Next Stop 150k feet: Aluminum Fin Can Extreme Wildman

Xrain

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*New Update on 2nd page!*


I have started work on my Level 3 Certification Rocket. Me and 3 other flyers are attempting our level 3 certs on April 11th at Lake Louise up here in Alaska.

Launch Site:

We have a 25,000' waiver with a few 2 hour windows up to 50,000' if needed. The lake is about 20,000 feet x 30,000 feet, pretty much flat, and clear of obstructions. It is a pretty fantastic launch site.

Basic Rocket Design:
The basis of my rocket is a Wildman Extreme Kit, with the main modification I am making being the addition of an aluminum fin can that I am machining myself.

Fincan:
I am going with an aluminum fin can for several reasons. First and foremost I want to move on to bigger faster rockets eventually, and this gives me a chance to practice methods to fabricate precision fin cans. Next my rocket will be landing on a frozen lake. If it lands in a spot with poor snow cover the ice is about as hard as concrete, making fin breakages common problems. So I am eliminating that issue on this rocket with the aluminum. Next my rocket sims to about mach 1.5 with a AT M1500G reload. I don't want to have anything to do with fin flutter and aluminum is pretty good in that respect. Lastly machining my fin can should let me get my tolerances to at least a thousands of an inch, so the GoPro on my rocket should get some nice footage. There is a slight concern about potential stresses in the aluminum from when it was manufactured warping the can when I machine off a majority of the metal. That issue I cant really do anything about until I make the can and see how large of an issue it will be. It might just be a slight shift of a few thousands, or it might be a pretty significant twist.

I have mostly been making the fixtures to hold the piece of aluminum to properly machine it in the mill. Oddly making your fixtures tends to take up majority of the overall machine time when you are fabricating something. I should have these fixtures completed tomorrow.

My fincan is based off the Binder Design 4" MaxQ Aerospace Fin Can https://binderdesign.com/store/page13.html

Main design difference is my can is being machined from a 4" ID x 5" OD x 12" long piece of 6061 aluminum, vs. the bent sheet metal method that this can normally uses.

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Here is a schematic of one of the 3 clamping pieces that will be cut out of that aluminum tubing. One of the more significant issues is I didn't read the fine print on McMaster well enough when I ordered that aluminum.
The length tolerances they provide is 1" :facepalm: So I the the piece I got from them is actually is around 11.4" long vs. the 12" that I was thinking I would get. Thankfully however, the aluminum is still long enough for the fin can but it does cut down on the amount that I can bevel the leading edge of the can.

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I am going the more difficult route of machining the can, since my Sheet metal bending skills leave a bit to be desired. Additionally I can better scale this method to larger diameters, and still retain relatively tight tolerances.

The fins I have purchased from Mike at Binder Design. I just got them in today and they look pretty fantastic.

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My wildman kit is still in the mail, I'm expecting it to get here in the next few days.

Thanks!
 
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beezwax

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I did a double-take when I read your post-- first because it's rare to see AK postings here (I'll be coming down to the Lake Louise launch in a couple weeks, very much looking forward to meeting everyone) second because I have the exact same project in my build pile. I bought one of the first 4" MaxQ fin-cans from Mike a year ago and also ordered an Extreme Wildman kit to build from. I asked Tim not to cut any fin slots in the airframe, otherwise stock kit....but I bet it's going to be another year at least before I get to start on that project so I'll be very interested to see yours. I hope you are just using an adapter for your 75mm cert motor and are leaving yourself the possibility of future minimum diameter flights? Milling the clamping plates for the fin-can yourself seems like you're taking the long way around, was that necessary in order to be used for the L3? I think I remember reading somewhere that pre-fabbed fin-cans couldn't be used in cert attempts. Since you are milling it why did you decide to reproduce the bent sheet metal design of the original instead of something that could take advantage of the thick stock you are starting with? Like slotting out fin channels with radiused "fillets":

https://www.rocketryforum.com/showt...rator-v1-1-is-progressing&p=509087#post509087

I don't have any milling experience but it's something I dream of adding to my hobby shop one day so I'd love to chat with you about your set-up. Best of luck with your build and your cert flight!
 

