How to draw huge radius in small area?

Not sure if this a math or rocket question, but...

Extreme example question, how would you plot or draw a section of a 50 foot radius on a piece of paper -without- having 50' of string, while sitting inside of a small tent in the woods?

Now, the real question...

Assuming the area working in is not big enough (but it is)

How does one draw a 205.3925" small radius 208.3933" large radius, with a 8.6375deg arc?

I need an 18+ foot trammel!


Yes, it's a transition...a big one

McKailas Dad said:

Not sure if this a math or rocket question, but...

Extreme example question, how would you plot or draw a section of a 50 foot radius on a piece of paper -without- having 50' of string, while sitting inside of a small tent in the woods?

Now, the real question...

Assuming the area working in is not big enough (but it is)

How does one draw a 205.3925" small radius 208.3933" large radius, with a 8.6375deg arc?

I need an 18+ foot trammel!


Yes, it's a transition...a big one

Click to expand...

This is a simple trig problem. Think of the place you're going to lay out the transition as a grid (x, y coordinates). Calculate and plot the values for the circle of the radius desired (one assumes that you have your grid in, for example, inches, you calculate the radius in the same units.

okay it probably hasn't occurred to Jeff yet, so I will ask. does anyone have an algorithm they would be willing to share so that one could code it in basic? thanks,
Rex

Trig ain't easy when you didn't pass algebra lol. 10 is cake, 15's pretty easy, but I gotta take off the other shoe to get to 20 :/

Maybe I'd better explain further. I'm making a posterboard transition going from 10 inch diameter down to. 9.856 in a 3 inch length. I'm making a second transition from 9.856 to down to 9.424 in another 3 inch length.

According to the online calculator here - https://www.rocketreviews.com/shroudtransistion-calculator.html

To 'draw that out', I would need a compass that would open to 208.39 and 205.39 inches, but only have to draw an arc 8.6375 degrees wide.

Seems like a narrow slice, but without a giant compass, straightedge, or long string, how can I hold it at the fulcrum point and draw an arc is if the point is theoretically too far away?

Yes, technically, I CAN lay out a 17 plus foot straightedge to draw/cut the first transition, but there's -got- to be an easier way...right?!

The second transition is more realistic (i.e .,smaller) to lay out. Going from 9.856" down to 9.424" in 3", the small radius would be 65.6139, the large 68.6216 with a 25.8531 degree arc.

A barely noticeable curve of a line drawn on an 8x10 piece of paper could represent a 1 mile radius, it would be presumably way less than 1 degree arc, but how do you draw it actual size radius without a 1 mile long string?

Rex, funny you should mention that. I'm using a nosecone spreadsheet I found a while back that I'm -trying- to modify a column and add and figure the numbers for the transition calculations. I know...nothing..about spreadsheets either


I have the EQUATION, but don't know -how- to do the math on it. Sin, L, y , r1, r2. Square root thingy in there too.

All the math is on page 149 in the "Handbook.."



After figuring the answer for "y", that was it. Lost me at Sin, big time.

lol, I've got that bit done;( https://www.rocketryforum.com/showthread.php?130467-programing-softwre-(Qb64) ). took me a bit to get the sequence of operation correct, but I get the right numbers now. what I don't get is how folks can get the software to plot the shroud/transition(what you're asking about). I'm reasonably sure they don't tell the computer; first you need a piece of virtual string a mile long....
Rex

er...maybe one could try asking 'Cortana' .
Rex

Rex, it took me long enough to figure out how to modify a spreadsheet to add a Column D and have it automatically calculate Column B*2.

So, the equation input string may be what I'm looking for, but for in a spreadsheet version.

I would be curious to learn how to do it 'on paper', but an algorithm I can punch in to figure it automatically in OpenOffice would work too.

Get Columns E, F, G to read small radius, large radius, and degrees of arc based on the numbers that were calculated from Columns A and B?

Perfect! But, no clue...


And, I still need to know how to DRAW it,

Open Rocket will print transition templates. I'd be better off trusting open rocket, or drawing it in a CAD program then printing it, than trusting I could get closer than that. It would be challenging finding something in the shop that length square and rigid enough to do the job well.

