Alright, I've got an engineering project coming up at school - a mechanical pitch-back machine. You pitch a baseball into a machine, it throws it back to you. We can't use anything electronic or any powered motors. It has to be purely mechanical.

I see about 2 ways of doing this, springs or compressed air. I chose the latter. I was thinking of putting a 11 gallon tank filled with about 120 -150 psi hooked up to a regulator to set it at the proper output psi, this would be hooked up to a valve to release the air when you want the ball thrown back to you, and all this hooked up to the pneumatic cylinder http://www.aircylinderdirect.com/pro...rcylinders.jsp.

So, what I need from y'all in the know is a little help picking out which one I should get. The ball will drop down into 3" pvc pipe which will set it up to be hit by the cylinder and spit it out back to the user. Do you have to have an electrical circuit when using these cylinders, or can you use a valve that will be release by the user that will release the air to push the cylinder? About what size cylinder would I need to be able to shoot a baseball 20ft?

Must be able to receive 5 ***** and return them.

Thanks for the help.

 

I hate to be a party pooper, but isn't a pneumatic cylinder still considered a "motor"? I utilized pneumatic motors in my trade to stroke fire/smoke dampers open/closed. Althought they only stroke in a linear fashion, they are still considered actuator motors. As far as getting one to stroke enough and quick enough to spit a ball 20 feet, why not build an automatic potato gun out of pvc piping, utilize a can of hair spray (with mechanical fill valve....pushbutton) and an old Coleman campstove striker (mechanical).

All you would need to figure out is how much propellant is required to provide enough energy to push ball back to sender.....


Good luck


Gary

Disclaimer: I take no responsibility in resulting fires, shattered pvc barrels, knocked out windows....teeth....class mates or instructors. User should provide adequate fire protection devices (to put out small lab fires) and should don all protective clothing required to protect self from flying projectiles, (ie: full catchers gear comes to mind + safety glasses)

Happy shooting

 

sounds almost like how a PCP air rifle operates. only triggered electronically.

potatoe gun folks will sometimes use a electronic trigger used in lawn sprinklers. I've only constructed a potatoe gun using a mechanical valve.

 

The problem I see you have is getting that cylinder to accerate fast enough to give the baseball the velocity needed to fly 20ft after its launched at the approate angle from the ground.

If you familar with the john deere hydraulic bale kickers this will make perfect sense. When a bale is on that pan and trips the unit, hydraulic pressure is routed to the cylinder, however if it were allowed to cycle the piston unrestrained the bale probably wouldn't even make it to the wagon. There is a latch that holds the kicker pan in position till there is a preset amount of pressure on the kicker piston and when there is enough pressure the latch is unlatched hydraulically from the same hydraulic line as the main piston and kicker pan cycles very rapidly almost violent, enough to kick a 55lb. bale over the back of some of our wagons.

 

could you set it up so that the cylinder actuates an arm like a pitching machine?

 

Make your cylinder pullback and release a spring loaded mechanism and that chunks the ball. Maye you could get your cylinder to spray hair sprya into the cylinder and then use a smaller one to press a bbq lighter. BOOM and here it come flying back. I'd like to see that.

 

Hmm, well I don't know the first thing about pneumatic cylinders and I was going to explore this further this afternoon after my midterm. If it won't have the power to move the ball "fast" enough to get it back 20ft, I've got the stupid backup plan of 5 springs hooked to 5 arms launching 1 ball back each. Stupid, simple, but it gets the job done.

Hahahahaha!!! This was one of my initial ideas as well. I would love to ask the teach to demonstrate our pitch-back machine to the class... Then the ball comes flying out at a buck fifty and nails her in the stomach. Kinda like Happy Gilmore .

Yes.

So, what y'all are saying is that a pneumatic cylinder releases slowly with a lot of power? I pictured it releasing abruptly. You know, just hit the switch (valve) on the line and BAM! it kicks the rod out and retracts it real quick.

 

yeah, pneumatic cylinders do not have the punch to push a baseball that far...

personally, i think if you could go to a batting cage, you might get some idea of how to set it up, but the ones at batting cages are electric motor driven.

Youwould have to figure out how to change it over to an air system...

 

I work with this stuff all day every day. It's an interesting problem. Already noted that air cylinder may not have the guts to toss aball 20 feet by itself. You will need a valve that is fast acting and can pass a lot of gass quickly.. You could maybe use a ball valve operated by a husky air cylinder. This would get you the quick volume of high pressure air. You will need a good volume of 100 psi air unless you feel invincible and want to try using co2 or argon from a welding tank. I have done this and it is very very dangerous and takes a very high quality valve. The second step is to use some of the force generated by the air cylinder to operate a lever arm. say 4 to 1 or 5 to 1 For example set up so the air cylinder travels 2 inches and the ball end of the arm travels 8 or 10 inches. Maybe even longer stroke and arms. Check out catapults and trebuchets. This is how they work but not with air cylinders.

The idea of using a trigger to hold the arm while the air cylinder builds pressure inside it is interesting. Extremely dangerous if you use a large air cylinder. You can generate over 300 pounds force with just a 2 inch bore cylinder (3.14 x bore squared x pressure)

If I read this right you need to cycle the ball a few times. Now it starts getting complicated. How will you detect the ball has returned. How will you catch it and return it to the arm or thrower??

In order to get the size of air cylinder you will need to know the froce required to toss the ball 20 feet. Get out the machinery's hand book and look up the mechanics section. It's really a ballistics problem so you could do a Google on balistics or artillery and get the calculations required .. Not hard math either.

You got your work cut out for you... no party this week end

good luck