BASIC QUESTIONS ABOUT ARCH DESIGN FOR 2' x 5' PAN

[unclejohn]

Hi from Missouri.... hoping to graduate from simple concrete block structure under our 2x5 flat pan to a custom-made welded steel arch with insulation. In theory this will increase our fuel efficiency and save our knees when we throw fuel in. And hopefully control airflow better.

Question 1) How deep (front to back should the firebox be, either in inches or as a percentage of total length?

Question 2) to save $$ and cut down on weight, can I use 2 thicknesses of 1/2" durock concrete board instead of firebrick? I know it will deteriorate, but I can replace it after the season. I can easily cut durock sheets, it comes in sizes of 3'x5'.

Question 3) I don't have a cast iron grate. I will fab up a grate frame that can be dropped in and replaced if necessary. What steel sections should I use to fab a grate?

Question 4) I will install a port to connect tube from small vacuum cleaner to blow air in. Where should I place the port for the blower; in front of arch, under grate, in back of arch? side?

Question 5) We use 6" pipe for flue.... is that large enough for this unit?

Question 6) are there any websites or postings in mapletrader that you know of that could help me in my design/fab?

THanks. UncleJohn

[DocsMapleSyrup]

Question 1) How deep (front to back should the firebox be, either in inches or as a percentage of total length?

Question 2) to save $$ and cut down on weight, can I use 2 thicknesses of 1/2" durock concrete board instead of firebrick? I know it will deteriorate, but I can replace it after the season. I can easily cut durock sheets, it comes in sizes of 3'x5'.

Question 3) I don't have a cast iron grate. I will fab up a grate frame that can be dropped in and replaced if necessary. What steel sections should I use to fab a grate?

Question 4) I will install a port to connect tube from small vacuum cleaner to blow air in. Where should I place the port for the blower; in front of arch, under grate, in back of arch? side?

Question 5) We use 6" pipe for flue.... is that large enough for this unit?

Question 6) are there any websites or postings in mapletrader that you know of that could help me in my design/fab?

I would make sure that the firebox depth is deep enough so that you can alter your wood left to right then front to back. That way you alternate the way you put in your logs when you fire. I would consider making the firebox 18-20" deep to accommodate 16" length wood.

Myself, I would not consider durock as I don't believe it will hold up to the 800-1000 degree temps you will have in your arch. I used a combination of ceramic blanket and half split firebrick.

I built a grate made from 3/16" x 2" angle iron with the "V" of the angle iron up to trap ash and keep the grate from warping. Kinda like this [VVVVVVV]. I would allow 1/2" between the angle iron to hold the wood and allow the air to move up through the firebox. I also took out the firebrick on the floor to allow more air to flow up through the burning wood increasing the fire in the firebox.

The port I believe should be centered in the back of the arch blowing forward under the grate. This allows you to have the hose out of the way so it doesn't melt if embers fall out the door. You will need to make the arch air tight or you might blow ashes out the door and you may need to shut the blower off between firing.

I have a 2x8 evaporator and used 8" pipe. I think 6" will be fine to use.

When I built my arch, I posted a few photos along the way.

http://mapletrader.com/community/showthread.php?26583-2x8-Arch-Build

[Sugarmaker]

Add your blower under the grate at the rear of the firebox.
6 inch pip should be fine.
1/4 thick 2 x 2 angle iron will last for a while. Cast material is better.
firebox should be a least 2 foot deep front to back, would be a good start for your size rig.
Use splits (firebrick for better function on the sides of your fire box. durock may work just not familiar with the product?
Regards,
Chris

[fisheatingbagel]

Hi from Missouri.... hoping to graduate from simple concrete block structure under our 2x5 flat pan to a custom-made welded steel arch with insulation. In theory this will increase our fuel efficiency and save our knees when we throw fuel in. And hopefully control airflow better.

Question 1) How deep (front to back should the firebox be, either in inches or as a percentage of total length?

Question 2) to save $$ and cut down on weight, can I use 2 thicknesses of 1/2" durock concrete board instead of firebrick? I know it will deteriorate, but I can replace it after the season. I can easily cut durock sheets, it comes in sizes of 3'x5'.

Question 3) I don't have a cast iron grate. I will fab up a grate frame that can be dropped in and replaced if necessary. What steel sections should I use to fab a grate?

Question 4) I will install a port to connect tube from small vacuum cleaner to blow air in. Where should I place the port for the blower; in front of arch, under grate, in back of arch? side?

Question 5) We use 6" pipe for flue.... is that large enough for this unit?

Question 6) are there any websites or postings in mapletrader that you know of that could help me in my design/fab?

THanks. UncleJohnI've used cement board before as an arch skin, but the arch was still insulated. It held up fine for several seasons. It will deteriorate under enough heat - i.e. in contact with direct fire. I've put small pieces in a wood stove, and it eventually crumbled.

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