Dec 30, 2011 at 7:23 pm #1283531
This pack frame weighs about 1.5 ounces. It is similar to but about 1/2 ounce lighter than the frame I have used in my backpacks for about 10 years. I plan to use it for the next pack I build. Perhaps you can find a use for it.
This first photo shows the raw materials: two vertical spars, 1 horizontal spar, a loop of cord and two short sections of vynal tubing.
This second photo shows all of the pieces assembled. Assembly takes less than 1 minute.
(1) Thread looped string through horizontal spar so there is a loop of string sticking out of both ends of the horizontal spar.
(2) Slide short sections of vynal tubing onto both vertical spars.
(3) Insert a vertical spar through each of the loops described in #1 above. Make sure the loops wrap around the vynal tubing pieces.
(4) Repeatedly turn one of the vertical spars so the cord within the horizontal spar twists and shortens and tightens up against the vertical spars. (think child's rubber band propeller airplane)
(1) Pack bag could hang from the top of the vertical spars.
(2) Bottom of the vertical spars could connect to waist belt.
(3) The horizontal spar's reason for existing is to keep the vertical spars apart. It stays in place well won't carry much of a load.
(4) Traditional shoulder straps are a bit of a problem because they typically anchor somewhere near the mid point of a horizintal spar. I get around this by using a front bag and hanging it (like the back bag) from the tops of the vertical spars.
(5) This frame is very rugged. Like a palm tree it bends when stressed and thereby avoids snapping like a typical tree (or frame).
This frame took much much less time to create than this post.
But wait, there is more. I found that the frame easily folds up. See this photo:
By securing this folded up assembly with 2 or 3 short pieces of vynal tubing or velcro one is left with a pole that is very strong at the mid point because 3 pieces of tubing overlap. Hmmmmmm, must be some good use for this characteristic. Any ideas?Dec 30, 2011 at 7:50 pm #1817774
Sam FarringtonBPL Member
@scfhomeLocale: Chocorua NH, USA
Better not use nylon cord – when the temp drops, the nylon will expand, and no more secure connection.
I still like the kite fittings better, even if they are heavier (gasp!) To quote that great kite engineer, B. Franklin, "They really hold the sucker together!"Dec 30, 2011 at 9:58 pm #1817813
What type of string would you suggest?
Benny Franklin really had a way with words.
DarylDec 31, 2011 at 7:14 am #1817871
I'm not sure about this but I would think something like dyneema (zpacks, Lawson) or a polyester would work.Dec 31, 2011 at 8:46 am #1817900
Thanks for the idea. I have some low stretch 100 lb strength kite cord (dacron?) that is low stretch. I'll give it a try.
I think I'll soak the current model in water first, however, and see what happens with the waxed, twisted nylon that I used.
DarylJan 1, 2012 at 1:42 pm #1818301
Sam FarringtonBPL Member
@scfhomeLocale: Chocorua NH, USA
Probably any of the dyneema/spectra light cords available from the 'cottage' companies, as long as there is no nylon in it. I use it for flexi dog leashes and it doesn't appear to stretch.Jan 1, 2012 at 3:39 pm #1818355
Thanks for the info.
DarylJan 4, 2012 at 8:18 pm #1819969
The frame has been out in the rain for a few days and, as Samuel predicted, the nylon cord has stretched a bit and things have loosened up some.
I also reminded myself that the barbed nylon fittings this would replace only weigh 1/10 of an ounce each.
So I'm putting this idea in my tool bag for use on some other project and will probalby stick with the barbed nylon fittings for my next pack frame.Jan 5, 2012 at 7:18 am #1820075
Before you put this on the back burner …
There are way better options than what you are using for no stretch.
A super strong and ultralight way would be using a high strength no stretch fishing line like fireline.
Takes knots easily and you could just tie it on the right vertical pole run it through the cross bar around the left vertical pole back through the cross bar and around the second vertical bar and tighten with a truckers hitch. Then superglue it in place. (It would be too thin to twist tight I think but would be worth a try)
For securing your string tight just loop around the pole a few times and super glue it in place. (The line will glue to itself and the pole)
In fact you might be able to get it tight enough by just tying it off running it back and forth a few times turning it into a 4 or 6 to 1 pulley system and then looping it off and super gluing in place
It's so light that the length you ran around would be a couple of grams yet you could not physically break it or stretch it.Jan 5, 2012 at 9:01 am #1820115
I like your ideas and they are now on my todo list.
Your method eliminates the "propeller" aspect of assembly which was somewhat limiting anyway.
DarylJan 8, 2012 at 9:32 am #1821656
Photo below shows my attempt to mimic your idea using 100 lb kite string and granny knots. Works fine.
I also tried securing the loose line end and knot using Zap A Gap superglue from a kite store (not in photo). That secured everything just fine.
The twisting propeller technique still works with this thin line. I can cinch things up to the point of crushing the ends of the cross piece if I choose to.
The simple threading and knotting shown in the photo holds the horizontal member in place but also allows for adjustments by sliding it up or down the vertical spars.
This non-twisting technique also allows multiple cross pieces to be tied on if desired. The twisting propeller technique can only be used for one cross piece.
Still not sure when, where or if I'll use this apparatus but I like having the option in my head as I goof around with various projects.
Thanks for the help.
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