Easy to make "Internal" Grip Launcher

[SaskAlex]

Well, the reason I put "Internal" in quotation marks is that this isn't really an internal grip launcher. It's a no grip launcher. Nothing holds the bottle on the launch tube because there is nothing pushing it off. You have to use a spliced bottle, an FTC rocket, or something else that has an upper bulk head made from a bottle neck. The launcher seals on both the top and bottom bottle necks, so there is nothing pushing the rocket off as you pressurize. Check out the (quick) drawing below. Note that the main PVC pipe in the drawing is shown much shorter than it actually is. The rocket is placed over the launcher and the o-ring makes the seal with the upper bottle neck. Teflon tape must be used for the seal between the nozzle and the launcher, unless you wanted to put grooves for o-rings at a different spot for each rocket you use.

Pump air through the left schrader valve to pressurize the rocket, and then pump air through the right one to launch it. All this pressure has to overcome is the friction at the o-ring and teflon seals, and it only has to push the rocket up far enough that the top bottle neck no longer seals. From that point on, the internal pressure of the rocket will push it off the launcher like on any other launcher. With my pump and 25' air line this only takes two strokes.

This launcher certainly has some drawbacks- teflon seal instead of o-ring, can't launch a single bottle, etc., but it has some nice advantages. There is nothing gripping the nozzle, so you can put on any kind of fins or fairings that you want. Also, using a pump to launch instead of a pull string means you can't pull your launcher over.

This should also be very easy to make out of metal piping, which I plan on doing. So far, I've only had it up to about 100 psi since it's all PVC. One possible point of failure is the collapse of the 1/4" vinyl tubing under the external pressure in the launcher. I think it would take a lot of pressure to make that happen though. This is the stiffer white stuff, not the clear flexible tubing.

Let me know what you think,
Alex

[SaskAlex]

Well I've got the new metal version all done, along with a stand. It uses a four foot 1/2" galvanized pipe. Does anybody know of a better pipe than galvanized? It's just a little rough, and quite a tight fit, but it should do the job. So far I've only had this up to 100 psi as well, but I hope to get it up to 200-300 psi soon. Has anybody tried a teflon tape seal on the nozzle at high pressures? I think that is my most likely point of failure, but my fingers are crossed.

[RaZias]

Nice launcher, by the way...why you have 2 air inputs ? I have noticed in your last photo that you putted to hoses connected to it.

[SaskAlex]

Razias, it works the same way as the pvc launcher described above. The launcher seals on both the top and bottom bottle necks of your rocket (it has to be a spliced bottle), so as you pressurize with the first air line nothing pushes the rocket off of the launcher. The second air line is connected to a hose inside the launcher and creates pressure between the upper seal and the upper bottle cap. This is what releases the rocket.

As far as I know this is a completely new design. If that description is hard to follow let me know and I can make up some diagrams to explain it better.

Alex

[U.S. Water Rockets1]

Razias, it works the same way as the pvc launcher described above. The launcher seals on both the top and bottom bottle necks of your rocket (it has to be a spliced bottle), so as you pressurize with the first air line nothing pushes the rocket off of the launcher. The second air line is connected to a hose inside the launcher and creates pressure between the upper seal and the upper bottle cap. This is what releases the rocket.

As far as I know this is a completely new design. If that description is hard to follow let me know and I can make up some diagrams to explain it better.

Alex

This looks like a completely new idea. It's very clever too. The space above the o-ring in the top of the rocket becomes a low pressure area equal to the low pressure area under the nozzle and the two are in complete balance and cancel each other out. Adding the small amount of air to the upper o-ring area causes an imbalance that launches the rocket.

This is a great new idea! Thanks for sharing!!!!! This could be one of the biggest innovations to come along in the past 5 years or more!!! What do you want to name your invention???

[SaskAlex]

Well thanks for the positive reply USWR. If I had to name it I guess I'd call it a pneumatic release double seal launcher. I know that seems like a long name, but you could use the double seal method with other means of pushing the rocket up, like a lever that pushed on the nozzle. That might actually be easier to build for those who don't have a lathe because the top piece would be simpler.

Alex

[nonickname]

This is essentially a balanced spool valve which is manually unbalanced.

Clever, but I'm looking for something which will shoot a larger range of rockets.

[RaZias]

I guess i need a diagram to understand it.

