Horizon - 2 Stage Water Rocket

Water Rockets NSW

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CATO
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Re: Horizon - 2 Stage Water Rocket

Postby CATO » Fri Jun 14, 2019 10:01 am

Hi George,

You need to put some chlorine in your pool mate.... :-)
"In thrust we trust"

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Re: Horizon - 2 Stage Water Rocket

Postby strud » Fri Jun 14, 2019 12:36 pm

Hi George,

Maybe to assist with mandrel removal, you can make up some flush or internal caps for the PVC mandrel, put some fittings in them and run a low (say 2 bar?) pressure on the tube during curing (with a vacuum sleeve/heat shrink etc) on the outer. Then after initial cure, drop the pressure from the mandrel then pull a vacuum (or maybe it's not required) to give you the reduction in diameter to assist with withdrawal.

Alternatively you could let the whole thing sit in the sun to cure (PVC expanded from increased temp) then remove from mandrel first thing in the morning or put in an cool room (AC) before removal.

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Re: Horizon - 2 Stage Water Rocket

Postby Aquaman33 » Fri Jun 14, 2019 3:09 pm

Another great video George.

A wonderful resource for anyone that has some sleeves on order! :D

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Re: Horizon - 2 Stage Water Rocket

Postby air.command » Fri Jun 14, 2019 3:42 pm

strud wrote:Hi George,

Maybe to assist with mandrel removal, you can make up some flush or internal caps for the PVC mandrel, put some fittings in them and run a low (say 2 bar?) pressure on the tube during curing (with a vacuum sleeve/heat shrink etc) on the outer. Then after initial cure, drop the pressure from the mandrel then pull a vacuum (or maybe it's not required) to give you the reduction in diameter to assist with withdrawal.

Alternatively you could let the whole thing sit in the sun to cure (PVC expanded from increased temp) then remove from mandrel first thing in the morning or put in an cool room (AC) before removal.


Interesting idea with pressurising the mandrel while it cures. I can check to see how much expansion you would get with a couple of bar. Easy enough to seal a PVC pipe with a couple of PVC endcaps. One advantage of being in vacuum sleeve is that you wouldn't need to put it on a rotisserie.

A couple of questions on post curing. Does the tube have to be on a mandrel when you do that? My concern was that if the epoxy glass transition temperature is below the curing temperature. Would a thin tube sag without it being on a mandrel? If the mandrel is made of PVC would that make the PVC also soft at the curing temperature?
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Re: Horizon - 2 Stage Water Rocket

Postby strud » Fri Jun 14, 2019 6:38 pm

Usually these epoxies will cure at room temp to some degree or maybe you need to ensure they get to say 40degC to have enough stiffness to be self supporting. At those temps you could still leave it on the mandrel ie after pulling it off and removing the glad bake etc

How would you heat that tube length?

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Re: Horizon - 2 Stage Water Rocket

Postby air.command » Fri Jun 14, 2019 7:05 pm

strud wrote:How would you heat that tube length?

I would need to build a custom heat box. These tubes are about 2.5m long.
I was just looking back through this forum and found some discussion about post cure: https://forum.ausrocketry.com/viewtopic.php?t=3841&start=45
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Re: Horizon - 2 Stage Water Rocket

Postby air.command » Thu Jul 18, 2019 9:15 am

Here is a video that describes the parachute deployment mechanism for the sustainer. The internal structure is mostly 3D printed. We tried 3D printing the nosecone outer shell as well, but found that the fiberglass is a lot stronger and lighter. The whole thing is designed to handle accelerations of 100G+.

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Re: Horizon - 2 Stage Water Rocket

Postby Aquaman33 » Fri Jul 19, 2019 8:15 am

The quality of your 3d prints look superb George.

What printer and filament are you using?

Did you do lots of finishing work?

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Re: Horizon - 2 Stage Water Rocket

Postby air.command » Fri Jul 19, 2019 8:36 am

Aquaman33 wrote:The quality of your 3d prints look superb George.

What printer and filament are you using?

Did you do lots of finishing work?

We are using the Maker Gear M2 (https://www.makergear.com/products/m2) We bought it because it had good print quality reviews (https://www.3dhubs.com/3d-printers/makergear-m2), though it is a little on the expensive side. We are pretty happy with how its been printing. We have only been printing with PLA so far but we do have a roll of ABS yet to try. We've tried a few different brands of PLA and I can definitely tell the difference in material quality.

