Need Advice on Building Rope Cutter using specific items

KMoffett

Joined Dec 19, 2007
2,918
She's permanently seated in a chair so I'd have to place random "seemingly harmless" items around her. Yes I've tried with the necklace, if it's a long enough chain it's pretty easy to bounce up into your mouth.
The battery could be on a shelf under a work bench behind her. If she could scoot the chair back to the bench she would have access to it at hand level.
 

Thread Starter

Triple9Nickel

Joined May 31, 2020
28
The battery could be on a shelf under a work bench behind her. If she could scoot the chair back to the bench she would have access to it at hand level.
That's a great idea. My 6V lantern battery arrives tomorrow so I'll be burning some ropes and will report back. With the D batteries you can smell the "warming" but it never gets quite hot enough to do real damage.
 

MrSalts

Joined Apr 2, 2020
2,767
I'd go with a non-electrical solution, it is much easier.

She could run the rope against either...
- a rusty door hinge,
- a piece of broken glass (she could break a window pane or a drinking glass or a glass from a hurricane lamp to get the broken glass piece,
- she could make an obsidian knife by chipping a piece of lava (obsidian) which was used as a scalpel in early surgeries, Usually made by striking the obsidian to cleave off a ring on the outside edge to make a sharp edge (likely good videos on YouTube)
- she could spin a blade on an old grinder and touch the rope to it until it comes to a stop and repeat until the road is cut
- she could use a piece of sheet metal like a license plate to cut the rope (again, Rusty is better)
- She could use her serrated necklace as a "rope saw" to cut the rope (ironic, since in this case, the necklace is the "rope" in the rope saw).
- she could find a piece of steel cable, wrap it around something heavy like a bucket of paint, throw it out the window (And down the cliff?) and use the unspooling cable as a rope saw to cut the rope.

much more believable, more understandable with the reader as few people know what a foam cutter is or even why the wire would get hot (unless your heroine does some McGyver-like thinking out loud (I hope not because McGyvers explanations to himself is really stupid to do while he does it, he should be taking while he is in the thinking/ideation stage).

MrS
 

Thread Starter

Triple9Nickel

Joined May 31, 2020
28
I'd go with a non-electrical solution, it is much easier.

She could run the rope against either...
- a rusty door hinge,
- a piece of broken glass (she could break a window pane or a drinking glass or a glass from a hurricane lamp to get the broken glass piece,
- she could make an obsidian knife by chipping a piece of lava (obsidian) which was used as a scalpel in early surgeries, Usually made by striking the obsidian to cleave off a ring on the outside edge to make a sharp edge (likely good videos on YouTube)
- she could spin a blade on an old grinder and touch the rope to it until it comes to a stop and repeat until the road is cut
- she could use a piece of sheet metal like a license plate to cut the rope (again, Rusty is better)
- She could use her serrated necklace as a "rope saw" to cut the rope (ironic, since in this case, the necklace is the "rope" in the rope saw).
- she could find a piece of steel cable, wrap it around something heavy like a bucket of paint, throw it out the window (And down the cliff?) and use the unspooling cable as a rope saw to cut the rope.

much more believable, more understandable with the reader as few people know what a foam cutter is or even why the wire would get hot (unless your heroine does some McGyver-like thinking out loud (I hope not because McGyvers explanations to himself is really stupid to do while he does it, he should be taking while he is in the thinking/ideation stage).

MrS
Appreciate the suggestions. Since the character is an electrical engineer, I'd like to try and find a related solution. That said, the serrated necklace is interesting, how exactly would that work, just back and forth like a saw until it snaps?
 

MrSalts

Joined Apr 2, 2020
2,767
how exactly would that work, just back and forth like a saw until it snaps?
yes, just like my wife's favorite necklace against my forearm on our first date. The blood on my forearm and the back of her neck was a bit shocking when the movie was over. It is pearls with little gold cones inset into each. I think it is plastic but don't tell her.

Please don't make her a 1-dimensional engineer. is she going to be the kind of engineer that says "my car died, I'll first assume it to be an electrical problem because I'm an electrical engineer."

Emphesize Engineer, not electrical, in electrical engineer. An engineer is a keen observer, memorizer of odd facts and a problem solver. When her car breaks down she knows it is a fuel or air issue based on how it sputtered before stopping, or a mechanical issue because of the noise or vibration it made, or...

the best part of being an engineer is the chemistry, physics. and Tour of Engineering Disciplines Classses and mandatory Elective in non'electrical Engineering engineering classes. (Power transfer systems and polymer forming processes were my two electives)

anyhow, I hope you make her more like McGyver who used all the tools in the shack.
 

Thread Starter

Triple9Nickel

Joined May 31, 2020
28
Please don't make her a 1-dimensional engineer. is she going to be the kind of engineer that says "my car died, I'll first assume it to be an electrical problem because I'm an electrical engineer."

