Author Topic: Inserting foam into shoulder straps  (Read 1912 times)

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Bootcat

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Inserting foam into shoulder straps
« on: June 08, 2016, 06:14:28 AM »
Hello gents,

Currently I force the foam piece into a plastic tube, insert the tube into the shoulder strap, pinch and retract the tube while massaging the foam to fill the strap.
I'm aware that the industry uses metal tubes cut lengthwise where the insertion of the foam is much quicker. However, that means manufacturing a special tool for each needed width (not even sure if that requires cutting a metal tube or rolling a metal sheet).
Someone suggested that I try to pull the foam wrapped in a plastic bag through the strap then remove the bag.
Another suggestion was to use the kind of square plastic tube used to run electrical cables in buildings (top is removable so foam insertion is fast).

What method are you using?
 

Fouinard

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Re: Inserting foam into shoulder straps
« Reply #1 on: June 08, 2016, 07:37:36 AM »
When the straps are straight, I generally use 2 flat aluminium sections above and below the foam and push it inside the fabric, but it tends to compress the foam a bit and you have to play with it so it relaxes.
When the straps are curved with closed end, like most backpacks, I start to turn the fabric inside out on 3 or 4 cm so the round end of the foam sit inside it, then I start to roll the fabric over the foam like a condom... This way you can squeeze the fabric to get a tight fit, and also can control in which way the seam allowance turns inside.

Misadventure Gear

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Re: Inserting foam into shoulder straps
« Reply #2 on: June 08, 2016, 11:34:20 PM »
A few years ago, I made some strap stuffing jigs out of 1" and 1/2" conduit. I took a section approx 24" long, and cut a slot down one side using an angle grinder. The slot was about 1/3rd of the circumference of the pipe. I left a few inches at the end uncut, for a handle. Next, I clamped it in a vice and carefully opened the edges of the slot so that the pipe was U-shaped, instead of a C along the slot. Then the fun started. Using a Dremel tool and files, I worked all the edges to remove burs. This was very time consuming, but I found that any burr will slice the foam as it slides out. I also worked it over with an emory cloth to polish the inside of the slot to make it easier to slide the foam out. It worked fine at this point, but I sent it over to my friend, who powder coated it in a high gloss finish.

In use, I'll drop a few drops of sewing machine oil inside the slot, then fold the foam in half lengthwise and lay it in as well. I use 1/2" foam in the 1" conduit, and it works with straight, S-shaped or J-shaped shoulder straps. The S-shaped foam can be tricky to hold in the straight conduit, but it can be done. Instead of rolling the strap sheath down over foam like a condom, I just shove the thing into the sheath, pinch and hold the foam in place, then slide out the pipe. Then I massage things around so the foam opens up and lays flat. I pretty much never use the 1/2" conduit, even with 1/4" foam, because the 1" pipe just works better.... If your gonna make one, don't waste your time on the smaller conduit.

At one point, I started to make several more, with the intention of offering them for sale to gear makers. I ended up moving on to other stuff in the middle of the deburring/polishing stage, and I'm pretty sure I'll never get around to finishing them. If you're interested in one as is, let me know, and we can work out a trade or something. I'll work on getting a pic up.
« Last Edit: June 09, 2016, 01:25:56 AM by Misadventure Gear »

Misadventure Gear

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Re: Inserting foam into shoulder straps
« Reply #3 on: June 09, 2016, 01:24:36 AM »
Heres some pics of the unfinished jigs. If anyone is interested in one, I'd like $15 each, or $25 for a set of the two sizes, plus shipping.  I'm open to PayPal or trade for materials.  They are unfinished.  You will need to do some filing and sanding to remove burrs and rust.  I powder coated mine to make it more slick, but that's not required if you polish it well. 















« Last Edit: June 09, 2016, 01:29:20 AM by Misadventure Gear »

Bootcat

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Re: Inserting foam into shoulder straps
« Reply #4 on: June 09, 2016, 07:01:43 AM »
Thanks for the input! The

Misadventure, these are very nice jigs! I was surprised that you exposed so much foam surface (instead of cutting a slot just wide enough to insert the foam). I'm afraid the shipping to Europe will kill the good deal you're offering, I suppose I should just build these jigs like you did. Out of curiosity what is the sheet thickness of your tubes?

Misadventure Gear

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Re: Inserting foam into shoulder straps
« Reply #5 on: June 09, 2016, 03:26:54 PM »
The pipe I used is your standard EMT electrical conduit available in 10' lengths at any home improvement store. I made the slot wide so that I could fold the foam in half along the long axis. This makes it narrower and easier to slide fully into the sheath and to its final position.

http://m.homedepot.com/p/Allied-Tube-Conduit-1-in-EMT-Conduit-101568/100400409

Bootcat

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Re: Inserting foam into shoulder straps
« Reply #6 on: June 10, 2016, 03:19:19 AM »
Over here electric cables run in plastic pipes. Your tube seems to be 1,5mm thick, I'll find myself something similar and give i a try.

Fouinard

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Bootcat

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Re: Inserting foam into shoulder straps
« Reply #8 on: October 27, 2016, 03:38:32 AM »
End result for me: I found electrical conduits (Merlin Gerin Electric, rectangular section, 30x10mm) that proved to do the job well for my padded slings. I have yet to try the bigger size with curved shoulder straps.