btrettel's Nerf blog

random thoughts about the ballistics of foam darts

Archive for the ‘NerfEngrWiki’ Category

Pneumatic gun model on NerfEngrWiki

Posted by btrettel on January 17, 2011

While what I have posted is far from complete, I have started posting a derivation of a relatively simple model of a pneumatic gun on NerfEngrWiki. Feel free to use the comments section to ask questions, etc., if you have any. I don’t suspect many people will have questions, but I do know a few folks are carefully examining what I have developed.

I also have started working on a page about valves with a focus on modeling the flow through valves for pneumatic gun models. So far I have used this page to derive in detail (something I have not seen before) one of the valve flow equations that I have seen.

More pages will be developed. I’d appreciate any contributions that can be made, too.

Posted in Interior ballistics, NerfEngrWiki | Leave a Comment »

Kinetic energy density on NerfEngrWiki

Posted by btrettel on January 10, 2011

Today I nearly finished a page on kinetic energy density for NerfEngrWiki. KED is one of the more important concepts in the safety of Nerf guns (and that much was admitted by chiefthe, a former Hasbro engineer). I detail the most important topics about kinetic energy density, however, I do not make any suggestions about what critical KED value to design for. I do not think enough data is available to make that decision. However, I intend to limit the most powerful blasters I make to a KED of 20\tfrac{\text{mJ}}{\text{mm}^2}.

Posted in NerfEngrWiki, Terminal ballistics | Leave a Comment »