Can a UDS air intake be too tall?

[gotwood]

Originally Posted by Browser

I don't s'pose it'd be anything like the height of the intake means the air is trying to get in via the shortest path i.e. one of the vents rather than the intake pipe?

The hot air is going to exit the ports on the lid...hot air rises.
This will create negative pressure inside the drum and draw air from you intake in.

[cajun_1]

Well after reading this thread ... think I need to enlarge my exhaust. I have 4 3/4" intakes and a 1 1/4" exhaust. On my last smoke..I fought the temps. ... seems 2" exhaust is the norm ... would think all the holes in the lid equal 2".

[timzcardz]

Originally Posted by chinesebob

Off topic but N8man - how did you build yours on to the wheels like that?

Is that "lawnmower mod"?

[timzcardz]

Originally Posted by gotwood

The hot air is going to exit the ports on the lid...hot air rises.
This will create negative pressure inside the drum and draw air from you intake in.

Actually the tall intake may partially act in a chimney effect trying to draw the hot air up also. It may not actually exhasut, but the effect may be rather balanced and create a standstill in the intake riser.

To better understand this, if you cover the exhaust vents and open boththe the lower and upper intakes, I'm sure you would find that your higher intake would definitely now act as an exhaust port.

[Harbormaster]

I haven't built a UDS, but here's something for you from left field.
When I was taking S.C.U.B.A. courses, we learned about snorkel design.
The one thing that sticks out, is that if you increased the length of the snorkel, you also had to increase the diameter of the snorkel to get the same airflow.
So, if you have a longer air intake on your UDS, you will also need to have a larger diameter pipe to facilitate the same airflow.
I also am thinking about when using my offset, I'm pretty sure that my exhaust opening is typically about 2-3 times the size as my intake opening. The cool air that is coming into to your cooker is going to expand a lot when it gets burned and gets hot. You need to have a bigger place for that air to go out than come in.

[tntitan]

i think you are wasting your money my (4)1" pipes down at the bottom with 1 ball valve works fine those smoke stack things look good though

[Divemaster]

Originally Posted by Harbormaster

I haven't built a UDS, but here's something for you from left field.
When I was taking S.C.U.B.A. courses, we learned about snorkel design.
The one thing that sticks out, is that if you increased the length of the snorkel, you also had to increase the diameter of the snorkel to get the same airflow.
So, if you have a longer air intake on your UDS, you will also need to have a larger diameter pipe to facilitate the same airflow.
I also am thinking about when using my offset, I'm pretty sure that my exhaust opening is typically about 2-3 times the size as my intake opening. The cool air that is coming into to your cooker is going to expand a lot when it gets burned and gets hot. You need to have a bigger place for that air to go out than come in.

I was going to say the same thing... If you want to have a long intake, you need to increase the size of the pipe you use...

[Mark]

Yes; at some point FAA regulations kick in. (smartass mode)

I know it seems to be a tradition using steel pipes & brass ball valves and such for intake & exhaust, but that's all unnecessary. There are simpler and cheaper ways to control air flow. And nothing to stub your toe on. You can easily duplicate what Weber uses on its kettle tops. It works on the bottom too for inlet air.

[Harbormaster]

Originally Posted by Divemaster

I was going to say the same thing...

You mean I was right?
Someone call my wife.....





(I kid I kid, I knew I was right)

[h20loo]

I know everybody wants to get it right the first time but what is kind of neat about the UDS is how everybody makes it their own. Don't be afraid to try new stuff and when it works be sure to brag about it.

All the talk about intake pipe lenght got me out to my barrel tonight. I loaded it up and let it run wide open. It got up close to 330. I then ground the welds off and replaced my intake pipe with an 18" pipe shoved in 12"(same as original pipe). After 1/2hr the temp had climbed a few degrees but never over335. I put my original pipe back in and after a while the temp was running 331 to 332 pretty steady.
It appears on my barrel that the slightly constricted bend and 30" of pipe have little effect on the intake.

[SoEzzy]

I'm working on the whole problem too!

I'll introduce my variation, with pictures in a couple of weeks time.

Secret plans in the works, I could tell you about it, but then I'd have to kill myself.

[FatDaddy]

Is it possible to have too much exhaust? i have 8 9/16" holes in my lid spaced equally around the lid. and 1/2" intakes. would this cause it to not run as hot?

[keale]

For my UDS, too much exhaust cause it to run HOT.

[Single Fin Smoker]

What do you need pipes for? With my luck I'd bend or break dim sunbitches.

I got 3 holes down around the bottom. With opening only the front ball valve I stay right at 220 to 230(till the roosters fark the chickens if need be). With ball valve and side nipple open, I'm up at 275 to 300(perfect for spatchcocked chickens).

How much lift do you have under your fire box?

[Single Fin Smoker]

Oh Keale, I've learnt the hard way-----you CANNOT leave your lid off for too long, with turning it into a jet rocket booster.