Path: ...!weretis.net!feeder9.news.weretis.net!news.quux.org!eternal-september.org!feeder2.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Don Y Newsgroups: sci.electronics.design Subject: Re: OT: Repeatably lobbing "projectiles" Date: Thu, 21 Nov 2024 04:31:45 -0700 Organization: A noiseless patient Spider Lines: 45 Message-ID: References: <1r3d9xi.enxrc8qj8b90N%liz@poppyrecords.invalid.invalid> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Thu, 21 Nov 2024 12:31:54 +0100 (CET) Injection-Info: dont-email.me; posting-host="3cee58121027d9a8e4865ed6f7ca0aa0"; logging-data="662347"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19SgepBnAl+76YoVHBK7Fco" User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Cancel-Lock: sha1:XAYNnqI0ZY3ZSsPlwkRyCb/uO6g= Content-Language: en-US In-Reply-To: <1r3d9xi.enxrc8qj8b90N%liz@poppyrecords.invalid.invalid> Bytes: 3151 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) The "release" seems to be a big problem -- getting a (home brewed) mechanism that cleanly releases so the stored energy can be transferred to the projectile as a step function. A similar problem exists if STRETCHING the spring to a particular amount of extension. There is a bit of twisting moment on the release mechanism from the tension in the spring mechanism. So, any slop in the "manufacture" results in a variable amount of binding. And, you need a lot of (electromechanical) force to disengage the release from the mechanism. I've been trying to get a feel for what we could do pneumatically or hydraulically in the belief that we could just buy premade valves that are (hopefully?) more repeatable. So, the controller would simply monitor the pressure in the "launch chamber" and open the release valve when the desired pressure had been achieved (simultaneously disabling the source of said pressure). Ideally, we want to be able to say "lob this projectile X feet" (along an azimuth that is separately selected). And, at a high enough angle that it ONLY impacts that location (none shorter nor longer).