Xrain

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I did a double-take when I read your post-- first because it's rare to see AK postings here (I'll be coming down to the Lake Louise launch in a couple weeks, very much looking forward to meeting everyone) second because I have the exact same project in my build pile. I bought one of the first 4" MaxQ fin-cans from Mike a year ago and also ordered an Extreme Wildman kit to build from. I asked Tim not to cut any fin slots in the airframe, otherwise stock kit....but I bet it's going to be another year at least before I get to start on that project so I'll be very interested to see yours. I hope you are just using an adapter for your 75mm cert motor and are leaving yourself the possibility of future minimum diameter flights? Milling the clamping plates for the fin-can yourself seems like you're taking the long way around, was that necessary in order to be used for the L3? I think I remember reading somewhere that pre-fabbed fin-cans couldn't be used in cert attempts. Since you are milling it why did you decide to reproduce the bent sheet metal design of the original instead of something that could take advantage of the thick stock you are starting with? Like slotting out fin channels with radiused "fillets":

https://www.rocketryforum.com/showt...rator-v1-1-is-progressing&p=509087#post509087

I don't have any milling experience but it's something I dream of adding to my hobby shop one day so I'd love to chat with you about your set-up. Best of luck with your build and your cert flight!

And here I was thinking I was original, to find out that someone is using the same kit and fincan in the same town as me! Must be something in the water... Considering there are about 15 HPR certed people in the state perhaps I should go enter into the lottery.

Shoot me a PM I am in Fairbanks as well, I'd be happy to meet with you and we could coordinate things if you are heading to Lake Louise as well!

It is a requirement in the cert rules to make your own fincan, so prefab fincans are expressly prohibited.
Machining the clamps were definitely not necessary for a level 3 cert. I am just miserable at bending sheet metal straight, and I like machining more anyway. I also seem to be starting a collection of large diameter thick walled metal tubing...

I am using the 75mm motor mount, since all the motor casing I have access to are 75mm, and I don't feel particularly compelled to buy a 98mm right now.

My design is slightly different than the sheet metal design as I am using thicker walls. But its similar since I am trying to minimize weight. That piece of aluminum currently weighs about 18 lbs, a bit heavy to be sticking on the tail end of my rocket. Meaning I am cutting off any bits that aren't really necessary. Fillets aren't really necessary since I have plenty of strength and would complicate machining a bit. Reason being I would have to use a little more unusual endmill for those fillets, meaning I would have to change tooling in the middle of my cutting. I might put some very small fillets in if we have a convenient end mill around, but I'll have to see.

With fin channels the problem is currently I need every bit of that 0.5" wall for me to be able to bolt the fin in. I would have to go with a larger wall thickness and the next size that conveniently fits has a 1" wall thickness. Meaning I would be cutting close to 30 lbs of aluminum off of it, I am already being pretty environmentally unfriendly as it is. ;) That additional wall thickness also would exacerbate any problems of residual stress in the metal, so my flanges might get warped when that stress is released from cutting off the additional metal. There is some .75" tubing that would require the ID to be bored, but that's adding a whole nother machining step. Not to mention 12" boring bars cost a small fortune.

So the clamping fin can will do pretty well for what I want it to do, and I am getting more accuracy from the machining than the sheet metal since the channel cut from the round to separate the 3 pieces will be the exact thickness of the fins. If that is actually going to get me anything, well we will just have to compare when you build yours! :D
 
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markkoelsch

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First, I think this is cool.

Secondly, please leave the 75mm motor mount out of the rocket. Use an adapter down to 75mm, but if you are going to the trouble of this fin can why limit yourself in the future?


Mark Koelsch
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dixontj93060

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It is a requirement in the cert rules to make your own fincan, so prefab fincans are expressly prohibited.

Yes, but the exact statement in the Tripoli rules goes like this: "Commercially available pre-fabricated fin cans, either as part of a kit or obtained separately, may not be used for level 3 certification flights." Seems fine in that you are building the can/sleeve, but becomes a gray area with respect to "obtained separately" if you use pre-fab fins from Binder (I assume you discussed this with your TAPs though).
 