Emphesize Engineer, not electrical, in electrical engineer. An engineer is a keen observer, memorizer of odd facts and a problem solver. When her car breaks down she knows it is a fuel or air issue based on how it sputtered before stopping, or a mechanical issue because of the noise or vibration it made, or...

the best part of being an engineer is the chemistry, physics. and Tour of Engineering Disciplines Classses and mandatory Elective in non'electrical Engineering engineering classes. (Power transfer systems and polymer forming processes were my two electives)

anyhow, I hope you make her more like McGyver who used all the tools in the shack.
That is most certainly the plan and I will keep all of this in mind.
 

WBahn

Joined Mar 31, 2012
29,978
The battery could be on a shelf under a work bench behind her. If she could scoot the chair back to the bench she would have access to it at hand level.
But she'll need to be able to use the battery in its existing location as moving a battery the s
Emphesize Engineer, not electrical, in electrical engineer. An engineer is a keen observer, memorizer of odd facts and a problem solver.
While "memorizing" odd facts is at play, it is much more the case (for good engineers) that they "understand" odd facts. This creates the impression that they have memorized far more than they actually have because they can take relatively small pieces of information that truly is memorized and combine that with their understanding of the relationships between them and their context and then reconstruct a lot of other information that was not memorized or even synthesize new information. It's actually quite akin to targeted data compression -- their understanding of the concepts forms the compression and decompression algorithm and the handful of memorized facts are the pseudorandom data values that must be retained.

the best part of being an engineer is the chemistry, physics. and Tour of Engineering Disciplines Classses and mandatory Elective in non'electrical Engineering engineering classes. (Power transfer systems and polymer forming processes were my two electives)
As an undergrad engineering physics major I took all kinds of courses completely unrelated to my major/minor. Courses such as Soils and Concrete, Map Reading, Introduction to Metallurgy, Strength of Materials, Writing Fiction. My program required 132 semester hours and I ended up with 177 and how I wished I could have taken two or three more courses each semester -- in fact, I usually enrolled for one or two courses more than I knew I would be able to handle and then after the first couple of weeks decided which of the "fun" courses I would keep and drop the others.

So it was a shock to me when, as a grad student helping out with academic advising for the Engineering Department, how frequently I would have someone that was absolutely opposed to taking a single credit hour more than was absolutely required (even though, at the time, there was a single set tuition for full-time students regardless of how many hours they took). I had one person that claimed they wanted to get into embedded systems, so I recommended the Embedded Systems course, which was a 4-credit hour course because of the embedded (no pun intended) hands-on lab component. They wouldn't even consider it because they only needed three more hours of tech electives. That pretty much told me all I needed to know about the kind of engineer that person was going to be.

anyhow, I hope you make her more like McGyver who used all the tools in the shack.
Except, unlike McGyver, have a few of those tools originate in a universe whose laws of physics are at least passingly similar to those in this one.
 

Thread Starter

Triple9Nickel

Joined May 31, 2020
28
Quick update: I tested with a 6V battery and it works beautifully. Heats up a wire earring and cuts clean through 1/4" poly rope in a matter of seconds.

Thanks for all of your suggestions and feedback. Special thanks to @MisterBill2 for suggesting I lose the conducting wire altogether and simply place the "blade" directly across the two battery leads.

One question, and this is not EE-specific, but I like the way engineers think. If I want to complicate things, and say, fill the room with a gas leak, would the hot wire cause the room to explode? Or does that happen only if there is a flame or spark? Obviously this is something I'm unable to test out.
 

Thread Starter

Triple9Nickel

Joined May 31, 2020
28
You will get an arc when you connect or remove the conductor from across the battery terminals...then boom! :(
Yikes. Okay then. I didn't see sparks today because I was testing outside in daylight. I suppose an arc is logical.

Would you happen to know if there is a "window of flammability"? Like if a bad guy turns the gas on, then my character has, say, 5 minutes to burn herself free until the gas levels are high enough to blow? I can't even think of what field of consultant I would ask about this question. Fire department?
 

hrs

Joined Jun 13, 2014
394
Yikes. Okay then. I didn't see sparks today because I was testing outside in daylight. I suppose an arc is logical.

Would you happen to know if there is a "window of flammability"? Like if a bad guy turns the gas on, then my character has, say, 5 minutes to burn herself free until the gas levels are high enough to blow? I can't even think of what field of consultant I would ask about this question. Fire department?
If your gas is mostly methane, have a look at this:
https://en.wikipedia.org/wiki/Flammability_diagram
 

Thread Starter

Triple9Nickel

Joined May 31, 2020
28
If your gas is mostly methane, have a look at this:
https://en.wikipedia.org/wiki/Flammability_diagram
Oh wow, a Flammability Limits chart, awesome. What I'm understanding here is that lower-upper flam limits are 5-15%, so theoretically (I know it's a stretch) if she cut herself out of the ropes before the gas hit the 5% mark then the battery arc wouldn't ignite the shack and blow it up. So I could increase the size of the room to buy her some time, or find a gas with a higher LFL. Super helpful, thank you again.

Maybe the bad guys start a fire on the far side of the shed so she can see her doom coming. But that gives her time to get herslf free. tension...Tension...TENSION!
Agreed on tension, though ideally I'd like to find something that ends in a boom. The fire is actually visually perfect, makes more great visuals and tension (ticking clock, as you said), but I was thinking it would be cool if bad guy turns the gas on, she has until her "lower flammability limit" to escape, then we "forget" the room is filled with gas and maybe the scene comes back here later and BLAM.

