What inventions can solve everyday problems?

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The discussion revolves around the concept of inventing a heated butter knife to solve the problem of spreading cold, refrigerated butter without tearing bread. Participants express enthusiasm for the idea, highlighting the challenges of heating the knife without affecting the handle and ensuring the design is practical and marketable. Various heating methods are debated, including using battery-operated resistance wire, and the feasibility of creating a detachable blade for easy cleaning is discussed. Concerns about food safety when reheating butter and the potential for food poisoning are raised. Suggestions for materials and design considerations include using nichrome wire for heating and exploring existing technologies like heated knives for other applications. The conversation also touches on the importance of creativity in invention, with some participants sharing their experiences and knowledge of electrical components and design principles. Overall, the thread emphasizes the inventive process and the collaborative brainstorming of practical solutions.
  • #31
The first thing to do is assess feasibility :

Can you deliver enough power to heat a knife edge by at least 10C (18F) in not too long a time ? What kind of resistance wire would you use (Ni-Cr, nichrome wire/ribbon ?) and what aspect ratio is required to get the right resistance ? Is it possible to get the required resistance out of a wire that can be embedded in a (~ 2 or 3 mm thick) blade ?


Here are a few design aspects to keep in mind :

You need a thermally conductive, yet electrically insulating thermal short between the resistor and the knife edge. Mica or silicone rubber might work for this.

The knife edge itself needs to be a moderate thermal conductor (to transfer heat from its inside surface to the outside) with a low heat capacity. The right material needs to be picked that match these criteria...this part is not too hard.

The rest of the knife, especially the neighbouring material to the knife edge, must be a good thermal insulator...and be reasonably (not especially, but fairly) strong if you're using it in the blade. A high density plastic could work. Or you might just be able to get away with an all stainless steel blade - but you have to do the calculations to make sure.

The blade design, I think may be the hardest part. The resistance wire (part of the circuit) needs to be inside the blade, near the knife-edge. To do this, I would think the blade itself will need to be made in 2 or more pieces that get welded or brazed (or joined some way) together. If the knife edge is a different material than the rest of the blade, that's an additional step of work. This however, is only a detail, and can be solved.

For the handle, I think a high density plastic will work fine. These are pretty strong, yet very easy to machine.

I think I've made several assumptions (about your level, capability, access to machining tools, etc) before starting this post. Maybe I should have checked first...
 
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  • #32

I am in 10th grade but I am taking AP Physics, AP Calc and other AP classes. I don't have any experience with electricity and heat.
Will I be able to get any of these materials at a Home Depot or other local store or will I have to order them online?
 
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  • #33
Shay10825 said:
I am in 10th grade but I am taking AP Physics, AP Calc and other AP classes. I don't have any experience with electricity and heat.
Will I be able to get any of these materials at a Home Depot or other local store or will I have to order them online?

Okay, how about for the handle, rather than machining plastic, maybe you could modify a small flashlight...just use the handle of it, since that's already made to fit batteries (once we work out what size batteries you'll need to get enough heat for the blade, you can choose an appropriately sized battery). I'm not sure what type of plastic those use though, so need to check they won't just melt.

I like your idea of being able to disconnect the blade from the battery compartment to wash the blade. I would also suggest including an o-ring on the threaded part between the handle and blade to make it a bit more waterproof during use (the o-rings you'll find in the plumbing section of any hardware store).

Toaster wire...you probably can get it at a hardware store...Radio Shack is the other fun place to shop for electrical/electronic components, but might also be able to find old toasters at garage sales or in the trash. Ask around, you may have some relatives with some old toaster in the basement that someone always meant to fix and never did.

Of course you don't really want it to get as hot as a toaster, or you'll just melt your butter rather than cut it, and likely burn your hands or start a fire. You'd want an on/off switch too.

I can't help much with how to make that work...I know of the electromagnet around a nail trick, but that's not useful for your purpose (I used one of those for a 6th grade science fair project...made a simple alarm for a door...I don't recall anyone making anything that heated).
 
  • #34
Ivan Seeking said:
Really this is dangerous if you don't use all of the butter immediately. Diary products should be kept at < = 55 degrees until ready for use. So heating the entire stick and putting back in the fridge creates opportunities for food poisoning.

An interesting fact from the National Centers for Disease Control:
~80% of all cases thought to be influenza is actually minor food poisoning.