Sailorbill

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Are you using a CNC mill for this? I can't imagine trying this on a "manual" mill. I have watched our machinists as they work on large projects that would be easy on a CNC but they are limited to our two old Bridgeports. They have power feeds and a DRO but even with those this would take for ever.
For fillets couldn't you a ball nose end mill when you get to the tabs? I would think that would make the fin tabs stronger than square corners.

Good luck.
 

Xrain

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First, I think this is cool.

Secondly, please leave the 75mm motor mount out of the rocket. Use an adapter down to 75mm, but if you are going to the trouble of this fin can why limit yourself in the future?


Mark Koelsch

Well the beautiful thing about using a clamping fin can, is all I need to make it a 98mm minimum diameter is buy another aft body tube and a bulkhead. Glue them together and bolt my fins on.


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The beautiful thing about a clamp on fin can is that all I need to do to make it a 98mm minimum diameter is buy another aft body tube and glue a bulkhead in it. Then just swap my fin can over and voila! So if I get around to buying a 98mm case and reload a new $80 body tube wont be a big deal.

Yes, but the exact statement in the Tripoli rules goes like this: "Commercially available pre-fabricated fin cans, either as part of a kit or obtained separately, may not be used for level 3 certification flights." Seems fine in that you are building the can/sleeve, but becomes a gray area with respect to "obtained separately" if you use pre-fab fins from Binder (I assume you discussed this with your TAPs though).

Yep it has all been discussed and approved by my L3CC. Buying fins doesn't really seem much like a grey area as I see it, as far as I know many people have purchased fins for their level 3s they just tend to be g10 instead of aluminum. I thought the intent of the make your own fin can rule is to make sure you know how to keep your fins well aligned and attached. Plus the fin can tends to be 80% of the work on a rocket anyway. The rules also specify that you allowed to have others build components to your specification and use them in your rocket.

I am getting NAR level 3 certed since that is the club we have up here. https://aknorthstars.org/wp/
Though there will also be a TAP coming to the launch as well.

Are you using a CNC mill for this? I can't imagine trying this on a "manual" mill. I have watched our machinists as they work on large projects that would be easy on a CNC but they are limited to our two old Bridgeports. They have power feeds and a DRO but even with those this would take for ever.
For fillets couldn't you a ball nose end mill when you get to the tabs? I would think that would make the fin tabs stronger than square corners.

Good luck.

No I am using a manual Sharp mill. It has autofeed so it isn't that bad. It is being mounted to a rotary table, which is what most of my work has gone into making appropriate fixtures to mount it. CNC is not as easy as you would think, if I was going to make 5 of these fincans I would use a CNC (we have a HAAS VF2 if I felt really compelled to CNC it). But it would take me much more time to get the CNC fixtures setup and proof out my code to mill the can than it will take to make the same part once or twice on a manual mill. You have to remember that a CNC is perfectly happy to ram the mill head right into the table at maximum speed if you let it, so you have to be very careful on your first few runs on a CNC to make sure your code is behaving how you expect it to. If I was doing a more complicated shape a CNC would make sense, but this fin can requires relatively simple machining procedures so I am fine with a manual mill.

That is the end mill to use, I would have to slow my feed rates when I am clearing out the extra metal in between the flanges with that ball end since the radius is smaller at the end of the mill. So I'd have to chance tooling in the middle of my cutting. I think I might be able to add some fillets, I'll have to see what end mills we have around first. If I have to order one I wont have enough time to get it in town.
 
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dixontj93060

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Yep it has all been discussed and approved by my L3CC. Buying fins doesn't really seem much like a grey area as I see it, as far as I know many people have purchased fins for their level 3s they just tend to be g10 instead of aluminum. I thought the intent of the make your own fin can rule is to make sure you know how to keep your fins well aligned and attached. Plus the fin can tends to be 80% of the work on a rocket anyway. The rules also specify that you allowed to have others build components to your specification and use them in your rocket.

I am getting NAR level 3 certed since that is the club we have up here. https://aknorthstars.org/wp/
Though there will also be a TAP coming to the launch as well.

