Stumps mini clone from existing box 24% over

[LeonardK]

When I really started to look at how to build the mini GF like the forum does, not trying to make my first box/idea work, it seemed so much better.

Although 16ga skin may be called for, some have opted for 14ga to skin the boxes. Me too. Better to weld .035" fluxcore.

I've decided for 2" sq tube. 1/4 may be really good but 20ft is 109#, 3/16 is 87#...22# difference.



What thickness do you think is best?



Starting by building fireboxes, is ashtray OK out of 1/4"... thinking it is because you put a tray in there too, so the tray would burn up instead of the structure.






Leonard

[mp4]

3/16 is more than plenty for your tube steal.

1/4 for your ash pan is overkill in my opinion. It isn't subject to heat that would require anything more that what you use for your skins...I would use scrap from them to make it.

[LeonardK]

Hi
Tackling .5" plate cuts with plasma torch, think I like gas better

Those who have built and are using Gravity Feed smokers, as you look at how yours is holding up, would you make the firebox taller now to better survive the heat???

I have 3-5/16 above the burn window, close to plan. I'm hoping this lasts at least 10yrs. Being I have more .5" plate and other stuff, planning on cutting more for more fireboxes/GFs.




As a matter of hindsight, would you make your firebox taller to last longer?

Leonard

[LeonardK]

Victor Cutmaster 42

At first using stock tips on .5" seemed tough cutting with 240v, then switched to tips with larger orifice, kind of like using a #2 with gas instead of a zero tip

Just in case anyone else has some similar issues. I'm gonna pierce with the junky worn out ones then switch to better tips for cutting. Hard to pierce but easy to cut.

[LivnDream]

what plasma torch you runnin on the cutmaster 42 sl40 sl60

[LeonardK]

Hi
I like to see all these interesting modifications that make things work better. Michael303 mod mini.

All they had at welding supply store was 60A tips? guess. Looked at box... 4200-SL60 OK so maybe that has something to do with why those tips work better. As with gas I like bigger tips but they use more gas, doesn't matter with plasma tho. So next time I need tips (tips?) wonder if they got 80 amp or 100 amp, they would work better?

I really don't understand amps in this regard because at 240v this just couldn't be pulling 60a unless the tip voltage is low and current is raised like in step-down transformers. Got curiosity up to see what voltage at tip is for cutting max setting on 240v.

[LeonardK]

Here's two GF furnaces finished, but, I see I forgot to weld bottom of one.

BBQ supply seems to favor the 1.5" insulation implying most of you are building your GFs using 1.5" and not 2" tubing, is 1.5" OK or what most are using?

It would be some cheaper and lighter

[LeonardK]

Some people can cut real nice or have the grill teeth machined.
I just couldn't cut neat enough with the plasma and it would be a pierce for each of the 9 windows thru half inch plate.

Later I figured a trick, line em up and drag the rod over them clamped with wood so each is held. All tacks done in about a minute. Best I could make this look using square stock.

Since this is not a bought plan for the furnace, just mine, and I did it some different, hoping to manage ash better, thought I'd post it and since I made many others that were not quite up to par or good. This one is scale and cutting the 3/16" for chute into even 24" leaves total height including some random both ends... 37" tall few inches to trim later... or make CC bigger

My plans are to make 3 racks having 6" space between using 3/4" angle for racks and make CC about 31" tall internal

For durability, I painted outside with that BBQ paint from home depot, should make furnace last 2x as long.

As expensive as Tel-Tru are, I'm going to only put them on the one I intend to keep and use, they're $58 at BBQ supply, but they sure look nice!

Leonard

[LeonardK]

Working on furnaces, the 4th one here shows that different grill track, thought THIS time, to weld side plates and supports before installing the furnace bottom.

Furnace grill track gen appearance is different to improve ash management

Leonard

[LeonardK]

Hi I'm now back on this smoker cooker project after finishing a 16x36 reverse flow smoker.

There were a few things holding up construction on this one and am still considering the 23x24x38 box VS forum size more common 18x22x29

Looking at numbers, offset and rev flow use FB that's 1/3 of CC

Mini burn area 6x9.5x2.5 = 142.5 inches and 1/80th of CC

80th = 142.5


My box would need burn area of 80th = 262 sq inches or 70th 300 sq inches

When I put the idea of a GF furnace for the rev flow BigT said someone had already done that and it used a lot of fuel
On a 9 hr cook it uses about 16# or more of coal/wood

Thinking about that rev flow a member put a GF on, I wonder if the furnace had a large cross section, maybe even square-ish where the central area inerted much higher up causing more burn than desired

Using the rev flo, tray is 14x33 and when cooking two briskets or brisket and pork butt have to put one tray over the other to get them to fit long ways

Makes me think about using the bigger box for the reasons of tray sizes

Finished 16x36 rev flo but tray was 100 deg colder at original position, now 5.75 inches from top

This looks as good as if not better than a tel tru

So about the bigger box used as internal part of GF cabinet......

If I built a bigger GF furnace to use this box and a ratio of 70 instead of 80, would a narrow burn area help keep the inerted area tight so it would not burn an excessive amount of fuel

Burn grate 3" tall needs about 100 sq inches so this could be 6x16.66 or 7x14.285
Burn grate 2.5" tall needs about 120 sq inches so this could be 6x20 or 7x17.14

What about the narrow burn area of 6" to get a better efficiency and inert better, a bigger box would need a bigger furnace ... or there would be longer times to get up to temperature.... that could be shortened using a guru with a fan

Leonard

[LeonardK]

I thought the Guru with that big Pit Bull fan would shorten time to cook temp.