[SaskAlex]

Nonickname- ya, it really is only good for certain people. For me right now, I'm almost exclusively launching heat shrunk spliced bottles, so it's great. And I still have my other internal grip launcher for single bottles, or if I want to play with T-nozzles, two-stage, etc.

Razias- I'm kinda busy the next two days, but I will try and get around to those diagrams soonish.

[nonickname]

Have you posted your other launcher here? I like internal grip launchers, and am looking for a nice one to make now I have my lathe.

[Spaceman Spiff]

I love this idea.... I'm gonna try it on my FTC test rocket because I have a double bottle end on it just like it needs! Cool!

[SaskAlex]

Have you posted your other launcher here? I like internal grip launchers, and am looking for a nice one to make now I have my lathe.

I made a website about my other launcher a long time ago. Forgive the poor graphics, I'm not much of an artist. That's not my latest version, I now have one that's basically the same but with a copper pipe inside of the PVC pipe so it can handle higher pressures. It's quite a bit of work to make, but it can launch anything with a standard bottle neck and requires no release cord. You just take pressure off of the air line to launch. [update- the website I mentioned no longer exists but I made thread about the launcher here http://www.wra2.org/forum/viewtopic.php?f=10&t=894]

On the topic of internal grip- other than USWR's twist and lock, anyone know of other types? I haven't really seen any.

Alex

[SaskAlex]

I love this idea.... I'm gonna try it on my FTC test rocket because I have a double bottle end on it just like it needs! Cool!

Good luck, and let me know how it goes. I should mention now that when I pressure tested mine the seal between the air hose and the aluminum piece began to leak at about 140 psi. The problem was that the hole I drilled in the aluminum piece was slightly too big and the glues I used just didn't seal it up well enough. I took it apart and made the top piece over again, this time with PVC. Super glue seems to make a real good bond between PVC and the air line, so this works great. I've tested it up to 200 psi and no leaks yet. I hope to get it up to 300 psi soon.

Lesson learned- with that internal air line glued in on both ends, you can't take the launcher apart once it's built. Make sure all your connections are good and get air-tight seals the first time around.

Alex

[U.S. Water Rockets1]

Have you posted your other launcher here? I like internal grip launchers, and am looking for a nice one to make now I have my lathe.

I made a website about my other launcher a long time ago. Forgive the poor graphics, I'm not much of an artist. http://www.geocities.com/af_wr/. That's not my latest version, I now have one that's basically the same but with a copper pipe inside of the PVC pipe so it can handle higher pressures. It's quite a bit of work to make, but it can launch anything with a standard bottle neck and requires no release cord. You just take pressure off of the air line to launch.

On the topic of internal grip- other than USWR's twist and lock, anyone know of other types? I haven't really seen any.

Alex

With higher pressures, we had to add more lobes to our launcher to distribute the force more evenly. Putting it on only 2 small lobes caused too much stress at high pressures. It works fine for standard rockets but it's a lot of work to modify a bottle neck and then have it get ruined in a crash, so we made a version that grabs a screw-on nozzle that can be swapped out to other bottles when one gets ruined.

[SaskAlex]

Have you posted your other launcher here? I like internal grip launchers, and am looking for a nice one to make now I have my lathe.

I made a website about my other launcher a long time ago. Forgive the poor graphics, I'm not much of an artist. http://www.wra2.org/forum/viewtopic.php?f=10&t=894. That's not my latest version, I now have one that's basically the same but with a copper pipe inside of the PVC pipe so it can handle higher pressures. It's quite a bit of work to make, but it can launch anything with a standard bottle neck and requires no release cord. You just take pressure off of the air line to launch.

On the topic of internal grip- other than USWR's twist and lock, anyone know of other types? I haven't really seen any.

Alex

With higher pressures, we had to add more lobes to our launcher to distribute the force more evenly. Putting it on only 2 small lobes caused too much stress at high pressures. It works fine for standard rockets but it's a lot of work to modify a bottle neck and then have it get ruined in a crash, so we made a version that grabs a screw-on nozzle that can be swapped out to other bottles when one gets ruined.

Actually, there are four lobes, itls just difficult to see in the pictures. I haven't had any problems yet with pressures up to 200 psi and regular bottle necks. But I did think I might start runnig into problems with higher pressures, and that's mostly why I built this new launcher. The screw on nozzle idea is really cool too.

Alex