Good suggestion, I tried it in OpenRocket, it would take 5 pages, but it actually -would- print.

I'm looking for an easy way to make multiple passes in the same arc via something 'rigid'.

Drawing it is just for reference, it's accurately -cutting- that arc at a particular angle in degrees is what I'm trying to ultimately accomplish.

Is there a way to cheat mathematically and/or mechanically to use a 60" trammel or beam compass to follow the same arc as one that is three times longer? Not a fixed point, but an arc moving fulcrum?!

I'm thinking a few new #11 Exacto blades, but I'm not quite that far yet

Based strictly on the dimensions in this post (#4), specifically the 10" diameter, how the devil do you get to a curve radius measured in hundreds of feet? :y: So I took these dimensions and stuffed them into SketchUp and it produced the following plot. I'm thinking that when you plugged your numbers into that calculator, your units may have been wrong, ie inch vs cm and radius vs diameter. Take a look at the "drawing" and see how the numbers match with the real world. Hope this helps!

Google "cone template generator". Here's a couple examples.

https://www.blocklayer.com/cone-patternseng.aspx

https://www.templatemaker.nl/index.php?template=cone&lang=en

If it's too big for you to print same it as a PDF and take it to Kinkos and have them plot it for you.

This is the way that I've always done it: https://woodgears.ca/shop-tricks/large_arc.html

Essentially just two straight pieces that, when laid against two (outside) points on the curve, they intersect at the third (middle) point. Then just slide from one side to the other.

How about just making disks the diameter of the two airframes, joining them with a dowel the correct length, then rolling it on your material. Trace out the path of the two disks. An index mark on each of the disks will mark the start and end of the transition piece.
-Ken

new2hpr said:

How about just making disks the diameter of the two airframes, joining them with a dowel the correct length, then rolling it on your material. Trace out the path of the two disks. An index mark on each of the disks will mark the start and end of the transition piece.

Click to expand...

Way too practical. We need a solution with frickin' lasers, preferably mounted on sharks.

Seriously though, that is a great and incredibly simple solution!

You can use a drawing program like Corel Draw where you draw it at scale, then just print out the relevant portion of the arc on a plotter.

Diggr said:

Based strictly on the dimensions in this post (#4), specifically the 10" diameter, how the devil do you get to a curve radius measured in hundreds of feet? :y: So I took these dimensions and stuffed them into SketchUp and it produced the following plot. I'm thinking that when you plugged your numbers into that calculator, your units may have been wrong, ie inch vs cm and radius vs diameter. Take a look at the "drawing" and see how the numbers match with the real world. Hope this helps!

Click to expand...

Your pic from SketchUp shows a 5 inch diameter, and I need 10. The 1 mile radius drawn on 8x10 was hypothetical, but theoretically has to be possible.

I'm making a 'fixture' on my kitchen island to mark and cut the -second- biggest transition. The counter is 36" wide, so it's just enough room to lay out a 25.8 degree arc from a ~70" beam. This transition will fit on one sheet of of posterboard, but, I had to turn the sheet a few degrees off 90.

I'm making the 'beam' with 3 pieces of aluminum angle, 1/16"x3/4", bolted together in the middle. I drilled a hole for a pivot point on one end, measured 68.621" from that, and drilled a 1/16" hole. I may as well drill another hole at 65.613 for the small end.

The point of a brand new #11 blade fits centered through the 1/16" hole, with -just- enough exposed on the other side to cut. I'm thinking of gluing a small block perpendicular to the hole to keep the blade square but free.

Lasers? Sharks?! Oh, that was a couple days ago, I'm onto DNA disrupters on luminescent llamas by now. Pfft...lasers..ha

I'll have to take some pics. I'm thinking even Rube Goldberg might be proud

It's the -first- (biggest, longest) one that's gonna be the most difficult.


Btw, I've done this before, just not this large. I've made 5.25" transitions made of posterboard...

