>I've been looking through the archives about uniflow clunk
>tanks and I see two basic versions: 1) the uniflow tube is
>flexable and attached to the clunk weight. It's position
>relative to the fuel pick up is fixed. As the clunk moves so
>does the uniflow tube. and 2) the uniflow tube is solid,
>bent slightly "L" shaped, and extend back to area near the
>fuel pick up. It's position is fixed realtive to the tank
>and can be adjusted by rotating the stopper plug or the vent
>tube itself.
>
>OK. Assuming that the actual uniflow tube end in the tank
>can be positioned above or below the needle valve. Does it
>matter where the centerline of the TANK is relative to the
>needle valve in either of these configurations? In the
>second of these configurations if the centerline of the tank
>is either somewhat above or below the needle valve, Can the
>position of the uniflow vent tube be positioned to give even
>engine runs in upright and inverted flight?
On the metal wedge tanks, the uniflow tube and the pick up tube are on the same center line (or nearly so). There is, thus, as much fuel above (when inverted) as there is below when upright. This results in constant pressure within the tank. When you move this uniflow tube up or down, you can vary the pressure from upright to inverted due to its location in relation to the fuel head. It will also not be as perfect as a uniflow as it would be if the uniflow tube followed the pickup, or the uniflow and pick up tube were otherwise affixed together.
That said, with the fixed uniflow tube location, you can vary the pressure somewhat from inverted to upright simply by moving the uniflow tube. This variance of pressure is not insstantaneous, however, and there will be more variation in this type of set-up than if you fixed the location of the uniflow halfway and moved the tank up and down to even the engine run.
>For example: a 6oz tank might be 2in. diameter and the tank
>is mounted up against the engine mounts the centerline of
>the tank is 1/2 in. below the needle valve for an inverted
>engine installation. With type 1 tank does it matter? with
>type 2 tank can the position of the end of the uniflow tube
>be positioned to give even engine runs in upright and
>inverted flight?
It does matter for both types of installation. If the uniflow tube follows the pickup tube, or is affixed halfway between bottom and top, then you will need to adjust the height of the tank to even out engine runs. If you rely solely on the movement of the uniflow tube as in the type 2 tank above, you can move the uniflow to somewhat achieve even engine runs, but in the case where the end would normally tend to run too rich, there will be a time lag, depending on the size and fullness of the tank as the pressure evens out through the establishment of a partial vacuum.
>
>If the rule of thumb for metal tanks is to have +/- 1/4in.
>vertical adjustment above and below the needle valve center
>line, would this also apply to the vertical adjustment range
>of a type 2 tank uniflow vent tube?
Yes, for best results.
>And, should the end of the type 2 uniflow tube be located
>slightly aft or inboard of the fuel pickup clunk range of
>motion along the outside wall of the tank?
Probably inboard so that it does not interfere with the motion of the clunk. Otherwise, as close as one can get to the "deepest" part of the fuel, the better.