Sunday, September 20, 2015

Welding the new oven base

Putting a new base under the oven presented several challenges.
1) The underside of the hearth slab was cast to the top of a brick wall and had no requirement for being flat.
2) The slab on which the oven sits is designed t drain water and so is not parallel with the oven slab.
3) There is an I-beam which acts as center support and was cast in place. This also needed to be tight up against the hearth slab.

Our solution was a steel stand with jack screws spaced around the top (See below) This stand would then be encased in treated plywood, covered with lime stucco, and decorated with fresco designs.

Step 1 The stand:

Welded up a stand using 2x2
structural tubing. There are plates tapped for 3/8 bolts spaced the upper beam. This is constructed of 4 panels which bolt to together at the corners.

Here is the stand painted and in place.  We used fiber board (usually used for concrete expansion joints) under the stand to even out irregularities in the slab surface.

Jack screws under the I-beam and along one edge shown below.
If you do the math the 20 jack screws in this design only need to exert 150 lb load to support the 3000 lb oven. Hence the rather skinny looking 3/8 bolts.We went around several time tightening all the crews evenly until the oven was 1/8" off the jacks and called it good.

A piece of 3/8x 1 1/2 inch steel with a 1/2 inch drill point depression to capture the end of the bolt and a piece of the fiber board used earlier seemed to make a pretty good support pad.

Next wee needed to modify the chimney. The original design used a 3x12 inch chimney which worked really well but was a pain to seal where it penetrated the roof. So, We decided to used a more conventional insulated round chimney pipe for the upper portion.

Here is the existing chimney which is formed by 2 1x4 ft x 1/8 ich plates joined by 2 pieces of 3 in channel.
The plan is to cut off 1 foot to salvage material to make the modifications and then make the actual changes to the next foot.

First we grind off the welds

Then use wedges to hold the plates back to give room to cur off the channel

And there ya go.

After cutting off the top 1 foot of plate we trim the sides to create a taper to fit the new chimney size

Next we bend one side out to accommodate the new pipe size.

Then cut one to the 12x12 plates from the top section in half diagonally.

Grind, grind, fit, fit, clamp, clamp
All ready for tack and weld

The second plate salvaged from the first operation is cut to fit the top and includes a circular hole for the new chimney.

Add the new chimney adapter

Install through roof

and Viola!

Monday, August 17, 2015

Oven 2.0
In the event you have a large tree fall on your wood burning oven you may find this blog helpful
The basic situation is that a tree fell on our carport (see earlier posts about that) 
Being steel lined, the oven itself is virtually indestructible. The brick base on which it sits, not so much. So how to build a new base under an existing 3000 lb oven? What follows is our solution. 

Here you see the basic structure. We are rebuilding the carport at the same time.  Hence no roof just yet.

Damage to the base is wide spread

Found these jacks on Amazon for $10 each. Rated at 6000 lbs , so 3000lb oven/ 6 jacks no problem.

Blocked up the jacks and demolished the wall

In the best Harry Potter tradition

Wingardium Leviosa
Remember to "swish and flick"
And you have an oven floating in space

This really only took about 3 hours to do

Next post "Welding The New Base"