I suppose a way to have both options, is if there is some explosive chemical or other material in the barn, so our hero escapes, the barn continues to burn, and then explodes. The downside (besides pyro costs) is if the structure is continuously burning, then it's unlikely characters would "forget" it's flammable and accidentally blow themselves up, etc.

This is definitely the first time I'd pitched story ideas on a public forum, it's interesting to read what everyone enjoys about a good story.
 

atferrari

Joined Jan 6, 2004
4,764
While she plays within the limits live or explode, make sure she does not get intoxicated even with a low tenor of gas in the room. With the fumes of crude oil and subproducts, most of people risk to feel bad quite quickly.
 

Thread Starter

Triple9Nickel

Joined May 31, 2020
28
While she plays within the limits live or explode, make sure she does not get intoxicated even with a low tenor of gas in the room. With the fumes of crude oil and subproducts, most of people risk to feel bad quite quickly.
Agreed, my initial thought was that the bad guy turns on the gas to kill her, and she's got only a few minutes before:
A) she dies from toxic inhalation, and
B) she can make this thermal blade using a battery before the room hits the lower flammable limit.

I'm guessing she'd have 5 minutes tops? Maybe 10 depending on the size of the room. Anyone have any experience with inhaling gas? (joking not joking)
 

atferrari

Joined Jan 6, 2004
4,764
Agreed, my initial thought was that the bad guy turns on the gas to kill her, and she's got only a few minutes before:
A) she dies from toxic inhalation, and
B) she can make this thermal blade using a battery before the room hits the lower flammable limit.

I'm guessing she'd have 5 minutes tops? Maybe 10 depending on the size of the room. Anyone have any experience with inhaling gas? (joking not joking)
We experienced an incident in the oven in our kitchen (LPG). Since the housekeeper opened the valve until the unexpected explosion it took what I believe was two minutes. Gas was flowing freely with the valve completely open.

Depending where the kitchen? oven? heater? is (big or small room) you could have some more time, I guess. But you know, I won't be there; have other things to do. :eek:
 

ci139

Joined Jul 11, 2016
1,898
use the mains (not for your experiments of course twist some solid steel wire around the rope and BANG . . . cloud of sparks . . . unless it's heating fan , air gun , etc. or the proper diameter wire that won't explode but heat up "long" enough to stay in one piece until it melts through the nylon . . . and won't blow ?6A fuses) . . .
if it's "out of nowhere" -- the most batteries you might find would be expired , half (read mostly) empty , or near empty or decomposed
. . . but even empty batteries might induce a spark to lit up some flammable liquids as nail polish remover wetted fibers or dust

the TO220 TO126 can also heat up significantly using over 2A
the last one uses step down transformer (that is present in misc cheap ... yet powerful equippment)
 
Last edited:

WBahn

Joined Mar 31, 2012
29,978
Agreed, my initial thought was that the bad guy turns on the gas to kill her, and she's got only a few minutes before:
A) she dies from toxic inhalation, and
B) she can make this thermal blade using a battery before the room hits the lower flammable limit.

I'm guessing she'd have 5 minutes tops? Maybe 10 depending on the size of the room. Anyone have any experience with inhaling gas? (joking not joking)
Most heating gases, such as propane, natural gas, LNG, etc, in use today have little to no toxic effect themselves -- that's another one of those stereotypical things that the movies constantly get wrong. The primary concern is simple asphyxiation because oxygen is being displaced, but the at the explosive limits this is not too much of an issue because there's still plenty of air -- this is pretty much required because there has to be enough oxygen in the air to support combustion of the gas.

Also, PLEASE do not pull the over-used gimmick of the building exploding just as the heroes are escaping. Similarly, please, no bombs with blinking lights or countdown displays or that are disabled by the hero having to pick the green wire or the red wire.
 

Thread Starter

Triple9Nickel

Joined May 31, 2020
28
Also, PLEASE do not pull the over-used gimmick of the building exploding just as the heroes are escaping. Similarly, please, no bombs with blinking lights or countdown displays or that are disabled by the hero having to pick the green wire or the red wire.
Well boy, you're taking all the fun out of this. I really had my heart set on churning out a terrible cliché.

That said, OF COURSE we want the building to explode at some point, that's sort of what people pay to see. But I promise you, no crappy bombs or ridiculous escape timings.
 

gerty

Joined Aug 30, 2007
1,305
I had some former jailbirds students a couple of years ago.Their form of electrical ignition Read cigarette lighter, is a simple gum wrapper and a AAA battery. They demonstrated this by taking a gum wrapper, tearing a piece out of the middle(causing a narrow hot spot) touching the foil side of the wrapper to the top and bottom battery terminals. Tearing the piece out causes the wrapper to get very hot very fast, igniting the white paper backing. Not tearing the wrapper will cause it to only get warm before battery death, however a D cell will do warmer/longer. We did not try to melt anything with this, but the torn wrapper will definitely light a fire..
I asked if they were the ones that came up with this idea, they said "nah, prisoners just have all the time in the world to come up with this stuff."
 
Top