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The Science Behind The T-Rex Steak

WileECoyoteWileECoyote Posts: 516
edited 7:29AM in EggHead Forum
TNW was kind enough to post my report on his site a few months ago about some heat damage that occurred to my new custom egg table, and a lot of research that I did to determine the proper base for my large egg to resolve the problem. I modified my table as shown in the report and I haven’t had any trouble since then but I was still wondering just how hot various spots on the egg would really get during a typical high-temperature cook like T-rex steaks. So I decided to run some more tests to find out.

First I purchased a digital Fluke thermocouple meter with ten Type-K thermocouple heat sensors that are rated up to 2000°F. This equipment came from a Sun Microsystems laboratory and it was certified for accuracy, and the sensors were brand new so I knew that the readings would be reliable. It took a while for me to find the instruction manual, figure out how to program the meter, and build three wiring block harnesses to connect all of the sensors but I just finished it tonight and tested it out. Everything works perfectly.

The T-Rex Test:

I went out to the egg table around 5:30 pm and connected the thermocouple heat sensors to various spots on the interior and exterior of the egg. I used thin aluminum adhesive tape to hold the sensors to the outside of the egg and I also connected a few sensors to my firebrick base. Then I took an initial reading of all the sensors before I lit the egg. They were all within 2°F of the outdoor temperature so I had a green light to proceed. Here are some photos of the egg wired and ready for takeoff:

heatsensors01.jpg
heatsensors02.jpg
heatsensors03.jpg
heatsensors04.jpg
heatsensors05.jpg

For this test I decided to cook the steaks exactly like I normally do; no deviations at all from my normal T-Rex cooking routine. I started with a nearly full load of Wicked Good Charcoal, bottom vent wide open, top vent wide open, and a stainless steel fine mesh strainer set over the top vent to contain sparks. I lit the egg with rubbing alcohol and proceeded to take temperature readings every 5 minutes during the warm up and cooking cycle. After the steaks were on I closed the bottom vent halfway but made no other adjustments. I flipped the steaks once after 5 minutes and removed them after 10 minutes. I closed the bottom vent all the way and then placed the ceramic cap on top to shut the egg down. I took additional temperature readings for several hours after the egg was shut down. The resulting temperature readings can be seen in the graphs below. Click here for the Excel file which contains the graphs and all related data.

exteriortemps.png
interiortemps.png
firebricktemps.png

Observations:

The exterior of the egg does indeed get quite hot with peaks as high as 400°F. The bottom of the egg is actually one of the hottest exterior spots which confirms my initial research and testing; however there are a few other spots which get almost as hot so we need to be very careful around an egg that has been cooking for a while at moderate to high temperatures.

The interior egg temperatures all followed the same basic curve with the exception of the bottom which got hotter faster and was at times even hotter than the heat exiting from the top vent. This is further evidence why it is so important to select the proper base for the egg, especially when you are mounting the egg inside a table.

The ceramic feet obviously did a great job of keeping heat away from the support base with the firebrick being more than 200°F cooler than the egg base at peak temperatures. In fact the bottom of the firebrick actually got slightly colder during the first hour while the egg was heating up, which I suspect was due to a slight draft of cooler outside air being drawn into the table as the lump started to catch. But then the firebrick heated rapidly during the last 2 hours even as the egg was cooling down, apparently because it was absorbing the heat from the exterior of the egg and holding it almost as long as the egg itself. So the air gap created by the feet is critical but it alone is not enough. A substantial support base is still required to handle temperatures which approach and exceed the UL-recommended maximum temperature threshold for wood surfaces adjacent to heating devices in residential areas (see my other report for details).

Another surprise was that the grate was actually the lowest interior temperature but I suspect this was partially due to the placement of the grate sensor near the inside rim of the egg. I would have liked to place it in the center of the grate but I didn’t have the high temp. protective sleeving on hand yet to protect the sensor wire and I didn’t want to ruin the sensor so early in my testing.

This test has convinced me that the air gap between the egg and base is even more critical than I originally thought, as is the air circulation around the egg and support base. All the more reason for everyone to be super careful about how we design our tables and what we decide to place under or near our eggs. I can’t draw too many other conclusions yet but I will perform more testing and let you know how it turns out. By all means share your thoughts and feedback, especially if you have a Stoker and have conducted similar tests.

Comments

  • WileECoyoteWileECoyote Posts: 516
    Oh yeah. Almost forgot. The steaks turned out wonderful for simple T-Rex:

    trexsteak1.jpg
    trexsteak2.jpg

    Very tender and flavorful, nice char but still medium inside. Quite a nice way to wind up the evening after a round of testing outside in my BGE lab... :)
  • Kew_el_steveKew_el_steve Posts: 354
    Absolutely great!!! Nice Job!!!

    As an engineer, it's nice to see some empirical data on this subject.


