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Hey guys, New to building my own. I work in a precision machine shop and would like to make one from scratch. Are there any good resources you'd recommend?? Was hoping to make an MPR entirely from aluminium. Is this plausible? Would the body be too heavy? Any advice for a newbie is appreciated. Thanks!

With kindness,
Casey
 

Old School Doug

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I can't speak to the engineering issue but the bigger problem is that using aluminum for construction would violate the very 1st NAR safety rule. "Materials. I will use only lightweight, non-metal parts for the nose, body, and fins of my rocket. " So you can rule out launching it at any NAR sanctioned event. That doesn't even address the potential safety hazard of a motor CATO creating a field of shrapnel or a recovery mishap causing a ballistic (lawn dart) event.

Sorry to throw water on your idea but it's better for you to be aware than not.
 
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I can't speak to the engineering issue but the bigger problem is that using aluminum for construction would violate the very 1st NAR safety rule. "Materials. I will use only lightweight, non-metal parts for the nose, body, and fins of my rocket. " So you can rule out launching it at any NAR sanctioned event. That doesn't even address the potential safety hazard of a motor CATO creating a field of shrapnel or a recovery mishap causing a ballistic (lawn dart) event.

Sorry to throw water on your idea but it's better for you to be aware than not.
No, it's much appreciated!! As mentioned, I'm new to it and have yet to consider many aspects. Through the bit of research I've done, I see that people who machine their own use aluminium for everything but the body and nose. I wasn't sure of the reason, but this makes sense.
 

Nytrunner

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Hi Ohio!

Although the safety codes may modify your vision a bit, I think there's plenty of room for a machinist to go wild. Motor hardware for research motors if you join Tripoli, mounting-doodads and E-bays, various and other sundry components for high power rockets that aren't structural (see notes below)

There are two distinct classes of "hobby" rockets in the regulatory world
-Model rockets: (under 1500grams total launch weight, under 125 grams propellant weight) Doug mentioned the rules for this kind of rocket (includes Low and Mid power rockets)
-High-power rockets: (over 1500 grams total launch weight, under 40,960 N-s of total impulse) For this type, metal may be used (paraphrase) "where necessary for structural integrity"
For example, there are metal fin cans for high velocity flights (although composite fins can be made to survive also with appropriate skill), many composite nosecones have a metal tip, some folks make custom metal mounting hardware or brackets in their electronic bays, I've seen some precision metal cone/socket self-centering interstage couplers for complex rockets (on this forum too), some have used metal bolted fin brackets so their fins are removable instead of permanently fixed, etc....The design space is wide!
It's really a gray area of determining if it's necessary for structural integrity since high power rockets can be made bulletproof just with composite materials

What you may be really interested in is producing motor hardware and learning about making your own rocket motors! For that, Tripoli Rocketry Association is the way to go.
 

ether

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Here is one situation an aluminum body tube came in handy, but as stated above this is HPR at the extremes of commercial motors
 

David Schwantz

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I am not an NAR member, so will not address that. But Tripoli does allow it. Here is the link to the code. I have built and launched rockets with quite a bit of aluminum in their construction. the legs on the grain bin are of aluminum and go up through the body to the NC. The braces are also as are the "feet".


But a thought that might help you, the body is cardboard covered in aluminum tape. It is metal, just really thin. But sure looks like aluminum. Could you do that with a cardboard or glass tube and achieve what you are after?
 

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ether

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how do you do recovery? via separation of top "nose cone" or from the bottom?
 

ether

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That is awesome, has it flown?
 

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Welcome to the forum Ohio. Lots of friendly and helpful people here.

apogeerockets.com has good educational stuff on building rockets. Their Peak of Flight newsletter has an amazing amount of information and is free to browse on the site. You could also try your local library for books on model and high-power rocketry.

I would also check around if there is a club near you so you can attend a launch day and ask some questions.

As others have said, aluminium as an airframe is mostly out, except for the really fast flights. Even then with the relevant build it can be done with composites (there is one flight to M3.6 that I know of that was successful).
 

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It might be worth reviewing how most HPR rockets are built. Here's an old video showing basic techniques in building a standard kit.
jcrocket.com/kitbuilding.shtml

Using more exotic materials (composites, non-ductile metals) is certainly done, but usually only as needed since they are more expensive and require uncommon tools. Since you have a machine shop, the latter isn't an issue, but you still may want to be familiar with the standard techniques so you can better understand discussions.
 
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It might be worth reviewing how most HPR rockets are built. Here's an old video showing basic techniques in building a standard kit.
jcrocket.com/kitbuilding.shtml

Using more exotic materials (composites, non-ductile metals) is certainly done, but usually only as needed since they are more expensive and require uncommon tools. Since you have a machine shop, the latter isn't an issue, but you still may want to be familiar with the standard techniques so you can better understand discussions.
Thanks for the link!! What a great community this is. Thank you all for your input!
 

BABAR

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Hey guys, New to building my own. I work in a precision machine shop and would like to make one from scratch. Are there any good resources you'd recommend?? Was hoping to make an MPR entirely from aluminium. Is this plausible? Would the body be too heavy? Any advice for a newbie is appreciated. Thanks!

With kindness,
Casey
Since you own a machine shop, are you limited to machining metals? Wondering if you have the tools to turn your own wooden cones, cut and bevel plywood fins. Cardboard or phenolic tubes can be purchased, or you can check with carpet stores or other sources for throw away cardboard tubes (huge advantage if you can turn your own nose cones, as you can customize them to whatever cast off tube size you can get from a carpet store or other source.)

