Tom Stormcrowe

OK, Niles,straight talk:


They've had 12V Microwaves out for years. There are durability issues though. As to the weight? That's primarily in the shielding, and there's a reason one needs FDA approval....

A Microwave enclosure needs to be an environment isolated by a Faraday Cage, since it's using High Energy RF Emissions to heat the H2O molecules contained in the food. It's a radiation source and can stop a pacemaker cold. If you use it with insufficient shielding, there is also secondary cascade radiation to contend with. That's the reason, other than the power requirements, that it's essentially, at the current level of emitter tech, power supply tech, and shielding materials available, it's fundamentally unworkable.

Niles H.

ATTACK THIS:


https://www.thewavebox.com/news/video.cfm

Good clips: the G4TV clip, and the EXTRA clip. ("One of the worst things about enjoying the outdoors is....")

*****
(No wonder some people hate the United States.)

*****
This is just the ticket for someone making the transition from nature lover to mainstream.

*****
Just saw another product -- the Rocket Grill -- that started some wheels turning.

*****
The ultimate in portability might actually be along the lines of having a radiologist friend share some material.

There are reasons why the prime choice in portable battery packs on small spacecraft is along these lines. It makes sense.

*****
I still think that ultra-portable microwaves are a possibility.

That WaveBox thing is like the first portable/transportable computers (like the Osbornes).

It could probaly be shaved down to something more like a PDA.

Tom Stormcrowe

I'm not saying it wouldn't be really nice, mind you, just that at current capability it's not practical. Give them some time though and I'm pretty certain that there isn't a single issue that we couldn't get past to make it workable, if the profit is there.

Niles H.

Just saw this post. (I was busy with the videos.)

Yeah, I knew about the shielding.

But the ABS is not that kind of shielding, and it could be dispensed with.

That would lose a lot of weight and bulk.

And also, the Faraday Cage, for this application, does not need to be so heavy.

It could even be flexible, like the BakePacker hood.

Also, if you are DIYing the whole thing, and you do not have a pacemaker [or even if you do, come to think of it], and you are in circumstances (or on trips) that allow for distance protection, you might be able to get away with dispensing with it.

*****
Also, a Faraday Cage could be built into the bowl-shell-microwave container.

*****
Plus, there seem to be some options for the microwave generating units.

*****
Something tells me that the whole thing could be sized down far more than I have yet seen.

matthew_deaner

Well, why don't you build one and prove us all wrong?

Niles H.

I'm working on it, but tend to take my time.

And sometimes to get distracted by other things.

(Especially when life seems to enjoy throwing delicious curve balls.)

atman

That would help keep the unwanted suitors off for sure.

spinner

Wavebox puts out 660 watts@12 volts connected directly to a car battery. Thats a minimum of 55 amps for as long as the unit is running. A fairly substantial battery would be required. Not small, not light, not easy to recharge on the road. At the 235 watts output from a car power jack, there is not enough power to pop popcorn.

I have no doubts that the size/weight issues could be overcome, but the power consumtion issues would remain a major problem. For a group of people who can obsess over whether an extra pair of bike shorts might be too much weight, a microwave of any size seems a bit , dare I say, frivolous

brotherdan

What about infrared cookers? They aren't great for cooking dishes that require the boiling of water, which is where microwaves excel, but they do cook things like meat quite fast. Commercially available infrared cookers are rather bulky, but you could easily remove the light and use some kind of light, flexible container to cook inside. I'm guessing the power consumption would be minimal compared to a microwave, so you could get away with a much smaller battery.

gregw

I think an easier and lighter system would be to get a time machine and travel back to earlier in the day when you weren't hungry and then you don't need to cook anything. The only thing you need for your bike touring time machine is a Flux Capacitor, they are available here:

https://kalecoauto.com/index.php?main...products_id=28

staehpj1

If you were capable of solving the battery issues there are about a million other applications where the battery technology would be better used.

Niles H.

Good points.

However, some microwaves only require 500 watts.

These have relatively large cooking chambers.

A (much) smaller chamber, with more focused waves, would probably require less power.

