Nose cones

[SolarYellow]

I've realized I spend too much time thinking about off-the-shelf nose cones and what they'd be good for.

The reality is, very few of them are really ideal for anything except duplicating or up/downscaling other model rockets. They are generally not performance optimized and generally don't work just right as scale nose cones for specific sounding rockets or other scale subjects.

For example, why is it that, after 80 or more years of the Von Karman nose cone geometry being defined and 60-70 years of having research validating its excellence, there aren't any mass-produced Von Karman nose cones for MPR or HPR rockets? The vast majority of LPR and MPR commercial nose cones are overly long ogive or variations on that. Considering the data I've looked at, it seems that any nose cone meant for a rocket that would go transonic up to about Mach 1.5 and back should just be a Von Karman with a fineness ratio in the range of 3.5:1 to 5:1. I've been looking a lot and can't name a single commercial cone (*haven't scrubbed the entire Semroc catalog) that fits that description.

Although everyone knows it's the most efficient shape below the transonic range (where all Estes-powered rockets live), ellipticals are seriously limited. The only tooled plastic elliptical cones I can name after a ton of OCD are the Estes PNC-20B, NC-60L, NC-80b, and the BT-60 Astron Sprint. There's a really nice BT-50 cone used on the glider for the Super Orbital Transport, but it doesn't seem to be available any other way. Of those mentioned, the NC-60L and NC-80b look kinda dumb and nerfy, although they are probably close to ideal technically for the Bertha rockets.

This OCD I have seems to be a habit from built from decades of working with systems where the parts are much more difficult and expensive to build, so being an applications guru and figuring out what parts could interchange and be applied effectively in unexpected places had a ton of value. Now, I have a 3D printer and can make any nose cone I want. I need to forget about the goofy OTS stuff and just think about what I want to build, then build it. In rockets, I need to forget about the box of what has already been commercially tooled. It's not enabling, it's limiting. And it's become a massive waste of time. I need to change my thinking to just be, "What's the best thing to build?" and focus on building that.

 

[Cape Byron]

Three words: 3D print er.

Okay, that was facetious but that's the way to get what you want when you want it.

Lots of people here with the skills and the equipment. I'm sure many would be happy to help.

 

[bad_idea]

Considering the data I've looked at, it seems that any nose cone meant for a rocket that would go transonic up to about Mach 1.5 and back should just be a Von Karman with a fineness ratio in the range of 3.5:1 to 5:1. I've been looking a lot and can't name a single commercial cone (*haven't scrubbed the entire Semroc catalog) that fits that description.

Composite Warehouse purports to have 5:1 von Kármán cones in several high power sizes, but CW is famous for taking money months or years before shipping. Performance Hobbies carries a few which I've heard are made by Composite Warehouse, but most are out of stock. Wildman makes 5:1 von Kármán cones too.

Curiously I've seen the Wildman and CW cones of the same size side by side, and the CW was considerably longer. Not having measured them, I don't know the aspect ratio of either, but clearly at least one of them was not 5:1.

 

[SolarYellow]

Now, I have a 3D printer and can make any nose cone I want.

Three words: 3D print er.

We are in full agreement. But just to be pedantic, I would choose the words, "three dimensional printer."

 

[Ez2cDave]

https://www.shapeways.com/product/Q2QV3C2WL/nose-cone-0-98-in-5-to-1-von-karman

https://www.printables.com/model/157671-von-karman-haack-series-nose-cone

 

[SolarYellow]

That Shapeways cone is pretty darned expensive for a BT-50 cone.

There are several nose cone generators for OpenSCAD that will do Von Karman cones. I like OpenSCAD because it works well with how my brain works, so I've been able to take other people's part generators and hack around with them, as well as building my own stuff from scratch.

 

[bad_idea]

I like OpenSCAD because it works well with how my brain works, so I've been able to take other people's part generators and hack around with them, as well as building my own stuff from scratch.

It seems to work very well for the design-once, scale-arbitrarily case that fits so many rocketry needs.

 

[SolarYellow]

OpenSCAD is beautifully simple for simple objects. It can get fiddly at an almost exponential rate as the complexity of a design grows. I really need to figure out how to use modules and presets. I initially just started opening files created by others and hacking around in them, and was successful in what I tried to do. I've been able to do some more stuff simplistically with a lot of repetition, but I need to get more efficient at using the tools it includes.

The nose cone generators I've messed with mostly generate solids, which have to be shelled in the slicer. My next direction will be extending them to create shelled parts and then building features to locate components within them, like thread inserts for retaining ebays, etc.

Will also be extending fin can generator geometry with the idea of making integral boat tails and such.

I'm able to play in parallel with AutoCAD and F360, so lots of learning and rocket stuff to do that doesn't involve sanding bubbles in TB III fillets.

 

[OzHybrid]

OpenSCAD is beautifully simple for simple objects. It can get fiddly at an almost exponential rate as the complexity of a design grows. I really need to figure out how to use modules and presets. I initially just started opening files created by others and hacking around in them, and was successful in what I tried to do. I've been able to do some more stuff simplistically with a lot of repetition, but I need to get more efficient at using the tools it includes.

The nose cone generators I've messed with mostly generate solids, which have to be shelled in the slicer. My next direction will be extending them to create shelled parts and then building features to locate components within them, like thread inserts for retaining ebays, etc.

Will also be extending fin can generator geometry with the idea of making integral boat tails and such.

I'm able to play in parallel with AutoCAD and F360, so lots of learning and rocket stuff to do that doesn't involve sanding bubbles in TB III fillets.

For rocketry, I define my modules/components generally with center set to false. center=false. That way when you combine another module you know it starts off sitting on the xy plane. Good luck with SCAD. It's a lot of fun.
If you create something that's useful or manage to fix someone elses work, share it so we can all use it.