Aluminum Nose Cone Tip Scrap Build

[Redneck_Pyro]

No that wasn't a typo, I meant scrap.

While I was planning out my L3 project I decided to pick up an Extreme Wildman kit to keep my hands busy. When I got it and saw the aluminum nose cone tip I decided that all of my high power nose cones from then on would require aluminum tips just like it. I then decided that if I were going to start putting nose cone tips on my rockets like the one that came with the Wildman kit I had better figure out how to make that happen. The logical way to go about something like this would be to hire someone to machine it for me. I have never been very keen on doing things the logical way. So, I set about figuring out how to do it myself.
What I ended up doing was taking something like this:


(Actually the picture is of a water pump, I ended up using a turbo charger and some of my wife's Christmas cookie cutters)

and turning it into something like this:



and this:


(I liked the look of the carbon inclusions so I decided to leave them in)

And when they are installed on a nose cone they look like this:



I wasn't sure if anyone would be interested in the process I came up with as well as the mistakes that I made along the way. If people are interested I would be happy to write the whole thing up and post it here.

 

[GregGleason]

Sure!

I have now idea how you did this so please post.

Greg

 

[chadrog]

I'm guessing you needed a vacuum cleaner?

 

[Redneck_Pyro]

I tried a vacuum cleaner but the air flow was to high. We switched to using just a regular house fan. Seriously. This is a video of our very first attempt at casting aluminum, unfortunately we had way to much water in the sand and we created foamed aluminum nose cone tips. They were very light, but very fragile.

[video=youtube_share;gXnhMXlRgTU]https://youtu.be/gXnhMXlRgTU[/video]

But really, the idea of casting nose cone tips seams far more difficult than it really is. All you need is a metal bucket, some special concrete, a fan, a metal pipe, charcoal, and a crucible to hold the molten metal. The first crucible I tried was an empty small propane canister like what you use with Coleman stoves and it worked like a champ for awhile. After a couple of melts it started leaking and had to be retired. A coffee can also works, but usually only once.

When I started this I had set myself a budget of no more than $75.00. So I tried to do everything as cheap as possible.

Here is my original shopping list:
6 Gallon Metal Trash Can from Home Depot - $16.00
I chose the 6 gallon size because it would be easier to put away in my garage when I was done.
Bag o' Portland Cement from Home Depot - $5.00
Bag o' Play Sand from Home Depot - $4.00
Big Bag o' Perlite from Home Depot - $17.00
Box o' Long skinny machine screws and Nuts - $ Don't remember what they cost at Home Depot
8" diameter stick o' Sonotube from HD - $6.00
1" x 12" Black Steel Nipple from HD -$6.00
Fragrance Free Clay Cat Litter from Petsmart -$4.00
Charcoal

Everything else I was able to find around the house, those things consisted of something to blow air into the concrete bucket, and a steel can to hold the aluminum.

This is what it looked like when I was all finished putting the furnace together:


Getting the concrete concoction mixed and cured correctly can be kind of tricky, and I will get into those details later.

 

[dixontj93060]

Interesting, very interesting.

 

[CarVac]

It sounds cheaper (assuming you already have a lathe) to turn one rather than cast one...

 

[Scott Evil]

We do this at a rate of 190 tons per hour (and with Iron) where I work but you make it look easy. :blush:

Sounds like a great way to turn my PR 5:1 7.5" NC into the one I really want but can't just purchase.

Any and all details on how you got this machined down and to fit and attatch correctly/straight you could demonstrate would be awesome if you can share.

What flavor aluminum did you use?

-S

 

[Redneck_Pyro]

It sounds cheaper (assuming you already have a lathe) to turn one rather than cast one...

I did not have a lathe at the time and I thought this might get me out of buying one. It didn't. It probably would have been cheaper to pay someone to do it for me, just not nearly as much fun.

 

[Redneck_Pyro]

We do this at a rate of 190 tons per hour (and with Iron) where I work but you make it look easy. :blush:

Sounds like a great way to turn my PR 5:1 7.5" NC into the one I really want but can't just purchase.

Any and all details on how you got this machined down and to fit and attatch correctly/straight you could demonstrate would be awesome if you can share.

What flavor aluminum did you use?

-S

I will get more written up on the process later tonight, don't you worry.

The aluminum alloy I used is kind of a trade secret. But it consists of a mixture of broken car parts, hard drives, some square tubing that someone gave me, and baking stuff that I scrounged from the kitchen while my wife was away. Very technical stuff with lots of gas chromatographs, and scanning electron microscopes used along the way.