But if you expose yourself to those pathogens from early childhood, you build up an immunity. :smile: :bugeye: Shouldn't the microwaves kill the germs? What type of radiation do they use to kill germs on irradiated food? Of course, storing it for about 30-45 min at 350 degrees F prior to use, preferably mixed with chocolate, flour, eggs, and baking powder, also works. :-p

Don't worry, I don't actually do this (the microwaving thing), I was just giving you a hard time for nearly sending my parents to visit me (thankfully Ivan swerved away from them, so they stayed in FL where they belong!). :biggrin:
 
  • #35
Gokul43201 said:
Can you deliver enough power to heat a knife edge by at least 10C (18F) in not too long a time ? What kind of resistance wire would you use (Ni-Cr, nichrome wire/ribbon ?) and what aspect ratio is required to get the right resistance ? Is it possible to get the required resistance out of a wire that can be embedded in a (~ 2 or 3 mm thick) blade ?


. . . but you have to do the calculations to make sure.

How can I find this? Is there a formula or something that I am suppose to use?
 
  • #36
oh good. I see that Gokul43201 replaced my Cadmium with Chromium.
 
  • #37
Humm... I think I'll just use soft margarine.
 
  • #38
Yuk!
 
  • #39
Did anyone look up paneity?
I've been waiting years to use that word! :biggrin:
 
  • #40
Ivan Seeking said:
Did anyone look up paneity?
I've been waiting years to use that word! :biggrin:

:smile: Now I did. I read that post too quickly the first time and just thought it was some sort of material science type terminology and skipped over it. :smile: Yes, I can imagine that's a tough one to fit into conversation very often. Glad you finally got to use it.

Tsu...I agree with you about margerine Okay for cooking some things, but no good on bread! Though, I did have butter with honey whipped into it once, and thought that was heavenly on bread, and very spreadable straight from the fridge.
 
  • #41
Ivan Seeking said:
Did anyone look up paneity?

Ah ! From 'le pain' or whatever was it's root, I guess...
 
  • #42
When I build this I will have the blade screw on the handle. Will I have the battery connected to the toaster wire that's connected to the conductor? If so then that means that the wire would have to go through the middle of the end of the blade (screw) to the handle with the battery. If this happens then I can't unscrew the blade. I don't know if this is how you would do this.
 
  • #43
Shay, I think this a pretty difficult thing to do for a 10th Grader with little time.
 
  • #44
I'll make it. :smile:
 
  • #45
Does a hot curlier or one of those cup warmers have the same wire that the toaster has (the wire I need to make the blade heat)?
 
  • #46
You can't just use any heater wire. It has to have the right resistivity and aspect ratio. You can buy nichrome wire online.

I suggest you start a thread in the Engineering section on design details for a knife warmer.
 
  • #47
OK I will. Thanks :smile:
 
  • #48
Ivan Seeking said:
Did anyone look up paneity?
I've been waiting years to use that word! :biggrin:

Where in the world did you ever hear or read that word the first time?!?

Did you decide one weekend to go through the 'P's in the dictionary?
 
  • #49
enigma said:
Where in the world did you ever hear or read that word the first time?!?

Did you decide one weekend to go through the 'P's in the dictionary?

Sounds like one of those Word A Day calendars is to blame. :smile:
 
  • #50
We used to hang out with a crowd that liked to play The Dictionary Game at get togethers.

We know how to party! :-p
 
  • #51
Really these obscure words can come in as handy as a good strigil.
 
  • #52
You're a dork, Ivan. :-p

I'm jealous...
 
  • #53
Wouldn't it be simpler and make more sense to have a knife warmer that you could place any standard knife into and would be warmed? It could be a small cradle that you rest the knife blade in.

edit - Nevermind, I see where The Bob already suggested this.
 
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  • #54
Gokul43201 said:
You can't just use any heater wire. It has to have the right resistivity and aspect ratio. You can buy nichrome wire online.

I suggest you start a thread in the Engineering section on design details for a knife warmer.

I was thinking of budget sensitivity. If money is an issue improvisation can be quite very helpful. I made my first robotic arm using the check valves from an old automotive fuel pump for flow control.
 
  • #55
Shay10825 said:
OK I will. Thanks :smile:

Let us know how it works out. :smile:
 

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