DIY Nose Cones

[Bruiser]

So I recently ordered a Mini Comanche to use as a parts bin for several sport scale models at about 1/20 scale powered by the 13mm engines. The first rocket I am thinking of modeling is a MIM-23 Hawk. I drew it up last night in Open Rocket and found that I will need to add 7/8 oz of weight to the PNC-20A nose cone for it to reach the magic (at least) one caliber of margin for stability. I've attached the file.

This led me to start thinking of what if I turned a nose cone using my drill press? I am going to need to diy some nose cones anyway as at least one of the next rockets will be a Nike Smoke or another Nike rocket similar to the Smoke but slightly different like the sustainer of the Nike-Nike rocket, but I digress...

Anyway, I am wondering what if I turned/made the nose cone out of something like basswood... Maybe I could hit the weight and have a nose cone that wouldn't be as easily nicked/damaged as one made out of balsa.

Does anyone think that would pose any problems or issues?

Thank you,
-Bob

 

[Gary Byrum]

Try using poplar as a cheap intro to lightly weighted wood. Plus it's way less likely to dent. Oh, and btw, I think you meant 13mm instead of 33mm.

 

[Bruiser]

Gary,

You are certainly correct; I did mean 13 mm engines. I went back and corrected my error

Poplar is a great choice too. I think dowels are either poplar or oak. Maybe I could start off with a 3/4" dowel and have little waste. I'd have to get the center of the dowel just right though. Off center just a slightly and I might end up without a shoulder. Hmmn...

-Bob

 

[Gary Byrum]

errrrr.....I've tried dowels many times and usually the best results were from a block. I even use a lathe and the dowels just never seem to work out. The PNC 20a is a great substitute for actual scale. The difference is negligible. I have a few different size drawings of my own. Built one using a BT 60 but it was more pseudo scale. Looked OK though.

 

[BABAR]

With scratch building, it is always a balance between how much your time is worth (in this case to hand make a nose cone) versus how much it costs to get it ordered and shipped to your door. Of course, there is always that additional and very real pride value of "I made this nose cone (body tube, launch lug, engine hook, whatever) MYSELF."

I still like Carl Sagan's quote in reference to Scratch Building:


if you wish to make an apple pie from scratch, you must first invent the universe

 

[Gary Byrum]

In my case, turning became a necessity. It was way hard to find specific sized nose cones for the birds I scale or build. Most everything is scratch anyway. And even if it were available online, chances are I'd make it myself because I'm a cheap skate and hate paying shipping charges. That differs when if by chance, I'm already ordering a bunch of other things from the vendor that stocked it.

 

[Bruiser]

I'm thinking along the lines of Gary. I'm cheap too and I hate paying more for the shipping than the part is. Also, I haven't been able to find a Nike Smoke cone to fit a BT20 and the cone for the sustainer on the Nike-Nike rocket would need to fit a BT20+ tube so I'm pretty much locked into creating my own. And yep, I realize it's kinda nuts. Sometimes I just ask myself "what would Sheldon do"

I figure the first one will be the hardest because I need to develop some sort of jig to attach to my drill press to turn it into a pseudo lathe. After that I bet it won't take long to turn out a little 3/4" x 3" cone

-Bob

 

[GlenP]

... I haven't been able to find a Nike Smoke cone to fit a BT20...

That conical nose would actually be a good candidate for making out of cardstock. First, you don't even have to invent the universe, just go to PayloadBay.Com and print up a transition template.

 

[Andrew_ASC]

Sheldon is a TV actor. I’m just a dorky mechanical engineer student. Not my first nosecone have rocket team experience.

It’s fun to play with university software. It’s fun to design your own nosecones. Kinda crazy like you said. Hahaha. You will have pride of making your own. That takes skills I don’t have.

 

[Bruiser]

It that Styrofoam? Looks very good!

I just ordered a rotary tool tp turn into a mini-lathe. I tried doing it on my drill press and I think I have a useable nose cone but I think I could do it better if the stock was horizontal. You Tube plants these ideas in my head

-Bob

 

[Andrew_ASC]

No. It’s nylon.

 

[Bruiser]

Is it printed? How did it go from the design to the actual item?

-Bob

 

[Andrew_ASC]

Yeah. You have many questions.

 

[Steve Shannon]

Yeah. You have many questions.

Don’t put it out there if you don’t want questions. This is a rocketry forum.

 

[Andrew_ASC]

More info is in the X1.4 HPR project thread. Scratch building a high power 24mm MD supersonic Mach 1.4 rocket. The nylon would be too heavy and process too costly for LPR uses I believe.

 

[Alan15578]

More info is in the X1.4 HPR project thread. Scratch building a high power 24mm MD supersonic Mach 1.4 rocket. The nylon would be too heavy and process too costly for LPR uses I believe.

Nylon? We did some supersonic MR trade studies and design testing decades ago. The fastest was a measured M1.42 using a vacuum formed 29mm CMR parabolic nose cone. The lighter weight trumped all the more exotic nose shapes. We also measured M1.1 with a 24mm E50.

Please, more real world measurement, and less over building and speculation.

 

[Andrew_ASC]

They could buy two to three Estes kits for the manufacturing price of my nosecone. A spring SEDS team pushed the material to M1.89 this year with “real world flight testing” on a multistage HPR build. As a college we don’t have the vacuum forming equipment you did. Or that kind of engineering expertise in trade studies.