 

[kenstarr]

Is that the Dave Gingery charcoal foundry? Got that book when I was 14 and do some crude castings now and again but never thought of that! My L3 will probably have the same setup! Good work and inspiration there!
ken

 

[Redneck_Pyro]

I don't know who came up with the original design, but I am sure my setup is pretty close to what you are thinking of. There are only so many ways to blow air through charcoal sitting in the bottom of a concrete lined trash can.

 

[TheAviator]

That is really cool. I wonder what else you could make like this...

 

[Redneck_Pyro]

It seems that when I was creating my list of supplies earlier I forgot to mention the electric coffee grinder that you need to borrow from some one. It is best to borrow it from someone that won't ask to many questions when they get it back.

But, on to how I made the foundry.
The first thing I did was drill a 1/2" hole about 2.5" from the bottom of the metal bucket. This hole is for the blower tube. After drilling the hole I used tin snips to cut the hole so that it was just big enough to fit the 1" black steel pipe. I then drilled holes about half way up the bucket that were the same size as the long skinny screws I picked up at Home Depot. In my case I used 2" #8 machine screws. These screws are to give the refractory something to hold on to when we pack the sides of the bucket. Once the holes were drilled I inserted the screws and fastened them to the bucket with nuts. When that was all said and done the bucket looked something like this:



I did the same thing to the lid, but I ended up not filling it full of refractory this is what the screws looked like on the inside:



The next step is to prepare the refractory, but before that can be done we need to make bentonite. I am not sure of the actual chemical reaction that takes place, but when you put clay cat litter into an electric grinder and run it a bit the cat litter turns into bentonite. I think it has something to do with cold fusion and perpetual motion. But, the reason we borrow someone else's coffee grinder rather than use our own is because who wants to drink coffee that was ground with the same machine that ground up cat litter? Anyway, I digress. The ground cat litter needs to make up a little more than a quarter of the total volume of refractory we intend to make. It seems like a lot of grinding but it goes a lot faster than it seems. I tried using a ball mill to grind the cat litter but it took a really long time to get it ground fine enough.
You can find detailed refractory formulas here: https://www.backyardmetalcasting.com/refractories.html In fact that site is where I got most of my ideas.

I did not put a metal spill hole in the bottom of my refractory, but I suppose you could do it if you wanted to. I actually made 2 separate batches, the first was just large enough to fill the bottom of the bucket about 2 inches deep and the second batch was for the walls of the bucket. With the first batch I packed the bottom of the bucket and let it sit for just long enough that it started to get firm. Once that happened I started mixing the second batch and then packed that around the sonotube that I had placed on top of the refractory base and in the center of the bucket. It is also important that you have your blow tube inserted before you start packing the sides. It would be a drag to have to drill that stuff out.

Once you have your bucket packed full of modified concrete you let it sit covered with a moist towel over night, then you can peel the sonotube out of the center of the bucket. I suppose if you forget to pull it out in time and it gives you a problem you can always burn it out later. But in order to get the refractory to cure properly it is important to keep it around room temperature and moist for a couple of days. This can be done by hiding the bucket somewhere in the house and placing a moist towel over the top of it and making sure to re-wet the towel every day for 2 or 3 days. After a week I took it outside so that I could finish the process of driving the moisture out of the refractory. It is important to make sure that the refractory is completely dry before using it to melt metal the first time. I was surprised how much energy tiny amounts of super heated steam can have. The finishing process consists of starting a small amount of charcoal in it, letting the charcoal burn out and the bucket cool. Then you repeat the process with a bigger hotter fire each time. Make sure you let it cool in between each burn. The first couple of curing burns I did I left the blow hole tube out of the bucket and let the charcoal fend for its own air. When I needed it hotter I took my house fan and pointed it toward the blow hole and moved it closer each time until on the last burn it was right next to and blowing directly into the tube.
Just like in this picture:



And here is a picture from one of my first melts:



And one small bit of advice, with a charcoal fired foundry the thicker the steel container the longer it takes to get the aluminum to a decent casting temperature. Thin containers like coffee cans will heat up quick and the aluminum will melt well, but you only get one or two melts out of a can. Also, make sure that the welding gloves you wear when working around the furnace are not your finest designer gloves because they will melt. I decided that my Gucci designer welding gloves should only be used for real welding and that I could slum it a bit with Harbor Freight gloves for melting.

 

[Scott Evil]

I will get more written up on the process later tonight, don't you worry.

