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moocrew

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Alright Im thinking of two or three new roc ideas before i start building I like to have a bit of an assortment to chose from then i pick my fav one to build first....some of you may have seen my first one http://www.rocketryforum.com/showthread.php?s=&threadid=9961
(BLue GAMe)

now heres my second one (see posted pic below)

As you see it has three transitions.
Ive tried making them myself before using the white foam then coating it with foam finish...didn't turn out horribly bad but it wasn't my best attempt at anything.
I don't have access to a wood lathe and i can't really afford to pay someone to make them for me unless they would be somewhere under or close to 10 bucks.
So i was wondering if anyone here had made a trans. anyother way?
if so and you could give me some ideas I would be greatful.

thnx in advance.
-matt



--- i haven't really thought of a good name for this one yet so i just gave it a name to save it with.
 

qMaxx

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You could just make paper transitions using heavy cardstock or even file folder material. RockSim and/or VCP can be used for calculating and printing the transitions, and for extra strength, you can either do a double layer or add balsa strips to the inside.

The smaller tube fits inside the larger using centering rings, and can be left open to allow ejection gasses to pass through, or blocked with a bulkhead.

See pic below:
 

Fore Check

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Balsa Machining has a pretty good selection of balsa transitions in stock - looking at your design, if those are "standard" body tubes, they should have everything you need. You'll just need to drill a hole through the lower most (largest) transition for your chute(s) to deploy from where you have them.


If you want more specific custom work (shaping, lengths, diameters) you could drop a line to Sandman.
 

Ryan S.

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if you have a power drill you could set up a makeshift lathe
 

moocrew

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wow thanks guys. I like all these ideas, but have some questions on them....

qMaxx- so i understand to center the tube with ct rings. but the card stock---folder paper...etc... is cut and basically wrapped around?...Ive made a flying saucer for MM before would it be anything like that? Also..there would be a seam i assume? If so how would i go about smoothing that out?

Ryan S.- What about a drill press? that would work wouldn't it? then what type of material should i use Balsa? where do you get the blocks for it?

Sorry if these seem like dumb or pointless questions i just want to make sure i completely understand.
Thnx again for all the replys and help.
and I'll defenitely check into the Balsa Mach. thing that could even be good for a later project.

thnx
-matt
 

sandman

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qMaxx- so i understand to center the tube with ct rings. but the card stock---folder paper...etc... is cut and basically wrapped around?
Bookmark this:

http://www.rocketreviews.com/tool_shroud.shtml

Just plug your numbers into it to make transitions. Practice making them until you get good enough to put them on a model...it's only paper!

What about a drill press?
A drill press is the next best thing to a lathe.

should i use Balsa? where do you get the blocks for it?
Yes! Use balsa. The best price I've found on balsa blocks is Balsa Machining Services (BMS)

http://www.balsamachining.com/

The balsa "squares" are under "construction supplies".

Make some sanding blocks from 40 or 60 grit paper glued to some scrap wood.

sandman
 

qMaxx

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Originally posted by moocrew
qMaxx- so i understand to center the tube with ct rings. but the card stock---folder paper...etc... is cut and basically wrapped around?...Ive made a flying saucer for MM before would it be anything like that? Also..there would be a seam i assume? If so how would i go about smoothing that out?
Yep, the card stock is printed out like a cone and you just curl it and glue the ends together. On something the size of the rocket you're planning, a single layer should be fine...maybe soak it with some CA for strength.

Yeah, there will be a seam, but you can either fill and sand it, trying to blend it smoothly if it's an overlap seam. Or, you can just butt the ends together and use a separate glue tab to attach the ends, which won't give you an overlap. You'll still have a thin seam, but it'll be easier to fill than an overlap seam.

As for the drill press, if you can't swing the cost of an actual press, you can fake it with a normal hand drill and a drill press stand (I got mine from Sears for about $30). It's basically a mount to hold a 3/8" or 1/2" drill vertically, and has an arm to lower and raise the drill just like a drill press. The table doesn't tilt though, and it's takes a bit of work to get the drill perfectly vertical. Also, the drill needs to have a trigger lock, although most have those. I've used mine to make several custom nose cones (including the 10 needed for a Delta II, in two different scales), centering rings, and other odds and ends. You can use a broken hacksaw blade for the rough shaping, then finish with different grades of sandpaper on blocks.
 

moocrew

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Qmaxx- I have a drill press not real good access to it all the time but is works well. So ill have to try that with some balsa.
You guys ever thought of painting nose cones while they are on the press?
 

qMaxx

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Not really painting, but Peter Alway suggests in The Art of Scale Model Rocketry that finishing (sanding and sealing) would be done quicker and easier while still chucked in the press.
 

moocrew

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can someone explain how that calc works? im pretty much clueless... :( :rolleyes:
 

sandman

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I'll do an example.

