My little Chinese BALLS 2012 Project

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Will this project meet its stated goals? [See slide 2]

Yes
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No votes
Not a snowballs chance in hell
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Maybe
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Total votes: 0

Passaretti
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Re: My BALLS 2012 Project

Postby Passaretti » Sun May 13, 2012 9:09 am

I like to build very early "mock-ups" of these sorts of projects. Helps me to wrap my head around things.... For this project, the plan is to also build a stand-in motor casing out of 98mm phenolic tube (with a layer or two of glass) to act as a booster vehicle for testing the recovery/payload section before BALLS. The motor mount will be 75mm so I can fly it on K-M's.

I'd like to get the payload/recovery section over 10kft and back (via the deployment strategy for Nevada) at least once before September ... we'll see how that goes.

Mike
Attachments
2012-05-12 11.38.13_.jpg
Mock-up Al fin-can, shown next to phenolic/cardboard mock-up of rocket shown next to a spray can.
2012-05-12 11.38.13_.jpg (238.73 KiB) Viewed 723 times
2012-05-12 11.04.41_.jpg
Putting together a mock-up of the final rocket configuration. 98mm OD phenolic tubing will be used to create the motor casing. The filament wound 98mm OD tube which will be used to create the recovery/payload section should be in from GLR next week. (75mm filament tube shown is for another project)
2012-05-11 20.27.02_.jpg
5:1 Performance Rocketry conical nosecone and some phenolic tubes to build the stand-in or mock-up motor casing. The nosecone will be modified heavily (SS or Ti tip, internal 75mm av-bay, the rest will be filled solid)
Mike Passaretti, TRA 5369

Passaretti
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Re: My BALLS 2012 Project

Postby Passaretti » Sun May 13, 2012 9:16 am

PK wrote:Two tips for using that stuff:

1: Preheat.
Maybe mount a heat gun/hairdryer somewhere, or use your boyfriends hair straightening wand (seriously those things have perfect cartridge heaters in them) to get the whole show up to >70-80 deg C before you start. It'll make a huge difference to the amount of heat you need and the time you have to work the joint.

2: Deal with the oxide layer
about 100mS after you rough the metal up with sandpaper, it starts forming a new oxide layer.
See if you can grab a small (think toothbrush) stainless wire brush.
Clean it, then put it into the braze pool while it's molten and scrub the oxide layer off the aluminium. you'll get a much better bond.

PK


One thing I did not do was tin the surfaces, guess I got a little carried away. The manufacturer also recommends wire brushing the surfaces under heat as you describe. Going to prep a piece of fin material for brazing to a 0.125" thick plate now - will practice on that. This stuff is cool!

I was contemplating trying to insulate the vast areas of the aluminum (which are not being brazed) that are effectively dumping heat into the ambient air, by covering them with ceramic tiles, etc. What do you think about that? The idea is to reduce the ability for the fin(s) to dump their heat. I could even stuff fiberglass insulation into the ID of the tube (when I get to that point).
Mike Passaretti, TRA 5369

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Re: My BALLS 2012 Project

Postby PK » Sun May 13, 2012 9:27 am

Passaretti wrote:I was contemplating trying to insulate the vast areas of the aluminum (which are not being brazed) that are effectively dumping heat into the ambient air, by covering them with ceramic tiles, etc. What do you think about that? The idea is to reduce the ability for the fin(s) to dump their heat. I could even stuff fiberglass insulation into the ID of the tube (when I get to that point).


If you insulate, the edges will still be cooler than the middle bits and you'll see some inconsistent results along the joint.

When the live steam boys silver solder their, thick walled, copper boilers up, they sit the whole thing in a hearth (bed of heated rocks).

This is essentially what you are trying for. Maybe build an open topped box and blast hot air in.
It really is worth doing. Especially when you have pieces of different thickness that will suck heat out at different rates...
PK

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Re: My BALLS 2012 Project

Postby OverTheTop » Sun May 13, 2012 10:24 am

As per what PK said, the breaking through of the oxide layer is very important. I used a scratching motion with the tip of the rod to achieve that when I was using it for my sidesteps. Also, the preheating works wonders in helping get a more consistent joint and enough heat into the joint.

Looking good!
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Re: My BALLS 2012 Project

Postby ROCKet STAR » Mon May 14, 2012 1:52 am

The Durafix does seem impressive. The one thing I was wondering was that given that it has a relatively low melting point, what affect the radiated heat from the motor case will have on its strength?
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Re: My BALLS 2012 Project

Postby OverTheTop » Mon May 14, 2012 7:30 am

I have heard of it being used for permanent repairs of alloy car engine heads and blocks so without any data I suspect it is quite good in our application. 200degC max (as per specification) of the rocket motor casings should not worry it I think.

It isn't ringing any alarm bells for me, but considering it is "rocket science" it is probably worth asking the question!
TRA #13430
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Passaretti
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Re: My BALLS 2012 Project

Postby Passaretti » Mon May 14, 2012 9:22 am

ROCKet STAR wrote:The Durafix does seem impressive. The one thing I was wondering was that given that it has a relatively low melting point, what affect the radiated heat from the motor case will have on its strength?


Indeed a good question. To put this one to bed, I could easily prepare a sample and stick in an 200degC oven for several minutes and evaluate the strength from there.

