Seat Foam Cutting with Hot Wire Jig

MEASURE TWICE

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Jul 13, 2010
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You can look up to buy Nichrome wire online and make a hot wire cutter. The Medium Density Foam I have needed to be cut at a precise arc radius curve of 8 inches. It is not for a seat on a motor bike, but some day yes maybe for a motor bike. It is for a pontoon boat.

My motor bike I did use two types of foam but it is not anything but cutting and taped, so it was never really finished very nice. Though it is definitely functional for trail riding as it has no pedals, just pegs instead, and licensed for Off Highway Vehicle stickered.

So, with pontoon at 16" dia that is 8" rad. The jig has adjustment for about a range around 6.5" to 9", but I could make it bigger. Smaller would be something I know how to do but would take a bit more working on.

The kiddie rims of 6" on two side of a platform with angle brackets you see. The two are ganged together with wood. The threaded rod juts out of the valve stem hole, another hole I drilled just the other side for the wood gang to synchronize both rims to move together. The threaded rod has nuts and washers that clamp the Nichrome 80 wire 24 Guage and 27inch length span. The old train transformer wit 15 volts ac had the right temperature and wire did not break when heated with current flowing.

There is flexible wire I scavenged from probably 20 years ago off a waffle iron power cord. Pulled the twin lead in half and sanded clean the strands and twisted to the Nichrome wire ends where I had it strung across the thread rods on the two rims ganged together.

My hand on the ganged wood part with slight pressure while I wore a gas mask and cut some nice arcs. Next to make the seat covers with fabric and zipper to be able to remove foam and clean an rinse out salt water and dry after a day sailing.

More later as I get to it. A few pictures attached.

Cutting the straight cut was a little hap hazard, but I used a fillet knife and it is a little ragged but with the fabric cover probably not even noticeable.

In the past I never thought of this project, but it finds you anyway. Most people would not need a softer seat, but you find when a spine is out of whack you have to adapt so nerves that are being disturbed by bulging disks don’t go even more on the attack. It is just like an electric shock and it is not something you want to have going on if you know ways to prevent it.

MT
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MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,450
542
113
CA
Have to eventually see about using next thickness gauge wire 22 if it can stay a bent form cutting. I have also thinner in 4 more sizes. I might need to buy thicker if it will not keep the shape. Also a straight cut using sort of like a guillotine or whatever. The fillet knife cutting for straight cut is a bit ragged look.

One other thing I have to wait and see what happens to the area that was cut with the hot wire. The surfaces have a gooey stuff speckled on them. I don't know if it will firm up and just adhere fully to the surfaces and not stay messy. I know I could try washing, rinse, & drying the foam and see what happens. The covers I am to make keep from having the stuff really go anywhere except the inside of the cover. I did not have any publication I read mention the goop?
 
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MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,450
542
113
CA
Looked at TinSmith on seat made of heavy leather. I am looking at using marine vinyl material. Good videos on making seat and sewing the box construction and also zipper. Around 10 to 20 dollars a yard by 54" standard have seen on Ebay and elsewhere. The breather vents I also looked into, but are ones that keep water out? Maybe test the closed cell foam with water as is mentioned for boat seats. Then maybe if holds air too much, a simple grommet as the small kit including tools are easier to be had for less. I would like stainless steel though.
 
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MEASURE TWICE

Well-Known Member
Jul 13, 2010
2,450
542
113
CA
Have to eventually see about using next thickness gauge wire 22 if it can stay a bent form cutting. I have also thinner in 4 more sizes. I might need to buy thicker if it will not keep the shape. Also a straight cut using sort of like a guillotine or whatever. The fillet knife cutting for straight cut is a bit ragged look.

One other thing I have to wait and see what happens to the area that was cut with the hot wire. The surfaces have a gooey stuff speckled on them. I don't know if it will firm up and just adhere fully to the surfaces and not stay messy. I know I could try washing, rinse, & drying the foam and see what happens. The covers I am to make keep from having the stuff really go anywhere except the inside of the cover. I did not have any publication I read mention the goop?
Good news, in about two weeks since the cutting was done, that sticky bit on the foam has gone away.

The vinyl marine light weight fabric I got was not in a roll and has some creases, but will go away after flattening out in the sun. The fabric had a huge amount of odor that would give a headache. It also just needed airing out. The manufacturer to seller to end user probably always has it in wrap that nothing escapes. VOC strong stuff, but OK since aired a couple of days.

Got 16 and 18 size for special sewing machine needles to see which work best. The 102 thread fits the needles and is synthetic polyester strong and waterproof. The new needles are special meant for leather and I'll use them or general purpose ones.

Making some plans out of construction paper or something to get things done right. Good videos on Youtube shown using plans, not so much how to make them. So I figure just measure and get shape right from the foam I have. Then order of transfer and assembly and small v cut marks on edges not showing of fabric to get aliment perfect when you fold.

Cutting I remember using paper forms, called dolls when doing printed circuit board layout to see how components best fit. I may do that to see how to effectively get the least amount of waste when I decide how to cut out panels and have least cut scrap material left over.

I bet there might be a program that scans and tells where to cut, if it is free online use, maybe could use.

MT
 
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