Hi all!
So I'm pretty new to all of this but I'm wondering if anyone can help me figure something out. I'm attempting to build a stunt air ram to launch performers for stunts in films. I began this project several years ago and had my father acquire some parts for me because he worked with pneumatic brake testers for work. He passed away shortly after the project began and it never got completed because I simply didn't have the knowledge for the project.
I currently have two linear actuators linked up to an air compressor via tubing, valves and quick-connects. My problem is that, if I'm understanding it correctly, I need a good amount of pressure built up so that when the cylinders are released, the force will be great enough to throw a performer 3-4 meters into the air. When we began this endeavor, we bought an air compressor that maxed out at 250 psi. Obviously, thats not enough pressure for the launch. I have it where if I build its pressure up and throw the valve open, the rods will shoot out but not at any velocity close to what is needed. I'm assuming its because the pressure needs to be built up in the actual chamber of the cylinder.
My problem is that I have no idea how to hold that pressure in without the rods engaging nor  how to configure it to release the rods instantly. Can anyone help me out with this?

Views: 709

Replies to This Discussion

Hi Niel:

Interesting dilemma. I don't pretend to know as much about pneumatics as some of the other folks on this forum but, for whatever reason, most of these more knowledgeable folks rarely offer any help or insight here.

With respect to your intended application, I do believe I can offer maybe one or two alternatives to achieve the same goal. I'm fully aware that some of the things I mention may have already gone through your mind and been dismissed. If so, please pardon the redundancy.

I tinker around with Big Bore Pneumatic Air Rifles and admittedly, I've never dealt with a projectile the size of a human stuntman; however, the pneumatic principles that apply in your application are basically the same.

First off, I would be inclined to ditch the 250 PSI compressor and feed my air supply needs off of a 4500 PSI Carbon Fiber Tank. The larger the tank, the more launches you will get provided you do not need the full 4500 PSI to complete a single launch sequence.

I have no clue how you've set up your hoses, regulators, actuators and such but, I'm fairly certain the same setup can be safely implemented with one or more of these Carbon Fiber air tanks.

As far as the issue of triggering your pneumatic device , with Air Rifles working in the 3000 PSI range a valve system is used. These Valve systems can be googled up for more information.

Depending if you want to initiate your launch sequence manually or electronically, I would look into some of the High Pressure valves.

As I stated above, I really don't know that much about pneumatics and all of its related gizmos and gadgets.

Whenever I need these kinds of answers I'll contact the companies that produce these items and ask them. Like here on this forum, sometimes the folks at these various companies don't want to bother with answering questions.

Not all engineers are like that. There are actually some pretty sharp cookies out there that are more than willing to help. Ideally, I like to initiate my inquiries with the salesman at these companies. If they think they're on the verge of making a sale, they are more helpful.

Another method used in Air Rifles that can apply to your application is a combination of pneumatics and Spring-Power.
In this method a compressed spring, when released, generates sufficient PSI to launch your projectile. Triggering these setups are generally easier.

With either method, I would prefer to trigger them manually but, that's just me. I've gotten alot of my ideas for trigger mechanisms on the youtube site. In the sections on "Home made" air rifles.

I hope this short reply wasn't more confusing than anything else. Best of luck on your project.

Incidently, I did an internet search on "How to build a Pneumatic Cannon" and it turned up multiple clever ideas on trigger mechanisms.

Tim Montano

U-Guy

SkunkWorks
So i've got a couple yrs. old scuba tank that's still full and i have no clue what its max psi is but it looks to be 3000...i figure that might be enough? i just don't know how to connect its valve to the quick-connect that i now have...would i just purchase a female quick-connect, drain the tank, install the female quick-connect, full the tank, connect my current set-up and use the standard ball valve that i currently have to trigger the release?

Tim Montano said:
Hi Niel:

Interesting dilemma. I don't pretend to know as much about pneumatics as some of the other folks on this forum but, for whatever reason, most of these more knowledgeable folks rarely offer any help or insight here.

With respect to your intended application, I do believe I can offer maybe one or two alternatives to achieve the same goal. I'm fully aware that some of the things I mention may have already gone through your mind and been dismissed. If so, please pardon the redundancy.

I tinker around with Big Bore Pneumatic Air Rifles and admittedly, I've never dealt with a projectile the size of a human stuntman; however, the pneumatic principles that apply in your application are basically the same.

First off, I would be inclined to ditch the 250 PSI compressor and feed my air supply needs off of a 4500 PSI Carbon Fiber Tank. The larger the tank, the more launches you will get provided you do not need the full 4500 PSI to complete a single launch sequence.

I have no clue how you've set up your hoses, regulators, actuators and such but, I'm fairly certain the same setup can be safely implemented with one or more of these Carbon Fiber air tanks.

As far as the issue of triggering your pneumatic device , with Air Rifles working in the 3000 PSI range a valve system is used. These Valve systems can be googled up for more information.

Depending if you want to initiate your launch sequence manually or electronically, I would look into some of the High Pressure valves.

As I stated above, I really don't know that much about pneumatics and all of its related gizmos and gadgets.

Whenever I need these kinds of answers I'll contact the companies that produce these items and ask them. Like here on this forum, sometimes the folks at these various companies don't want to bother with answering questions.

Not all engineers are like that. There are actually some pretty sharp cookies out there that are more than willing to help. Ideally, I like to initiate my inquiries with the salesman at these companies. If they think they're on the verge of making a sale, they are more helpful.