Played around with Durafix just a little bit longer today before I got bored. I joined a piece of fin stock to a 0.125" thick plate, stuck the whole thing in a vice and wrenched on it until failure. The purpose of the test piece was to better wet the areas to be joined. Brushing while heating certainly makes a difference, you can start to see the surface of the aluminum break down as the coarse brush bristles pass over it. The sample is shown below. The fillets ended up pretty thin, but still held on long enough for the thicker piece of plate to yield before the joint gave way. Have to wonder if the base metal has started to anneal ... Going to take some more practice and load tests but I'm liking where this is going so far.

Joined two pieces of 98mm OD phenolic (coupler) tube and reinforced with two layers of 5.8oz e-glass. Total length is 48.75 inches, which is exactly the length of the CTI 98mm 6GXL casing. Cut a set of fins out of 1/4" 7-ply birch plywood, put a ~10deg bevel on them and tacked to a piece of 4" body tube. Going to go tip-to-tip with a layer or two of glass next. This will form the stand-in fin-can for test flights leading up to Nevada.

After a late liquid lunch, some words of wisdom appeared on the fin-can ...

Mike
Attachments
IMG_6262_.jpg
IMG_6256_.jpg
IMG_6247_.jpg
IMG_6244_.jpg
IMG_6242_.jpg
Plywood/phenolic fin-can for test flights, aluminum mock-up fin-can and stand-in motor (98mm coupler tube w/ 2x 5.8oz e-glass).
IMG_6237_.jpg
IMG_6227_.jpg
Same goes for the "can", I'm going to wet both joints BEFORE fixturing the two pieces together for brazing.
IMG_6233_.jpg
Next time I am going to wet the bottom of the "fin" as well. You can see the absence of brazing material on the bottom of the "fin."
IMG_6226_.jpg
The aftermath ...
IMG_6213_.jpg
Durafix test sample, 0.125" + 0.187" plate ,butt joint
Mike Passaretti, TRA 5369

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Re: My BALLS 2012 Project

Postby Sumo310 » Mon May 14, 2012 1:22 pm

Good to see you've got some use out of the Durafix :)

I crack up every time I read "preassure". I hear there is a certain TRA L3 flier planning on building a H2O2 motor to 77km altitude, I wonder if we'll see him at BALLS this year.

THANKS.
L3

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Re: My BALLS 2012 Project

Postby PK » Mon May 14, 2012 1:27 pm

Sumo310 wrote:I crack up every time I read "preassure". I hear there is a certain TRA L3 flier planning on building a H2O2 motor to 77km altitude, I wonder if we'll see him at BALLS this year.

I really miss the guy!
PK

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Re: My BALLS 2012 Project

Postby cryoscum » Mon May 14, 2012 3:11 pm

PK wrote:I really miss the guy!
PK


I don't.
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Total impulse for 2016: 32,458 Ns (thus far)
Total impulse for 2015: 84,231 Ns
Total impulse for 2014: 40,757 Ns
Total impulse for 2013: 62,927 Ns

PK
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Re: My BALLS 2012 Project

Postby PK » Mon May 14, 2012 3:22 pm

cryoscum wrote:
PK wrote:I really miss the guy!
PK

I don't.

Wayne made us all look like high achievers. You make us look like a bunch of fat old bastards that don't do much.
No prizes for guessing who I wanted to vote off the island!

PK

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Re: My BALLS 2012 Project

Postby cryoscum » Mon May 14, 2012 4:24 pm

I am mortally wounded! Will have to send that case of Bundy to my REAL friends!!
I hear there's an opening at another club... :?
AMRS L3 | NAR L3 | QRS 089 | MDRA 224
AMRS Technical Advisory Group

Total impulse for 2016: 32,458 Ns (thus far)
Total impulse for 2015: 84,231 Ns
Total impulse for 2014: 40,757 Ns
Total impulse for 2013: 62,927 Ns

Sumo310
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Re: My BALLS 2012 Project

Postby Sumo310 » Tue May 15, 2012 11:04 am

Some added incentive for you, get the TRA altitude record with this flight, and secure 2 x CTI Pro98-6GXL reloads of your choice!

http://www.rocketryplanet.com/forums/sh ... post194900
L3

Passaretti
Mars...........................✓ N5800.........................✓ Next Mission ... ###,###
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Re: My BALLS 2012 Project

Postby Passaretti » Tue May 15, 2012 12:09 pm

Sumo310 wrote:Some added incentive for you, get the TRA altitude record with this flight, and secure 2 x CTI Pro98-6GXL reloads of your choice!

http://www.rocketryplanet.com/forums/sh ... post194900


Wow, it's going to be raining bits of stuff that was once attached to N5800's in Nevada ....

Early on, I realized that a project like this would be a contender for the N altitude record. However, I can't help but to see the pursuit of such as just a distraction to my main goal. Getting the rocket back in one piece, driving off the playa with it and a telling smile on my face is the only record I'm after.

That said, things at Black Rock just got a bit more interesting ...

Mike
Mike Passaretti, TRA 5369

Sumo310
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Re: My BALLS 2012 Project

Postby Sumo310 » Tue May 15, 2012 12:14 pm

Pussy..
L3


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