New home defense setup

[MrB+]

It's been a long time since I did any cutting, but I used stainless-steel fishing leader -- easier to find than NiChrome wire, especially at the sorts of stores this crowd frequents. Less fragile, too. It has enough resistance to heat like the NiChrome.

I made a bow from a piece of 1x2" 'furring' strip lumber and some heavy piano wire (Tammie's Hobbies, Beaverton). Piano wire was sized to be springy enough that I could just 'undersize' the cutting wire length between loop ends, and the piano wire would hold the cutting wire taught. Piano wire was nicked (nocked?) to keep the cutter in place.

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I used a Variac rather than light dimmer to power mine; either way, just be careful -- you have line voltage exposed at the wire, and even if you've dialed the power control clear down, depending on which direction you plug it in, you can still have +/- 170V flailing around at the wire. (The commercial unit probably has a polarized plug to avoid this last, assuming your house wiring is done right.)

MrB+
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Working my way up to A--

 

[MarkSBG]

It's been a long time since I did any cutting, but I used stainless-steel fishing leader -- easier to find than NiChrome wire, especially at the sorts of stores this crowd frequents. Less fragile, too. It has enough resistance to heat like the NiChrome.

Stainless steel is what I tried first. I thought that it expanded too much, but maybe it works in other situations. If you can't find Ni-Chrome wire (available at Norvacs in Beaverton) you can buy a hairdryer at goodwill and gut it for the heating element. It may need to be straightened, but it should be NiChrome.

I used a Variac rather than light dimmer to power mine; either way, just be careful -- you have line voltage exposed at the wire, and even if you've dialed the power control clear down, depending on which direction you plug it in, you can still have +/- 170V flailing around at the wire. (The commercial unit probably has a polarized plug to avoid this last, assuming your house wiring is done right.)

I probably should have mentioned that the current goes through a 25 volt 2 amp transformer before it ever sees the cutting wire. Yeah, using power straight from the wall could be very dangerous.

 

[Coolbreeze8804]

Ummm.... someone mentioned that the cuffs may be a bad idea, and then I read that there was a thread about that elsewhere.... I can't find that thread, but I do think it worth mentioning that the cuffs are a BAD IDEA. (Probably a felony level bad idea.) The whole idea of "holding" the bad guy for LEO to pick up frequently crosses into the unlawful confinement/kidnapping zone for over zealous DA's... Just my opinion tho...

the box on the other hand looks VERY nice... I cut my foam with a dremel or a hot knife, depending on what's getting cut...

 

[MrB+]

My bow was actually about 4' wide -- I was cutting foam cores for R/C airplane wings. Guess I had enough spring built into the piano wire to take up the expansion, it worked *fine* for me.

And just to be pedantic, since it's a safety thing, for folks that might want to try it, an 'autoformer,' the key component of a Variac doesn't provide isolation from the line. Most also include an isolation transformer to accomplish that. The 25 V 'power' transformer will provide isolation IF it doesn't have a strap between the primary and secondary. If it does, while the ends of the wire might only be 25 V apart, one end or the other can be swinging the full line voltage, if your power cord is mis-wired.

MrB+
Working up to being an A--

** Here's another minor survival skill -- when/if you ever need to check whether a piece of gear is powered up and you don't have a meter, etc, and have have to check with a finger --

First: Dry your fingers to minimize the connection quality, then

Second: Check by brushing lightly the points in question with fingers ON THE SAME HAND.

NEVER NEVER use both hands, a finger of each hand, to check, since this path has the current flowing across your chest. Likewise, with OPs hotwire arrangement, while the ends of the wire might only be 25 V apart, if you're miswired and get the line voltage between a hand and out your feet to the garage floor, it's again flowing across your chest. It takes about 10 mA across your heart to stop it, if I'm remembering correctly.

 

[Mark W.]

Where is Line Voltage 170V !!!!! In my house according to my Stereo system power conditioner BPA provides Silverton Oregon with a Steady 121-122V if you have 170V at your house (unless your plugged in to your range or dryer) you have a weird and serious problem.

 

[MrB+]

110-120 V RMS ~= 170 V Peak.

MrB+

 

[Nimh]

Another +1. I like it, and may borrow the idea. Thanks for posting up.