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The "Six Circles" Shooter Design by Jörg Sprave


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14 replies to this topic

#1 JoergS

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Posted 30 June 2011 - 11:10 PM


I have been making this style a lot lately, it simply works great and looks good, too.

I realized the beauty lies in the simple radius combination. So I limited the design down to those.

All I needed to create this wonderfully symmetrical design is six circles. Of course this should be sawed out of multiplex or other high quality plywood, 15 to 22 mm, and then some scales (palm swell) should be added, from any kind of material.

Fork height is adjustable to one's needs.

Here you see both the blueprints with the radius's, and the cutout.

Posted Image
Posted Image

Here is the pdf file.

Attached File  SixCircles PDF.pdf   242.95K   873 downloads

Will be making a nice frame soon!

Good luck making your own.

Jörg

Edited by JoergS, 16 July 2011 - 03:00 AM.


#2 shot in the foot

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Posted 01 July 2011 - 01:28 AM

I done one nearly the same as that last year sold it on a carboot, just a touch samer the one i made, jeff

#3 e~shot

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Posted 01 July 2011 - 02:55 AM

Thanks Jörg. is scale in CM ?

#4 JoergS

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Posted 01 July 2011 - 03:05 AM

Sure... would be a monster in inches, right? :lol:

#5 e~shot

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Posted 01 July 2011 - 03:07 AM

Sure... would be a monster in inches, right? :lol:


:rolling:

OK let me give a try to make a PDF of it

#6 jskeen

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Posted 01 July 2011 - 10:00 AM

That's bloody brilliant! Beautiful because of it's simplicity, not in spite of it. Did you pick that ratio of 2.5x5.5x12 by trial and error, or design? I almost immediately thought of the "Golden Mean" or "Divine Proportion" of 1.61803 to 1, but I can't seem to make it fit your design.

12 to 5.5 = 2.18 to 1
5.5 to 2.5 = 2.20 to 1
12 to 2.5 = 4.80 to 1

2.20 to 1 is the standard ratio of 70mm film, and is a formulaic constant used to calculate signal loss in radio frequency transmitters and hysteresis loss in transformers for high voltage power transmissions. Hmmmmm, makes you wonder.

Sorry, had a brief attack of engineers disease. If Tex reads this, I hope he don't catch it, as it's very contagious.

James

#7 jskeen

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Posted 01 July 2011 - 10:00 AM

sorry, double post

Edited by jskeen, 01 July 2011 - 10:01 AM.


#8 JoergS

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Posted 01 July 2011 - 01:59 PM

No such factor, just trial and error until it all made sense.

#9 Dayhiker

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Posted 01 July 2011 - 03:24 PM

That's bloody brilliant! Beautiful because of it's simplicity, not in spite of it. Did you pick that ratio of 2.5x5.5x12 by trial and error, or design? I almost immediately thought of the "Golden Mean" or "Divine Proportion" of 1.61803 to 1, but I can't seem to make it fit your design.

12 to 5.5 = 2.18 to 1
5.5 to 2.5 = 2.20 to 1
12 to 2.5 = 4.80 to 1

2.20 to 1 is the standard ratio of 70mm film, and is a formulaic constant used to calculate signal loss in radio frequency transmitters and hysteresis loss in transformers for high voltage power transmissions. Hmmmmm, makes you wonder.

Sorry, had a brief attack of engineers disease. If Tex reads this, I hope he don't catch it, as it's very contagious.

James


Skeen, I'm no engineer, but I've been trying to work the Golden Ratio into my designs since I started making slingshots. I just know it's gotta fit in there somewhere. :D

#10 Ted

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Posted 01 July 2011 - 07:08 PM

Thanks for sharing!

#11 NaturalFork

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Posted 01 July 2011 - 08:38 PM

Great design. I have been shooting the Cougar a lot lately. I think the cougar is your best design ... but that is just personal preference.

#12 shawnr5

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Posted 02 July 2011 - 09:37 AM

Looks great, but I think that your fork outside radius should be 6cm, not 5.5. I'm going to have to give this a go. Thanks for sharing with us.

#13 JoergS

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Posted 02 July 2011 - 11:50 AM

I think that your fork outside radius should be 6cm, not 5.5.


True - my bad. Yes, 6 cm.

Jörg

#14 shawnr5

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Posted 02 July 2011 - 01:39 PM


I think that your fork outside radius should be 6cm, not 5.5.


True - my bad. Yes, 6 cm.

Jörg


No worries. I'm going to get out the compass when I get home tonight, regardless. When I started the Angry Birds slingshot, I made myself a compass that will spin arcs from 6 inches to 28 inches radius, in 1/2 inch increments. This design may require breaking it out again. How would you band it if it were scaled up 3x?

Shawn

#15 jskeen

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Posted 09 July 2011 - 12:22 AM

I finally got my cheap knockoff..... um er.... tribute design? Whatever it is, I started with just the single value of the diameter of the forks, and calculated the rest using the ratio of 1.61803399 to 1 after much careful drawing and figuring, the final design I came out with is less than one inch different from the original in any dimension. Pretty interesting how closely experience and testing matched a mathematical formula that was used to design the Parthenon, among other things.




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