We usually don't do any finishing work on the 3D prints other than perhaps drill holes to the exact diameter or occasionally file a corner to get to the right dimensional accuracy. We often will print a part to see if it is dimentionally correct, and if not we adjust it in the CAD and re-print.
We use Simplify 3D as the slicer / 3D printer controller.
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Re: Horizon - 2 Stage Water Rocket

Postby Aquaman33 » Fri Jul 19, 2019 11:45 am

air.command wrote:
Aquaman33 wrote:The quality of your 3d prints look superb George.

What printer and filament are you using?

Did you do lots of finishing work?

We are using the Maker Gear M2 (https://www.makergear.com/products/m2) We bought it because it had good print quality reviews (https://www.3dhubs.com/3d-printers/makergear-m2), though it is a little on the expensive side. We are pretty happy with how its been printing. We have only been printing with PLA so far but we do have a roll of ABS yet to try. We've tried a few different brands of PLA and I can definitely tell the difference in material quality.

We usually don't do any finishing work on the 3D prints other than perhaps drill holes to the exact diameter or occasionally file a corner to get to the right dimensional accuracy. We often will print a part to see if it is dimentionally correct, and if not we adjust it in the CAD and re-print.
We use Simplify 3D as the slicer / 3D printer controller.


Thanks George.

Looks like a great printer.

I try to get my parts right first time, but like you I often need to adjust the CAD and try again. Luckily its a fairly quick process.

I have been researching different types of PLA and the so called "PLA+". Very hard to get good info as each manufacturer likes to keep their ingredients a secret. So you don't really know what you are buying.

But I have heard lots of good reports about PLA+ from 3DFillies. They claim its "10x stronger than PLA". I think I'll give that a try when my current batch of PLA runs out. https://3dfillies.com/plaplus-filament-175mm-1kg

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Re: Horizon - 2 Stage Water Rocket

Postby air.command » Fri Jul 19, 2019 11:51 am

The PLA+ that I have I don't like. It seems to have quite poor adhesion to the bed, and even inter-layer adhesion didn't seem that good. Now perhaps I need to change some settings on the printer, but so far I am not impressed. I don't remember the manufacturer, I would have to check tonight. I did a few test prints with it, but haven't used it since.
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Re: Horizon - 2 Stage Water Rocket

Postby air.command » Wed Sep 04, 2019 9:58 am

During the launch at Thunda 2 we had a bit of an unusual failure with the sustainer. It bent quite severely during pressurisation.



Here is an explanation video of what we think happened:



We have almost finished the rebuild now, just need to do a hydro pressure test tonight and then give it few coats of paint. We are hoping to fly it at the end of the month at Mullaley to see if it experiences the same issues. Hopefully we can get it launched at 1000psi.
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Re: Horizon - 2 Stage Water Rocket

Postby Aquaman33 » Wed Sep 04, 2019 12:25 pm

Another great video George. Some awesome science.

I think the white paint and new orientation of the carbon is the answer, but have you considered cooling the water and the air before it goes into the rocket?

Not sure how practical this would be and whether it would make any difference.

Keep up the great work. Can't wait to see it in action at Mullaley.

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Re: Horizon - 2 Stage Water Rocket

Postby air.command » Wed Sep 04, 2019 12:44 pm

Thanks Derek,
We've measured the air temperature above the water level in a previous test, the air bubbling up through the cold water had virtually no effect on cooling the air above the water as that is where it is compressed. The air being released from the scuba tank actually drops in temperature, but it quickly picks up heat again as it passes through the hoses and manifolds so by the time it gets into the rocket it is more or less at ambient temperature again.

One option I was thinking is if you could create foam in the rocket by the air bubbling up through the water, that would fill the rocket with bubbles giving you lots of wet surface area all throughout the air volume. As you compress the air, the bubbles get smaller and heat up, but transfer that heat to the bubble walls.
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Re: Horizon - 2 Stage Water Rocket

Postby Aquaman33 » Wed Sep 04, 2019 1:35 pm

Bubbles is an interesting idea. Certainly better heat transfer than air.

Alternatively you could build a misting sprinkler system attached to your launch tower. Maybe run it off a small reservoir and a battery or solar pump. I acknowledge that this is somewhat ridiculous idea, but it will look awesome!

Perhaps a small scale version of this.


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