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UDS Air Intakes

unclebubbas bbq

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Do you think that there is advantage to having tall upright air intakes over a ball valves at the charcoal basket level other than having to bend over to make an adjustment. Common sense tell me that there would be a better air draw but I really don't know
 

jimmyinsd

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common sense would say that the longer the small bore air intake tubing leading to the combustion point (coal basket) the more draft it would take( chimney height) to pull the combustion air.

with water, the longer the pipe the more resistance is created so I would assume it would be the same with gravity air flow.
 

JC in GB

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Do you think that there is advantage to having tall upright air intakes over a ball valves at the charcoal basket level other than having to bend over to make an adjustment. Common sense tell me that there would be a better air draw but I really don't know
Trying to force hot air to go down is never an easy task. The stand up air intake tubes will undoubtedly create friction and hamper free flow of air into the bottom of the chamber. The heat rising out of the top vent should create a sufficient draw but why hamper the airflow?

Advantage to having a ball valve is you can very easily attach a fan and pit controller to that valve and not have to worry about air flow and temp.

JC :emoji_cat:
 

bill1

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Is anything we do on this forum worth the money? I say sure it is!
I'm with Jimmy in SD on this one. The draft effect is like an air pump. Air doesn't weigh as much as water, but whenever you're pumping up, it helps to fill the feed end up high and "make gravity your friend".

The exception would be you don't want to pull in from so high up that the air is no longer cold and dense, but is air that's been heated by the cooker. So you might want to space those vertical pipes away from the smoker body and aim the intakes away as well. It's a little easier then to come up with various shades/covers that gives you control of how much air you suck in without having to buy expensive ball valves.

I even recommend using cheap pvc for these vertical pipes. If they're getting hot, they're too close to the smoker to do their job. The idea is to bring in cool air but from as high as is reasonable.
 

daveomak

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Do you think that there is advantage to having tall upright air intakes over a ball valves at the charcoal basket level other than having to bend over to make an adjustment. Common sense tell me that there would be a better air draw but I really don't know
Morning.... Draft is created by pressure differential.... If you have 2 holes, side by side, there is no pressure differential...
If one hole is 30" higher up on a tube from the 2nd hole, there is pressure differential.... Add in hot air inside the tube and cold air outside... a bigger pressure differential and DRAFT is created....
Natural draft is in danger from friction... A long tube used as an air intake, is a device that creates a lot of friction hampering the air flow greatly.... That long tube can also heat up any incoming air from radiated heat from the drum... also killing draft.....
The original UDS with air inlet valves at basket level, an air tight cooking chamber with exhaust holes at the top of the drum, is an almost perfect cooker... Consideration must be given to size of exhaust holes, placement and number.... Too small, or too few and draw is limited... Given air expands when heated, the exhaust holes must be greater in area than the inlet holes, or the air flow will be restricted... What's the perfect number ???? Enough so you can cook at 300-350 ish to get that chicken skin just right... Too few holes or too small, there will not be enough draft to cook properly...
I'm a fan of holes around the top of the sides of the drum.. with the bungs plugged... rebar can be inserted into those holes for hanging meats, when needed and providing even distribution of exhaust gasses for even heat....
Start with 8 each, 1/2" holes spaced around the top wall of the drum.. use a step drill.... add more if you feel it is necessary....
 

bill1

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I'd add it's easier to plug holes (whether on inlet or exhaust) during a cook than to drill them. (In this regard, I note that most folks forget what the U stands for in UDS so are loathe to accept this.) Little wads of aluminum foil do wonders at blocking all or part of a hole. Soup cans on top of inlet pipes work well to throttle flow. (Brass ball valves, to my mind, violate the entire low-cost philosophy of the UDS.) Pieces of taped toilet paper make a pretty good flowmeter...the angle of the paper away from gravity down tells you how much air/smoke flow you have. (But know your directions...don't let them get sucked in onto your meat.) Most importantly, have plenty of temperature probes inside monitoring both air and meat temp. (I err on the side of having many cheap probes than few good ones.) Above all, have fun. The whole purpose of a UDS is to look busy while drinking beer.
 

brute

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Joined Nov 6, 2015
Makes no difference one way or the other. I prefer taller intakes for the convince of not having to bend over
 

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