Great, just didn't want you to put the effort in for naught. Looking forward to the build.
 

beezwax

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You're in Fairbanks!? That is such great news, I've felt like I was alone on a desert island here re: HPR. I first moved up here twenty years ago to attend UAF but am only recently returned to the area. Will PM my contact details so we can get together sometime and talk rockets! :)
 

Xrain

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A small update, I only got a few hours in the machine shop today but still made some progress. But I did manage to get some more action oriented pictures this time around.

I'm still working on my fixture to hold the tube in the mill for machining. I was lathing a taper into two pieces of 5" dia x 1" thick aluminum.

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Managed to get the tapers completed, here are some pictures of the aluminum collar fitting onto the QD shiv that it will mate with to hold the work piece onto a 1 3/8" rod of steel.

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Lastly here is the steel rod being cut in the DoAll band saw.

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I should get about 7 hours of machine time tomorrow so I should get quite a bit more progress then.
 
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Xrain

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Made some more progress yesterday.

The fixture is finally pretty much completed with just one small operation left to do on the retention collars.

The first thing that was done was the steel shaft was faced off on either end, with a centering hole bored onto each end. A keyway was then milled into one end of the shaft to prevent the QD Shivs from slipping around the shaft.
The main aluminum tube that will be cut into the fin clamps was put in the lathe and the ends were faced off to true them.

Then a radial hole pattern was drilled and three of the 6 holes were tapped, while the other 3 where drilled as clearance holes into the collars.

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With that radial pattern drilled the only thing left is to lathe a small sholder onto the collars so they will fit into the tube to be milled.

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Bonus points to anyone who can figure out how those pieces will go together! :p

Also my kit finally got here! So I can finally start work on that part of the operation as well!
 
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blackbrandt

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Let's see...

The smaller tube goes through the collars and that assembly slides into the bigger tube?
 
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Xrain

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Let's see...

The smaller tube goes through the fins and that assembly slides into the bigger tube?

Good Guess, but the fins don't attach to these pieces... yet... Those collars are just hold to tube in the rotary table so I can mill the can out. It only took about 20 hours and now I can actually mill the fin can! :rolleyes:


On another note my kit finally got in today, so I present to you: Mr. Happy Nosecone and his two children!

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(5.5in for my friends rocket, and 4in for mine, anyone reading the EX section might see something familiar as well.)


The last machining operation that I had to make might make it easier to figure out what is going on with my fin can fixture.

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Here are the completed pieces for the fin can fixture.

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Here is the fixture partially assembled some of you have probably figured out how it will go together.

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And finally through the magic of taking a picture an hour and a half later, (only took 3 tries to get everything right!) we have the completed fincan fixture assembly!

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So if any of you guessed right on how it all went together, give yourself a pat on the back and a gold star!
Now all that is left with the fin can is... actually machining the fin can part...

Something interesting to note:
The aluminum fins from binder design are 0.88 of a pound lighter than the fiberglass ones that came with the kit.

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Honestly not something I expected, I was fully expecting my aluminum can to be much heavier than the normal setup. But taking into account the weight of the epoxy that I wont need to use, I am betting my fin can will not be much heavier than the normal fin attachment method.

And finally since there seems to be a thing for this kind of thing around here... ;)

The tubes from my kit taking a jacuzzi!

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The timeline I am tentatively planning at this point will be to do a majority of the machining for the fin can tomorrow, and at least get the basic joints on my kit glued together this weekend. It should leave me ample time to get the details of the electronics and accompanying sleds together by the launch next weekend.

Anyone have any questions about anything?
 
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beezwax

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Great pics, I can't wait to see the finished product :) very glad the kit made it, any news on the motors?
 

Xrain

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Yes, what brand of lathe is that?
Glad you found the thread!

