Re: OT: Repeatably lobbing "projectiles"

On 21/11/2024 11:37 pm, Don Y wrote:

On 11/21/2024 5:15 AM, Liz Tuddenham wrote:

Don Y <blockedofcourse@foo.invalid> wrote:
>

On 11/21/2024 2:53 AM, Liz Tuddenham wrote:

Bow and arrow?
>
That was actually meant seriously as the geometric arrantement of the
string acts as a variable-ratio transformer between the movement of the
propelling spring (bow) and the increasing velocity of the load (arrow).
This means that if you charge the spring with a known amount of energy,
it will always be transferred with the same high efficiency into the
load.
>
By varying the starting point of the arrow, and hence the spring
tension, you have an accurate repeatable energy input.

>
The "variable force constant launch angle" approach was
implemented on a similar principle:  pull a spring back to
a particular amount of compression and then release.
(This is how a pinball is launched, hence my inspiration)

>
That is a less efficient system because a lot of kinetic energy is left
in the spring after it has lost contact with the projectile.  The

 But the spring is fully extended (decompressed) when the projectile
departs.  (?)

The spring is moving as fast as the projectile when it separates from the projectile. The same objection applies to a bow and arrow, but there it is the relatively light bow-string which is moving as fast as the projectile, and the relatively heavy bow moves a lot more slowly than the string.
<snip>
--
Bill Sloman, Sydney