Pompei Oven Spreadsheet

[MikeD55]

So I downloaded it and printed it out. I’m trying to understand some of the measurements under jig setup. It says side tilt (Chipsters Jig); back tilt (Hendo’s jig) and side angle. How does this translate to taper, wedge and skew. Seems like these would be more universal terms.

thanks

[UtahBeehiver]

Attached in one version brickies diagram of various terms. So angle can be also called taper and/or wedge and bevel a skew or compound cut. So tilts are used on jigs to make compound angle bevel cuts. Bevel cut do NOT need to be the entire length (front to back) only where the two ID bricks start to overlap. Look at JR Pizza's build and he shows where only the first internal part of the brick need to be compound beveled.

[MikeD55]

[MikeD55]

Russel

Thank you. I’m trying to figure out how taper, wedge and skew correspond to side tilt (chipster), back tilt (hendo) and side angle on the spreadsheet

thanks

[rsandler]

Those figures are the settings to use in a brick cutting jig, rather than the final angles on the brick. MrChipster's jig is a contraption that tilts the brick sideways to achieve the desired bevel. Hendo's jig tilts the brick forward. I believe the spreadsheet has links to the forum posts on each jig. You only use one set of numbers or the other, depending on what kind of jig you're using. With either jig you need to rotate the brick horizontally to achieve the desired angle (as in Utah's diagram). The amount of the side angle is a function of the width of brick blank, and largely does not change with subsequent courses until you switch from 1/2 to 1/3 bricks.

[MikeD55]

Ahh ok. So it’s for those specific jigs then…

[JRPizza]

I am an engineer by trade and love math, spreadsheets and geometry, but like Russel likes to say, "mortar is your friend". I just adjusted my angles on the fly as I started each course and it worked out pretty good. I tried using the spread sheet but my inability to dial in a particular angle and how well those angles would apply to my build particulars had me making adjustments after the first few rows. When I build my next oven I'll use the same technique. More power to you if the spread sheet is helping you and kudo's to the folks that put time into it, but you can build an oven with nice tight internal surfaces without trying to dial in a set of per-determined angles. Once you have the internal faces tight you can just fill in the gaps with mortar and nobody (but you) will know the difference.

[MikeD55]

I understand what you’re saying but it seems to me the spreadsheet is made to work with two particular jigs where it should be the other way around. Have the spreadsheet list angles and measurements then one can adjust their jig (whatever it may be) to cut the angles the spreadsheet states. One can even fashion templates based off it. As it looks unless you have those two jigs the spreadsheet doesn’t work. Am I wrong?

[JRPizza]

Maybe that is why it didn't work for me - I was using my own jury rigged cutting jig
If you aren't going for minimum gaps side to side and front to back, and don't mind mixing up a ton of home brew, you can save quite a bit of time doing what I did. If you want a tight fitting interior surface, the only angles you need to worry about are those needed to eliminate the inverted Vee. Those angles are constant for each row and you can eyeball them or use a Tee-bevel to find the angle like I did. Once you get the correct side taper, the only dimensions you need to worry about is making the inner, lower face if a brick in a row same dimension as the top of the face of the brick below it (these will get progressively smaller if you are tapering). This will let you stagger all your joints which will align with the center of the brick below. When the bricks start to get narrow near the top, you can double the width and keep the joints aligned.

[UtahBeehiver]

The only thing consistent with these oven in inconsistency. You will find as you build, due to many variables, you cannot make a template that works for every case as you cut bricks, adjustments will be required. As you go up in courses, you will see the Inverted V joint unless you adjust the bevel of the internal brick joint.

[MikeD55]

So I was playing around with the program and I can’t make it seem
to work with a low dome, say 15” with a 6.5” soldier course. Any suggestions?

[david s]

Deviating from a hemisphere introduces structural weakness that requires either buttressing or bracing. The problem is exacerbated by thermal expansion and contraction cycling. The further you deviate from the ideal form, which would be a catenary dome (the point of an egg), the greater the problem. A catenary dome is unsuitable as it results in a high roof, the opposite of what you are trying to achieve. The next best form is a hemisphere and its structural strength as well as ease of construction has proved its popularity over the centuries as the preferred form. To investigate the problem further research buttressing and steel bracing of domes. Building with brick units also creates a far more vulnerable problem than cast sections.

[MikeD55]

I understand but I’d like to do a low dome (Neapolitan). Can I manipulate the spreadsheet to work in that application?

[david s]

As the radius of the arc for the low dome is much larger, you need to lower the centre of the IT pivot point below floor level for the upper dome section. This may prove difficult and a movable template might be a better method.

[MikeD55]

I understand. I was referring to the spreadsheet. Not sure if it could be made to work for a low dome.