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-   -   Indespensible tool (http://www.fornobravo.com/forum/f8/indespensible-tool-14584.html)

knary 10-14-2010 08:00 AM

Indespensible tool
 
Greetings:

I am new to the forum and have found a wealth of information here in preparation for my build. I plan to build a 42" Pompeii. In scanning the forum, I have found several posts regarding the "indespensible tool" and its variations. Several people have stated that they would either pass their tool along to the "community" or build one for those interested. I do not know how to weld and would love to get one of these tools prior to building the dome. Can anyone help me out? Thanks

fxpose 10-14-2010 09:42 AM

Re: Indespensible tool
 
Several variations of this tool require no welding at all to build. In fact, I believe the majority of the I-tool users here didn't have to weld any part of their tool, including the one I used.

DaveW 10-14-2010 10:24 AM

Re: Indespensible tool
 
A friend welded one up for me but if you are building a half-sphere dome all you need is a stick. Attach it to the center with a hinge and mark your dome diameter on the stick. Then all you have to do is make sure your bricks line up with the mark and that the stick rests flat on the top of each brick as you build the dome. I would send you mine but i pitched it.

dave

knary 10-14-2010 11:12 AM

Re: Indespensible tool
 
Obviously this whole oven building experience is new to me, so please bear with me. I did see some variations that do not require welding and will pursue building my own indispensable tool. For a 42" oven, I assume the tool should be 21". That would create a dome height of approximately 21 1/2" when factoring in the width of the plywood base. That is 3" higher than recommended. Does it matter? Is there a technique to create a lower dome height? Thanks again.

gdest 10-22-2010 07:34 AM

Re: Indespensible tool
 
Take some advise here from the slowest oven builder known to man. Your playwood base can be made from 1/8" luan. Now you will also find out that once you draw your radius (21") and set your first course, your indenspensable tool will be a little shy depending upon how high your shoulder course is. Now that is all said and done, don't worry about the small stuff.

Gary

DaveW 10-22-2010 08:04 AM

Re: Indespensible tool
 
1 Attachment(s)
Quote:

Originally Posted by knary (Post 100716)
Does it matter? Is there a technique to create a lower dome height? Thanks again.

If you use a hinge to attach the indispensable tool so that the hinge pin is an inch or two from the center pivot you will achieve a slightly lower dome.

We built a 38 inch oven. You can see the indispensable tool is hinged only about one inch from the center. Therefore the tool is 18inches long rather than 19. If I used the tool for all of the bricks I would have achieved an 18inch dome with a small flat center two inches in diameter. But the tool is just a starting point not an exact science.

Happy Building!

Dave

dmun 10-22-2010 09:43 AM

Re: Indespensible tool
 
You can also make the length adjustable, so the upper courses are closer to the pivot point.

Remember: The strongest dome is an inverted catenary shape. That is very high, too high for a practical oven. The hemisphere shape, what you get with a plain pivot arm, is nearly as strong, but lacks the resemblance to the domes they make in Naples. The flatter the dome, the more side thrust, and the more engineering challenges. Very flat domes, particularly with high soldier courses, need side buttressing or reinforcing to succeed.

fxpose 10-22-2010 10:00 AM

Re: Indespensible tool
 
1 Attachment(s)
Here's a crude, but effective off axis I-tool I used which required no welding at all.

You will find that no matter how well you design your I-tool it will require slight adjustments as you go and you'll quickly adapt to it.

terrihoward 10-22-2010 12:09 PM

Re: Indespensible tool
 
Hello.....

I just finished my oven and have a tool you can borrow. I am in Leavenworth Washington. I will try and e-mail you directly.

knary 10-23-2010 05:38 AM

Re: Indespensible tool
 
Thanks Terri, but I built a version that I think will work for my build.


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