Which lathe? :D

The blue one that has been used the most in the pictures is a Romi-Bridgeport. Funnily Bridgeport didn't really have anything to do with the lathe other than attach their name to it.
If you are looking for a lathe I probably wouldn't recommend the Romi. It does a decent job cutting things but it has a few "features" that make it a bit of a pain. The main issue is the tailstock doesn't have a horizontal slot inside it, so it relies only on the taper to hold the tools. So if you feed too quick or have a bit of oil on the tool's taper the tool will spin inside the tailstock and likely destroy both the tool and the tailstock. The other issue while kinda small is all the speed swivels on the handles are made from plastic with a metal rod in them, and aren't nearly as nice as the all metal handles on the other lathes. I'm not sure if it came this way but the handle on the compound falls out if you pull on it. A huge pain if you are trying to get a good finish by feeding smoothly and a part of the handle pulls out and falls into the chip well making you have to change your hand position mid feed. :mad:

The HAAS lathe that can be seen in a few of the pictures is a VL-2

The big lathe that can be seen next to the red table is a Monarch circa 1953 and the best manual lathe in the shop.
The best lathes we have in the shop is a small 10EE Monarch and that large 13" Monarch. They are definitely the best lathes I have used. Built like tanks, smooth and precise, and they have all these very well engineered features (like actually designed to be repairable). There is another Monarch I have used in another shop that is 80 years old, and has been through 2 floods and a fire. Biggest problem with it is the thread size selector handle wont stay in gear without a bungee strap. They still make the 10EE's just they way they made them in the 40's new today (with updated electronics). They run a little bit above $85,000 new. Used you can find a decent one for $8,000 or so.

There is also a Clausing lathe in the shop that I have used a few times, it is a little long in the tooth, but it is very user friendly and well thought out.
 

Binder Design

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The big lathe that can be seen next to the red table is a Monarch circa 1953 and the best manual lathe in the shop.

Thanks! My current lathe is an import. While it does nice work, it is too light to do any heavy hogging, so large bores like nozzle carriers and smoke wells in bulkheads kill a lot of time.
 

Xrain

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Thanks! My current lathe is an import. While it does nice work, it is too light to do any heavy hogging, so large bores like nozzle carriers and smoke wells in bulkheads kill a lot of time.

Any of the larger monarchs that is in decent shape would make light work of something like that. Though there are many good brands that will work well, pretty much any of the older American lathes will work, I am just a bit of a monarch nerd. My dream lathe is a Monarch 1000EE. The US government during the cold war pretty much just went to monarch and gave them an open check book and said make the best lathe you can and they succeeded. It has a really cool feature called constant surface velocity, so what it does is as you adjust the compound on the lath it adjusts the spindle speed to maintain the same feed rate. So even if you are facing off a 16" diameter round the surface finish will be the same all the way in.

Mmmmm.... HAAS VL-2.... :D
If you like the VL-2 we also have a VF-2 and a ST-10 (I think that's the model #). Both have rotary tool holders and auto tool changers. I've been trying to come up with a good enough excuse for a while now to use them. ;)

Anyway

Fincan Build Update:


I finally got the tube held in the mill in the fixture I built. Though the road has been a bit rocky. The problem that I ran into twice was the tube wasn't held rotationally in the fixture well enough. So on beginning some cuts across the tube the bit would start to mill into the tube, then grab hold of it and just spin it around in the fixture. :facepalm: My beautiful tube which I had dial indicated and aligned in the mill to within one one-thousands of an inch is now completely out of alignment.

To fix this I had to undo the setup on the mill pull the fixture off, put a gear puller on one of the end fixtures and separate them enough to blow the chips and debris out of the gap between the fixture and the tube, align it back the way it was, hammer it back down. Then I would as one of the shop mentors put it "Gorilla" the bolts down to make the fixture hold tighter. So the first time it happened we did this fix and it worked for quite a while, I managed to get the rough cuts done for the flanges (with some nice fillets now since you all asked for them) and about quarter of the rough cuts between the flanges.

Then of course since the force holding the tube in had been reduced since there was less surface area to hold onto the tube spun again in the fixture. This second time however we lathed 6 1/8" aluminum pins and then drilled holes through the fixture and the tube where the flanges will be cut. Then pinned the tube to the fixture in 6 different locations. This should fix the problem, and so far has. Nice thing about the pins being aluminum is that they can just be cut through like the rest of the tube when the time comes to cut out the flanges.

