Shiny new technique: Metal Spinning!

So I have decided to complete readdress my approach to regenerative cooling. After seeing the BPM-5 build by Copenhagen Suborbitals, where they used metal spinning to spin their chambers out of steel, I looked into what it would take to do something similar by hand on my mini lathe.

In my typical fashion after seeing a cool video then reading most of an article online, I decide to commit fully to spinning an aluminum combustion chamber. I modified my matlab rocket design scripts to given me the right dimensions for a 250 lbf chamber and get to work on the mandrel that I will need so that I can smoosh the aluminum into shape.

Shop press needs reinforcement

I tried to press out the inner race of a deep groove ball bearing and those things can take a lot more force than I anticipated. That is 3"x 1/2" thick plate/ I heated it up, straightened it in the press and tacked 2 more pieces of 3/8" thick x 3" plates in place. Then followed up with 200A full penetration 6011 welds to make sure it  stays in place. The cross beam alone has to weigh close to 50 lbs now.

Paradigm shift

Now that I have a welding machine that can weld aluminum my paradigm has shifted. I see the designs in my head from a whole new perspective. For injectors for instance, typically I went from idea to what seals can I buy to how I can make sure that it all bolts together to making sure there was enough rooms for flanges and a way for me to get a pressure transducer in there...

Now, I have a design in my head and as long as I can nest the components I can weld it in place. If I need a way to mount it to a load cell, I can just tack a bracket on after. There is so much more flexibility in modularity compared to the integrated unit conceptual approach I have grown accustomed to.

While my brain is reprogramming itself, I continue to invest in my capabilities. My milling machine on a rolling cart seemed like a good idea at the time but it turns out the cart is a giant resonance chamber. I had to move the mill so why not build myself a crane! Great welding project to keep honing my skills on. While I was at it I figured I'd build myself a shop press as well.

The boom is 2x2x1/4" square tube with a nested 1.5x1.5x1/4 extensible boom and a 4 ton HF jack to actuate the arm.

The shop press part is a 20 ton low profile jack and 2 3" wide by 1/2" thick steel flat bar pieces 30" long with 1" thick press plates.

Capability Upgrades

A lot has been going on behind the scenes. Since my last post in 2017 I bought my first house. One firm requirement was that I needed a shop space.  Welcome to my fab lab.

My 7x14 lathe and X2D milling machine on rolling carts.

185 lb 1/2" plate top 3" I-beam welding table

 AHP Alpha TIG 201x AC/DC tig welding machine

Learning how to stack dimes

Autogenous Weld Shot

I know nothing about welding outside of my 90 amp HF mig welder. After that fell apart, I converted it to a buzz box that barely burned 3/32 welding rods. Thannk god that is over. The whole setup was failry cheap and the AHP welder is a dream to work with.
Totals were:
AHP 201x = $750
Argon Bottle = $180
Antra Hood = $100
Welding table = ~$300 in materials
Consumables = ~$50
I managed to go from nothing to something for less than $1400 total. I've still got a lot to learn but at least I have the tools to learn with.

I will soon start working on aluminum to expand my tool set for my rocket designs.

Down the microelectronic wormhole...

So I started this months ago, fully aware that this time around I would have to put in all the time building the data acquisition computer that I had skipped during my first rocket build. I knew that it would be a challenge. Now I know, I had no idea.

@TLDR Don't bother. Just buy a usb NI-DAQ 600X on ebay for less than $250. Set up your load cells, collect your data, and get it over with.

Now back to don't bother... I tried everything. I bought every arduino known to man. Then I hooked them all up and created archaic forms of multi-core multi-threaded processors with amplifiers and signal conditioners, one Chinese microcontroller + 2 months of shipping at a time. I spent a whopping $50 so far for a box of basically useless micro controllers that I have been able to get down to 497 Hz refresh rate. What a joke.
I have been building headers and bit banging my code over to a windows and then a Linux cpu. I have NI fpga's, computational servers, professional licenses for LabView and Matlab, experience writing Java and C, these are just some of other resources at my disposal for prototyping and I'm telling you now... 16 bit resolution at 200k samples per second is all you need and if not, reconsider what you are doing.
I bought the biggest and best micro processors and then coded them from scratch to no avail. The 2, 3, $400 dollars that NI costs is very worth it. I wish I could tell you I'm biased because I'm doing a review but no. It's just the truth, don't reinvent the wheel. There are no wheels in a rocket. 

