# Pseudotapers from different tube types



## hoggif (Apr 6, 2013)

I wonder if anyone has chronied combination pseudotapers made from different tubes?

I really like pseudotapers but I guess longevity may be compromised because the short section must be maxing out. If you use something a bit heavier the maxing may not be that bad or it could be just avoided. (Or it may last longer just because it is a bit heavier tube).

Here's couple pictures of one way to make them (as a proof of concept and to try out how reliable they are):





  








Combination pseudotaper




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hoggif


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May 20, 2013


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3



loop from 2040 and the single line from 1745 (pouch end)






The connection is made by spreading up the single tube and pushing the loop ends into it with the aid of forceps. A couple constrictor knots should hold it.




  








Combination tube connection




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hoggif


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May 20, 2013




Connected with a couple constrictor knots. Colors are from the paint I use to "glue" the knots...






(The color is from the paint I use to lock the knots. It also color codes band types. If you look very closely the pictures you should be able to figure out which tubing is my avatar pseudotapers made of.)


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## boby (Oct 7, 2012)

Speed calculations (attached) indicate a pure 1745-1745 pseudo-taper is comparable to or better than a 2040-1745 mixed pseudo-taper, for a given pull force and draw.


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## hoggif (Apr 6, 2013)

In case anyone wonders how much each band type scretches, this will give about 32cm for the 2040s and 61cm for the 1745. That calculates to about 300% of the original length of 11cm) for the 2040s and 550% of the original lenght of 11cm 1745. (Very roughly measured at my draw lenght).

In my theoretical model assuming force comparing directly to surface area and the tubes acting like ideal springs with constant spring factor (k) I predicted 360% and 500% (it also assumed end connection instead of a loss of lenght due to band going around the forks and connection point was not modelled). This rough model seems to roughly correlate with my rough measurement. 

Without a chrony this is not too meaningfull because I can only eyeball if it does anything to the speed. This experiment is about longevity of bands anyway.

The pull force is between 2040T and 2040-double as expected (not measured) and it seems to give more kick to 10mm steel than 2040 pseudotaper at same lenght.


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## hoggif (Apr 6, 2013)

boby said:


> Speed calculations (attached) indicate a pure 1745-1745 pseudo-taper is comparable to or better than a 2040-1745 mixed pseudo-taper, for a given pull force and draw.


What does your calculations estimate for different types such as 2040s with 1842?

(And is there a way to estimate effect on life time of the bands? Scretching one part more gives you probably more speed but at the impact on life time)

..and for the more difficult binding different types are not as nice unless one really gains something.


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## boby (Oct 7, 2012)

hoggif said:


> boby said:
> 
> 
> > Speed calculations (attached) indicate a pure 1745-1745 pseudo-taper is comparable to or better than a 2040-1745 mixed pseudo-taper, for a given pull force and draw.
> ...


The calculations in the table include info for 2040 by itself (rows labeled 2040-2040), and such rows cover both untapered (rows with la/(la+lb) = 0 or 1) or pseudo-tapered. I do not have 1842 so I have no density or force vs pull data to make calculations for it. Sorry.

As for lifetime, 1745 seems to last longer than 2040, but for me pseudo-tapers always broke at the joint between the 1-tube and 2-tube sections, and this seemed rather premature. I might get 200 shots for that case, vs 800 shots for a well attached single (untapered) 1745 tube. So I don't think that that premature breakage is fundamental and linked to high stretch factors, but is rather something that might be avoided by better single to double tube attachment methods. (I used a short 1745 sleeve with constrictor knots for the joint.)


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