No specs on site about fan are given, but it's a 12v DC brushless 25cfm fan uses .5 amps... now that gives me something to start with for what will get GF to temp. And the smaller Guru fan Pit Viper is 10cfm better suited for temp control

Reviews are sure helpful and I'm sure not going to buy anything Guru, they are not reliable or durable or water resistant


And everything Guru is expensive!


All I think is needed for the GF is a fan to accelerate start ups and after opening door like when you foil something and resume.

Instead I found on Amazon a 12v 42cfm fan uses 1 amp 2 ball bearings and claimed by a certain user very long lasting, my use of fan to switch on to get up to temperature only, then unplug and use just valve opening naturally aspirated

When reading about the GF others own or demo, they find putting wood in the chute makes the significant difference in smoke rather than just wood below burn grate in the ash tray





Following that up, Do you that have Mini GFs find you would like a larger furnace to more easily fit wood chunks and better prevent bridging or clogs???

Not really big, but, the furnace starts out 9.5 x 6 inches internal.





How much better would this work if say the furnace were 9.5 x 7.5 to be less susceptable to clogs with wood in the chute????






OR would this not work so good because it would burn too much, and need to be quenched/starved too much of air????

I believe a small fire burning hot makes a good chemistry ( from AmazingRibs.com )






After about 7 cooks in my Rev Flow smoker, I'm really liking that smoke flavor, maybe not at its strongest tho

I'm getting ready to buy a Dewalt DWM120 portaband and need more stuff to finish this GF so it will be a slow build







It just seems like such a big investment to build the Mini and then wish the furnace was bigger to be able to fit wood chunks in the chute.




What are your thoughts about your GF and the size of the furnace, clogs, and using wood in the Chute??????


Furnace Size??????????????






Leonard

[Diggerg]

Why use wood in the chute? Most just put chunks in the Ashlan to smoulder as the ashdrops down in a gf

[LeonardK]

...

[Diggerg]

I'm not personally a fan of heavily smoked flavour so if leave my chute as it's. But each to their own and I can't see why it wouldn't work. Maybe @FrankCox could help?

[LeonardK]

I have been over the figures and possibilities for different sizes starting with 23x24x38 internal.... too much volume for the Mini furnace

Thought about the spacing, looked at this composite stumps pic I made has figures on an old round grill I used 1.31 sq feet and wanted twice that at least like about 3 sq feet per rack

Just ignore the furnace in this pic, purpose is for planning vertical spacing in the GF cabinet


This plan cuts the existing box down to 18x24x30 ... almost the Mini but over the last year have read comments about how long it takes to get up to temperature but that they cook rock solid without temp management like a Guru but could benefit from a fan to accelerate heat-up

The Guru fan specs are about .7 amp from mfr seller, 25cfm claimed, runs on 12v DC ( PitBull fan)

Not really needing temp management, I found this blower fan on Amazon uses about 1amp 12v 42cfm, will switch on whenever starting up or opening door to foil or check meats

I'm not going to build really fast, but I think I've really nailed the final plan

Good thing here is an idea to use an isolation plate with four 1.25" holes for the area of the 2.5" damper pipe area, to slide in place bottom of any of the two top rack slots. If I just wanted to smoke some burgers a little hot and fast, close off 2 shelves, use bottom that has 3 sq feet sitting over the heater and with only 7965 cubic inches, will heat up a lot faster than the Mini

So if I close top shelf it's a little smaller than the Mini 91% and cooking on 6 sq ft of rack, close 2 off 69% vol of Mini and 3 sq ft of rack



Leonard

[LeonardK]

I worked on this today, taking my time, made mistakes before.

Here's a vertical plan, mainly intending racks 18x24, have 3 foot each, gotta burn WOOD to get that deep strong smoke flavor

So, to make it a little easier for wood, making furnace 7.5 x 9.5 x 2.5 just a hair bigger so wood won't have to be quite so small

When smoking I will mix wood and charcoal in same 50/50-ish amounts just like I do with my RevFlo smoker

Saving $$$ for insulation and other parts, but starting tomorrow I can build box with rack slots, heat diffuser, grease pan, stack, racks

Going slow because of many reasons, learned a lot lately... got to burn WOOD for good smoke flavor, if I'd built it earlier, would not have liked it. Going to try it with one of the stock GF furnaces I already have built, then make the larger furnace and insulate, too.

Leonard

[LeonardK]

Now is just about the windup before I get the stuff and build the GF. You know I just finished the RevFlow a few months ago. Smokes real good but only has 3 sq foot of rack to cook on.

Here is a scale side view of the wood burning GF I plan to build that will have a large stick burner box where typical ashbox is on the Mini GF But I plan on using WOOD in the larger furnace shown in the picture, maybe JUST WOOD in the GF furnace.

Burning wood in a GF furnace ( bigger 7.5 x 9.5 x 2.5 ) should make meat just as smoky as cooked in my RevFlo

After hearing a few related podcasts Frank made (APPLE, Wood needs more air for Combustion, etc), one question about how good this will work for making smoke flavor in THIS GF:

Smoke is made up of particles, and we like it to stick to the meat we cook, The RevFlo furnace = 1/3 CC and the GF furnace = 1/8 CC... less flow translates to less particles of smoke. BUT, Will This Be Significant If I Want to Get Really Smoky Meat in My GF???

So will the reduction of flow in the GF negatively affect the ability to get a STRONG smoky flavor like in my Reverse Flow smoker?????

Frank?

Anyone who really knows???


Leonard