Water Injected Tennis Balls

Post questions and info about safe and unsafe materials that can be or should not be used to construct a launcher. Also post things about different universal accessories for your cannon (breech loader, muzzle break, etc.)

Postby Velocity » Sun Apr 30, 2006 8:55 pm

Today I went out to shoot my dual supah valve+ cannon out at an abandoned field. The ammo was tennis balls that were slightly deflated. The distances achieved were not good at all... the maximum with a tennis ball was over 150'.

I did not water inject them before hand for a few reasons.

1) The tennis balls would not fit inside of my 2.5" sch. 40 barrel with water in them; they barely fit even without water (it was a HUGE struggle to get them in the barrel, even though they were loaded in the breach!)

2) I did not have proper means of filling them with water... No hypodermic needle was availible, so I would have to cut them with a knife and fill them with water from the hose nozzle... which would yield unpredictable results and would undoubtedly leak.

3) I did not think that it would be necessary for great distances.


Well next time I go out, I will use my 6' long, 3" sch. 80 barrel, and use a hypodermic needle to inject the water.

But I have a few questions. As this cannon was for a school project, I would appreciate answers that were explanatory, scientific, and intelligent, not just "because" or "yes".

1) Why does an "empty" tennis ball travel such short distances?
2) Why would a water-injected tennis ball travel farther?

These next two questions are just general questions, not for school

1) Does anyone experience an overly tight fit of tennis balls in 2.5" sch. 40 PVC pipe (the brand in Harvel)?
2) How much greater DOES a water-injected tennis ball fly then an "empty" tennis ball?

Thank you SOOO much for helping me out here :D!
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Postby ryanpowell167 » Sun Apr 30, 2006 9:28 pm

I know the answer for first qeustion 2.
They fly farther because they are heavier and more muzzle energy can be imparted onto them. They have more inertia from the weight... Dont know the others because ive never really owned a TB barrel, that stuff is rare here...
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Postby Orbit » Mon May 01, 2006 10:32 pm

The heavier it is = more pressure built up behind it = farther shot.
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Postby sgort87 » Mon May 01, 2006 11:34 pm

Not quite. Generally there is a smaller muzzle velocity of larger-mass projectiles because they are harder to move. But just because of that fact they keep their speed much better than less-dense objects. Because of the larger mass air resistance has a significantly smaller effect on the velocity of the ball resulting in a much farther flight.

As for the other question harvelplastics.com says their 2.5" sch 40 pipe has an ID of 2.445". A tennis ball is said to have an OD of 2 1/2 to 2 5/8 so there's your problem. Your balls are too big and your pipe is too small. Hah...
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Postby saladtossser » Mon May 01, 2006 11:38 pm

not fitting? burn the hair off it.
who was it that did just that?
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Postby Ian2accurate » Tue May 02, 2006 4:03 pm

Its not necessarily the weight that affects it directly, but the density. A tennis ball is filled with air so it is not very dense, and so (as Gort said) it would be more heavily impacted by its drag. The hair on a tennis ball is meant to slow it down quicker (ie. more air resistance) so it will stay to the ground and such in a tennis match. You could wrap it in tape or something, but since its already too big, I would just singe the hair off.
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Postby BewareOfDog » Tue May 02, 2006 7:11 pm

<b>I did not water inject them before hand for a few reasons."</b> :

1) By putting a long chamfer on the inside of your barrel, it wil allow tennis balls to be loaded very easily. I've been doing this on all of my tennis ball combustions for a long time.
<center><a href="http://img.villagephotos.com/p/2003-9/398596/untitled.JPG">Example</a>
</center>
This is easily accomplished with a large, <a href="http://www.demaxindustry.com/pic/product_1033003172.jpg">Half-Round Wood Rasp</a>.

If your breech loading, then I assume that you're using some type of threaded adapter? -The I.D. of the threaded portion of the adapter is slightly smaller than the I.D. of the pipe itself, so that may be yet another one of your problems.

2.) Threading, or epoxying, a basketball needle into a 3/4" PVC Female-Threaded cap works great for filling tennis balls. Simply thread the modified cap onto a 3/4" pipe nipple, and use a garden hose-3/4" adapter on the other end. (TURN THE WATER ON S-L-O-W-L-Y), unless you want to inject water underneath your skin! :x

Sharpening the end of the needled with a file or someting similiar will alow the needle to poke right into the ball.- Do it slowly and carefully with each ball, or the needle will undoubtedly break.

3.)It is necessary. <---Period


<b>"These next two questions are just general questions, not for school"</b>

1) Yes, mostly all brand-name tennis balls have a lot of fuzz, and are an extremely tight fit inside of 2.5" SCH40 pipe. As another suggestion, buy some "Fun Balls" at Wal-Mart.- They come in a package of 20, and are of different colors with smiley faces on them.
They're less than $5 for 20, have little fuzz, and practically load themselves.

2)Depending on your barrel length, I've found that they'll go about 1-1/2 to 2 times farther, than an empty one.
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Postby billy_bob_95 » Thu Jul 20, 2006 4:02 pm

The best fit I have found for tennis balls is to take a piece of 3" sch 40 pvc and sleeve it with another piece of 3" sch 40 pvc. The way I done this was to cut a piece of 3" pvc the same length as the barrel on the spud gun, and then using the table saw cut a 1/2" to 1" strip (I didn't acutally measure this just a guess)out of the pvc the entire length of the pipe. I then used a c clamp to compress the end of the pipe together, and got it started down the 3" barrel. Once I had the end of the pvc in the barrel I removed the clamp. To my surprised all it took to get the pipe pressed in the barrel was several good smacks with a hammer. It went in rather easy. After I had the pipe drove all the way into the barrel I used the miter saw to trim the end of the barrel since it was a little damaged from the hammer. Tennis ball now fits snug in the barrel, but it not a fight to get it in the barrel. I think it will fit snug enough I haven't got a chance to test it yet living in the city and all. Also if you are looking for used tennis ball to use as ammo check e-bay. I got 110 balls for about .34 a ball shipping and all. They looked almost brand new and should be easy to find and reuse.
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Postby Freefall » Thu Jul 20, 2006 4:29 pm

There are different types of tennis balls.

Commonly, you'll see "regular" or "extra duty" felt. The extra duty felt is thicker, and so will be more difficult to fit in your barrel.

Less commonly, you may find slightly oversized "Type 3" balls, intended to slow the play on fast courts. The most common type 3 ball is Wilson's "Rally" ball. Avoid these, as they will be extremely tight. Look for "Type 2" balls instead.
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Postby c0mpl3x » Thu Jul 20, 2006 4:48 pm

DR, i prefer a <br><br><img src="http://www.tool-up.co.uk/tooldev/images/items/15505.jpg"><br>half round mill bastard as opposed to a wood rasp, the smaller files will work in a 1/2" pvc pipe for chamfering, too 8)
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