The UK is suffering from some pretty horrendous weather. Lots of snow in a country that is normally pretty temperate and bear in mind that people here lose the ability to drive if there is more than an inch of snow on the ground.

This coming weekend I shall be driving half way up the country to spend a long weekend in a field with 2000 other people who are just as stupid as me. (I shall also be testing out my Frontier Stove)

So I've decided that if I am indeed going to be sleeping under canvas, I'm going to be snug and warm doing so... And without either suffocating from carbon monoxide or turning my tent into a toasty conflagration. 

The solution I've come up with (aside from ludicrous amounts of bedding on my camp bed) is to make a storage heater.

The principle is simple enough. An object with a high thermal energy storage capacity is heated up... then when the heat source is removed it stays hot and radiating heat for quite some time.

Modern storage heaters tend to use ceramics... but in this project I shall be using house bricks and sand (to fill the gaps)

This Instructable involves very very hot items (such as fire, heated steel and brick). Do not place the storage heater anywhere it could do damage to people or property. I am not responsible for anyone being a muppet.

Step 1: Materials Needed

The parts needed for this project should be simple enough for anyone to obtain.
  • A metal tin big enough to hold some bricks - In this case I've used an army surplus ammo tin.
  • Some house bricks. (I advise you to find spare ones rather than removing any from your house)
  • Some sand. Any sand.
Tools needed
  • A Persuadertron 5000 TM - If you can't find one of these, then a large hammer will just have to do.
  • A chisel... screwdriver... or other blunt instrument you don't mind splitting a brick with (your head does not count)
  • Either the same screwdriver or another that you can lever the rubber seal out with.

Step 2: Removing the Rubber Seal

Bearing in mind that you're going to expose this poor ammo tin to vast amounts of thermal energy (you're gonna dump it on the fire).... It's probably a good idea to remove anything flammable or melty (technical term there) from the box.

In the case of this particular ammo box it has a rubber seal around the inside of the lid.
So we need to remove this for two reasons.
Firstly, you don't want melting, stinky plastic dripping down the outside (or inside) of the box.
Secondly, if the box is sealed.... and you heat it.... very bad things could happen (seriously, don't try this) Essentially, the box must NOT be airtight.

I used a screwdriver to lever up the edge of the rubber seal and just yanked it out.

Step 3: Filling the Box With Bricks

My apologies, but for some reason I don't have any photos of me putting the bricks in the box... it was just too cold in the garden.

I found that an ammo tin of this size would handle about 3.75 bricks.

The first three fitted in nicely at one end of the box. Leaving just enough room to to get the last 0.75 of a brick squeezed in the end. This last brick needed a bit of coersion to fit. I had to use a Persuadertron 5000TM (a lump hammer) and of course I first needed to split the brick so that it was only three quarters it's normal length (more use of the Persuadertron and this time a chisel too)

Make sure that none of the bricks come above the level of the top of the box... otherwise the lid won't close.

Step 4: Filling the Gaps With Sand

I didn't like the fact that I had all this left over space down the side of the bricks. I figured this was just wasted volume that could be soaking up valuable heat. So I decided to scoop some sand in there.

I'm not going to describe how to transfer sand from a bag to a box... if you can't work that one out you really shouldn't be attempting Instructables (or using a knife and fork unsupervised)

Step 5: Epilogue

I now have a very heavy metal box.

This weekend I shall plonk this thing down on a camp fire and after a few hours move it to my tent.

One thing that's pretty important. This thing is going to be VERY hot. I'll be using hand protection (probably something technical like a tea towel) and DO NOT put it on anything that can burn.
My intention is to put it on a paving slab or something else non flammable. Definitely do not put it on the groundsheet of your tent (it'll melt straight through it) and don't put it anywhere that someone could accidentally touch it.

Providing I don't die of hypothermia, I'll update the Instructable on how this went.

If you like this, please vote for me :D

Stay warm, people!

UPDATE 03/04/2013 : I did indeed try this out last weekend (30th March) and it did seem to work well.
The only problem I had was that it was so bitterly cold (allegedly -10C one night although I don't fully believe this), that other people objected to the box being dumped on the camp fire (it blocked out so much heat).
The hot box was useful but certainly no replacement for a good hot water bottle under a lot of bedding.
<p>Thanks for the tip! Ready to attempt winter camping!</p>
<p>This makes me glad that it doesn't quite get that cold where we are for us to need one of these, but it looks like something simple and cheap enough to make for people who need a bit of extra warmth. Could make sense for us to make a few for our customers to take out to their storage units in winter since the units without climate control can get quite a bit nippy!</p>
The best bricks to use are the ones out of an old storage heater. They have a very high heat capacity and are heated to 600+ degrees centigrade when in an insulated storage heater. You can get an old storage heater for as low as a &pound;1 on ebay (because people dont want to strip and take them to the tip (they way a ton) and can have as many as 24 bricks. These bricks are also could for making solar barbeques and solar ovens.
Won't the paint burn on the box?
In the first depression here in the states, people used rocks or bricks heated at the side of the fireplace to bring to bed with them. Or, a baked potato or two! The idea is even more ancient; glad to see it now has a neat rectangle and handle on it these days!
This is a cool idea. I can't wait to see how it turned out. I have been in similar situations wishing I had something to warm the tent a bit.
Thats a really good idea. Ill give it a shot on my next camping trip.
I like your idea of heating your tent without using anything like fire inside the tent. I imagine this might be a bit TOO hot during the first hour or so.. then it might get cool too quick and your tent will again need the box re-heated. I wonder if the hot metal box could be placed inside an insulated box so the heat could be let out slowly. This would make the heat last longer, and not be a danger to touch during the 1st few minutes of heat. The only thing I can think of that will insulate the box is FIBERGLASS batting... or maybe placing it inside ANOTHER metal box. Might make the heat stay a few hours longer and more evenly heat during those hours, rather than SUPERHOT the 1st hour... then quickly cold again inside the tent.
Agreed. However, instead of constructing a second Fiberglass insulated box, perhaps you could wrap a section or two of Fiberglas batting around the hot box. This insulating &quot;blanket&quot; could then be unwrapped to expose more of the hot box.as needed, thus allowing for more complete control of the heat inside the tent AND eliminate the need to construct a second metal box. The &quot;blanket&quot; can be stuffed inside a plastic trash bag for storage - all in all, a lightweight and inexpensive way to moderate/control the heat...

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