@NationalInstuments Please give me a sponsorship.

I will use the arduinos for all of the automation and electronic and pneumatic controls. I also plan to use the HX711 24-bit ADC load cell converters for the tanks because 100 Hz resolution is more than enough and at 24-bits I will be able to see femtograms apparently. For these I will have 3 arduino nanos embedded in the stand and they will communicated to a central arduino mega to report ambient conditions, tank weights, and switch/relay status via Serial. I will pick up the serial stream in LabView and use it to actuate some indicators and dials.  I will keep you updated as I make this important, stress-relieving shift.

Took a break from making a metal thing to making a wooden thing!

Turning wood on a metal lathe

One of my other hobbies, outside of rocket building, is gardening. Specifically, I grow hot peppers and not just hot peppers but crazy hot peppers.

The species I am growing this year are:

"Ghost Peppers"

Naga Morich

Bin Jolokia (sourced from Bangladesh)

Bhut Jolokia

Peach Bhut Jolokia

"Big Black Mama" -Naga Morich Crossed with a 7 pot Douglah

"Not Ghost Peppers"

Georgia Flame

Fatali ("Devil's Tongue")

Chocolate Habenero

Urfa Biber

What do I do with these peppers?

I like to make hot sauces. Favoring fermenting, I usually coarsely grind them into a pepper mash mixed with 2% by weight of an exotic salt like black or pink salt. A dash of kimchi juice is blended in to provide a head start for the lactobacillis culture that preserves the peppers as they age for several months in mason jars. This year I am going to be swapping out the mason jars for wooden barrels... or so I thought.

After scouring the tubes of the interwebs, I found that small wooden barrels go for around ~$50 each. Since I need a few of them, I couldn't find myself paying that much. Feeling down about my prospects, I had an epiphany! Maybe I could use some of the oak and cherry wood that has been seasoning since I collected it during Hurricane Matthew for use in my smoker could be turned down into some kind of fermentation vessel.

And so it began...

I also made a cap for it but I will get a picture of that added later.

So my lathe is a little too small to turn most of this so I ran to Harbor Freight and picked up a die grinder and some rasps.

To bore the inside out, I progressively center drilled a few inches of depth then reaming it with the die grinder until I could fit the drill chuck in to drill a few inches farther. Eventually it got too deep and I have to use my hand drill for the pilot holes. Eventually I got to the bottom and viola!

Now it is wrapped up in a brown paper bag to let it finish drying out slowly to hopefully avoid the splitting red oak is known for. I have also learned that is there exists food safe wood glue that I can use to patch up any leaks that I am sure I will find.

Though this turned out to be a fun weekend project I still feel that I will still buy one or two wooden barrels for some of the mashes that I plan to age for several years. I will post some updates as I go along.

I made a thing! Fuel tank load cell mounts on the thrust stand

Instrumenting the thrust stand

Being that I intend to be use this thrust stand to completely profile my rocket motors, I have been spending a lot of effort building the microcontrollers, software and data acquisition modules. In a sense, I feel like I am playing catch up for all of the work I didn't do on my first motor.

Since there are no moving parts in a pressure-fed liquid rocket motor, there are only a few places you can collect valuable data and even then you must interpolate it into something meaningful. One module in particular affords a lot of insight into the performance characteristics of the motors and that is the mass flow rates for the fuel and oxidizer.

Mounting rail for the load cell

I fashioned a bracket out of a 1 ft length of 2 inch wide 1/8 steel flat bar. I welded it to a 1.5" c-channel that is welded to the top of the frame.

Back of the mounting bracket

I wanted the load cell hanging from the mounting bracket and bolted to the top of the skate so I welded a pad onto the top of the bracket.

Next the skate is made of a 1ft piece of 4 inch 1/8" steel flatbar with 2 1/2" square tubes holding a piece of 1/4" steel flat bar that is threaded for the m4 bolts that fit my v-groove bearings.

Skate the the tank is mounted to

Once assembled the grooves in the skate bearings slide over the 2" flat bar mount to provide a sturdy linear bearing.

Linear bearing

Load cell mounts

The load cell is mounted between the two tabs seen in the picture above.

Load cell mounted

Closer picture of the load cell

I zip tied the tank on until I figure out a better way to hold the 2ft long tank against the skate.

Holding the tank that I made back in Ohio.

Now that I see the concept works, I am making another taller one that will have a universal mount to allow me to hold a variety including CO2, N2O and flight ready tanks.