 

[Alan15578]

They could buy two to three Estes kits for the manufacturing price of my nosecone. A spring SEDS team pushed the material to M1.89 this year with “real world flight testing” on a multistage HPR build. As a college we don’t have the vacuum forming equipment you did. Or that kind of engineering expertise in trade studies.

Sorry, we are drifting away from the original focus of this thread. But just to clarify my response: "We" referred to a group of four udergrads doing a group senior project in the Aerospace Engineering department of Iowa State University. I served as their project advisor. The amount of "engineering expertise in trade studies" is debatable as I had to let the students do their own work. They did design, build, and fly several rockets with different nose shapes, and recorded flight performance data for each flight. The student responsible for doing the flight data analysis could not figure out how to do it properly, and each of the four students had to write a report on their portion of the project and make a presentation showing their poor results. I however did the data analysis myself and verified the achieved supersonic performance. It was not like we had university expertise, just four students who just wanted to get it over with. The CMR nose cone was just a commercial model rocket part that I had in my personal supplies. The department had a nice selection of composite materials available, but the rockets the students built were rather mundane, 1/16" plywood fins, some nose cones turned from solid pine. I was impressed that they had no flight failures, except for a broken shock cord. And we did beat Chuck Mund's old record of M1.3, with better documentation, using a slightly less capable motor. I submitted an NARAM R&D report, a fusion of the four students reports, plus my data analysis and conclusions. I can't comment on the college HPR competitions, except to say that some participants may be overthinking the problem and making it harder than it needs to be.

As for DIY nose cones in general, you need to creatively use whatever tools you have available. With some skill, you could carve a good nosecone with cub scout pocket knife. Many people have used an electric hand drill clamped in a large vise. I've always turned nose cones between centers on a real wood lathe, with good results.

 

[GlenP]

...sport scale models...powered by the 13mm engines. The first rocket I am thinking of modeling is a MIM-23 Hawk...and found that I will need to add 7/8 oz of weight...

How important is it that you maintain scale? Another option is to stretch the body tube a little. 7/8oz is a large fraction of the 3oz max liftoff weight for the A10 engine. With a stretched body tube you maybe able to add less nose weight and get higher apogee as well with an overall lighter weight rocket. Also, you could make the fins slightly larger than scale, but that may also shift c.g. to the rear along with c.p., might work okay with thin light balsa sheet stock like you would probably use for typical 13mm power.

 

[Gary Byrum]

+2 - I agree. I've done pseudo scale rockets and most people can't tell the difference. Put being perfect behind you.

 

[milehigh]

There's an old woodcarver's saying that can be applied to turning nose cones as well:

"Take a piece of wood and remove all the parts that don't look like a nose cone."

I know this doesn't help, but it's amusing nonetheless.

 

[Bat-mite]

There's an old woodcarver's saying that can be applied to turning nose cones as well:

"Take a piece of wood and remove all the parts that don't look like a nose cone."

I know this doesn't help, but it's amusing nonetheless.

I think that's how Michelangelo's David got sculpted, except with a block of stone.

 

[neil_w]

When I first saw your post I thought "OMG 7/8 oz is a huge amount of nose weight for a 13mm rocket". And so I took a look at the OR file. My overriding comment would be that you need to clean it up a lot before you can make any estimates of your nose weight. For example:
1) The fins are 1/8" cardboard, which means that they're way too thick, and weigh a ton. Switching it to 3/32" balsa makes a huge different.
2) The body tube is cardboard, .079" wall thickness. Try using a real BT-20 from the parts database.
3) The tail cone is also thick cardboard.

So, I'd say get that all straightened out. 13mm rockets need to be light, each error like that has a large impact on things.

Once you get a more accurate idea of the nose weight required (it'll certainly still require *some*), you can see what your material options are for the nose. It may be that a heavier wood will give you a more accurate weight. I don't know if that'll make it easier or harder to obtain, and/or easier or harder to turn, but you'll have a clearer idea of your options.

 

[Bruiser]

Hey Neil,

Thank you for pointing those things out. I'll go back in and fix them. I planned on balsa for the fins so I don't know how it got set to cardboard. I selected BT-20 from the database. I thought it was a standard tube so I'll get that fixed too along with the tail cone which should just be paper.

This was only my second try using open rocket so I have a lot to learn with it. Really appreciate the tips there.

BTW, I tried using my drill press for a Nike Smoke nose cone. I started with a 5" long piece of 7/8" dowel which I squared to the drill press with two combination squares to drill 1/8" pilot holes at each end. Then I drilled out one end to 3/16ths and glued in a dowel. I glued a 1/8" dowel in the other end. I chucked up the 3/16" in the drill press and I set the height so the 1/8" dowel was situated in a hole that I had drill in a block of wood that I had clamped to the table. I turned on the drill press and started sanding and the 3/16th dowel broke. I drilled it out and screwed in a bolt that I cut the head off and re-tried.

Well it turned out that when I drilled out the dowel I must have gone it at an angle because I had a little wobble there. I was able to turn out a pretty decent cone but the shoulder is a little off. I am going to try working on it a little by hand to see if I can get it "straightened" out. It's just a little off.

I watched some you tube videos and I decided I am going to build a mini lathe with a rotary tool. I ordered one from Amazon that looks like it'll do the trick. Once it comes in I'll figure out what size to make the base and what-not.

Anyway, thanks again for the inputs.

-Bob

 

[Bruiser]

I made the corrections and it has dropped the weight need down to .3 ounces.



I've also started to build my rotary tool lathe for turning small nose cones

-Bob