16 replies to this topic

[Vicious-V]

Damn, haven't been here for awhile...I hope this is Nerf-related.

I'm going to be building a tennis ball mortar. It'll use a 100lb. spring. The cocker will have a foot pedal so I can just stomp down on it to cock it. The whole thing will be made out of metal. I have a few questions though.

1) What should I use for the trigger catch and trigger system that can handle a 100lb. spring?
2) The tennis ball fits pretty tight in the barrel, will the plunger be able to propel it?
3) What should I do to make this airtight?
4) What should the size of the plunger be for maximum performance?
5) What should I put at the end of the plunger so the slam won't snap apart the whole thing?

Thanks...

[pat 1st Lt]

1) Some type of metal, I assume. PVC can't handle it, wood probably wouldn't work very well, so go for some type of metal bar.

2) Yes.

3) I think you shouldn't use a plunger: I think you should just have some kind of foot-pedal that would depress the spring. The spring would have some kind of follower VERY FIRMLY [i][u]attached to the end, which would be curved to accomodate a tennis ball. And it would be housed in whatever your barrel material is, and then house that in the next biggest size of PVC pipe, and house that in the next biggest size, so that if it breaks it won't send giant shards of pointy death flying hundreds of yards. So, you'd put a tennis ball in, push the spring down, and let go.

4)See above.

5)See above.



Your welcome.



Sincerely,
Pat

[Vicious-V]

I don't get what you're saying...You mean to ram it?

[z80]

Just buy the book "Backyard Balistics" and build the tennis ball mortar, its a basic combustion based ball shooter.

[davidbowie]

Don't buy the book. You already know how to build a basic tennis ball combustion. Just do that.

Why do you want to make a springer?

Depending on how much money you have, you might be able to get a supah and get some real power. Even a modded 1" sprinkler might be enough for your purposes.

[LastManAlive]

And don't use the combustion idea in the book either.

Do this.

Find a size of PVC that a tennis ball can fit inside of. Take a tennis ball to the hardware store and find the right size. You want it to be tight enough for the ball to barely fit or loose enought that the ball falls out. Aim for about 1/4 of an inch or less of clearance for the ball.

You need to next find a peice of steel pipe that the PVC fits in. Again, tight enough to get in with very little clearance. You want to get a tight as you can but stil be able to get it in the steel. Have the steel cut to about 3 feet long.

To keep the PVC in there snug as a bug, get a very strong glue too. I am just guessing, thus I am open to suggestions on a better glue, but get some Epoxy. Either ask someone at the store for Epoxy glue, or look by the duct tape, paint primer and other glues in the stores.

Before you leave the store, find a screw on cap that fits the Steel pipe (both ends of the pipe should have threads on them) as well as a steel nut if the cap doesn't already have a nut like structure on the outside (like a PVC cap). This will be so you can get the mortar open with a pipe wrench...BTW, get one of those too if you don't have one. But wait, you will need propelant!

You need to go to the gril seciton of the hardware store you are at. You need to find a reploacement grill lighter. I suggest the manual one, not the electric one. As for propelant, suggestions are open as well here, but I have used AquaNet level 3 fragranced hairspray. It seems to work best.

Checkout and get back home to assemble this bad boy.

Now, take your steel pipe which you had cut to 3 feet, and cut the PVC to the same length making sure to stand them both up and measure them. You may even want to have them cut this in the store for you too if you are at an Ace hardware.

You first need to cut 1 foot of the PVC off. You now need to put a layer of PVC cement (taking you have some) on the inside of the PVC. Make layer after layer until the tennis ball is stoped in the PVC by the cement.

Now, have someone hold the steel pipe sturdy for you, and have the epoxy mixture (or other glue mixture) ready to apply. Put the foot long peice of PVC at the bottom of the steel (the theaded area) and start applying the glue mixture inch by inch while you slide the PVC into the steel pipe making sure to twist it as the inches go into the pipe. Make sure that you are puting it in with the layered cement first. Do the other peice as well going thorugh the other side of the steel. When the PVC is all the way in, finish the gap left in between the PVC and the steel.

Now hou are ready to get the cap and trigger prepared. Take the cap and epoxy the nut to the outside in the center as best you can. Drill 2 holes about 1/8 of an inch apart in the hole in the nut. Now, with the little bit of epoxy left over, and put the two wire ends from the grill igniter into the holes and epoxy them in. Make sure you get a spark when you press the button on the igniter.

You are ready to shoot!

Place the ball in the end of the barrel and let it hit the cement ring. Now, spray the hairspray in the chamber for 3 seconds, and spray it real quick 3 more times. Twist the cap on all the way real fast, and fire.

Now, with the pipe wrench, screw the cap back off fast. NEVER leave the cap on there. Hair spray can glue it in place. When you are done shooting it, take the cap off and take the gun to a hose. Spray the whole gun down including the threads with hot water.

Hope it works for you. I also hope you don't blow your hands off in the process...if you do, don't blame Nerfhaven. Blame me.

I used this method for making my potatoe gun minus the use of the steel, but htat is just to keep the PVC together.

