Empirical formulae ???

[Andrew Leigh]

Anyone got formulae for UDS's? Flow, volume etc.? Or is it a copy cat exercise?

Why two pipes with ball valves and one extra inlet with a nipple. Extra inlet for a short term boost on the fire?

Why two pipes and not one pipe of larger diameter. Must be a good reason rather than symmetry?

 

[ironhorse07]

Uhhh, yeah, ok...

 

[Andrew Leigh]

I am not being pedantic, I actually would like to understand the process of flow through a smoker. We don't smoke in this country so these are very foreign concepts. So perhaps I should rephrase.

On UDS's the trend is to have two inlets, each controlled by a ball valve. Some UDS's will have an extra inlet that is merely a nipple with a cap to close it. So the two ball valve controlled inlets I can understand will give good control over the fresh air intake. Why would one want the third intake and what would the purpose be?

And again why two ball valves, why not increase the valve size and have one ball valve? It there a reason for this, do the two smaller valves provide for better control?

 

[oldsmokerdude]

One of the potential issues with an UDS is that if it gets too much air the temp could get way out of control. A single larger inlet would be more difficult to manage than the "standard" three inlet design. So you essentially answer yourself in your question; it is for better and more accurate air control. An added benefit is that by evenly spacing the inlets around the drum, you get better distributed air flow resulting in a more uniform smoke flow through the smoker.

 

[Andrew Leigh]

Thank you I understand.

Can you explain the third inlet though, it has no ball valve. Is this like a "turbo" function?

 

[ironhorse07]

Thank you I understand.

Can you explain the third inlet though, it has no ball valve. Is this like a "turbo" function?

To provide more air during startup. It takes more BTUs to raise temperature than to maintain temperature, hence the additional combustion air.

 

[daveomak]

Andrew, evening.... FWIK, originally the UDS was designed with 1... 1/2" full flow ball valve... 3 nipples equally spaced around the drum, 2 with pipe caps..... All 3 open at start up as another member has mentioned... As the temp got close to desired, 1 nipple was capped... as the temp got close yet, the ball valve was closed down partially... after repeated use, one could determine the "optimum" setting of the ball valve for a "ball park" temperature control point... and consistently return to that setting.... ALSO... do to restrictive air flow from friction loss... extension pipes to make adjustment easier, screwed stuff up not to mention the additional costs.. AND.... folks did not pay the extra $$$$ for full flow valves...
About nipple sizes... a 3/4" nipple flows twice the air as a 1/2".... or so it says in fine print somewhere.... so regulating temperature based on inlet air flow, it is easier and more of a fine tune using 1/2" nipples and 1 ball valve....
Some will say "My 3/4" or my 1" ball valve work just fine"..... Well, they probably do... but for fine tuning 1/2" are the "cats pajamas"....
Full flow ball valve..... 2" x 1/2" NPT nipple... 1/2" conduit nuts to hold the nipple to the drum...
A simple, yet very effective, smoking machine...
About the exhaust.... sometimes, one exhaust will direct air flow through 1 part of the smoker... could make for a part that was hotter than the rest... Personally, I'm a fan of 3 each, 3/4" nipples out the side of the top of the drum, with caps available for closure.. lid air tight and water tight in the event of rain... and a lid with a clamping band to make the drum air tight... only air in and air out is what you determine... makes for a very good smoker.....

 

[Andrew Leigh]

Thanks gentlemen, the responses are of great value to me. I can now set about finding buying the required materials and putting pen to paper. I like do do a simple CAD drawing before moving on, will posy for comment before making any beginner errors.