Another method used in Air Rifles that can apply to your application is a combination of pneumatics and Spring-Power.
In this method a compressed spring, when released, generates sufficient PSI to launch your projectile. Triggering these setups are generally easier.

With either method, I would prefer to trigger them manually but, that's just me. I've gotten alot of my ideas for trigger mechanisms on the youtube site. In the sections on "Home made" air rifles.

I hope this short reply wasn't more confusing than anything else. Best of luck on your project.

Incidently, I did an internet search on "How to build a Pneumatic Cannon" and it turned up multiple clever ideas on trigger mechanisms.

Tim Montano

U-Guy

SkunkWorks
Hi Neil:

The short answer to your questions are, "I don't know exactly."

One important safely issue you do have to bear in mind is that you are going from the 250 PSI that your compressor was putting out, to the 3000-Plus PSI stored in your scuba tank. (yes, scuba tanks are generally rated at 3000 PSI)

There is a very real possibility that the air-fittings such as the quick disconnectors, regulators and hoses you now have may not be rated to withstand the higher pressures. You'll want to check to be sure. You don't want this project blowing up in your face.

You'll need to do some calculating to determine what volume of air to release in order to supply enough "Ram-Momentum" to launch your stuntman. I absolutely suck at math so in my case that would mean I'd be running back and forth to the filling station to recharge my tank.

In my minds-eye I see it going like this:

I have my high-pressure air tank connected to a secondary tank with a shut-off valve in between the two. This secondary tank will hold the calculated volume of air that will launch your stuntman. Both of these tanks must have some way of telling how much air is in each one. (ie. high pressure air guages) Your secondary tank must be rated to safely hold the higher pressure.

The ball valve you mentioned must be rated to withstand the higher pressures you're working with as well. This ball valve, or whatever method you decide to use to trigger you air dump, is situated in between your Air Ram and your secondary tank.

I picture it being just that simple.

My description is most likely over-simplified but, I'm hoping you get the picture. For me, the hard part would be calculating the volume of air needing to be released in order to achieve your goal.

I believe if I were working on a similar project, I would go ahead and start out with the lower pressures that your compressor is outputting just to get a feel for what to expect at higher air pressures. Depending on the function of your Air-Rams, it may be that those lower air pressures will do the job.

Since I don't know the details of your equipment and specific goals with this project, I really can't give specific answers. Right now I'm just throwing out suggestions as to how I might go about making this "Stuntman Cannon" work.

Tim Montano

U-Guy

SkunkWorks



Neil Adamson said:
So i've got a couple yrs. old scuba tank that's still full and i have no clue what its max psi is but it looks to be 3000...i figure that might be enough? i just don't know how to connect its valve to the quick-connect that i now have...would i just purchase a female quick-connect, drain the tank, install the female quick-connect, full the tank, connect my current set-up and use the standard ball valve that i currently have to trigger the release?
Tim Montano said:
Hi Niel:

Interesting dilemma. I don't pretend to know as much about pneumatics as some of the other folks on this forum but, for whatever reason, most of these more knowledgeable folks rarely offer any help or insight here. With respect to your intended application, I do believe I can offer maybe one or two alternatives to achieve the same goal. I'm fully aware that some of the things I mention may have already gone through your mind and been dismissed. If so, please pardon the redundancy.
I tinker around with Big Bore Pneumatic Air Rifles and admittedly, I've never dealt with a projectile the size of a human stuntman; however, the pneumatic principles that apply in your application are basically the same.

First off, I would be inclined to ditch the 250 PSI compressor and feed my air supply needs off of a 4500 PSI Carbon Fiber Tank. The larger the tank, the more launches you will get provided you do not need the full 4500 PSI to complete a single launch sequence.

I have no clue how you've set up your hoses, regulators, actuators and such but, I'm fairly certain the same setup can be safely implemented with one or more of these Carbon Fiber air tanks.

As far as the issue of triggering your pneumatic device , with Air Rifles working in the 3000 PSI range a valve system is used. These Valve systems can be googled up for more information.

Depending if you want to initiate your launch sequence manually or electronically, I would look into some of the High Pressure valves.

As I stated above, I really don't know that much about pneumatics and all of its related gizmos and gadgets.

Whenever I need these kinds of answers I'll contact the companies that produce these items and ask them. Like here on this forum, sometimes the folks at these various companies don't want to bother with answering questions.

Not all engineers are like that. There are actually some pretty sharp cookies out there that are more than willing to help. Ideally, I like to initiate my inquiries with the salesman at these companies. If they think they're on the verge of making a sale, they are more helpful.

Another method used in Air Rifles that can apply to your application is a combination of pneumatics and Spring-Power.
In this method a compressed spring, when released, generates sufficient PSI to launch your projectile. Triggering these setups are generally easier.

With either method, I would prefer to trigger them manually but, that's just me. I've gotten alot of my ideas for trigger mechanisms on the youtube site. In the sections on "Home made" air rifles.

I hope this short reply wasn't more confusing than anything else. Best of luck on your project.

Incidently, I did an internet search on "How to build a Pneumatic Cannon" and it turned up multiple clever ideas on trigger mechanisms.

Tim Montano

U-Guy

SkunkWorks

RSS

Members

© 2019   Created by Marshall Matheson.   Powered by

Badges  |  Report an Issue  |  Terms of Service