Even if it were a three- or four-hundred watt microwave, I don't think it would be so bad. I haven't done the calculations yet, but I would guess that a rechargeable battery (made for power tools, or for bike lights -- or those high-capacity, fast-discharge, fast-recharge battery packs that kids who race RC cars use and cycle frequently) has enough amp hours to do the job, especially in light of the fact that microwaves are so quick. They can cook things in a couple of minutes that take many times longer on stoves (that are burning fuel all the while).

*****
The same people who obsess over the bike shorts often carry stoves, pots, fuel and fuel canisters.

They end up going out of their way to refuel.

Over time they can spend quite a bit of money and time on these things (if they ever bothered to total it all up), and quite a bit of time cooking and cleaning....

*****
There are a few other things about microwaves that are to like: No fumes and smoke to breathe is one of them. Winter morning tent cooking is another.

No carbon monoxide. No fossil fuels. No flames. Less risk of fires and mishaps.

*****
They may be able to get down around one or two pounds (possibly less), and be at least as compact as most conventional cooking systems.

I would love to take one apart and actually see that (little) unit that generates the microwaves. It may happen soon....

The ionizing-radiation thing may be an urban legend. Initial research indicates that it is. Will check into it some more.

The media have caused some semi-hysteria over microwaves and these sorts of things.

Microwaves were used for years by chiropractors to relax people's muscles.

The devices were called 'diathermy machines.'

When you lie down, they put something that looks like a heating pad under your back. That heating pad is not an ordinary heating pad, though (they don't always tell you this). It is a microwave heating pad designed to help relax the muscles.

Great fun.

Niles H.

https://www.youtube.com/watch?v=_lNfBZTz2xQ&NR=1

Speedo

I love to calculate things.

Let's take 8 oz of water, that's 227 grams. Heat it from room temperature to the boiling point that's a diffrence of 77.8 deg C. So it will take 17700 calories, which is the same as 73900 joules, which is the same as 20.5 Ah. I found a dive light site where you can get a 9 Ah battery that weighs 3.25 kg. So scaling that up you would need 7.4 kg or 16.3 lbs of battery to heat up 8 ounces of water.

That would be for a 100 percent efficient system.

Double check my numbers, but I think I'll leave the microwave at home.

Speedo

Niles H.

You may be correct. But there may be an error somewhere along the way. I don't know. It does sound excessive and counter-intuitive; but I'm certainly open to the facts.


How did you arrive at 17700 calories, 73900 joules, and how did you equate that with 20.5Ah ?

Also, I have seen lighter batteries with more capacity than that. Aren't there AA batteries with well over 2500mAh capacities? They don't weigh anywhere near that much.

Niles H.

https://www.nimhbattery.com/sanyo-270...-batteries.htm

30 grams per cell....

Tom Stormcrowe

Niles,

When I point out shortcomings in an idea, so you know, it's not because I want to discourage you, or that I'm making fun of you......you'll know when I'm teasing you, as you know. It's because I see the idea as interesting enough to critique and hopefully get you thinking about how to overcome the issue in the critique

Frankly, the idea is interesting and I'd LOVE to see you make it workable, because if you do, a unit light enough and power skimpy enough for bike touring will make you filthy rich......

Alternative applications: Space Program, think about it, lifting to orbit is bloody expensive. That makes a true lightweight microwave of extreme interest to NASA or the ESA, for one example.

Niles H.

Thanks, Tom -- it's easy to see things in various ways (and people often do); and it rarely hurts to check in and clarify, even if there are sometimes no misunderstandings going on. So thanks for doing so.

I don't know where this might go; even if it is just playing around (safely) with some magnetron tubes and variable power supplies, it will be interesting.

*****
How's this for entertainment on a long winter's night:


https://www.youtube.com/watch?v=vCNNqgKqnaQ

Speedo

I did screw up along the way. I forgot about the battery voltage.

Trying again

Warming 227 grams of water to 77.8 degrees C is 17700 calories. (just multiply them)
Coverting calories to joules multiply by 4.19 joules/calorie to get 73900 joules.

Battery is NiMH. 14.4 volts 9 Ah and weighs 3.35 kg. I'll scale to get the battery we need.