[NinjZ]

Combustion itself is a bad idea. I have seen my share of exploded spud guns. My one friend lost a finger from it. use compressed air, it's easier.

[davidbowie]

A well-built combustion cannon is extremely safe. The thing is, people who build combustions tend to know less about spudguns, and build unsafe cannons. A basic propane combustion built with solid-core SCH-40 pressure rated pipe and fittings and properly solvent-welded (cleaner, primer, glue, half-twist) will be safe.

[LastManAlive]

That's why I said to use steel pipe. Hairspray shouldn't make that much sombustion to blow steel apart.

Besides, I have never messed with propane, but I see that it is being used more now.

I noticed that Tippmann has made a pump action propane paintball gun.

I guess if you use the right ratios on the gas, it would be safe.

[davidbowie]

Quote

I guess if you use the right ratios on the gas, it would be safe.

Too much propane will make for a WEAKER combustion, not a chamber-shattering blast. There's NO WAY a standard combustion cannon will generate more than 120 psi at normal atmospheric pressure.

The reason people think PVC combustions are unsafe is usually because you see a lot more grenaded combustions than pneumatics. The thing is, these failed combustions are almost always badly made.

[LastManAlive]

I believe that people feel unsafe about combustion blasters, is that they ahve seen one go wrong. In fact I have.

I have seen a nice 15 foot radius cleared out by a black powder spud gun have a "tater" stick in teh barrel.

I don't know how it actually got stuck, but it did. He poured some black powder in the designated area, and lit a cherry bomb in the designated area. I got the hell out of dodge.

I have also had my own "tater" gun have a mishap. I once didn't screw the cap on tight enough and my friend suffered from a flame to the eye area. He didn't have any eyelashes or eyebrows for 2 weeks on his left eye.


Make sure you do these things correctly, because they CAN be dangerous.

As to the compressed air method, it is safer, but it is not nessisarily easier. You need a GOOD seal to the air chamber, you need a fairly large air tank to house enough air to lauch a projectile like a tennis ball, and you also need a good seal in the barrel much like a nerf dart or you will most likely get nowhere. Getting these things are fairly easy, but to get them to work together, it can get fairly difficult.

It is your disicision though. Pick whatever method you like best for your mortar. Good luck!

[davidbowie]

BLACK POWDER!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?!

Well no wonder!!!!!!!

[Vicious-V]

I already know how to build combustions LastManAlive...The reason I want to make it spring-powered is so that I don't have to worry about compressing air or getting the right fuel mixture. It gets boring having to refill or refuel after every shot.

So can you help me with building a springer?

Edited by Vicious-V, 01 July 2006 - 01:05 PM.

[davidbowie]

Spring power gets a whole lot harder at that size.

Instead, you should build a one-touch propane system like on Sgort's Proton Pack or Boogie's RevolverX, which can be found here:

http://advancedspuds.com/revolverx.htm

It has a vent fan/check valve, propane meter, ignition system, and chamber fan, all controlled from a single project box. The revolver stuff isn't necessary, but you should check out these specific parts:

http://advancedspuds.../checkvalve.htm
http://advancedspuds.com/revxfan.htm
http://advancedspuds.com/revxfuel.htm
http://advancedspuds.com/revxspark.htm
http://advancedspuds...electronics.htm

It would be even easier to operate than a springer, and much cooler. You should take this over to Spudtech, and they will be more helpful if you do decide on combustion.

[Vicious-V]

Yeh, I've been registered there for awhile now...I guess I'll just make a combustion or hybrid.

[kaiman299]

I don't get why everybody is saying to make it combustion. He can do most anything if he puts his mind to it!

Ok for your trigger, I would go with an oversized double clothespin trigger. I would use those big siczor clamp things, put a hole through the front, and then stick a huge bolt in there.

For the plunger, just make it the same size as your tube, and have about 2-3' of draw. As for making it airtight.....Maybe a huge o-ring or just go with pipe insulation.

To get the endcap on there... get a piece of PVC pipe one size smaller (for instance, one size smaller than 3/4" would be 2/4" or 1/2") Cut about a 3 inch length and hammer it in there. Then secure the end with a endcap and glue it on with primer and cement.

Have fun, and where the hell will you get a 100 lb. spring?

[davidbowie]

You would need a sledgehammer to open that trigger. 100lbs of force pushing on the pin is going to make it difficult, plus the return spring is fairly strong to begin with, and a BOLT has threads, which will dig into the chamber wall, especially if they have a 100lb spring pushing them in.

A springer that big is quite possible, but absolutely every connection will be under huge amounts of stress. Anything that could handle it would most likely be very expensive and still a bit dangerous.

Instead, you might want to think about making a giant mounted slingshot. Use a 4" thinwall cap for the cup, and 2 48" bungees on each side, mounted to a frame. Mount a gravity latch to the back of the frame, and put a loop of strong tie-down rope through the back of the cup to catch in it. I made one of these last summer, and it was a blast. Eggs, golfballs, tennis balls, water-filled party balloons, and bags of mud could be seen flying through the air.