Self-Feeding Log Grate
When you use large diameter, unsplit logs, the fire only occurs between the logs. When you have two 8" diameter logs next to each other, the parts of each log that burns up are those parts nearest the other log. After a while, the logs become "D-shaped" and therefore unbalanced and gravity makes them try to roll apart. If thick logs roll apart, each soon goes out because a single log cannot maintain the necessary temperature for burning by itself.
Thus the need for "Self-Feeding" grates, where the sides slope toward the middle. When the logs burn as described above, they roll together rather than apart, keeping the fire going.
Many years ago, we used to include a self-feeding grate with every JUCA. Then when we had to consider a price increase, we contacted hundreds of owners and were surprised to find that many did NOT use the grate in their JUCA! Seems that they felt that they could make the fire burn LONGER by building their fires directly on the castable firebrick floor of the JUCA. Others insisted that it was NECESSARY to burn the fire up on a grate to allow better draft air flow under the fire, for better combustion.
We then did extensive research to check this out. Except for that rolling-apart situation, our experiments seemed to show minimal advantage to EITHER argument. The fire DID seem to last longer on the floor, but only an increase from 10 hours to 10.5 hours. The fire DID statistically burn more completely up on the grate, but only by a few thousandths of one percent.
It's your call on whether to use a grate or not. You could always get one later if you don't get one now!
Two Types of Self-Feeding GrateThere are two different styles of self-feeding grates, steel and cast-iron. The steel grates are made of steel rods which are bent and welded together, to create an open framework that supports the logs but also allows very easy airflow under the fire.
Steel bar grates are made of round, square, rectangular or diamond-shaped rods. Various companies claim advantages of one or another but we tend to doubt that there is much difference.
The cast-iron self-feeding grates are usually similar to the picture at the right. It is actually bolted together and the log holder area is usually pretty thick cast-iron with a bunch of slots in it.
They both do the job well. Some people like the massiveness of a cast-iron grate. Other people like the steel grate for being less obvious! Since most people tend to use their fireplace intermittently, probably either one will last the entire time you are in that house. If you truly intend to use the fireplace 24-hours a day to continuously heat the whole house (like a JUCA was designed to do!) then there might be cause to seriously consider the more expensive cast-iron grate. Ball-park prices (for good self-feeding grates) are $50 for a steel bar grate and $100 for a cast-iron grate. Lower quality grates of both types are on the market for somewhat less cost. Mass merchandisers sell scrawny grates for $15! In all cases, you pretty much get what you pay for!
Another style is made of heavier (thicker) steel or cast-iron, but the bottom is flat. This kind is made for burning split wood pieces 2-5 inches thick, as in a normal fireplace. Because normal fireplaces are quite inefficient, they NEED hotter, split-wood fires to produce enough radiant heat into the room, and so flat-bottom grates are usable there. The wedge-shaped pieces of wood are never going to roll apart! It's just when you get to burning full-diameter, round logs, where the self-feeding feature of a Vee-shaped bottom comes into play.
We have a supplier of the heavy cast-iron version of the self-feeding grate. They cost about double as much (roughly $100), but some people really want cast-iron! If there is interest in this, we can supply them. Since they are pretty heavy, there is likely to be some freight charge that might be added, unless you are close to Indiana!
The substantial depth is necessary for hard coal so the heat from the pieces burning at the bottom (you can't start the fire from the top!) weave through the coal pieces above, warming and pyrolyzing them, preparing them for later being on fire. Hard coal burning is a VERY different technology than either wood or soft coal burning. Even things like the shape of the firebox can affect a hard coal fire. It is generally very difficult to properly burn hard coal in any woodstove (even ours!) If burning hard coal is intended in a fireplace, the special very odd shaped coal grate is absolutely necessary. We are not aware of any US manufacturers of them, and most seem to be made in England.
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E-mail to: JUCA1@mb-soft.com