Here's an Excel spreadsheet that makes a tracing template. Just adjust the printer to make the grid block 1" x 1"

View attachment largediametercircletemplate.xls

Bob

McKailas Dad said:

Your pic from SketchUp shows a 5 inch diameter, and I need 10. The 1 mile radius drawn on 8x10 was hypothetical, but theoretically has to be possible.

I'm ... Rube Goldberg might be proud

It's the -first- (biggest, longest) one that's gonna be the most difficult.


Btw, I've done this before, just not this large. I've made 5.25" transitions made of posterboard...

Click to expand...

I finally pulled my head out of my butt and remembered that "when all else fails - just read the problem." I missed that what you're doing is to draw two conical transitions that are developed out flat. I plugged your numbers into the online calculator you cited, and then crunched the same numbers with the formulas on page 149. And both methods produce the same results. Imagine that. Your method for the smaller of the two seems the only practical way to go without investing in some elaborate jigs and tools.

Do you have access at work to a good CAD program that can print a drawing 1:1? I had a copy of ACAD but with the demise of my last laptop I can't do things like that any more. I'm going to put out some feelers to the place I used to work and my younger son to see if I can come up with a dwg file you can take to a place like FEDEX and have printed.

Other than that good luck. And bye-the-bye what are you building that uses transitions that size?

If you're used to AutoCAD, just pick up Draftsight. It's a free 2D package from the folks who make Solidworks. Almost 100% command compatible with good old ACAD, even the function key shortcuts!
-Ken

I fabricated my beam fixture to mark and/or CUT all but the largest transition.

The fulcrum....







I cut a couple small windows to see the markings on the protractor.

The cutter...

That used to be an electrical ground terminal iirc. The exposed blade fits through the predetermined 1/16 " hole in the aluminum angle.

The beam?

Yup, 70+ inches long. 3 pcs 1/16"x3/4" aluminum angle, overlapped and bolted together. Light but sturdy, it'll work.



I should start a different thread on the REAL reason I'm doing all this. I am making a total of -11- different transitions......

There's a company that sells a product that looks like a tape measure, but has a pencil on the end. It's made to do what you are doing.

I'd just draw all of them to scale one sheet and get them printed out at an output place. It'd cost maybe $10 around my area to do that.

The cutter, through hole in beam -



Plenty of blade sticking out, is adjustable height, and replaces easy. The handle is optional and not necessary, more for guidance.




I know, there are a million ways to draw, plot, or print a template. I should have been more specific, it's how mark it so I can CUT it short, of doing it freehand.

Also, more importantly , if there was a way to NOT use a 17 foot long beam...

ChrisAttebery said:

Google "cone template generator". Here's a couple examples.

https://www.blocklayer.com/cone-patternseng.aspx

https://www.templatemaker.nl/index.php?template=cone&lang=en

If it's too big for you to print same it as a PDF and take it to Kinkos and have them plot it for you.

Click to expand...

Bookmarked these! Thanks!

Almost ready to go.



That piece is 22" x 28".
The black tape lines are at 26 degrees, the program calls for 25.8 arc, and even going past there's room on the posterboard. Just fits.

Almost to the mark...I'll have to cheat a little to square the ends. Long, but not too long.

I'll be cutting inside of the lines, I just penciled in for visual stimulation.

I'll have to adjust the height of the blade, there's actually too much exposed out the bottom to cut correctly.

Just the tip?

I'll finish showing the 'how' here , then I'll start a the 'why', in another thread, if anybody is curious.

McKailas Dad said:

......

I'll finish showing the 'how' here , then I'll start a the 'why', in another thread, if anybody is curious.

Click to expand...

Yes, very curious! Please put a link to the "why" thread hereso I don't miss it. I'd love to know what you're building, how many, and what precisely is the material you're cutting and how thick?

Your circle cutter is quite clever but I'm thinking that you may have reached pretty much the practical upper limit as far as radius is concerned. I look forward to the "why".

Diggr

All have been cut.

Ten of them. All of them cut out from using only 2 pieces of 22x28 posterboard.

I think I can fudge a little and not make the largest one. I have to make something else first to find out

A hint...they all fit together, and the the --smallest-- transition was the most difficult.

Well, it was an interesting math problem, anyway.