#31  
Old 03-06-2013, 10:02 AM
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Default Re: Mortar Joints

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Originally Posted by K79 View Post
Can you explain the jig setup to me?
I could try, but others have done it so much better

The original guide by hendo
http://www.fornobravo.com/forum/f28/...tilt-2802.html (Twist and Tilt)

and I always give mad props to Russell for his jig design, shown here

http://www.fornobravo.com/forum/f28/...tml#post147037 (Tapering on a 10" saw?)

I used a series of two wedges made of wood (not brick as Hendo shows) because I could cut with my miter saw. But a hinged design like Russell's would be the way I would go if I had to do it over again.
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  #32  
Old 08-23-2013, 02:22 AM
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Default Re: Mortar Joints

Hi Guys regarding mortar joints:

On the bag of fire cement I have, it states that it is NOT to be used with any other building material.
It has a resistance up to 1000 deg C
It also states that the maximum joint size is 8mm.

I have tried the home brew mix with my mortar to no effect although I shall endeavour to keep experimenting, but until I sort this out I cant progress.

I did have success with the mortar on its own.

So here is my dilema

1) I know its important to keep the inside close but its the back which maybe as wide as 15-20mm. I know you guys have said 'just stuff the back with mortar' but are you referring to the home brew or refractory on its own? (as this would be over the recommended fill)

2) If I placed a very thin shin between the large gaps and then had 8mm either side of the shim would this get me out of the problem.?

3) Must the inside bricks touch OR should there be just a slight gap for mortar?

Sorry but my lack of building knowledge adds to my confusion and wish for clarification from you experts out there.

Paul
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  #33  
Old 08-23-2013, 02:57 AM
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Default Re: Mortar Joints

Quote:
Originally Posted by yorkshireknight View Post
Hi Guys regarding mortar joints:

On the bag of fire cement I have, it states that it is NOT to be used with any other building material.
It has a resistance up to 1000 deg C
It also states that the maximum joint size is 8mm.

I have tried the home brew mix with my mortar to no effect although I shall endeavour to keep experimenting, but until I sort this out I cant progress.

I did have success with the mortar on its own.

So here is my dilema

1) I know its important to keep the inside close but its the back which maybe as wide as 15-20mm. I know you guys have said 'just stuff the back with mortar' but are you referring to the home brew or refractory on its own? (as this would be over the recommended fill)

2) If I placed a very thin shin between the large gaps and then had 8mm either side of the shim would this get me out of the problem.?

3) Must the inside bricks touch OR should there be just a slight gap for mortar?

Sorry but my lack of building knowledge adds to my confusion and wish for clarification from you experts out there.

Paul
The refractory cement probably contained calcium aluminate if it can withstand 1000 C. If you are using this mixed with homebrew ( "I have tried the homebrew mix with my mortar...") it will react badly with the lime and accelerate the brew to go off way too fast. This is probably why they state not to be used with any other materials. 1000C is way over what you need, the homebrew on its own is quite sufficient. Perhaps you could save your refractory mortar for the top third of the dome which will get the hottest.
Yes, use offcut wedges to fill the larger gaps in the back. You will have plenty of offcuts from your saw.
A slight mortar gap or none on the inside, it makes little difference.
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  #34  
Old 08-23-2013, 03:03 AM
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Default Re: Mortar Joints

Aim for the smallest joints possible on the inside. Use wedges when possible and stuff the rest with mortar. That's what I did and no issues with mine to date.
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  #35  
Old 08-23-2013, 03:23 AM
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Default Re: Mortar Joints

Thanks Dave & K79,

You say the homebrew is quite sufficient on its own, but there lieth my problem at the moment, I cant find any other type of refractory cement although I do have a young lady at the building suppliers who speaks good enough English to understand what I need.
If I can not source another type should I go with this and use the wedges, which as you rightly point out I have plenty of.
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  #36  
Old 08-23-2013, 04:44 AM
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Default Re: Mortar Joints

Surely you must be able to get Portland cement and hydrated lime. The recipe is 4:1:1:1 sand, lime, clay,Portland cement.
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  #37  
Old 08-23-2013, 05:43 AM
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Default Re: Mortar Joints

I used refractory cement similar to what you refer. With a 3 sand 1 cement .5 fire clay. However I used arch bricks which left my joins around that 3 - 8 mm mark you refer.

I also copied Russell's jig a little more elaborate and infinitely adjustable, but still Russell's idea, works a treat. I went with a brick to brick fit inside the dome. Maximum rear joint on mine would be 6mm.
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  #38  
Old 08-23-2013, 09:17 AM
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Smile Re: Mortar Joints

Yes I can get Portland cement David and I've sourced lime as of today.

So are you saying I can use the home brew with this 1000 deg C fire cement I have?
I will purchase some Lime and fine sand and give the home brew another go.
I did attempt the home brew but it was with a sand/lime premixed, but it failed to work.
Thanks for the that anyway David

Colin, thanks too for your input I shall shim or endeavour to get joints closer, but first I will purchase a bag of lime to experiment with.

Paul
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  #39  
Old 08-23-2013, 09:47 AM
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Default Re: Mortar Joints

Today I made my IT from a castor wheel and a piece of wood.
I think I may have to exchange the big lump underneath for a slimmer one, it is at a 90 deg angle to the top part should this be so?

I also made the template for the arch many thanks to those who gave me some idea how to do it, geometry is all Greek to me.

I am nearly ready for sticking bricks together (when I learn how)
as always if you see anything out of order please feel fee to criticise.
Paul
PS a picture of the fire cement I bought.
Attached Thumbnails
Mortar Joints-fc-008.jpg   Mortar Joints-arch-template-001.jpg   Mortar Joints-arch-template-002.jpg   Mortar Joints-arch-template-004.jpg  
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  #40  
Old 08-23-2013, 09:52 AM
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Default Re: Mortar Joints

That IT design won't work. The arm of your IT needs to hit the center of the brick on each course.

See this post for explanation: http://www.fornobravo.com/forum/8/tr...tml#post132328 (Trouble with setback on brick courses. Need advice.)
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