    THIS NEEDS TO BE A STICKY!!!
  • WileECoyoteWileECoyote Posts: 516
    Yes, it is a large egg. And please do not adjust your monitors... I painted it gold a few months ago to match my table. :)

    On that note, here is a blast from the past with an egg twist for all of you old TV-show buffs. See if you can name this show:

    "There is nothing wrong with your egg. Do not attempt to adjust the color. We are controlling the cook. If we wish to make it hotter, we will open the draft vent. If we wish to make it cooler, we will tune the daisy wheel. We will control the horizontal grate. We will control the vertical dome. We can roll the ABts, make them flutter. We can change the spices to a soft taste or sharpen them to flavorful clarity. For the next hour sit quietly and we will control all that you see and taste. We repeat: there is nothing wrong with your egg. You are about to participate in a great adventure. You are about to experience the awe and mystery which reaches from the inner mind to... The Big Green Egg."
  • Grandpas GrubGrandpas Grub Posts: 14,226
    Thanks for the update.

    GG
  • lowercasebilllowercasebill Posts: 5,218
    twilight zone.
    thanks for your efforts ... wonderful to see real science meet the egg....especially when it involves our safety
  • AngieAngie Posts: 25
    A few questions for you. Did you use lump charcoal? How do you start the fire with rubbing alcohol? Do you always use the alcohol? Did you leave the dome open the entire cooking time? I am new at this and trying to learn.
  • Beanie-BeanBeanie-Bean Posts: 3,092
    Thank you, ACME super-genius! I appreciate the time and effort (and expense!) you went to get this valuable data and information out here for us. I'm still using the EggNests for both cookers, and will probably continue to do so until I can figure out a safe way to have them installed into a properly-designed table with adequate "air" between the bases of the BGEs and their respective support surfaces.

    I'm still tripping over the gold paint! I remember seeing the mod you did a while back, and it's good to see that your paint job is holding up well.

    Oh yeah, the steak looked good, too--

    Thanks again,
  • civil eggineercivil eggineer Posts: 1,547
    Fantastic data collection and graphing display. As much as I enjoyed it ... I think you may have OCD. I now because I R one. :laugh:
  • Photo EggPhoto Egg Posts: 7,633
    Thank you for all the time and money you put into this project. It's a real eye opener...
    I would sure like to see data on the XL.
    The bottom base has so much more surface area and the XL holds so much lump I bet the exterior bottom temps will really get hot. Add the fact the XL does not use the little green feet for a buffer might be a real problem child.
    I would like to see your data on a 600-700 degree cleaning cycle.
    Take care,
    Darian
    Thank you,
    Darian

    Galveston Texas
  • RascalRascal Posts: 3,753
    I like the alcohol method and use it exclusively. Here are a few videos describing it:
  • East Cobb EggyEast Cobb Eggy Posts: 1,162
    Nice Gold EGG.

    What kind of paint did you use?

    Greg
  • That is a reference to "The Outer Limits", not the "Twilight Zone"
  • WileECoyoteWileECoyote Posts: 516
    Good guess on the show Bill, close but not correct. Fossil wins the prize: the Outer Limits shows always started with that crazy announcement.

    I plan to repeat this test with some other cooking cycles including a high-temp cleanout that will run for 2+ hours. I didn't have my TruTemp gauge installed for this test because I used the hole for a thermocouple sensor but I think the TruTemp gauge would have read between 650-750 at the peak because the egg was hot enough during this cook to clean the inside of the base and dome until they were almost completely white.

    Angie: I used Wicked Good Weekend Warrior lump charcoal which is what I always use. I have tried every possible lighting method and determined that rubbing alcohol is the best. I made the videos and posted them on YouTube to show people how it works and why it is the best method in my opinion. Rascal posted the correct links to the videos.

    Photo Egg: I suspect that the base of the XL may get a little hotter but not too much. I think BGE may have avoided use of the feet on the XL because the feet might not have provided enough support for the extra weight of the fully loaded XL egg. If I owned an XL then I would order a spare set of feet and use at least 6 of them around the perimeter plus I would try to cut the lip off of one or two to support the middle. The main thing is to get air flowing under and around the egg and support base. If you set the egg directly on the support base then you transfer all of the heat directly to the base which is not good unless you have a really large base and/or a super cooling method.

    East Coast: I used high-temp engine paint from an auto parts store. There is a very detailed thread with lots of pics on the forum. It explains how I painted it and the results have been eggcelent! Paint still looks like the day I sprayed it even after several months of heavy use. I highly recommend a paint job for the egg and I am really partial to the gold color. It matches my table and also my truck. If we ever decide to enter some BBQ competitions then we will compete as Mr. & Mrs. Goose with the Golden Egg... :)
  • BacchusBacchus Posts: 6,019
    "Science" ?

    It's poetry in motion
    And when she turned her eyes to me
    As deep as any ocean
    As sweet as any harmony
    She blinded me with science
    And failed me in geometry
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