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Water Rocket Launcher

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Gary Lewis

Water Rocket Launcher

Administrator

No, it isn't a Ford. But the vision was planted in my brain (thanks, Paul) right here on the forum, so what better place to record it?

The plan is to make a rocket launcher, as shown in the link below, with my grandtwins. And then to make rockets and fire them.

Here are the documents that would be good to read:

Water Rocket Launcher

Water Rockets

All About Water Rockets

Water Rocket Construction

Gary, AKA "Gary fellow": Profile

Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI

ArdWrknTrk

Re: Water Rocket Launcher

Administrator

"Plugin not supported" sigh....

I hope your whole family can have fun with this Gary!

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Water Rocket Launcher

Administrator

Yeah, my computer didn't like it either.

But I do hope with you that the whole family can have fun with it. Thanks!

As for what I did today towards that, I gathered the parts I have, bought most of the rest from the hardware store, and did some modification for the rest.

The stoppers the parts store has are w/o hole. So I put the one I got in the lathe and drilled a hole in it, a bit smaller than the 1/4" of the barb that will connect it to the hose.

And another thing the store didn't have was rubber bands. Not to fear, an old bicycle inner tube will suffice there.

Last, I need some way to attach the new tire pump to the hose, and preferably with a Schrader valve. But, the store didn't have what I needed so I made one. I took a valve stem and cut the rubber off it and got down to the brass stem. That measured .234" when I got done. And I had a 1/4" hose barb fitting, which I drilled out to .231". I then coated the inside of the barb and the outside of the stem with blue Loctite and tapped them together. Looks like this:

Now I have to find some plastic pieces for the fins. Any suggestions?

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Water Rocket Launcher

Administrator

Any Loctite primer?
Don't these things take ferrous/ferric ions to catalyze?

Foam from a butcher tray?
You don't want thin, sharp plastic.
obviously cardboard won't work if you think you're going to launch them off the boat.

Swing test is good for empty stability but at launch, water is to the rear.
Silly Putty or Plasticine may stick to the front of the bottle to add weight forward.

You might try 3 v/s 4 fins.
4 fins will add 33% more correcting force for a given planform, but will add the frontal and surface area to drag as well.

Maybe it's deep for a nine year old to understand TNSTAAFL.
That there are always consequences along with advantages.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Water Rocket Launcher

Administrator

I don't have any Loctite primer. But the Loctite set up. How do I know? Because the first round I started to put the pieces together the wrong way 'round. Had them just barely started and realized that the hose barb was pointing the wrong way.

But the barb didn't want to come off. It'd been maybe 3 minutes when I realized it, so I was sure it couldn't have set up. I got a drift and tapped them apart, which wasn't easy, and then had to scrape the hardened Loctite off of the parts.

There's plenty of interference in the fit, so the Loctite is really just to ensure it seals. And it certainly did. I pulled a vacuum on it and it held.

As for the fins, I've discovered that we have several 1 gallon water and milk bottles. And they have flat panels on the sides that will work nicely. Easily cut, thin but not brittle, and the hot-melt glue will probably adhere to them nicely. And, I'd planned on 3 fins.

Hadn't thought about the weight, but Silly Putty would work nicely. Thanks!

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Big Blue's Transformation

Administrator

You only have a few days until your family arrives, and Big Blue takes a back burner.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Big Blue's Transformation

Administrator

Yes! And by then the shop has to be clean as we are going to build ROCKETS! And, I hope to take them to the lake to shoot them off.

Ordered a bicycle tire pump that is to be in on Friday. Going to the hardware store tomorrow to get all of the parts in the NASA parts list for a water rocket launcher. I think they'll enjoy making the launcher as well as turning the several 2 liter pop bottles I've scrounged into rockets.

Initially I was a little surprised at how NASA designed it. It is hard to tell from the illustration below, but the hose runs through the tee (9) and the top nipple (8) and connects to a barb splicer which also holds the stopper. So, why not connect the hose to a barbed fitting at the inlet to the tee and then use a similar barbed fitting on the top of the tee instead of the nipple?

And then I realized several problems with that. First, you'd have to seal the bottom of the tee where the other nipple is. Second, they adjust the interface of the stopper and the bottle by screwing the nipple up or down. But that wouldn't be easy if you'd tightened it all down.

So, I guess I'll build it as they suggested. However, I doubt I'll use all brass components.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Big Blue's Transformation

Administrator

Maybe you can even get them to sit still for a real rocket launch!?!? (Insert teachable moment here)

Don't bore them too much. Maybe T-15:00, or even 10

Explain to them that this is the first time a private company has sent man to orbit in the International Space Station.
And for eight long years we've had to pay the Russians $85M each, to get our astronauts to space.

