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Golf ball challenge! Help appreciated.

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Marshmallow cannon GB precision test

Unread postAuthor: Technician1002 » Thu Oct 22, 2009 2:10 pm

I was out playing today. It's my weekend. I didn't build a sturdy stand or anything. I just leaned the barrel against a sawhorse and started lobbing golf balls.

According to GGDT my barrel is way too long for the pressure and small tank, and it performed pretty much as expected. Lots of balls failed to eject under low pressure and when I got the pressure up to where they did eject, they went pretty far. I expected this. I played some more with only loading the ball part way into the barrel to simulate a short barrel. The results are fantastic. Nice easy lobs, even some accurate 10 foot shots into a bucket. :D

I need to get more time to play, but I need to get to finishing up the sanding on the 2.5 inch barrel so it will be ready for my trip in a couple weeks to machine the piston for it.

Edit:
Played some more. The tight fit of golfballs in my GB barrel cause lots of variation in my shots. Low pressure distance is very hard to control. The shots vary by 15 feet at 10 yards, very poor repeatability. I'm thinking a foam (swim noodle) on the Tennis ball barrel will do very well. The volume will be too little to expel the sabot. The sabot will accelerate the ball in a very repeatable fashion and the ball would eject from the sabot still in the barrel. I don't have time to test it today. Maybe I'll make progress tomorrow.

Edit, I played some more today and had much better luck on precision distance shots. Due to the size of my yard, I setup for some 10 yard launches. The change I made is I used a larger barrel and a foam sabot. This permitted less air than will empty the barrel to be used. In all my testing the sabot was never ejected. I don't have a stand yet, so I was simply leaning it on a sawhorse. After I got the distance dialed in, I grabbed the camera with low batteries and got a quick shot. The distance was right on, but due to using the sawhorse, I missed the center and hit the rim of my garden cart. With a fixed stand this could easily put the golf ball in a bucket at 10 yards.

[youtube]http://www.youtube.com/watch?v=g496mBQox7Y[/youtube]
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Attachments
Tank Fill.JPG
First I took my torch post for soldering and added a ball valve and quick connect. This enabled me to fill an obsolete propane tank with air.
Field Kit.JPG
The field kit is the propane tank and a welding regulator with a quick connect added. I tried to remove the inlet POL fitting but failed. That is why the regulator has ugly wrench marks. :( I was going to simply put a quick connect on it so I could simply connect it to my compressor. With the small cannon and low pressure I got lots of shots :D
12PSI.jpg
Close up of the regulator set to 12 PSI. This pressure and below worked well with the golf ball part way down the barrel and is about the lowest pressure that ejected the ball at all when it was pushed all the way in.
foamsabot.JPG
Foam sabot made from a swim noodle
Golfball in sabot.JPG
Even at 45 degrees the golf ball sits in the sabot.
Frame before impact.jpg
Video frame grab of the ball on the way to the target.
Ball rebound.jpg
Next frame shows the ball rebounding off the edge.
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Unread postAuthor: mysticjbyrd » Wed Oct 28, 2009 6:26 pm

I like the Foam sabot made from a swim noodle. I had an idea of using some window and door foam, but scrapped the idea as I thought it would not compress evenly and would throw the ball off.

I then came up with the idea of making a piston out of wax. Cheap and can be molded to any shape.
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Unread postAuthor: Technician1002 » Wed Oct 28, 2009 8:02 pm

mysticjbyrd wrote:I like the Foam sabot made from a swim noodle. I had an idea of using some window and door foam, but scrapped the idea as I thought it would not compress evenly and would throw the ball off.

I then came up with the idea of making a piston out of wax. Cheap and can be molded to any shape.


When using the foam sabot, the key is low pressure. It is a gentle lob out to the target. It is not a power shot. 20 to 50 yards can be achieved by a good pitcher. A long barrel low pressure launch applies less force over a longer distance to reach the same launch speeds.

The swim noodle was a repeatability experiment for accuracy. Dropping balls within 1 foot of each other in distance was achieved at 10 yards. It should do well at 20-50 yards in a competition with a sturdy launch platform and precision alignment.

Edit; Friday It was raining today, so I played some inside and made a pop bottle golf ball sabot for the tennis ball barrel. It should compress less on higher power shots.

Edit Friday 30 October. Played some more with the pop bottles and found the diameter was slightly large so friction was a problem. Tried various water bottles. Met with sweet success with Talking Rain brand sparkling water bottles. They are just small enough to drop into my TB barrel without rubbing. I dialed the pressure on down and was able to bounce a few balls in the barrel with to little power to eject it. I found the pressure to lob balls out clearing the end by less than 1 foot. We have a high degree of power control now. The advantage of the lose sabot is it does not need shoved back down. It slides back by gravity between shots. To make the sabot I cut the top off and use the top as a sabot. Works like a charm.
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Attachments
Pop Bottle Sabot.jpg
Forming the end of a bottle to a golf ball.
Pop Bottle Sabot1.jpg
A nice pocket is formed. This may work well with eggs.
Pop Bottle Sabot2.jpg
This rides a little higher than I would like. I'll try again later to make a deeper socket.
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