The aluminum alloy I used is kind of a trade secret. But it consists of a mixture of broken car parts, hard drives, some square tubing that someone gave me, and baking stuff that I scrounged from the kitchen while my wife was away. Very technical stuff with lots of gas chromatographs, and scanning electron microscopes used along the way.

:headbang:

 

[Redneck_Pyro]

We tried adding beer cans to impart a nice cold, crisp, refreshing flavor to the alloy but it didn't work. The flavor kept floating to the top and had to be scraped off.

 

[Redneck_Pyro]

So, now that the furnace is ready to melt aluminum and you have some sort of crucible that can handle the heat it is time to fire the thing up for real. I use matchlight charcoal to get the thing started and then once it is going I use the regular stuff to keep it going. Adding matchlight charcoal when it is already going led to big flames shooting out and singing the hair on my arms.

I mentioned earlier about using the wrong end of a vacuum to blow air into the bucket but it was awfully loud and if the hose got too close to the end of the pipe it would blow hot embers all over the yard (the wife gets mad when I set the backyard on fire, and it happens to me more than I would like to admit) and a lot of ash would inevitably land in the molten aluminum. We then tried just a regular house fan and it worked just fine, but it was kind of big so we settled on using a blower that I think was used to cool servers in a rack or something. It was small and didn't move too much air.

Well, now you are ready for the casting part.

 

[kenstarr]

Several years back I picked up some stainless steel ice cream shake mixing cups from ebay for use as a crucible. I figured it was a bit safer than an old steel can.
-Ken

 

[Redneck_Pyro]

Before you start casting anything you need to make the green sand. I used the ground cat litter and sand that I had left over from making the refractory. If you want to make your own, there is a video that will show you how https://www.youtube.com/watch?v=U7ut_2nqiGk

Or you can buy high quality pre-made stuff. I couldn't bring myself to buying and then shipping magic dirt clear across the country so I made my own. The quality of your green sand determines how nice your casting turns out. I thought making the stuff was boring so my green sand is of a relatively poor quality, but I was going to machine it down to the exact shape I wanted it anyway.

To see how to make a sand casting mold check out this site: https://www.foundry101.com/new_page_7.htm

A couple of notes on flasks. I am lazy so I tried to see what I could get away with that would require the least bit of effort to procure. The first thing we tried was a simple cardboard box. The cardboard flexed too much to really pack the sand the way it needs and then when you pour in molten aluminum it has a tendency to catch on fire. It would be my least recommended approach. Then we tried a coffee can. The coffee can still had a lot of flex in it so that each time we tried to pack the sand it would flex just enough for the sand to not hold its shape very well. I would recommend making a flask like the one seen in the casting instructions. I finally got around to making mine and it definitely works the best.

This is a picture of my coffee can flask (btw I drink Chock Full O Nuts, best coffee ever):

 

[Redneck_Pyro]

Several years back I picked up some stainless steel ice cream shake mixing cups from ebay for use as a crucible. I figured it was a bit safer than an old steel can.
-Ken

My wife got tired of me burning out the bottom of my cans and spilling molten aluminum all over the back porch so she made me this:



Problem was that it was so heavy duty I had to upgrade from charcoal to my "Oscillation Overthruster".



That burner uses propane and waste oil and could probably melt steel if I wanted it to.

 

[Redneck_Pyro]

So once I had all of my sand casting supplies together, I needed to make a positive mold of the tip of my nose cone. The nose cone is from a Gizmo XL so it is 8" in diameter and 2ft. long. So, I went and picked up one of those Alumilite casting kits and used that to make a resin mold of just the tip. This is what it looked like:


I also screwed on a piece of plywood at that had a larger diameter than the base of the nose cone tip. This was because sometimes when the aluminum cools it leaves a little depression in the center of the piece. And, since the plywood base was a larger diameter than the tip that I wanted I was able to create a nice little marker telling me where to cut.

This is what one of my first castings looked like right after I took it out of the mold:

 

[Fe Dude]

nice little melter! One thing you might want to try is a spreu and cup to pour into ontop of your piece. this would help keep shrinkage and slag inclusions to a minimum.

 

[Redneck_Pyro]

Agreed, the pictures I have are from my early attempts when I was trying to find short cuts. When I finally realized that there was a reason people had been doing it the right way for hundreds of years and short cuts don't really work I started doing it the right way as well.

