"Contents Under Pressure" - Static Test Cato

[conman13]

Thanks for the heads up. I've ordered from them before so I've had a similar experience. This tubing will all be turned down anyway so small dings and gashes won't matter that much.

Alex

Interesting I got my 38mm mandrel from them. It was all wrapped in bubble wrap and in a cardboard box.

 

[patelldp]

Hard to capture in the pic, but you can see the point of the sharp ding on the left. The case was turned down .01" on the diameter, and there's an ovular depression area around the ding that didn't get machined at all.

As mentioned, three successful flights on the case. 2 sparky, one blue.

 

[AlnessW]

Just catching up with this thread... SWEET!!

As for using retention pins - I wish you could have heard Steve's commentary right after the Huevos CATO down at BALLS!

 

[Aksrockets]

The parts from speedy metals showed up today and the graphite showed up about a week ago. Shown here is the graphite (top), forward closure upper (middle left), nozzle carrier (middle right) and forward closure lower (bottom)


The graphite i got wasn't the finest, but it'll work.


Alex

 

[flynfrog]

That graphite looks pretty bad not sure Id use it. I was just picturing how cool a fiber glass case with a clearish resin would be might have to fly a chase rocket beside it just to film it or do a ground burn.

 

[Aksrockets]

The nozzle carrier is hot off the lathe! I machined a tailcone into the last half inch cause ya know, why not? Its a little over 3/16in thick, which will give our pins plenty of room to dig in.


Here it is on the back of a 54mm fincan.

I think it "turned" out alright.

Alex

 

[patelldp]

What kind of lathe are you using?

 

[Aksrockets]

What kind of lathe are you using?

Somewhat crappy harbor freight 7 x 10 inch. Nothing too special.

Alex

 

[CarVac]

How does it retain the graphite? I don't see any lip.

 

[Aksrockets]

How does it retain the graphite? I don't see any lip.

The graphite will have a lip that will but up against the end of the carrier.

Alex

 

[CarVac]

The graphite will have a lip that will but up against the end of the carrier.

Alex

So it will have the graphite in tension?

 

[patelldp]

The graphite will have a lip that will but up against the end of the carrier.

Alex

Oooooh...not sure if I'd go that route. What's the shear strength of your graphite? I'd recommend making the nozzle holder with an internal lip to load the graphite in compression rather than shear.

 

[Aksrockets]

Oooooh...not sure if I'd go that route. What's the shear strength of your graphite? I'd recommend making the nozzle holder with an internal lip to load the graphite in compression rather than shear.

True, I had not thought about the nozzle failing that way. It'll be easy for me to machine an inner lip by taking off some of the inner wall. I'm really considering just using my Loki 54 #42 nozzle for this and turning it down slightly to match the ID of the nozzle carrier with a step.

Alex

 

[Loki Research]

Or.... you could purchase a Loki Research Single-use phenolic/graphite composite nozzle and retain it with your pinned in tail cone.
The lower OD of the nozzle is 1.710" and the length past the shoulder is 1.58".
You can even specify throat size and exit diameter with a maximum exit of 1.60".
They have been hydro-static tested to 2,400psi and held there for 4 minutes.
It will work. ;-) It's the best of both worlds. You can find them listed with the 54mm hardware.

 

[DeeRoc29]

Alex, I think your design should work just fine depending on how much graphite "lip" you have forward of the carrier. You don't necessarily need another lip at the aft end of the aluminum carrier. Graphite is tough. I made one like this. It worked.

 

[DeeRoc29]

BTW, Alex, what is the ID of your motor case? Cool looking project!

 

[Aksrockets]

DeeRoc, That looks awesome! Exactly what I had in mind for this project. ID of the motor case is ~2.14in.

Glad I have a lot of options on the table, I'll definitely consider a Loki phenolic/graphite one too. However, I already have a #42, so I may use that for testing. If I see a need for a phenolic nozzle, I'll buy one. I like the price point on those as well! Shame they arn't reusable.

Alex

 

[DeeRoc29]

2.14", that's what I thought. I'm sorry if you already said earlier in this thread but what are you using for liner/casting tubes? AT/CTI 54mm cases are basically 2.0" ID, so you should be able to get a bit more propellant into your motor than any other 54 commercial motor.

 

[CarVac]

Alex, I think your design should work just fine depending on how much graphite "lip" you have forward of the carrier. You don't necessarily need another lip at the aft end of the aluminum carrier. Graphite is tough. I made one like this. It worked.

What matters is specifically the length of the section in front of the lip, so as to spread the shear stress out more. Not the depth of the step.

 

[A5tr0 An0n]

Alex, I think your design should work just fine depending on how much graphite "lip" you have forward of the carrier. You don't necessarily need another lip at the aft end of the aluminum carrier. Graphite is tough. I made one like this. It worked.

Those holes look like they are for pins and not bolts, if so were they removable? Every pinned motor that I have had a hand in making has been single use i.e. the pins are epoxied in. If that was not the case with your design I would like to hear more on that.

