Alterations to RS.

[trenchn]

OK I have had a test burn as stated earlier. I have since taken a few bits off and am about to make a few alterations which I hope will be improvements. I have lengthened the fuel/draught tunel by about four inches. It is now about nine inches long. I am increasing the heat riser by about nine inches to about 25". I am then hoping that the exhaust will travel along underneath my raised hot plates and then travel downwards before entering the chimney and exiting.
My questions/ concerns are as follows.
I currently have the stove in an "L" configuration, but could easily convert to a "J". Would this be better?
On my test burn the cast iron hot plate got hot enough to cook on, but not especially hot, certainly not the sort of temperatures mentioned in some of the posts on this site. I am slightly concerned that a lot of the ehat is escaping out of the chimney as the air coming out of it is very hot.Can I do anything to stop this without adversely affecting the through draft?
Currently the passge which runs underneath my two hot plates is smaller in cross section than any other part of the stove. Will this cause any problems? I would guess that it is less than half the size of the heat riser, etc.
I have the fuel/draught entry split in half, would I get better results if the fuel part was bigger than the draught part?
Can anyone reccommend a site that will give me the basic ratios of height, cross section, etc?
Thanks for any help.
Cheers
Nick

[matthewwalker]

I prefer a "J", but either should work. Did you restrict the inlet yet? Almost for sure part of your problem is the small horizontal sectional area compared to inlet size.

In the photo, is your feed the horizontal slots under the black soot marks? Like, top for wood, bottom for air? If so, that's just huge. My six inch outdoor cooker has an inlet size restricted down to about 3"x3". Go light it off and put bricks over most of the inlet and report back, I bet it will work way better. Like total inlet cross sectional area of about half of your smallest system section, so half of whatever that horizontal run is. I know it sounds nuts, but how hard is it to try?

[trenchn]

Hi matt,
Thanks for your reply. I have attached a better photo so that you can see the feed. Would you reduce the sir and fuel inlet size, or just the air? Having just re-read your post I think you are saying reduce the overall size of the fuel/air inlet.
I have read that you should keep the cross section constant throughout the unit, but a lot of people, yourself included, don't seem to think that is so important.
Any thoughts?
Cheers
Nick

[matthewwalker]

Yes, I would restrict overall csa at the inlet there. A lot! I think that keeping the whole system csa constant is important to get the thing in the ball park, but after that, a little tweaking is usually needed. In your case I would consider system size to be the smallest area you have in there, which sounds like it's that horizontal run under the griddles.

Most installs I've seen, folks either use bricks or the like to slide over the inlet to adjust inlet size, or restrict it more permanently once they find out what works.

Like I said, you don't need to rebuild or redesign yet, just go outside, light it, and block off most of the inlet. See what happens.