I don’t know how much aluminum costs, but I am thinking that possibly with the tools you have you may be able to build lighter and cheaper (not sure about easier) with conventional materials (cardboard, wood, fiberglass, etc) vs aluminum. More importantly, it keeps you within the Low Power Model Rocket Safety code (which applies I believe to mid power as well, I don’t think metal is allowed until you get to High Power, and I SUSPECT you will have to build, fly, and recover one NON-metal High Power rocket to get a NAR or Tripoli certification flight before you can fly any metal rockets.)

As mentioned, best advice it to join a local club and talk to people experienced in high power rockets before you start experimenting with aluminum or other metal key rocket components (fins, body, nose cone).

Wishing you safe flights, straight trails, and intact recoveries with short walks!
 

OverTheTop

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Babar reminded me of a technique I use on my lathe and mill. For machining balsa and fiberglass I use a Dremel or a dental drill mounted in the toolpost or quill, as a toolpost grinder, to get really good surface finishes on softer material. Works a treat. Air-operated dental drills, with spindle speeds of up to 480k rpm, are avialable on eBay for around $100 or so.
 
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jqavins

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You asked up front about the weight of building in aluminum, and that hasn't been addressed much.

How thin can you get a tube wall? I suppose you would start with pipe then face the ends; bore the inside to your desired ID, leaving a good smooth surface; then turn the outside down giving a good quality surface there too. And you'd check the wall thickness as you go. How thin would you dare to go? The thinner the lighter, obviously.

Now take π∙Diameter×Thickness×Length times 2.7 g/cm³ (density of aluminum). Compare that to the weights of rolled paper tubes you can buy or scrounge; those would be about π×Diameter×Thickness×Length times 1.2 g/cm³ (google's quick answer to "density of paper"). Does aluminum's greater strength let you get down to 44% of the paper tubes's wall thickness, and can you get there without running into machining limitations? Do I sound skeptical? I am.

LOC precision sells a heavy wall tube that's good for 38 mm motor mounts, and airframe tubes for 38 mm min diameter rockets or rockets with smaller motor diameters (most often 29 mm in this context, but not exclusively). That tube's wall thickness is 47.5 mils, so for equal weight in aluminium you'd be at 21 mils. That level of precision in most sorts of cuts? Easy, for an experienced operator like yourself. (Heck, so easy even I might be able to pull it off.) But cutting that as a wall thickness in particular? Sounds more challenging to me, but you're the expert. Worth doing? I doubt it.

Welcome to the hobby and to the forum. And please don't let insensitive jerks like me discourage you.
 
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You asked up front about the weight of building in aluminum, and that hasn't been addressed much.

How thin can you get a tube wall? I suppose you would start with pipe then face the ends; bore the inside to your desired ID, leaving a good smooth surface; then turn the outside down giving a good quality surface there too. And you'd check the wall thickness as you go. How thin would you dare to go? The thinner the lighter, obviously.

Now take π∙Diameter×Thickness×Length times 2.7 g/cm³ (density of aluminum). Compare that to the weights of rolled paper tubes you can buy or scrounge; those would be about π×Diameter×Thickness×Length times 1.2 g/cm³ (google's quick answer to "density of paper"). Does aluminum's greater strength let you get down to 44% of the paper tubes's wall thickness, and can you get there without running into machining limitations? Do I sound skeptical? I am.

LOC precision sells a heavy wall tube that's good for 38 mm motor mounts, and airframe tubes for 38 mm min diameter rockets or rockets with smaller motor diameters (most often 29 mm in this context, but not exclusively). That tube's wall thickness is 47.5 mils, so for equal weight in aluminium you'd be at 21 mils. That level of precision in most sorts of cuts? Easy, for an experienced operator like yourself. (Heck, so easy even I might be able to pull it off.) But cutting that as a wall thickness in particular? Sounds more challenging to me, but you're the expert. Worth doing? I doubt it.

Welcome to the hobby and to the forum. And please don't let insensitive jerks like me discourage you.
Thanks Joe! Input is always appreciated but especially when it's direct as you were. Wall thickness can be quite an issue for machining purposes. It would be possible to get the wall thickness down to around 1.25mm though as long as length does not exceed 5" (just for our capabilities). potentially could skimp a bit more off even. Turning outside diameter would not be necessary after a good polish. My thoughts now are to reduce the overall length of the rocket while keeping the same diameter to accommodate the 29mm motor I will be using. As far as it being worth it or not is irrelevant to my agenda. Obviously traditional methods are much more practical. I was just going to give it a go and see what was possible. Sure would put on a good show for our shops anniversary party.
 

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How thin can you get a tube wall? I suppose you would start with pipe then face the ends; bore the inside to your desired ID, leaving a good smooth surface;
Well, due to a misspent youth, I'd approach it a bit differently. Find a local Hang Glider pilot, and ask if he has any gliders on his junk pile. An inner leading edge on my old glider is about 3 meters of 60mm OD x 0.8mm wall 7075 tubing - weighing about 160 g/m. Support it on both ends and stand in the middle, and you'll see somewhere on the order of 3-6 cm of deflection. If the safety code didn't disallow such things, I'd have turned it into a rocket a long time ago (and there's no grooves to fill!). Lots of different rocket-sized diameter tubing in various gliders, though sadly none is likely perfect for a minimum diameter rocket. Newer gliders use carbon fiber cross bars/leading edges in these kinds of sizes.

I'm not sure how you'd firmly attach fins to such a tube, though.
 
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