 

[DeeRoc29]

Those holes look like they are for pins and not bolts, if so were they removable? Every pinned motor that I have had a hand in making has been single use i.e. the pins are epoxied in. If that was not the case with your design I would like to hear more on that.

Dowel pins, yes. No epoxy. The pins drop out when the case is rotated allowing for reloading. I'm sure the aluminum around the holes yields a little during the burn, but honestly I don't notice a difference when I reinsert the pins. I plan on firing the motor again.

 

[Loki Research]

ID of the motor case is ~2.14in.

Sorry, I must have overlooked that as well. All my nozzles are made for standard 54mm tubing, ~1.939" ID. You'd have to make a sleeve for the upper section of my SU nozzle and use 1/16" thick o-rings to seal it on the outside. It would work, but then you start getting into more failure points which isn't a good thing on a first run design.

 

[Just_Keep_Flying (Masonh)]

Or.... you could purchase a Loki Research Single-use phenolic/graphite composite nozzle and retain it with your pinned in tail cone.
The lower OD of the nozzle is 1.710" and the length past the shoulder is 1.58".
You can even specify throat size and exit diameter with a maximum exit of 1.60".
They have been hydro-static tested to 2,400psi and held there for 4 minutes.
It will work. ;-) It's the best of both worlds. You can find them listed with the 54mm hardware.

View attachment 246417 View attachment 246418

TO be entirely honest, I just want one to mount and put in a shiny glass case. That is a work of art, Scott.

 

[Aksrockets]

Ive machined an inner lip in the carrier. First time machining internals and I got a bit of "chatter", so its not the smooth finish I wanted. However, it'll work just fine. I now need to turn a small lip in the nozzle to get it to recede further into the carrier. I will have to wait until I get external chuck jaws. Here's some photos.



As you can see, the nozzle still needs to go back about 1/2in into the carrier.

Alex

 

[Aksrockets]

I'm preparing to weld the forward closure. If you missed it earlier in the thread, the plan is to weld this length of aluminum tubing to this aluminum round stock. The tubing will serve as both the AV bay, and the place to anchor the forward retention pins. After welding, they will both be turned down to the correct diameter.
Compared to steel, aluminum is very tough to weld. It's much more finicky, it cracks and it has a tough oxide layer. I've been practicing my aluminum TIG welding, and I think I'm about ready. In preparation tonight, I meticulously cleaned them with a stainless steel pad to remove any grime and wiped them down with Acetone. That should give me a good, clean weld. Since I'll be trying to achieve full penetration, I will be using a purge gas setup.
Here are the weld parameters I'll be using.

Welder: Lincoln Square Wave 175
Filler Rod: 4043 3/32
Amps: 120-135
Amperage control: foot pedal.
Shielding gas: 20cfh Argon
Purge gas: 5-10cfh Argon
Tungsten: 3/32 pure or 3/32in 2% thoriated.


They'll be welded either tomorrow or sometime next week. Wish me luck!

Because of the nature of this design, it's not likely that a poor weld will result in a failure, however I still want to do a good job.



Alex

 

[REK]

Stay calm and focused and have fun. Good luck Alex.


Alexander Solis

TRA - Level 1
Mariah 54 - CTI RedLightning- I-100 - 6,345 Feet

 

[flynfrog]

If your foot control sucks like mine does find a welder with a pulser I use it for thicker Aluminum makes nice even beads and acts as a timer for moving. Then again I am a hack

 

[Random Flying Object]

I'm preparing to weld the forward closure. If you missed it earlier in the thread, the plan is to weld this length of aluminum tubing to this aluminum round stock. The tubing will serve as both the AV bay, and the place to anchor the forward retention pins. After welding, they will both be turned down to the correct diameter.
Compared to steel, aluminum is very tough to weld. It's much more finicky, it cracks and it has a tough oxide layer. I've been practicing my aluminum TIG welding, and I think I'm about ready. In preparation tonight, I meticulously cleaned them with a stainless steel pad to remove any grime and wiped them down with Acetone. That should give me a good, clean weld. Since I'll be trying to achieve full penetration, I will be using a purge gas setup.
Here are the weld parameters I'll be using.

Welder: Lincoln Square Wave 175
Filler Rod: 4043 3/32
Amps: 120-135
Amperage control: foot pedal.
Shielding gas: 20cfh Argon
Purge gas: 5-10cfh Argon
Tungsten: 3/32 pure or 3/32in 2% thoriated.


They'll be welded either tomorrow or sometime next week. Wish me luck!

Because of the nature of this design, it's not likely that a poor weld will result in a failure, however I still want to do a good job.

View attachment 248229

Alex

I have welded much Al with a TIG. I have a few pointers for you.

