Lump Trivia ... The Beginning

Jeepster47

Ever wonder how much lump it takes to fill a large egg to a certain level?  Empirically we learn to fill the egg to various levels for certain cooks, but how much lump is in the egg at that level?  I need that data for another reason, so thought I'd share this piece of trivia.

All measurements were made with new, fresh, right-out-of-the-bag Rockwood lump.  A KAB was used as a screen to make sure that fines, extra large pieces, and rocks were removed from the measured fill.  This provided a reasonable level of consistency.  A Polder scale was used to weight the lump ... weights recorded to a tenth of an ounce.  A thin wire KAB (original version) was installed for all measurements ... the OEM grate wasn't installed.

1) When the KAB first came out, it seemed like filling to the top of the basket was the correct fill level ... seemed wrong to bury the handles.  This picture is of a 2 pound 12 ounce fill ... 3 pounds is the correct number for a fill to the top of the KAB.



2) The main fill level for most "regular" cooks is the top of the fire bowl.  It takes 5 pounds of lump to fill to that level:



3) We mentor new eggers to fill the egg to the bottom of the fire ring notches for a long low-n-slow.  It takes 10 pounds of lump to fill to that level:



The interesting result was how much difference there was in the amount of lump between a KAB fill and a fire bowl fill.  Since there is always a small amount of unburned lump in the bottom of the KAB after a cook, a fill to the top of the fire bowl doubles the usable lump from a top of the KAB fill.

Lit

Have to take into account lump type also. More dense lumps like FOGO or wicked good probably add 20% weight to your numbers.

stlcharcoal

Keep humidity in mind.....charcoal sucks up moisture like crazy and can raise/lower the pounds per cubic foot.

BTW, since your a numbers guy, figure a bulk density of 16.0 #/ft3 for 80% carbon w/ 5% moisture content.   

brimee

I think you have far to much spare time....

stlcharcoal

Lit said:

Have to take into account lump type also. More dense lumps like FOGO or wicked good probably add 20% weight to your numbers.

Yes, absolutely.  South & Central American stuff will have a much higher bulk density because those woods are more dense (cashew, walnut, etc.)  Our stuff is primarily oak, but if there happens to be more hickory, it could be heavier.  Likewise if it's more cherry or maple, it could be lower.

Also, the lower the carbonization (the more wood left), the higher the bulk density as well.

Chunk size will change the volume numbers because of the shape of the firebox, but not the bulk density or BTU's per pound.

Long story short, there's a million different factors, none of which will ever be constant.  But that's the average number though.....about a half bag (10#) to fill the large up.

lousubcap

@Jeepster47 - Thanks for empirically confirming what has been loosely tossed around here in other threads.  You have provided great documentation with your other lump discovery posts as well.  Lump burn rate at various temps if I recall correctly (obviously not bookmarked).  
May be time for a density and BTU output study since we are two days from Friday.  
All kidding aside, I appreciate your pursuit of quantifiable performance parameters for operating the BGE-helps eliminate the voo-doo. 
Edit: I was composing and did not see the above density comments at the time.

buzd504

I can fit more lump under my platesetter than if I'm using the spider and stone, which sits lower in the fire ring.  The amount of lump in my fill is also affected by the type/amount of old, burned lump still in my firebox and how much smoke wood I am mixing in.

Carolina Q

Good Lord! And I thought Ron was bad. You don't measure and mark your potato slices... do you? Or mic your pizza dough?  

Jeepster47

@stlcharcoal ... the lump for each fill was kept in the basement, weighted, and then dumped into the egg.  So, the fill data is reasonably consistent for humidity .  As you pointed out there are so many variables that it is almost impossible to get beyond a couple of significant digits when measuring lump.

But, you do point out one mistake I may have made.  When I measured the remaining lump after a cook, it had been in the egg overnight.  Might have picked up a different level of humidity than when fresh.  For the next cook, I'll repeat the process and then bring the residual into the basement to reach the same humidity level as when the test was started.  See if there is an appreciable difference.

@brimee ... yep!

@buzd504 ... that's why I'm measuring "average" type set-ups while keeping the variables as consistent as possible.  If the final numbers were really important, I'd be sanding the lump and smoke wood into equal size round balls, etc.

@lousubcap ... @Ozzie_Isaac deserves the credit for starting this when he measured the fuel consumption for an XL. 

buzd504

Jeepster47 said:

@buzd504 ... that's why I'm measuring "average" type set-ups while keeping the variables as consistent as possible.  If the final numbers were really important, I'd be sanding the lump and smoke wood into equal size round balls, etc.

Of course.  I'm just offering some suggestions as to what may affect individual circumstances.  I certainly appreciate the grueling field work you are undertaking for the good of the rest of us.

Jeepster47

@buzd504 ... I didn't take offense with your comments ... no problems mate.  This thread is intended to give folks some simple numbers to adjust from ... 3lbs to the top of the KAB, 5lbs to the top of the fire bowl, and 10lbs to the bottom of the notches in the fire ring.

If you use a spider and stone with the legs down in the fire ring notches, that lowers the level of the lump about an inch ... so you have to take out about a pound and a quarter of lump. For a low-n-slow at 250 degrees, that's going to shorten your available cooking time by at least a couple of hours ... if you were close on lump for the last cook like this one, you might want to raise the spider out of the notches in the fire ring ... or use your plate setter.

blind99

Love the research!  Now if you really want to geek out you could figure out lump consumption rate at different temperatures. 

bud812

I don't have a KAB so I guess I'm screwed. 