I'd guess after the movement of the tube in the fixture, the tube is currently within 0.001 - 0.005" in most places; since I still have 0.020" left to cut on the faces that I have finished roughing I should be able to get it pretty close back to my goal of 0.001". The radial alignment of the fins from the dividing head I am using is within 0.002° granted heat expansion and other such variables means the real alignment tolerance is a bit higher than that. But still, definitely a step up on precision fin alignment compared to my previous method of a plumb line and a square (which still is a decent way). For those of you who aren't well acquainted with such measurements, a brand new dollar bill is .0046" of an inch in thickness.
If you were to stand on the ground, fire a laser at the moon and draw a line by moving your laser 0.002° the line the laser would draw on the moon would be 8.3 miles long. Honestly this level of alignment isn't really required for this application, it is more just as a personal challenge to improve my machining abilities.


Here is the fixture between centers in the dividing head on the mill.

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The first rough cuts for cutting the flanges out of the metal. If you look closely you can see the fillets. It takes a little over 5 minutes for the mill to complete a pass so about 12 passes an hour...

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Here all the rough cuts on the flange edges are completed, just starting to clear out between the flanges.

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Close up of between the flanges getting cleared.

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Finally starting to look like I am making progress!

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So long as nothing else goes wrong during milling it should be about another 6-8 hours of milling left to get the surface cutting done, then I just need to drill the bolt holes on each flange with the mill and the cut it out with a rotary saw. In total I've spent about 30 hours of machine time on this, so I can see the light at the end of the tunnel! :)
 
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botscott08

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This is looking very cool. I admire your fixturing solution. What did that piece of pipe set you back?
 

Xrain

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This is looking very cool. I admire your fixturing solution. What did that piece of pipe set you back?

The pipe was from McMaster https://www.mcmaster.com/#9056k57/=rfgwxc $81 for the tube + $45 in shipping.
I would have gotten it locally since it would have been around $60 and wouldn't needed shipping but no one had this specific size of pipe.

If you ever use a fixture like this either do the pin method if you can, or just have all-thread go all the way though and clamp the dickens out of it.
 

CCotner

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Very cool to see machine shops on TRF! Great plan, cool work!
 

botscott08

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The pipe was from McMaster https://www.mcmaster.com/#9056k57/=rfgwxc $81 for the tube + $45 in shipping.
I would have gotten it locally since it would have been around $60 and wouldn't needed shipping but no one had this specific size of pipe.

If you ever use a fixture like this either do the pin method if you can, or just have all-thread go all the way though and clamp the dickens out of it.

Your advice comes at a great time. I was hoping to machine some large, truncated steel cones with a central bore for a steel shaft to align anything cylindrical but clearly that will slip in a scenario like yours. It might still work for hole drilling and slotting of tubes though.

I'm curious how you'll machine the flanges once you've cut the tube apart. I was imagining a concave fixture the diameter and length of your pipe and with flanges machined that match up with those on your part. I don't have a lathe big enough make that big concave shape but the VMC ought to do just fine.

Take a look at these flat head binding posts. They're not cheap but the fin can would look really slick without bolts protruding.
https://www.mcmaster.com/#98096a101/=rfi1du
 
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Xrain

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Your advice comes at a great time. I was hoping to machine so large, truncated steel cones with a central bore for a steel shaft to align anything cylindrical but clearly that will slip in a scenario like yours. It might still work for hole drilling and slotting of tubes though.

I'm curious how you'll machine the flanges once you've cut the tube apart. I was imagining a concave fixture the diameter and length of your pipe and with flanges machined that match up with those on your part. I don't have a lathe big enough make that big concave shape but the VMC ought to do just fine.

The flanges have already been milled for the most part, you can see one of them here:

d95435a6-77d5-43d7-86f9-76c713ee3d68_zpsfd3c6acf.jpg


The depth is a little bit misleading in the picture but it is currently 0.345" down from the surface (remember I only have 0.500 to work with). I will just finish the surface down to 0.375 after I have finished the rest of the roughing and drilled the flange holes. Then using a rotary saw bit in the mill run that back and forth along the channel to cut it out and release each of the 3 pieces.

So all of the machining operations will be completed on the fincan before I cut the tube apart.

