Impact mechanism possibilities??
Impact mechanism possibilities??
(OP)
I am a Geotech Engineer and have become invloved in the design of a hammer impact unit.
We need to build a mechnanical device that will push a rod horizonatlly and hit a
plate horizontally. The striker rod will be activated by a switch and upon activation it will shoot out and strike an anvil. We are hoping the impact rod will achieve at least a velocity of 4 m/sec. We need the rod to strike the anvil with at least 50 Juoules of energy. After impact we will measure the waves this device causes in the earth. The device then needs to be able to repeat the striking procedure for 1000's of hits. Approx 30 seconds between strikes is the time frame we are hoping for, or less. We are going to enclose this device inside a sealed chamber.
My question: What kind of device would use to create the desired impact?
The two items impacting need to be steel, and the impact needs to be steel on steel.
(Similar to gently swinging a 8 kg sledge against a steel block)
As far as I can see hydraulic power would be to slow to push a striker rod out at 5 m/s.
Also hydraulic power supply issues eliminates this possibility. Would an air actuated pneumatic cylinder work? Do pneumatic cylinders stand up to repeated impacts?
What do you think about linear thrust actuators? I did not see any that achieved the desired speed. Would you recommend the use of simple tension or compression springs for propelling the striker against the anvil for a design?
Any ideas or simple solutions that you have are greatly appreciated. Feel free to shoot down any of my comments as un-acceptable or expand on them as you see fit.
Coneboy
Geotech Pro Eng
We need to build a mechnanical device that will push a rod horizonatlly and hit a
plate horizontally. The striker rod will be activated by a switch and upon activation it will shoot out and strike an anvil. We are hoping the impact rod will achieve at least a velocity of 4 m/sec. We need the rod to strike the anvil with at least 50 Juoules of energy. After impact we will measure the waves this device causes in the earth. The device then needs to be able to repeat the striking procedure for 1000's of hits. Approx 30 seconds between strikes is the time frame we are hoping for, or less. We are going to enclose this device inside a sealed chamber.
My question: What kind of device would use to create the desired impact?
The two items impacting need to be steel, and the impact needs to be steel on steel.
(Similar to gently swinging a 8 kg sledge against a steel block)
As far as I can see hydraulic power would be to slow to push a striker rod out at 5 m/s.
Also hydraulic power supply issues eliminates this possibility. Would an air actuated pneumatic cylinder work? Do pneumatic cylinders stand up to repeated impacts?
What do you think about linear thrust actuators? I did not see any that achieved the desired speed. Would you recommend the use of simple tension or compression springs for propelling the striker against the anvil for a design?
Any ideas or simple solutions that you have are greatly appreciated. Feel free to shoot down any of my comments as un-acceptable or expand on them as you see fit.
Coneboy
Geotech Pro Eng





RE: Impact mechanism possibilities??
Doesn't gravity work well enough? Two strikes per minute gives lots of time for the hired-hand to line up the sledge for each shot. I can keep up sledge-hammering once per 5-10 seconds for several minutes at a time, but I'm sure you could find a burly guy who can swing a sledge once every 30 seconds and not get tired all day.
But I get that you want a higher level of control than this, so set aside the old-fashioned way for a minute. Would a pile-driver work? Lifts a fixed mass and drops it at regular intervals. In your case, the mass swings around a pivot and strikes the target at the bottom of the arc, rather than dropping straight down. If there really is 30 seconds between hits, the average power requirement is pretty small. Still within the human-power potential, BTW. If this has to run unattended by people, then a small electric motor can lift the mass. You then need a mechanism to hold it up and drop it at the correct time. Still less complicated than ramming it down with hydraulics or springs.
STF
RE: Impact mechanism possibilities??
A big ol' gravity powered swinging hammer should work just fine.
Now all you need to worry about is the hoisting mechanism.
Mike Halloran
Pembroke Pines, FL, USA
RE: Impact mechanism possibilities??
You can look up MIL-S-901 and related documentation to see what's done for ballistic shock testing: http://en.wikipedia.org/wiki/MIL-S-901
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RE: Impact mechanism possibilities??
