Reducing/Dampening Noise and Vibrations in a High impact system 1

[ucme92]

Hello all,

This is my first time logged onto this site and I was hoping to get some in acoustics andvibrations which I am not altogether familiar with. My background is Engineering Design and Analysis. I am currently working on a project to build a sort of automated air vortex cannon.

If you arent familiar with an air vortex canon, it basically shoots a large volume of air out of a long nozzle at a high velocities by moving a well sealed bag or plate very fast. I have tried to recreate this effect with piston cylinder configuration design, and this works fairly well.

The way my project works is that it uses a rack and pinion drive train system to draw back a piston platen through a tube. Behind the piston is a powerful spring and so when the piston reaches the end of its motion, the spring is released allowing the piston to fire at a high muzzle velocity.

As you can imagine, I have to stop the piston at the end of travel.This is where I encounter problems. One of my specifications is to keep the entire system at a noise level below 60dB. However, because the speed is so fast, the impact is also really great causing the system to shoot up to an 80dB noise level.

I have tried to use things such as sorbothane pads, rubber, foam, etc to act as dampers between the piston and stops during impact but because there is still a fair amount of metal in the system, it only goes so well in reducing the impact noise by about 5dB. I have thought about bulding enclosures but havent done any yet.

I would be very appreciative if anyone here has some more experienc with building such and can point me in a better/right direction.

Thanks for your time/

 

[drawoh]

ucme92,

If you were to use a crank to drive your piston, it would decelerate to a halt without hitting anything. You need to design some sort of piston action.

--
JHG

 

[ucme92]

Thanks,

I have actually thought about using a slider crank but found it might be harder to achieve the speeds I want with control but I think if I attached some sort of slider crank to the system I have so far to act as a stop it could work. Are you familiar with what magnitude of forces that a slider crank can take?

 

[GregLocock]

A piston in a car engine moves at 60 m/s and can handle several tons of force.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[DubMac]

Go look at Enidine Corp out of Buffalo, NY. I know they make all kinds of recoil products, shocks and such. Mostly hydraulically orificed damper configurations.

 

[ehbadger]

Can you affix your spring to the piston? Spring will compress, release, and hold the piston at the end of the expansion, and return to neutral. No need for a hard stop for the piston. Without seeing the details of the assembly this may or may not work. If the piston needs to travel much further than the distance from spring neutral to spring compressed it won't work.

dark red are the fixed points
green is the piston
purple is the spring

Loading:
___________________
|QQQQ|D <-------------

Release/Expansion:
____________________
| Q---Q---Q---Q |D ----------->

Neutral:
____________________
| Q-Q-Q-Q |D <---------->

 

[ucme92]

yeah I need a fixed location where I can pick up the rack on the piston every time. I thought about that idea but over time the spring would lose elasticity and hence that fixed position. So the system requires some sort of preload