The booster recovery is always exciting too!

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

ArdWrknTrk

Re: Big Blue's Transformation

Administrator

In reply to this post by Gary Lewis

You could build that with threaded sch-40 PVC for $2.
I don't think you can get a floor flange though.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Nothing Special

Re: Big Blue's Transformation

In reply to this post by Gary Lewis

I made a bottle launcher similar to that to use with Cub and Boy Scouts. But mine has a Schrader valve so I use an air compressor on it.

How old are your grandkids? With older Cub Scouts and Boy Scouts (say above about 8) it was a lot of fun to put a tennis ball on top of the bottle. The much denser ball carries much better than the bottle, and the boys loved trying to track it and catch it (I don't think they were ever successful!).

We also experimented with how much water was in the bottle. A bottle more than half-full seemed rather sluggish. Going all the way down to no water seemed to improve the height, and certainly the launch velocity (the tennis ball went higher!). But no water was louder (which bothered only the adults with tinnitus) and no water wasn't as messy (so the kids liked it better with water)

Bob
Sorry, no '80 - '86 Ford trucks
"Oswald": 1997 F-250HD crew cab short box, 460, E4OD, 4.10 gears
"Pluto": 1971 Bronco, 302, NV3550 5 speed, Atlas 4.3:1 transfer case, 33" tires
"the motorhome": 2015 E-450-based 28' class C motorhome, 6.8L V-10
"the Dodge": 2007 Dodge 2500, 6.7L Cummins

Gary Lewis

Re: Big Blue's Transformation

Administrator

Jim - I'll check out the brake line and see if it'll go in that clip. Thanks.

As for the Sched 40, if they have it I'll get that instead. I don't think the material makes much difference as there won't be much force there.

Bob - They will be 9 in August. And they are very inquisitive, so they should really like this.

I'm going to put a Schrader valve in the end of the hose so we can clamp the air pump's hose to it. And I'd use my air compressor, but want to be able to shoot them off at the lake, so will use the pump.

The tennis ball is a good idea, but I'm not sure we have any old ones around here. The last one we had was used for firing Coke cans using fire crackers.

However, some instructions I've seen say to put a bit of ballast, like clay, in the very nose of the rockets. Most cut another bottle and glue the part with the lid on the top of the rocket's body to have a more pointed end, and they put the ballast right at the cap.

Noise? Are these things noisy? I didn't expect that.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Big Blue's Transformation

Administrator

It doesn't matter that it's *specifically* schedule 40, just that's what you'd find at a hardware or box store.
The important thing is that it threads so you can adjust the stopper force.
If you use plastic put a bit of Vaseline on the threads like antisieze, so they don't get stuck.

With REAL rockets that don't have vectored thrust and active guidance it is very important to have weight forward.
Specifically the CP - CG relationship.
In hobby rocketry the safe rule of thumb is the balance point should be one rocket diameter ahead of the center of pressure.
This makes for stable liftoff, before the fins can act as a correcting force.

For an example of this, go out in the yard and try to throw a sledgehammer handle first in a safe direction.

But water rockets aren't likely to fly through you, set fire to anything, or blow up if they hit something.
A little squiggle while they gain speed enough to stabilize might be fun!
You also might try canted fletching like I pointed out to Bill.
Arrows work this way, as do bullets from a rifled barrel.
Spin not only is stabilizing gyroscopically, it averages out any vectored thrust from the nozzle.

Is it noisy if you trip the blow-off of your compressor?
Sound is just pressure waves.
Shake up a bottle of pop and listen to the hiss when you crack it open.
Now put all that hiss into a microsecond, and increase that pressure (sound pressure) to however high you can pump it up.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Big Blue's Transformation

Administrator

Good tips on the construction, thanks.

On the balance, weighting, etc, we probably won't have as much time on the lake as shifting things would require. They'll want to ski as they just learned how last summer, so we may want to add the ballast before going.

However, if we were to use tape instead of hot-melt we could pull the "nose cone" off and add weight. Or, we could pour weight into the nose cone via the cap if the weight was something like sand. Hmmm...

As for the noise, I was hoping that expelling the water would both take time as well as break up the "crack" of releasing air at ~50 psi. (Yes, popping the hose off the disconnect at 120 psi certainly has a "crack" to it.) Not that having a bit of noise is a bad thing, but I don't want their mother (our daughter) to object.

