# Air flow splitting in two directions

• Misc.

## Summary:

I need this pump to fill up two balloons at once, somethinf is wrong with the airflow?

## Main Question or Discussion Point

Basically the air pump on the left turns on and when it does, the balloon on the right fills up but the other does not. I also tried putting the pump upright but the left one just doesn’t seem to fill? Any ideas of why? There’s no air leak or blockage or anything

#### Attachments

• 171.1 KB Views: 69

256bits
Gold Member
If you have ever tried tried to blow up a balloon by yourself, it gets easier as the balloon gets bigger.

Spinnor and Lnewqban
phinds
Gold Member
2019 Award
Try constraining the expansion of the one on the right and see what happens.

What you need is a pneumatic flow divider. It lets equal amounts of air through both branches when a line splits.

Tom.G
From:
http://scipp.ucsc.edu/outreach/balloon/labs/InflationExp.htm

As you can see, and @256bits said above, the required inflation pressure is highest at the start of inflation. As soon as one balloon starts to inflate the pressure decreases and, due to the variations between balloons, when one starts inflating it keeps the pressure low enough that the other one can't inflate.

Cheers,
Tom

Rive and Spinnor
... Any ideas of why?...
I would try switching the locations of the balloons.

If the pink balloon still fills up first, being on the left side of the tee, the problem may be in slight differences in the thickness or material of the walls, since each baloon, being of different color, may have been manufactured in different machines or by different processes.

If you could stop the air pump and still keep some pressure in the system, the value of the static pressure inside the plastic hose, tee and each balloon at zero air flow should be exactly the same.

Last edited:
russ_watters
Averagesupernova
Gold Member
Experiment: Blow up a single balloon. Take a short length of pipe that the neck of a balloon can slip over and seal. Slip a deflated balloon over one end of the pipe. Then slip the inflated balloon over the other end of the pipe while pinching the neck to prevent deflation. Now release the inflated balloon allowing it to drain into the other through the pipe. My guess is it won't inflate the other balloon which would support what is said in post #2 causing the imbalance.
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I think an orifice in-line with each balloon would balance things out assuming your pump is able to build enough pressure to get a significant drop across each orifice.

berkeman
Mentor
If you have ever tried tried to blow up a balloon by yourself, it gets easier as the balloon gets bigger.
Try constraining the expansion of the one on the right and see what happens.
It's kind of fun to think up mechanisms that could be added to the setup to ensure that both balloons end up fully inflated. Since the poster seems to be doing a home science experiment, maybe it's a good exercise for them to try to think up some ways that the setup could be made to work with some additions to it.

@Gurleen -- can you come up with a couple ways that you could add to your setup to make both balloons blow up?