Misterious brick moving in a batchbox

[dvawolk]

Hi, good people!

I am just before the start of a new thread about building a BRMH 180mm... But i would really like to share this thing with you. As a interesting anomaly and i think this is something that all should know when building stoves...

In 2013 i built my first BRHM, 6" system. And it is working fine (but it is not perfect!).
My first BRMH

In 2014/15 i began to notice that the upper left brick at the port began to move to the left (on the photo below it is obvious what i am talking about :-).
It was just 1-2 mm, but at the end of burning season it surely was 5mm to the left... And in 2015/16 it went even more to the left, about 8mm... Then it stopped, i would say that because of the obstacles inside the bell and maybe some other things... Proportions aren't exact now, because P-channel is slightly larger than before, i think i will put there a small slice of shamott brick to come back to the right dimension...



I build it using only clay mortar and clean shamott bricks...

CONCLUSION

I am sure that the brick is moving (was moving :-) because of different temperatures in the near places and consequentially because of the expansions/cnotractions in the material... (any more thoughts??)

PREVENTIVE SOLUTIONS

This can be an awkward problem... So what to do to prevent this from the beginning?
A week or so back i saw a brick firebox being made at local stovebuilder school (unfortunately i was in a hurry). They bore holes in the brick and connect them with a 3mm diameter iron (it was a welding wire). I would say that it is wise to make some kind of "wedge" or a connection to prevent any kind of moving...

I am also thinking that the hole in the brick has to be a millimeter or so wider than a metal connection so that there is a place for expansion...


What do you think? Have you seen that happen before? What is the preventive solution for this - if i still stay with a clay mortar... Any info regarding this unconvenience would be highly appreciated...


Have a nice weekend,
Klemen

[Vortex]

Hi Klemen, I've had this happen on one side of the firebox in my original vortex stove (which has fireclay mortar). It seems to be caused by differential expansion, where one side of the brick is getting a lot hotter than the other, and so as one side expands more than the other it gradually squeezes itself out of position.

I've had to consider it a lot while designing my new stove, as it has no mortar between the bricks. I've designed it so each brick holds those around it in place, but I had thought that if it turns out to be a problem, I would drill a hole or grind a groove in the top and bottom of each brick and put a small piece of metal in to stop them moving - good to know I was on the right track

[dvawolk]

Thanks vortex :-)

Oh, and photos are visible again...

There is an interesting reply regarding this by Peter, in this thread:

May 14, 2017 12:37:16 GMT -8 peterberg said:

This is a tricky question. All the bricks are expanding while getting hot, nothing new. Shrinking would be fairly even at both ends of each when the pressure of other bricks on top is very well distributed. When one end of a brick is recieving more pressure from above than the other end it will eventually wander to the side where it is fixed best. Some people build steel frames around the firebox in order to keep things in place.