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Engine basics => Engine set up tips => Topic started by: wwwarbird on May 01, 2011, 12:31:09 AM
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I've got a 3 ounce Brodak #BH-557 Wide Wedge Uniflow tank with all tubes facing forward that I need to plumb. I can't remember, do I cap off the fill or the overflow tube, or does it even matter?
Thanks! H^^
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Cap the overflow, Wayne. That is the "standard" method.
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If you cap off the uniflow tube, then you've just made a standard tank with an odd fill method.
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Thanks Bill and I got ya but bear with me guys, I never use uniflow so I'm extra dumb on this one. Which one would be considered the "uniflow" tube, the fill or the overflow?
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Thanks Bill and I got ya but bear with me guys, I never use uniflow so I'm extra dumb on this one. Which one would be considered the "uniflow" tube, the fill or the overflow?
I am not sure as to the answer but you can test the tank to find out - just put a small amount of fuel into the tank, set it down on the fuel pickup side and try and syringe some of the fuel out. The tube that is successful is the uniflow pipe as it will be almost at the same level as the fuel feed pipe.
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Here's a cutaway view of a uniflow tank, the way I might make it. Note that the tubes could come out of the tank any old which way -- the important part to the performance of the tank is the relative locations of the feed and vent tube openings inside the tank, and the fact that there are no leaks (including the overflow tube).
You'll often see uniflow tanks where the feed tube comes out the front face of the tank (contrary to my drawing) at the point of the outboard side, the vent tube comes out the top, and the overflow comes out the bottom. But don't trust me -- check your tank.
Come to think of it -- didn't your tank come with documentation? There should be a picture of the tank with the various tubes labeled.
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I have the same question ,wayne. i have one to plumb and no direction either. thanks rd
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According to the only diagram available, the one in Brodak's catalog for the tank, the three tubes are labeled pickup, fill, and overflow. They all face forward. I'll assume the one they're showing as "fill" is the "uniflow" tube and give it a try. It's the one towards the center of the firewall in the photo.
Thanks!
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According to the only diagram available, the one in Brodak's catalog for the tank, the three tubes are labeled pickup, fill, and overflow. They all face forward. I'll assume the one they're showing as "fill" is the "uniflow" tube and give it a try. It's the one towards the center of the firewall in the photo.
That sounds right -- 'pickup' and 'overflow' are pretty unambiguous, and you generally fill the tank through the uniflow vent, so that's probably what they mean.
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...and then when running I want the overflow capped and the uniflow open, correct?
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...and then when running I want the overflow capped and the uniflow open, correct?
Absolutely. The uniflow needs to be the only vent open to the atmosphere, or the magic doesn't work.
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That's what I thought, just making sure.
Thanks guys! H^^
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Sorry, Wayne, been off the 'puter, hit and miss..........
Sounds like you got i right. The "fill" is the uniflow vent. You can run it to a tube facing forward, or hook it to the muffler. Muffler pressure does tend to even out the run just a tiny bit more from my experiences. Seems I have pretty much gone to using muffler pressure on all the non piped planes. It will change the initial setting of the needle a little bit, but things seem to run more constant and at the end of the tank seems to be more even when it comes to shutting off in a LOT of cases. I was running a square metal tank (no wedge on the side) on my OS .20FP BBTU and when I didn't run muffler pressure, it was very erratic when the tank was almost empty. Hooking the line to the muffler nipple made it shut down with just a couple burps right at the end. It also made the tank run basically completely dry, which it may or may not do without the muffler pressure.
Bill