Jeepster47

blind99 said:

Love the research!  Now if you really want to geek out you could figure out lump consumption rate at different temperatures. 

I see you have a large ... so, I'll do 250* and leave 350* to you ... okay?

Jeepster47

bud812 said:

I don't have a KAB so I guess I'm screwed. 

No ... no ... my dealer still has some of the original KABs left on the shelf.  Or, we could negotiate a price on one of my old ones ...

anton

The medium takes five pounds to fill to top of fire ring. My go to move, fill all the way up, then top off next cook.
Another insightful post, thanks dude.

bud812

Jeepster47 said:

bud812 said:

I don't have a KAB so I guess I'm screwed. 

No ... no ... my dealer still has some of the original KABs left on the shelf.  Or, we could negotiate a price on one of my old ones ...

Naw, I'll just fill er up every time.

stlcharcoal

Jeepster47 said:

But, you do point out one mistake I may have made.  When I measured the remaining lump after a cook, it had been in the egg overnight.  Might have picked up a different level of humidity than when fresh.  For the next cook, I'll repeat the process and then bring the residual into the basement to reach the same humidity level as when the test was started.  See if there is an appreciable difference.

Please don't do that--it's carbon monoxide and fire hazard.  It's really not going to make a difference after you have cooked on it for a few hours.  We're talking a few ounces if anything.  You're probably going to lose more than that into the ash clean-out as you remove it anyway--since it's so brittle at that point.

You are way over thinking this........you need to go back to work!!   

blind99

Jeepster47 said:

blind99 said:

Love the research!  Now if you really want to geek out you could figure out lump consumption rate at different temperatures. 

I see you have a large ... so, I'll do 250* and leave 350* to you ... okay?

I think it's fairly useless information but I'm curious to know! im working this weekend but sometime when I have a chance I'll do it. 

HeavyG

Jeepster47 said:

... 3lbs to the top of the KAB, 5lbs to the top of the fire bowl, and 10lbs to the bottom of the notches in the fire ring.

I'll assume those numbers are the resulting average taken from say...at least ten trials to fill at each of those respective level yes?

theyolksonyou

You really need to identify the key inputs, run some full factorial DOEs and the develop a regression equation with an R2 of at least 80. 

theyolksonyou

Don't forget to look at your residuals. I don't mean ash and dust either. 

bgebrent

It's simple.  2pieR squared minus the residual times the size of your egg.  You're over thinking it

blind99

Obviously the answer is 42. 

Jeepster47

The funny thing is that I studied to be test engineer, so took all those probability and statistic classes.  Then I went off to work.  My first test was a cyclic failure test on an engine bracket.  Did the calculations and determined that I'd need at least 17 test samples to definitively identify the S/N curve for that bracket.  Mentioned the situation to my boss ... proudly I might add.  He pulled out some graph paper, filled in the axis scales, and drew in the single data point.  Then he pulled out a French curve, played with it on the paper for a few seconds, and drew the S/N curve for that bracket.  That's when I knew business was going to be different than school.

theyolksonyou

Had that school/real life discussion today with another "seasoned" guy about my vintage. We had lunch with a couple of rookies. I remember being them

northGAcock

bgebrent said:

It's simple.  2pieR squared minus the residual times the size of your egg.  You're over thinking it

There you go Brent......throwing around that Kentucky education at us.

Jeepster47

stlcharcoal said:

Jeepster47 said:

But, you do point out one mistake I may have made.  When I measured the remaining lump after a cook, it had been in the egg overnight.  Might have picked up a different level of humidity than when fresh.  For the next cook, I'll repeat the process and then bring the residual into the basement to reach the same humidity level as when the test was started.  See if there is an appreciable difference.

Please don't do that--it's carbon monoxide and fire hazard.  It's really not going to make a difference after you have cooked on it for a few hours.  We're talking a few ounces if anything.  You're probably going to lose more than that into the ash clean-out as you remove it anyway--since it's so brittle at that point.

You are way over thinking this........you need to go back to work!!   

Okay, I sometimes do things the hard way ... but, you don't think I'm measuring the lump while it's still burning ... do you?

Jeepster47

theyolksonyou said:

Had that school/real life discussion today with another "seasoned" guy about my vintage. We had lunch with a couple of rookies. I remember being them

When you understand what's happening, those short cuts are legitimate.  That's the real advantage that the old timers have.  Can't be taught out of books, has to be learned on the job. 

bgebrent

northGAcock said:

bgebrent said:

It's simple.  2pieR squared minus the residual times the size of your egg.  You're over thinking it

There you go Brent......throwing around that Kentucky education at us.

Robin, I don't know what I'm talking about but got the education I paid for!

chadpsualum

@stlcharcoal ...if you assume that particle size varies from bag to bag is your figure of 16#/ft3 based on an average of a couple of trials?  When this check is made, do you shake/vibrate to pack as tightly as possible so you have a true compact bulk density (CBD)?  I ask because I work in the petrochemical industry, specifically with catalysts and we do similar measurements.