Go to Totally Tubular's web site,

http://www.wooshrocketry.org/misc/tt.htm

and download the pages. This will be for reference because it has the exact tube sizes

Now let's figure a transition for a BT-60 to a BT-20 for an example.

On the top line of the shroud calculator it says a T-20 (BT-20) tube is .736" in outside diameter. Type .736 into the top line marked "Small Diameter"

On the second line type in the size for a BT-60 (Totally Tubular's T-60) is 1.637. This is the line marked "Large Diameter".

Now deturmine how long you want the transition...let's make it 3" so on the next line type 3.0. This is the line marked "Height".

Then just click on "Calculate".

Now the first number 2.47808....is the small radius so set your compass as close as you can to that and draw an arc.

The second number 5.512 is the Large radius so set your compass to that and draw another arc but make sure you use the same center point for the compass.

The last number is the angle of the arc. You are going to need a protractor for this and make an angle equal to 53.46 degrees make sure both lines of the angle go through the center point of the arcs..

When you are finished just cut it out with some scissors "carefully" but leave a little tab to glue the ends.

I included a picture

sandman
 

moocrew

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yes i completely understand now. I ..uh..goofed a bit and was gettin strange numbers.

Thnx for the help.
I'll be posting construction pics and launch pics soon!

-matt
 

qMaxx

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Originally posted by moocrew
can someone explain how that calc works? im pretty much clueless... :( :rolleyes:
In the 3 top fields, put in your transition dimensions. Ex. - You want to go from a BT-60 to a BT-55, and the shroud is 2" long. In the first field, put in 1.325, the second, 1.637, and the third, 2.

Then click the "calculate" button.

It will then give you the measurements needed to draw the shroud out on a flat sheet of paper (you'll need a GOOD compass, and a pretty precise protractor and ruler - preferably a ruler that is divided in .1" increments - like an engineer's scale). It's okay if your arcs are in nice even degrees, but I've had several designs that come out to something like 132.836 degrees and such, which isn't easy to work out on a protractor that is only accurate to .5 degrees (although I can fudge .25 and .75 easily enough).

I prefer VCP or RockSim, as both of those will print the pattern for you.
 

DJ Delorie

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It will then give you the measurements needed to draw the shroud out on a flat sheet of paper
Oh come on, this is the computer age. I used that math as the basis for my own page, which generates a PDF for you - just print it on card stock and cut it out. It also already has all the common BT sizes in a pull-down menu (while still allowing custom sizes, in decimal or fractional inch or metric sizes).

http://www.delorie.com/rockets/transitions.html

I guessed on the tab size, let me know if a different default size would be better (it prints extra lines you can use to cut your own tab if needed)
 

moocrew

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thats..genius? lol
nice page thanks for the link...now all i have to do is figure how to print this on the board im using.....
 

Gus

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DJ Delorie

FANTASTIC!!!

What a great addition to the tools that are out there. Thanks a bunch.

But now that I've heaped all this praise on you, could I ask for one small additon?

Acrobat is notorious for not printing true to scale.

Would it be possible for you to add in a little "1 inch" line so we could check whether the printout needs to be adjusted?

Thanks, and again, what an absolutely fantastic gift to the rocketry community. :D
 

Gus

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Moocrew,

Some advice on paper transitions from the card modeling world.

Instead of using a tab on one end of the transition to glue it together, cut the tab off and glue it behind both edges. This leaves a surface without an edge.

The graphic attached below shows how to do this.

Its a good idea to cut the tab just a hair shorter than the transition so it's thickness won't leave a bulge where it attaches to the body tube.

Another hint, to apply good pressure to the transition glue joints while they dry, put a popsicle stick on the front and back of the joint and hold the two together with some of those little springy clamps available all over the place.

Also, white glue works just fine, and will bind two pieces of paper almost instantly if you use a really thin layer.
 

moocrew

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yeah i've caught on to moving the tab....i those little bumps were buggin the crap out of me.
But I hadn't thought of the popsicle stick thing yet..thanks!
-matt
 

DJ Delorie

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I have added a 1" square on the page so you can calibrate your prints. I can put a larger calibration mark on, but then it may start interfering with everything else on the page.

I also print the whole circle so you can cut along it outside the transition and make an arc-shaped tab if you want to use Gus's advice. I could probably add lines for that too ;)
 

Gus

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DJ,

Thanks for adding the calibration square!

I emailed Nick at EMRR and he indicated he'd contacted you and he's going to put a link to your site on his.

Tell your ISP to get ready! I've a feeling you're about to get lots of visits. :D
 

DJ Delorie

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I added more calibration marks and lines for both types of tabs, plus fin alignment marks just in case they're needed.

I don't have to worry about my ISP; the machine is in my basement and I have a full T1 connecting it. I did respond to Nick already.
 

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