Cheers
Greg Locock
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RE: Impact mechanism possibilities??
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RE: Impact mechanism possibilities??
"at least 50 Juoules of energy" ... ok, this is the requirement ... why define the mass of the impactor as 6.4kg (using the 4m/s) ?
"We are going to enclose this device inside a sealed chamber." ... how big is the box ? how portable ? how heavy ?
i think your (steel) impactor is going to be something like 4in3 (if i've done the conversion properly).
you say hydraulics are out, by possibly pnuematics. sure air pressure could create the force needed, but recharging in 30sec ? maybe you need a reserviour system (rather than a "direct drive" type of pump) ... a regulator on the outlet of the reserviour, a separate means to refill.
Quando Omni Flunkus Moritati
RE: Impact mechanism possibilities??
RE: Impact mechanism possibilities??
Quando Omni Flunkus Moritati
RE: Impact mechanism possibilities??
Ted
RE: Impact mechanism possibilities??
Please provide additional comments or thoughts if you can see an alternate idea.
We are really trying to keep it KISS.
hydtools: Yes, I am looking at rock breaker type hammer. They tend to have very fast and hard impacts which is good, but they are hard to control so that a single strike occurs. A chain driven swinging pendulum arm is also being considered.
Rb1957: Yes, recocking the impact hammer after each strike also needs to be assessed.
Compositepro: A gravity driven pendulum swing arm works great when you have lots of room. If space is limited then there might not be sufficiet room for a full swing of the arm as we will need a fair amount of impact energy.
Greglocock: A rope actuated pull system works great in other scenarios. Inside a sealed box there are some more challenges.
MikeHalloran: Yes, a charpy impact swing arm would work great, but I need it much smaller. What would you use for pulling the swing arm back?
Coneboy
RE: Impact mechanism possibilities??
Quando Omni Flunkus Moritati
RE: Impact mechanism possibilities??
Agree that a gravity pendulum will be more reliable/repeatable than a spring or pneumatic driven device. But spalling of the impactor/impactee and changes in their mass over time will need to be considered, as these will/may affect the delivered energy. Your sealed box will need to be opened occasionally to check for such damage.
"What would you use for pulling the swing arm back?"
Any of a thousand different mechanisms, actuated by pneumatic or hydraulic cylinders, or electric motors with gear or worm drives, or a big whomping electromagnet (e.g. solenoid). Why not use a semi-automatic rifle bullet as the impactor, then all of the mechanics will have been figured out already. You'd just need to purchase large-capacity magazines for the rifle...which will be a problem in the US.
RE: Impact mechanism possibilities??
c'mon smile, we know how much you guys south of the border Love your guns
Quando Omni Flunkus Moritati
RE: Impact mechanism possibilities??
Swing hammer. Lift with a simple disk cam.
RE: Impact mechanism possibilities??
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RE: Impact mechanism possibilities??
Yes we are considering the lever arm pendulum design as our most likely option.
The anvil and striker on the pendulum would be sizable so I am not worried about spalling over time and related changes in mass.
Yes, we will make the sealed box with a bolted cover so that we can check the contents periodically.
This box it will be mounted in will be about 0.5 meter wide, 2 meter long and about 1 meter high.
Estimating the weight of the box and enclosed impact unit at approx. 200 lbs.
Use of any kind of bullets is out of the question as it will be used in a sensitive area.
Minjulep
Diskcam device is being looked at.
Trying to adhere to KISS.
Thanks
Coneboy
RE: Impact mechanism possibilities??
If the chamber is sealed how does the energy get out?
What mechanism is typically used in this application?
RE: Impact mechanism possibilities??
http://www.giscogeo.com/pages/seixwsn.html
RE: Impact mechanism possibilities??
http://www.passcal.nmt.edu/content/passcal-obtains...
RE: Impact mechanism possibilities??
Those are great examples and ideas.
Thanks for posting those links.
A chain driven pulley for lifting and large elastics to accelerate the drop
weight so that it impacts with greater energy.
Very KISS
RE: Impact mechanism possibilities??