Aaron Tusmith wrote:...The cans are not filled... I look forward to seeing how it behaves as the season progresses,
Orin Raichart wrote:Hi Aaron,
Here's somethings you might want to consider:
-how many pound per square inch will my tin floor withstand?
-how thick does my top layer of cob need to be to stop cracking with the flexing of the tin can centers?
-how much does a tin can expand compared to cob in the hottest of summers?
-how much does a tin can contract compared to cob in the coldest of winters?
Do you fill each can with cob? If you didn't, you won't be able to put much weight at all on your floor...no rocket stove and certainly no waterbed.
One way to determine how many psi a empty tin can withstands is to use a 2x6" x8' board as a lever. Attach one end of the 2x6" to a stationary upright capable of a say 5 tons ( maybe use a steel beam with a platform that won't sink). Make sure your upright is taller than a 55 gallon barrel by atleast 8 inches. Place one of your cans in the middle of the 2x6" x8' at the 4' point making sure it is gravity level. Then hang a 55 gallon barrel whose weight you have already determine from the other end of the 2x6". Begin adding water 1 gallon at a time from a 1 gallon container until your tin can crushes.....using Force*distance where force is the weight of the water (8.333 pounds/gallon), you can determine how many pounds per square inch your floor will hold.
Or you can look up the failure point of thin wall tin which you will find isn't very much. Adobe bricks have about 300lb/square inch limit; i urge you to find both the tensile and compression failure limit of thin wall tin as soon as possible, if you did not fill each can with cob.
It is my humble opinion your building's walls would be better served than your floor to have been built with tin can....but even then I would need to find the heat expansion for tin to see how much cob I would need to cover them up with and I wouldn't have the weight of my roof on the tin can walls....the weight of the roof would need to be on pillars.
At any rate, good luck with your experiment....and be careful!!!
Deb Stephens wrote:
Orin, Are you an engineer?
Deb Stephens wrote:
I love how you determine the pounds per square inch using readily available materials! (What self-respecting homestead doesn't have a few 55 gal. barrels sitting around, right? ) This is something I have wondered about for many projects and now I have a way of finding out.
I do wonder if filling the cans with gravel or plain soil would make a difference. OR, what about adding a couple of layers of chicken wire over the top and pressing the cob (or a soil/cement mix) through the wire over the filled cans. If it is merely a question of filling the cans to prevent crushing, would something lightweight like sawdust -- which would add insulation -- also do the trick? Would any of those things materially affect the floor strength?
Deb Stephens wrote:
This is an intriguing idea and might be a good way to dispose of "trash" that otherwise would end up in a landfill. In fact, I've considered making trash walls similar to this to surround parts of my garden or to frame raised beds -- only I would use ferrocement rather than cob to cover the debris (basically hollow walls made of fence panels covered in chicken wire with cans, bottles, etc. filling the hollow space, then covering it all with cement to seal it). Walls would not need to be as tough as a floor, but the same questions about differing shrinkage/expansion rates might apply.
Dale Hodgins wrote:There has never been a better opportunity for someone to install time capsules in their home.
Thomas Tipton wrote:I wonder what might be achieved by adding sand in between the voids of the cans and topping off with a few layers of newsprint before adding the cob? Seems like I learn something new on Permies every day.