Carburettor rocket...?

[dongfang]

Hi,

Did any of you ever try to build a rocket that mixed air and water, and exhausted that? I mean, as an alternative to using foam as a mix.

I can think of some quite simple designs, and I will try evaluate one of them soon. But does any of you others have any experience with that?

Regards
Soren

[Mark Chen]

Hi,

Did any of you ever try to build a rocket that mixed air and water, and exhausted that? I mean, as an alternative to using foam as a mix.

I can think of some quite simple designs, and I will try evaluate one of them soon. But does any of you others have any experience with that?

Regards
Soren

Tim and I tried to design a nozzle that would blow air through the center and it was supposed to draw water out with it as the air went out but we never got it working. The air would always blow a lot of the water up the side of the bottle away from the exit and it would drain out after the pressure was dropped to zero, so it was dead weight. With smaller air volumes it worked much better but this is most likely because the water was being forced out like a normal water rocket and the air was just injecting into the water stream. With a C/D nozzle it would possibly have an effect. We have tested it as a way to make foam and this seems to be the best use for it.

[dongfang]

Hi,

Can you make a sketch of it, or is it documented somewhere?

Regards
Soren

[Mark Chen]

Hi,

Can you make a sketch of it, or is it documented somewhere?

Regards
Soren

Here is a sketch. What it shows is a short tube running down the center of the rocket bottle body. The tube is held in place by a pair of bottle bottom claw sections with a hole drilled in them for the tube. The claw sections had large holes cut in them with a knife so they would not impede the flow of water out the bottle. The bottle sections were inserted through a splice in the rocket which I didn't show in the sketch. The central tube made from different materials in different tests because we did many diameters of this tube to try and get it to work. All parts were glued in place with PL Premium so they would not move.

The rocket used a cable tie launcher, so we could use a full size nozzle opening. We didn't think a smaller opening would work because it would choke too much.

Our tests found that different distances between the tube and the nozzle opening would give very different results. Different diameter tubes would also give different results. The best results we achieved were using foam with this design and a 10mm tube set back from the nozzle about 30mm.

Is this the kind of thing you had in mind?

[Tim Chen]

Mark, your drawing sucks. :P

[RaZias]

Where is a silly draw but I hope you get the idea.
I think that additional air enters lateraly into the water stream it will creat bubbles.
Anyway it´s just a guess.

[RaZias]

I have resized the same image for better visualization

[Spaceman Spiff]

I have resized the same image for better visualization

Scan10541.JPG

Both designs look like they have potential. Have you tested this or is it just in the idea stage? I think if you made the pipes longer so the side tanks were above the water level of the main tank then you could get rid of the non return valves because the water would only fill to the level in the main tank in each of the little tubes. When you launched the water would get forced out and air would follow. You would have to make sure the pressure in the air tanks did not decrease faster than in the main tank though or water would be forced back up the tubes.

Even if there's only a little bit of gain from this system I think it's great because I like the way foam makes a "smoke trail" of vapor in the wake of the rocket! This could make foam for sure. Cool to see you guys are testing new ideas that nobody has tried before!

[dongfang]

Hi,

OK since I got several designe revealed in detail, I'll do the same.

I am evaluating this one. Looks OK so far. It is simple....

There is a reason for the long exhaust pipe, but let me see first if it works....

Regards
Soren

[RaZias]

I have resized the same image for better visualization

Scan10541.JPG

Both designs look like they have potential. Have you tested this or is it just in the idea stage? I think if you made the pipes longer so the side tanks were above the water level of the main tank then you could get rid of the non return valves because the water would only fill to the level in the main tank in each of the little tubes. When you launched the water would get forced out and air would follow. You would have to make sure the pressure in the air tanks did not decrease faster than in the main tank though or water would be forced back up the tubes.

Even if there's only a little bit of gain from this system I think it's great because I like the way foam makes a "smoke trail" of vapor in the wake of the rocket! This could make foam for sure. Cool to see you guys are testing new ideas that nobody has tried before!

It´s just an idea in stage because I have little time and I am a noobie.
Anyway one day I hope to make carburettor rockets because I love do develop things.
Right now I am testing a " zip tie reinforced chamber " maybe in 1 month I have the results.

[Mark Chen]

Mark, your drawing sucks. :P

Well you were "too busy" to help! :P

[Tim Chen]

Hi,

OK since I got several designe revealed in detail, I'll do the same.

I am evaluating this one. Looks OK so far. It is simple....

There is a reason for the long exhaust pipe, but let me see first if it works....

Regards
Soren

It looks like you are using the venturi effect to suck water out the holes in the tube. My experience is that your design will work as designed but you can only use a specific pressure with it because if you don't have enough air in the reserve then the air is gone before the water is and you are left with extra water in the rocket after burnout.

[RaZias]

This is an idea for testing my design without needing to build all the rocket.
First it´s necessary to open the tap to release the water.
After the water is flowing freely then it´s injected the air.
See the draw.

[dongfang]

Tim,

It looks like you are using the venturi effect to suck water out the holes in the tube

That's exactly what happened in my first experiment, so now I have to try with more or larger holes, a real venturi throat, or to choke the inflow or air slightly to get the same effect as with the choke on a carburettor.

Regards
Soren

[Spaceman Spiff]

Tim,

It looks like you are using the venturi effect to suck water out the holes in the tube

That's exactly what happened in my first experiment, so now I have to try with more or larger holes, a real venturi throat, or to choke the inflow or air slightly to get the same effect as with the choke on a carburettor.

Regards
Soren

Are you trying to stop the venturi effect by choking the air flow? I don't understand. Did you mean what Tim said about running out of air with water left over?