Gary, AKA "Gary fellow": Profile

Nothing Special

Re: Big Blue's Transformation

In reply to this post by ArdWrknTrk

Like Jim says, suddenly releasing compressed air isn't silent. With no water in the bottle it's like popping an air hose off under pressure. With water in the bottle it doesn't release as suddenly. But if I was near the launch pad (as I almost always was) I'd plug my ears. And we usually tried to have a pair of ear-muff-style hearing protectors (as well as safety glasses) for whatever kid was actually pulling the release.

The first time we launched rockets we used clay to weight the nose, and made nose cones and fins out of heavy paper (I think we used file folders). That was fun for the kids but took almost all of the 1 hour Cub Scout den meeting so we only got to launch each kid's rocket once.

The next time we just used plain 2 liter pop bottles (yes "pop", I'm from Minnesota). We got to do a LOT more launches and the kids enjoyed that more, so we never bothered making rockets again.

With the weighted nose, nose cone and fins the bottles definitely flew better. They went straighter and higher, and came down straighter and faster. The adults were a little more concerned about a rocket hitting a kid as it landed (because the kids definitely will want to chase the rocket as it flies). Personally I think the chance of the kids getting hurt by tripping as they ran was WAY higher than the chance of getting hurt by being hit with the rocket, but moms don't always see it the same way.

With the plain bottles they still go pretty high, but they do start tumbling pretty soon after they leave the launch pad, so they slow down pretty quick. And no one is afraid of getting hurt by an empty 2 liter bottle! (so the moms can focus on the real dangers of tripping or running into each other

) But as they get a little older having the more aerodynamic tennis ball does increase the fun (and it doesn't have to be an old one, stop at a Wal-Mart or something and pick up a can).

Still, I'd encourage you to make rockets the first time at least. That way they'll have that experience and you can let them have fun while learning physics. But I'd bet you'll end up just shooting off empty bottles eventually.

ArdWrknTrk

Re: Big Blue's Transformation

Administrator

In reply to this post by Gary Lewis

You wouldn't want something solid for a nose weight (too dangerous) but I have used tungsten 12Ga. slugs under MUCH stricter guidelines and distances that water rockets.

Maybe you could pour something like gelatin (Jell-O) into the nose?
Safe at those velocities.
Kids might like that, but messy when they land.
But a truly empty soda bottle has a mass to surface ratio that makes for a slower decent.

The water takes time to escape, so it's more of a woosh than a crack.
The denser the ejecta the better the thrust from a rocket.
You don't have an expansion (DeLaval) nozzle, so it's less important.

If you ever have rocket geek questions, I'm here to offer my best answers.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Big Blue's Transformation

Administrator

In reply to this post by Nothing Special

Well, it does seem like from what you are saying tht the noise will be loud enough to be a concern to their mother. But, surely it is less than a firecracker?

As for the rocket itself, part of the project will be to "build" them. We'll use the work table in the shop to cut, glue, tape, weight, whatever. And, I'd better find some styrofoam to make the fins out of as paper is gonna get wet in a hurry at the lake.

I think I have enough bottles to allow each kid to make two rockets - one with a nose cone and one w/o. So we could make the one with the nose cone as a "high-altitude" one with good fins and ballast, and do the other one with a blunt nose and put tennis balls on them - assuming they'll stay on while the boat rocks a bit.

Yes, a sleeve of tennis balls doesn't cost much, so I may add that to the mix as well.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Big Blue's Transformation

Administrator

In reply to this post by Gary Lewis

Your daughter doesn't object that you're setting of firecrackers with an accelerant under a metal projectile?

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.

Gary Lewis

Re: Big Blue's Transformation

Administrator

In reply to this post by ArdWrknTrk

Ok, once the 2nd cuppa is downed I'll print the list, head to the shop to check that I have the Schrader valve, look over the other plumbing parts I have, and then head to the hardware store.

It is gonna be fun!

Gary, AKA "Gary fellow": Profile

Gary Lewis

Re: Big Blue's Transformation

Administrator

In reply to this post by ArdWrknTrk

No, but she usually stays in the house or at least 50' away. In this case she'll be in a 25' boat, and while she can retreat to the bow, or even on an air mattress in the lake, she's not going to be too far from the swim platform/launch pad.

Basically, Pop-Pop is the dare devil and is the one that introduced her kids to driving a ZTR, going offroad in Rusty, setting off firecrackers, etc.

Gary, AKA "Gary fellow": Profile

ArdWrknTrk

Re: Big Blue's Transformation

Administrator

In reply to this post by Nothing Special

Great post, with lots of real world information!

I'd bet Matthew has done this with his boy scout troop a bunch of times too.

Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.