1. Don't use a SS brush to clean. You are actually scrubbing metals into the Al that will cause a bad weld. This is more critical when doing DC Al(yes, I said DC) but I am assuming you will be using AC. Speaking of, you won't need your waveform pushed toward cleaning as much as you think. You can set it for more penetration, but not too much with Ar.

2. I highly suggest a weld relief in the large heat mass part. If you machine these two parts correctly you could easily do a fusion weld that would hold just a good as a filler weld.

3. Depending on the thickness of the tube you may want to add a fillet to get good penetration. Otherwise the current used to create a full penetration weld will blow out the tube side of the weld.

4. Unless you have a fairly thick tube 3/32 electrode is too big, you won't be able to maintain good arc stability when you have to back off to keep your puddle from running up the tube. If you are having to use such a large electrode to get a stable puddle then it is past time to cut a weld relief in the thick piece.

5. Don't use Thoriated in this case. I am assuming you have the high freq on all the time, use pure tungsten, you will be happier with the weld.

6. You mentioned cracking in your welds. Too hot(yes I know Al is a hot weld) but don't go crazy. Also stop using that SS brush, it is contaminating the weld with crap you don't want. If your are welding freshly machined parts you don't need to scrub it down. Acid etch and wash if you can. Another possible cause of cracks can be a very shallow surface weld done on what should be a full penetration butt weld.

7. If you don't already know how to ball the electrode properly for AC welding go find a youtube video. It is easy, just sharpen and then strike a small arc on reverse DC, it will ball right up for you.

8. My last one. Fixture, fixture and more fixture. Al moves all over the place, fixture your pieces the best you can.

P.S. If you don't already have a water cooled torch you going to want one after dealing with Al.

Good luck with your weld.


Sent from my iPad using Rocketry Forum

 

[Random Flying Object]

If your foot control sucks like mine does find a welder with a pulser I use it for thicker Aluminum makes nice even beads and acts as a timer for moving. Then again I am a hack

Use that pulser to control the heat effected zone while doing DC work on SS and nickel alloys, it will give a really nice weld after it's dialed in.


Sent from my iPad using Rocketry Forum

 

[Aksrockets]

I have welded much Al with a TIG. I have a few pointers for you.

Glad we have a few TIG welders on the forum!

1. Don't use a SS brush to clean. You are actually scrubbing metals into the Al that will cause a bad weld. This is more critical when doing DC Al(yes, I said DC) but I am assuming you will be using AC. Speaking of, you won't need your waveform pushed toward cleaning as much as you think. You can set it for more penetration, but not too much with Ar.

I've always used an SS brush and I've had minimal contamination. I've only welded aluminum AC, but I've heard about DC+. It's never sounded fun.

I highly suggest a weld relief in the large heat mass part. If you machine these two parts correctly you could easily do a fusion weld that would hold just a good as a filler weld.

I've tried aluminum without a filler rod, but the results are never pretty. The two times i've done it I've gotten big, long cracks running the length of the weld. I'm pretty hesitant to try it on something that isn't practice.

Depending on the thickness of the tube you may want to add a fillet to get good penetration. Otherwise the current used to create a full penetration weld will blow out the tube side of the weld.

Not quite sure what you're getting at here. Fillet the Inside of the tube? The length of the tubing is too long to get a TIG torch in there comfortably (or at all). I'm really considering trimming the tube down after the weld. I would do this before, but it doesn't give me enough room for my purge setup.

Unless you have a fairly thick tube 3/32 electrode is too big, you won't be able to maintain good arc stability when you have to back off to keep your puddle from running up the tube. If you are having to use such a large electrode to get a stable puddle then it is past time to cut a weld relief in the thick piece.

It's 1/8in wall thickness. I've welded plenty of 1/8in aluminum and havn't had any arc problems. I DO have the option to go with a 1/16th but I doubt it could handle the amps.

. Don't use Thoriated in this case. I am assuming you have the high freq on all the time, use pure tungsten, you will be happier with the weld.

I'll try to use Pure if I can. I'll see if I can find any green bands in the tungsten drawer.

7. If you don't already know how to ball the electrode properly for AC welding go find a youtube video. It is easy, just sharpen and then strike a small arc on reverse DC, it will ball right up for you.

I always tend to either ball or put a small "land" on the tip. Both have worked fine.

8. My last one. Fixture, fixture and more fixture. Al moves all over the place, fixture your pieces the best you can.

I've been doing tubing by tacking it, then placing it in an upturned section of angle iron. Ah how I wish I had a welding lathe.

P.S. If you don't already have a water cooled torch you going to want one after dealing with Al.

I wish I had one. I've been smoking my gloves on some of the hotter welds I've done.

Talk about pulse

Pulse is never something I've played with. The Squarewave 175 doesn't have a pulse feature. I DO have access to Lincoln Power Mig 210 Multi-Process, but it's not currently set up for TIG and I don't want to go through all that bother to do something I've never had any experience with.

Thanks for the tips guys! I'll keep them in mind!

Edit: Also, I wasn't able to weld today.

Alex