9 Ah is 9*3600 coulombs = 32400 coulombs. Where I screwed up is I didn't use the battery voltage to get the amount of energy per coulomb. 14.4 V= 14.4 J/C, so the battery can deliver 14.4*32400=467 kJ.

Scaling the battery weight for what we need 3.35 kg * 73.9 kJ/467 kJ = 0.53 kg or 1.17 lbs of battery. Accounting for the 14.4 Volts scaled my original result down by 14.4. Sorry.

I think I'll take the cat can stove still.

Speedo

late

The Army spent a million bucks developing the Bakepacker. It weighs a couple ounces. It works. It doesn't need a zillion watts and it isn't dangerous. You put the thing in the bottom of the pot and it channels steam up around the item being cooked.

I used one for years. Made pizza, cranberry bread, you name it.

Niles H.

Good points.

However, some microwaves only require 500 watts.

These have relatively large cooking chambers.

A (much) smaller chamber, with more focused waves, would probably require less power.

Even if it were three or four hundred watts, I don't think it would be so bad. I haven't done the calculations yet, but I would guess that a rechargeable battery (made for power tools, or for bike lights -- or those high-capacity, fast-discharge, fast-recharge battery packs that kids who race RC cars use and cycle frequently) has enough amp hours to do the job, especially in light of the fact that microwaves are so quick. They can cook things in a couple of minutes that take many times longer on stoves (that are burning fuel all the while).

*****
The same people who obsess over the bike shorts often carry stoves, pots, fuel and fuel canisters.

They end up going out of their way to refuel.

Over time they can spend quite a bit of money and time on these things (if they ever bothered to total it all up), and quite a bit of time cooking and cleaning....

*****
There are a few other things about microwaves that are to like: No fumes and smoke to breathe is one of them. Winter morning tent cooking is another.

No carbon monoxide. No fossil fuels. No flames. Less risk of fires and mishaps.

*****
I would love to take one apart and actually see that (little) unit that generates the microwaves. It may happen soon....

The ionizing-radiation thing may be an urban legend. Initial research indicates that it is. Will check into it some more.

The media have caused some semi-hysteria over microwaves and these sorts of things.

Microwaves were used for years by chiropractors to relax people's muscles.

The devices were called 'diathermy machines.'

When you lie down, they put something that looks like a heating pad under your back. That heating pad is not an ordinary heating pad, though (they don't always tell you this). It is a microwave heating pad that is designed to help relax the muscles.

Great fun.

mooncricket

I'm happy using the microwaves at 7-Eleven

In Asia, they even dispense free hot water for your coffee, instant noodles, etc.

But, well, if we're just dreaming, I'd like to have a tiny generator that attaches to my wheel so that after I climbed a big hill, I could coast down, converting that descent energy into electricity that would boil enough water for a cup of coffee. A cup of boiling water to brew a cup of coffee. That's all I ask. On tour, it's all I need to make me happy.

brotherdan

I have a basta sidewall generator that I won't be using anymore. You could easily create a water heating element by just placing a resistor of some type inside the airspace inside an insulated mug and running a lead wire to the generator. Do you want the generator?

Speedo

Their "quickness" is related to their power. My 1300 W microwave can heat up my cup of coffee in 50 seconds. 240 W available from 12 V through a 20 A fuse would take over four and a half minutes.

The energy density of that bottle of fuel is pretty high. A much better way of carrying energy around than a big battery.

Well, no carbon monoxide and fossil fuels at the microwave itself. But something provides the energy to run it. I suppose you can imagine that your particular battery was charged by energy from a wind farm!

Have fun!

Speedo

Speedo

The energy density story tells it all.

The energy density of Naptha (white gas) per unit volume is 31.4 MJ/L. The density of Naptha is 0.665 kg/L. So the energy density of Naptha per unit mass is 47.2 MJ/kg.

The Battery University has a nice comparison of battery technologies. Ignoring everything else except energy density, we see that the highest energy density they have listed is 190 Wh/kg for Litium-Ion (cobalt). A Wh is 3600 J, so the top battery energy density is 0.684 MJ/kg.

47.2 MJ/kg vs 0.684 MJ/kg pays for a lot of inefficiency in the white gas stove.

Speedo