# Bolt on Gravity Feed ?...



## Cale Beecher (Mar 29, 2020)

Has anyone built a gravity feed shoot and fire box that can be bolted onto vertical smoker?..   I have a very large 2 door warmer converted into a pellet smoker.   I’d like to make it a gravity fed charcoal smoker.   I like the round chute idea like a Myron Mixon G series.   Any calculations or specifications that need to be considered?


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## krj (Mar 29, 2020)

Typical gravity feed hoppers are made of thicker metal to hold up to the heat longer. I like the idea of a bolt on feeder, but you should definitely take that extra weight into consideration. Likely because of the weight it'll need to attach at multiple places. Definitely needs to seal well to the chamber, and the hopper lid as well. Dimensionally, I'd personally go with a hopper at least 8"x8". As far as I know there aren't any flow calculators for GF's like there are for RF's. I personally run a controller and fan on my GF so it'll flow as much air as is needed for whatever temp I'm looking for.


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## Cale Beecher (Mar 29, 2020)

krj said:


> Typical gravity feed hoppers are made of thicker metal to hold up to the heat longer. I like the idea of a bolt on feeder, but you should definitely take that extra weight into consideration. Likely because of the weight it'll need to attach at multiple places. Definitely needs to seal well to the chamber, and the hopper lid as well. Dimensionally, I'd personally go with a hopper at least 8"x8". As far as I know there aren't any flow calculators for GF's like there are for RF's. I personally run a controller and fan on my GF so it'll flow as much air as is needed for whatever temp I'm looking for.


Sounds about like I thought.   I personally like the idea of using 8” diameter steel pipe instead of a square or trapezoid charcoal chute.  I feel like it would reduce bridging of the charcoal. 
My plan is to build  a frame out of 1” square tubing that will be skinned in 16ga  to hold the 8” pipe and fire box.   Idea is to drill holes (in tubing that would sit against the outside of the cabinet).  Inserts 4” long 3/8 bolts and weld them in before skinning the frame.  Creating a nice 3” stud to be left revealing which could be inserted into the cabinet and bolted on.


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## dacolson (Apr 1, 2020)

Seems like something you could do with a couple of channel brackets and a latch or two. Run 2 or 3  horizontal channels above and below the heat/smoke feeder inlet into the CC that the weight of the FB would hold firm. Run a vertical channel on the front of the CC that the FB would grab onto for stability. Put 2 or 3 latches on the opposite (back) side of the FB from the vertical channel that would suck the whole FB into the body of the CC to keep them sealed together. Put a high temp gasket between the two. The channels would need to be stout enough to hold the weight and the weld points on the CC would need to be onto the frame, not the skin. I'm thinking this would make the whole thing a bit more modular. Probably overthinking. Too much coffee already ...
I'm attaching a terrible freehand sketch that hopefully clarifies but probably will only be more confusing. Good luck!


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## Cale Beecher (Apr 2, 2020)

dacolson said:


> Seems like something you could do with a couple of channel brackets and a latch or two. Run 2 or 3  horizontal channels above and below the heat/smoke feeder inlet into the CC that the weight of the FB would hold firm. Run a vertical channel on the front of the CC that the FB would grab onto for stability. Put 2 or 3 latches on the opposite (back) side of the FB from the vertical channel that would suck the whole FB into the body of the CC to keep them sealed together. Put a high temp gasket between the two. The channels would need to be stout enough to hold the weight and the weld points on the CC would need to be onto the frame, not the skin. I'm thinking this would make the whole thing a bit more modular. Probably overthinking. Too much coffee already ...
> I'm attaching a terrible freehand sketch that hopefully clarifies but probably will only be more confusing. Good luck!
> 
> View attachment 438269


Wow that’s a cool idea to essentially make a French cleat with metal.   This doesn’t have to be removable though.   It’s just the fact that I’m adding it to an existing cabinet.


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## Alphonse (Apr 2, 2020)

Just some points that my son and I have kicked around in the recent past:
The seal on the top is imperative to keep flame front from traveling up the chute.  Your combustion air blower will produce a positive pressure and leakage at the top will create issues. 

Size the chute to hold 1000 cubic inches of charcoal minimum.  That's equivalent to a nominal 20 pounds of natural briquettes.   Minimizing ash is a good idea, so burning natural charcoal is the ticket.  I would not use KBB charcoal as an example. 

Ash collection and removal is important.  That opening will need to be sealed well too.  I'd consider some sort of cyclonic action in the exit of the burn chamber to separate ash from the hot gas stream.  Since you will likely be using a PID controller such as a BBQ Guru or FireBoard to control combustion air via a blower against your set point, pressure drop of the air flow is easy enough to contend with.  I  would consider using a Pit Bull fan for this reason.    

A round fuel feed chamber will plug flow a bit better than rectangular or square.   However a rectangular cross section may be easier to deal with from a fabrication viewpoint.    

Round, thin wall stainless steel conveying tubing or piping may be a viable solution for the chute.  This can be found surplus for time to time and would help keep the weight down.  

Fun stuff you are thinking about!


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