) but then the projectile starts to become a safety
issue.
 Now, we're looking at alternate ways of developing that propulsive
force -- e.g., controlled air or water (messy!) pressure.  But,
I suspect qualifying the release valves' performance will prove to
be a stumbling point (and, how it changes).
 Any other ideas, given latitude in the design of the projectile?

--
Martin Brown