If you are using a tailstock or something similar to push those steel cones against each other to grab the tube, you could probably just cut a small matching taper on each side of the tube you are working on and push them together. That might give enough friction to mill some. Just take light cuts and use really sharp tools until you get a feel for how much you can take.

That said, keyways or something that doesn't rely on just friction are always better.

Also for the rest of you:

Here is a really short video that I took that gives you a feel for how "fast" I can mill at. :D

[YOUTUBE]WvoBjHJb9oE[/YOUTUBE]

I kid about the speed, but I am intentionally going a bit slow since I don't want to risk the can. If I make a mistake at this point I am pretty much hosed.
 
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botscott08

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Ah, that makes sense. I have to finish my L3 rocket but I'll be trying a fin can like yours at some point. I look forward to seeing it all together.
 

Xrain

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Update:

I have finally finished the end milling portion of the fin can construction, and it is looking pretty good so far. All that is left for me to do is drill the holes into the flanges to bolt to the fins and then cut each piece apart from one another.


Here is a picture of the first level of roughing cuts taken on the tube. This first level of cuts was cut down to 0.1742" from the surface.

5e6d5bc0-7ca2-444e-95a7-9b24ac84c91b_zps917cf37e.jpg



Here is about 1/2 of the second level of cuts completed. this brings the cut depth down to the final value of 0.345" I have the option of going down to 0.375" for a finishing cut if I want to.

6ba7128a-30ee-4adc-b7a0-7267aa9adaaa_zps0876a9fd.jpg



Here is the very last cut from the centers between the flanges being finished, definitely starting to look like something.

8f085ef8-d2aa-4cb6-a200-0afc55e6c87b_zpsae6598e6.jpg



Here is the first of the finish cuts being taken on the flanges, getting a very nice finish on the flanges.

693d9fdf-7cb5-46e4-a8c0-5b6f78ecd38e_zps9c1a37f5.jpg



Here is a close up of one end of the flanges, you can see the fillet that the ball mill put into the flange. As well as the only pin that looks terrible and didn't completely seat into the assembly. :facepalm:

e4129921-3dbc-49e5-b8ec-b12a5e47066b_zps77975945.jpg



Here here we are finally, all of the end milling operations are done, and you can see the finish on the sides. The circles that the end mill aren't quite as consistent as I would like, but I really do like the faceted look of the fin can. I think I might just smooth some of the corners with a bit of sand paper and leave everything else how it is.

f7e2b440-bc99-44d3-8064-798a19e4f3ca_zps7e091839.jpg



Here is a side view of the completed cutting!

d76b337f-167a-4daf-9070-056899d488e7_zps7bdbe206.jpg



Lastly for anyone who is curious on how much aluminum gave it's life for the cause of my fin can fabrication here you go: :cool:

635c63d0-2f97-4c3c-a782-4e9bfeda5a6c_zps43cd26be.jpg


Note: My hand is level with the surface of the pile of chips.

So I should be able to get the last machining operations on the fin can completed tomorrow, and hopefully do a test fit on my rocket the day after.
 

dixontj93060

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I am watching this thread. Not being a machinist and only using a lathe (wood) once, I am having trouble getting to "point Z". Looks like you still have a super thick piece of tube stock even with the outside cuts. I'm assuming there will be an inside cutting step(?). No real question here, I'm sure it will become obvious in subsequent steps. BTW, the fluted look does make it very distinctive--like it.
 

botscott08

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I am watching this thread. Not being a machinist and only using a lathe (wood) once, I am having trouble getting to "point Z". Looks like you still have a super thick piece of tube stock even with the outside cuts. I'm assuming there will be an inside cutting step(?). No real question here, I'm sure it will become obvious in subsequent steps. BTW, the fluted look does make it very distinctive--like it.

What you see at the end of the tube that looks so thick is actually a fixture to hold the tube. The tube has a 4" ID so wall thickness is around 0.125".
 

dixontj93060

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What you see at the end of the tube that looks so thick is actually a fixture to hold the tube. The tube has a 4" ID so wall thickness is around 0.125".

OK, then another question. I assume there is a secondary step to route out the four tabs (which look solid to me now)?
 
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