Also, getting the water content of the sand just right helps a lot. The first mold we made foamed and bubbled like crazy since it was too wet, and the one pictured above was too dry and so the sand got pushed into the tip of the nose cone.

 

[Fe Dude]

Have you ever considered doing a loose sand styrofoam vaporization? The smoke is a bit nasty, but the results can be pretty good. Also, if you used a ceramic mold wash (i think thats what its called) you might be able to better fight sand inclusions, and get a better surface fresh out of the mold.

Typing from the phone, sorry for the block of text.

 

[BABAR]

Just out of curiosity, how does this type of nose cone tip relate to the high power model rocket safety code


Materials. I will use only lightweight materials such as paper, wood, rubber, plastic, fiberglass, or when necessary ductile metal, for the construction of my rocket.
https://www.nar.org/NARhpsc.html

Aluminum is definitely ductile, but is it necessary?

 

[Redneck_Pyro's_Wife]

Just out of curiosity, how does this type of nose cone tip relate to the high power model rocket safety code


Materials. I will use only lightweight materials such as paper, wood, rubber, plastic, fiberglass, or when necessary ductile metal, for the construction of my rocket.
https://www.nar.org/NARhpsc.html

Aluminum is definitely ductile, but is it necessary?

Actually yes Babar, aluminum is preferable over lead for weighting. Lead is not ductile so aluminum more closely adhears to the safety guideline and lead is in violation. Also, seems to me that replacing the cone's tip, with a solid/dense aluminum mass, would afford the builder a more effective method to move the center of gravity forward of the center of pressure though I'd require a mathematician's skills to provide a definative model. (I'd be thrilled if someone had the math & wanted to do it) Moreover aluminum adds an aesthetic quality that could never be equaled with chrome paint - it looks really cool. I've one last comment too...he made it - from inception to implementation to completion - that's my man!

 

[troj]

The aluminum alloy I used is kind of a trade secret. But it consists of a mixture of broken car parts, hard drives, some square tubing that someone gave me, and baking stuff that I scrounged from the kitchen while my wife was away. Very technical stuff with lots of gas chromatographs, and scanning electron microscopes used along the way.

Yeah, but when most people say that, they don't mean they used the chromatograph and electronic microscope for parts to melt down....

This is very cool. I'm with you -- maybe a lathe, or having someone else do it, would be easier. But there's something to be said for doing it yourself and trying something new.

-Kevin

 

[Daddyisabar]

We tried adding beer cans to impart a nice cold, crisp, refreshing flavor to the alloy but it didn't work. The flavor kept floating to the top and had to be scraped off.

UMMMMM...more beer....GOOD. UMMMM...more thrust...GOOD.

 

[Redneck_Pyro]

Have you ever considered doing a loose sand styrofoam vaporization? The smoke is a bit nasty, but the results can be pretty good. Also, if you used a ceramic mold wash (i think thats what its called) you might be able to better fight sand inclusions, and get a better surface fresh out of the mold.

Typing from the phone, sorry for the block of text.

We had considered that, but the problem we had was that we would have to make a styrofoam piece before we could start casting anything, and we never got around to doing it. We did try using ceramic clay as a mold, but it didn't perform much better than just casting it using straight green sand.

 

[Redneck_Pyro]

This is very cool. I'm with you -- maybe a lathe, or having someone else do it, would be easier. But there's something to be said for doing it yourself and trying something new.

-Kevin

The main thing I learned from this entire experiment in casting my own nose cones is that it would have been cheaper and easier to do it using virgin aluminum stock and cutting it on a lathe or even paying someone else to do the whole thing. However, the process of making the nose cone tip from scrap is what I call "Stupid Fun". There are definitely smarter, cheaper, and easier ways of achieving the same goal but they aren't nearly as much fun. In my opinion making a nose cone tip from scrap represents all of the best parts of rocketry. You get presented with a problem and then go on a journey of small successes and large failures until you finally arrive at the solution all the while learning about things you never thought you would need to know.

Rocketry and metal casting are both stupid fun, there is no real reason to do either but a great time is had while doing both.

 

[Redneck_Pyro]

Well I have to finish getting everything packed and ready for the NSL tomorrow. When I get back on Monday I hope to finish this up and answer any questions anyone might have. It was my intention when I started this project to make every mistake I could think of so that I would better remember how to do it right so if anyone wants to know "what happens if" and they don't have time to make it to the ER that weekend feel free to ask. I suffered a number of burns and other mishaps to verify that the wrong way of doing things was in fact the wrong way of doing things and why they were the wrong way.